FSN 411 complete notes.pdf

TAMIL NADU AGRICULTURAL UNIVERSITY FSN 411 – Food Quality, safety Standards and Certification (2+0) CENTRE FOR POST HARVEST TECHNOLOGY AGRICULTURAL ENGINEERING COLLEGE AND RESEARCH INSTITUTE TAMIL NADU AGRICULTURAL UNIVERSITY COIMBATORE – 641 003 2021 1 FSN 411 Food Quality, Safety Standards and Certification (2+0) Theory Unit – I: Food Quality and Physical Properties Food quality – definition and its role in food industry. Quality attributes – classification: Color and gloss – definition, different colors, color measurement by spectrophotometer, muncell color system and lovibond tintometer – role in food qualities. Role of viscosity and consistency in food quality; Physical properties – size and shape, weight, volume, weight volume ratio, length, width, diameter, symmetry, curvature, area. Defects – classification, genetic – physiological factors: structural, off color, character; entomological defects: holes, scars, lesions, off coloring, pathological defects, mechanical defects, extraneous or foreign materials defects. Unit – II: Quality attributes of Foods Measurement of defects: Improving visibility by dilution, white background, color differences, standardization of conditions, reference standards, counts and measures, isolation of defects by floatation, elution, electronic sorting and internal defects, flavor – definition and its role in food quality, taste – classification, taste qualities, relative intensity, reaction time, effect of disease, temperature and taste medium on taste, basic tastes, interaction of tastes, odor: definition, classification, neutral mechanisms, olfactory abnormalities, odor testing, techniques, thresholds, odor intensities, olfaction, visual, auditory, tactile and other senses, vision, audition, oral perception other than taste. Unit – III: Subjective evaluation of foods Factors influencing sensory measurements: attitudinal factors, motivation, psychological errors in judgements, relation between stimulus and perception adaptation, correlation of sensory and instrumental analysis, laboratory quality measurement, types of tests, panel selection and testing environment, serving procedures, instruction to judges, other procedures, consumer measurement. Factors influencing acceptance and preference, 2 objectives of consumer preference studies, information obtained from consumer study, factors influencing results from consumer surveys, methods of approach, development of the questionnaire, types of questionnaire, serving procedures, comparison of laboratory panels with consumer panels, limitations of consumer survey. Unit – IV: Quality evaluation of foods Quality of raw materials: sampling and methods of sampling, physical, chemical and microbial quality, quality of products during processing and after processing: color, taste, texture, flavor, appearance, factors influencing the food qualities: soil, field practices, harvesting practices, procedures, packaging, transportation, storage, conditions, processing conditions, packaging and storage conditions of finished products. Recording and reporting of quality. Quality inspection, quality control. Unit – V: Quality standards and certification Quality management and quality assurance – total Quality management, good manufacturing practices, good agricultural practices, good laboratory practices, Quality management systems, QSS, Quality circles, SQC, ISO system. National and International standards, plan documentation, types of records, auditing, surveillance, audit, mock audit, third party Quality certifying audit, auditors and lead auditors, certification, certification procedures, certifying bodies, accrediting bodies, international bodies. 3 Lecture – 1 Food Quality – Definition and its role in Food Industry Introduction Food is a major determinant of health, nutritional status and productivity of the population. It is, therefore, essential that the food we consume is wholesome and safe. Unsafe food can lead to a large number of food-borne diseases. Globally, food borne illness is a major problem of public health concern. Food-borne illness can not only result in mortality but can damage trade and tourism, lead to loss of earnings, unemployment and litigation and thus can impede economic growth, and therefore food safety and quality have gained worldwide significance. Food safety and quality are important at the home level, but are critical in large scale food production and processing, and also where food is freshly prepared and served. In the past, many foods were processed at home. Advancement in technology and processing, larger per capita incomes and better purchasing power as well as increased consumer demand have led to a variety of products of processed foods, food for health / functional foods being manufactured. Safety of such foods needs to be assessed. Definition of Food Quality Quality of foods may be defined as the composite of those characteristics that differentiate individual units of product; these characteristics should have significance in determining the degree of acceptability of that unit by the buyer. Some important characteristics of the food / food products are: Colour and gloss, viscosity and consistency, size and shape, texture and flavour. Nutritive values (vitamins, minerals) - hidden attributes. Quality is commonly thought of as degree of excellence. It may be considered as a set of specifications, which are to be met within given tolerances or limits. Quality Control may be defined as the maintenance of 4 quality at levels and tolerances acceptable to the buyer while minimizing cost for the vendor It is therefore a holistic concept integrating factors such as nutritional traits, sensorial properties (colour, texture, shape, appearance, taste, flavour, odour), social considerations, safety. Safety is a preliminary attribute and precursor of quality. In order to ensure that foods are safe and of good quality, across the world various governments and international bodies have laid down food standards that manufacturers/suppliers are expected to adhere to. Thus, all food service providers (those involved at all stages of pre- preparation and preparation/processing, packaging and service) should adhere to good manufacturing practices and ensure food safety. Salient points to be borne in mind are: 1. Quality of raw materials and water 2. Cleanliness – of the premises, personnel, equipment, food preparation and storage and serving areas 3. Storage of food at appropriate temperature 4. Food hygiene 5. Good service practices. Food Quality and Its role in Food Industry Quality of food stuff, raw as well as processed is of public health concern and must be addressed. In the past decade, safety challenges faced globally as well as in India have changed significantly and issues related to food quality and food safety have gained tremendous importance. A number of factors are responsible for this: With fast changing lifestyles and eating habits, more people are eating outside their homes. In commercial settings, foods are prepared in bulk handled by many persons, thus there are more chances of food getting contaminated. Further, food items are prepared many hours in advance, and may spoil if not stored appropriately. 5 There are many processed and packaged foods. Safety of these foods is important. Spices and condiments, oilseeds were processed at home in former times and purity of these were not a concern. In today’s world, prepackaged individual spices, condiments, spice powders and mixes are in demand, especially in cities and metros. Quality of even raw food stuff besides processed foods is of public health concern and must be addressed. Logistics governing transport of bulk food is complex and there is a long gap between processing and consumption. Thus risk assessment and safety management during mass production and mass distribution is critical. Microbial adaptations, antibiotic resistance, altered human susceptibility and international traveling have all contributed to increasing incidence of food-borne microbial diseases. There are still many food borne illnesses of unknown etiology. This is an issue of global public health concern and there is a need to detect, identify and recognise emerging pathogens and establish active surveillance networks, nationally and internationally. India is a signatory to the World Trade Organisation (WTO) non-tariff agreement, which has provided greater access to world markets and opportunities to all countries to enter international trade. In this scenario, it has become essential for every country to protect the safety and quality of foods and also ensure that imported foods are of good quality and safe to eat. Effective food standards and control systems are required to protect food production within the country as well as to facilitate trade with other nations. All food manufacturers are required to meet the given standards of quality and safety, and need to have their products regularly tested. Pollution in atmosphere, soil and water, including use of pesticides in agriculture, bring their share of contaminants. Also use of additives 6 such as preservatives, colourants, flavouring agents and other substances such as stabilisers makes the analysis of food for various components—both nutrients and contaminants—imperative. Owing to the above factors, there is a growing concern for safe, wholesome and nutritious foods in a highly dynamic food business environment, which in turn has greatly expanded the scope and has increased career opportunities in this sector. 7 Lecture – 2 Quality attributes, classification: color and gloss – definition, different colors, color measurement by spectrophotometer, munell color system and Lovibond tintometer, role in food qualities Quality Attributes The quality attributes referred to as sensory may readily be classified in accordance with the human senses by which they are perceived. The sensory attributes namely, the senses of sight, touch, taste and smell are given in Table 1.1. Table 1.1: Classification of Quality Attributes Sight Appearance Color Gloss Viscosity Size and shape Defects Touch Kinesthetic (Texture) Hand or finger feel Mouth feel Smell and taste Flavor Odor Taste Hidden Nutritive value Adulterants Toxicity Color and gloss Color is an appearance property due to spectral distribution of light. Glossiness, transparency, haziness, and turbidity are properties of materials due to the differences in reflectance and transmittance of light. Physically, color is a characteristic of light, measurable in terms of intensity and wavelength. It arises from the presence of light in greater intensities at some wavelengths than of others. 8 Light may be reflected, transmitted, absorbed, or refracted by the object being illuminated. Spectrophotometers are used to measure color of the products. Food Colours Colour is the first sensory quality by which foods are judged; food quality and flavour are closely associated with colour. Colour far outweighs flavour in the impression it makes on the consumer even when the flavour are pleasant. Colour powerfully influences the consumer’s ability to identify the flavour and quality. Colour is the general name of the all sensations arising from the activity of the retina of eye. Colour is important to many foods, both that are unprocessed and manufactured. Together with flavour and texture, colour plays an important role in food acceptability. The colours of foods are result of natural pigments or of added colours. Colour compounds are a unique class considering their structural diversity and extremely complex chemical and physical properties. Importance of Food Colours As food should also be attractive to the eye, colour plays a key role in defining its quality. Colour is the first characteristic of the food that is noticed and it determines our expectation of both flavour and quality. Colorants affect the identification of flavor as well as it affects sensing the actual level of sweetness in the food. 1. To overcome the damage to the appearance caused by processing and to preserve product identity. 2. To ensure color uniformity of food products that naturally varies in color. 3. To intensify the colors of certain manufactured foods. 4. To help protect flavour and light sensitive vitamins during storage by a sunscreen effect. 5. To serve as a visual indication of quality. 9 6. To give colour to certain foods such as sugar confectionery, soft drinks, sauces, ice lollies and soft drinks, this would otherwise be virtually colourless. Classification of Food Colors Colors added to food are regulated as food additives. In foods, coloring matter means those substances that when added restores or adds the color in foods. Synthetic colorants used commercially are also known as certified color additives. The added colorants can be classified as: A) Natural Colors Natural colorants are those that are extracted from animals, vegetables, fruits, minerals and spices used to color foods. e.g. carotenoids from annatto, paprika, saffron, anthocyanins, caramel, chlorophyll and turmeric. Carotenoids are used the most followed by the red pigment and brown colored caramels. I. Anthocyanins Anthocyanins are the water soluble compounds responsible for the red to blue colour of variety of fruits and vegetables. It can be derived from various sources including grapes, redcurrants and blackcurrants, raspberries, strawberries, apples, cherries, red cabbages, brinjal. They provide orange, red, blue, violet and magenta colours. II. Carotenoids Carotenoids are widely spread natural pigments in plants and animals. They provide natural yellow, orange or red colors. a) β-carotene Beta carotene occurs in nature usually associated with a number of chemically closely related pigments and extracts have been used as food colorants for many years. 10 It was first isolated from carrots and hence the name carotene was given to this yellow pigment. The carrot represents the most commonly known source of carotene. It also occurs in a wide variety of other fruits and vegetables including banana, jack fruit, maize, mango, papaya, pumpkin, watermelon, red pepper, spinach, peaches, apricots, oranges, broccoli, etc. It imparts yellow-to- orange colour in foods. It is used at a concentration of 0.13% to 2%. The most important application of oil soluble form of β-carotene is for coloring butter and margarine. In water-based products like ice-cream, yoghurts, etc., water soluble nor-bixin products are used. b) Canthaxanthin Canthaxanthin is a di-keto carotenoid pigment with an orange-red colour. Canthaxanthin is the principal pigment of the pink edible mushroom, Cantharellus cinnabarina. It is also isolated from algae, hydra and the brine shrimp. It widely occurs in water birds that feed on crustacean. Thus it is a major pigment of several flamingo species, occurring in their feathers, leg, skin, egg yolk, blood plasma and liver. It was first synthesized chemically in the year 1964. Canthaxanthin is used at 5 to 60 ppm levels to impart red colour to food products. It blends well with β-carotene to produce orange shades. Canthaxanthin is frequently used to enhance and standardize the colour of tomato products like juice, sauce, soup, and dehydrated powder. The other food applications include Russian and French dressings, fruit drinks, and ice cream. 11 c) Annatto Annatto is a natural colorant derived from pericarp of annatto (Bixa orellana L.) seeds. Annatto is fast growing shrub which produces cluster of pods containing 10 to 50 seeds. The seeds are covered with thin pulpy, bright orange resinous coating which serves as a source of colour. Annatto colour is generally used at a level of 0.5 to 30 ppm in food products resulting in hue ranging from light yellow to dark orange. The type of colour preparation employed and the product to be coloured also dictate the end effect. Oil-soluble annatto was formerly used in fat-based products like butter and margarine. However now it is also used in creams, spreads, desserts, etc. Water soluble annatto was traditionally used in cheese and cheese products. d) Betalain Betalain is found in wide range of fruits, vegetables, leaves of some plants and in underground part of beet-root. Among the different phenolic compounds that are relevant in plant foods, indigoids and indol derivatives represent the largest class. Betalain is the most noticeable group among indigoids. The betalain contain nitrogen in their ring structure and also contain glycoside residue. Betalain is defined as ‘a water soluble, indigoid pigment distributed in the cytoplasm responsible for most red, violate, orange and yellow colours found in flowers, fruit, some leaves and underground part of beet root’. Betalain colourants have been used in a wide variety of food products such as beverages, jams, jellies, ice cream, yoghurt, gelatin desserts, canned fruits, toppings, confections etc. It is a natural food colourant and relatively safe. It has various health benefits. 12 Betalain has no impact on environment. It gives consumers an appeal of fresh foods. The betalain can be used as colourant in organic foods, a developing concept in recent years. Since very low level of colour is used in food product it imparts very less technical defects to product. B) Nature identical synthetic colours: These are synthesized in the laboratories and a very limited range is available. C) Artificial colours: These are two types FD & C dyes and FD & C lakes. Dyes are water-soluble compounds that produce colour in solution. Lakes are made by combining dyes with alumina to form insoluble colourants. Coal tar is available in wide range of colours. Indigocarmine is an example of synthetic colour. D) Inorganic colours: PFA prohibits use of inorganic colour except titanium dioxide, which is permitted in chewing gum (Max limit 1.0 %). Food Colours Permited by FSSAI Natural colouring matter which may be used – Except as otherwise provided in the rules the following natural colouring principles whether isolated from natural colours or produced synthetically may be used in or upon any article of food. a) Carotenoids b) Chlorophyll c) Riboflavin (Lactoflavin) d) Caramel e) Annatto f) Saffron g) Curcumin or turmeric Addition of inorganic matter and pigments prohibited - Inorganic colouring matters and pigments shall not be added to any article of food; Provided that chewing gum may contain Titanium dioxide – (food grade) up to a maximum limit of 1 per cent. 13 Synthetic food colours which may be used - No synthetic food colours or a mixture thereof except the following shall be used in food S. No. Colour Common Name (1956) Colour index 1. Red Ponceu 4R 16255 Carmoisine 14720 Erythrosine 45430 2. Yellow Tartrazine 19140 Sunset yellow FCF 15985 3. Blue Indigo Carmine 73015 Brilliant Blue FCF 42090 4. Green Fast green FCF 42053 Use of Lake colours as colourant in foods Aluminium Lake of Sunset yellow FCF may be used in powdered dry beverages mix (powdered soft drink concentrate) upto a maximum limit of 0.04 percent weigh by weight. The maximum limit of colour content in final beverage for consumption shall not exceed 8.3 ppm and that of aluminium content shall not exceed 4.4ppm of the final beverage for consumption. Provided that the powdered dry beverages mix (powdered soft drink concentrate) label shall give clear instruction for reconstitution of product for making final beverage. Colour Measurement Colour is an important quality attribute of food products which influences consumer’s choice. Food scientist, food processors and marketers want the food to look appealing and consistent. Food processors use colour measuring instruments for checking and standardizing ingredient colour so that they can control colour of their final products, and analyse colour change in processing, transportation and storage. Also to communicate colour indices to their supply chain. Products in food industry can be in different shape / size, powder or granule, liquid or 14 paste or solid, transparent or opaque. Based on optical characteristics , food products are classified as, a) Opaque – Ex. Tomato, cheese, flour, rice b) Translucent – Ex. Fruit juices, jams c) Transparent – Ex. Soft drink, oil Opaque and translucent products are measured by reflection principle where as transparent products by transmission principle. Measurement Principle: Two principles are employed in colour measurement viz. colorimetry and spectrophotometry. Colorimetry Colorimetry quantifies colour by measuring three primary colour components of light which are seen by the human eye i.e. red, yellow and blue. In this principle secondary and tertiary colours like yellow, orange are not individually quantified. Instruments using colorimetry principle are generally called chromameters or colorimeter. They measure the colour much the same as human eye. Spectrophotometry In spectrophotometry the spectral reflectance or transmittance of a product is measured across the full spectrum of visible light (400 nm to 700 nm) to provide precise and accurate measurement. Instruments using this principle are called spectrophotometer. They are used in formulation and quality control of desired colours in prepared food products, in research and development of new products etc. Colour measurement instruments are widely used in virgin coconut oil production, desiccated coconut, chocolate, milk powder, peanut butter, tomato ketchup, orange juice, soft drinks, cereals, bakery and meat segments of food industry. Munsell system Another system for defining color space, called the Munsell system, is based on a color solid illustrated in Fig. 4. 15 The central vertical axis represents the locus of neutral colors with white at the top and black at the bottom. In this system, lightness of the sample, called value, is divided into a number of steps from 0 to 10. The distance of the sample from the central vertical axis is a function of the saturation or intensity of color and is called chroma on the Munsell map. Chroma is also divided into a series of steps, with the neutral axis or gray being 0, whereas a fully saturated sample has a chroma of 12. Color, or hue as it is called in the Munsell system, is presented by different planes around the vertical axis of the Munsell solid. In this system, the whole solid is divided into ten equal vertical segments with five principal hues (red, yellow, green, blue, and purple) occupying the central planes of alternate segments while intermediate hues (yellow-red, green-yellow, blue-green, purple-blue and red-purple) occupy the remaining planes. Each hue segment is further divided into ten sections numbered 1 to 10, with the main hue segment always numbering 5. The hue of a sample is designated by a number, indicating the section of the segment, followed by symbols which show the color of the segment involved. For example, 10P 16 indicates the hue section 10 of the purple segment. To complete the specification of the sample, the value quantity follows the hue which is then followed by a stroke and then the chroma. Here the color defined at 10 P 5/8 has the hue 10 P, the value 5, and the chroma of 8. Lovibond tintometer Light reflected from a white background passes through the cell containing the sample, and hence to the viewing tube, where it illuminates one-half of the field of view. The other half of the field of view is illuminated by light from the background, which passes through the color standards. A blue ‘daylight’ filter is incorporated in the viewing tube; in older models of the apparatus blue diffusing screens are fitted in the light cabinet and there are no colour filters in the viewing tube. The color standards are mounted in racks of up to nine slides each, arranged so that the colours may be moved into the field of view as required. The value of the standard or combination of standards which gives the best match is recorded as the colour of the material. If the material is too bright to be matched by the standard glasses, its colour is dulled by interposing glasses of neutral tint between the sample and the viewing tube. For some purposes, a standardized depth of material is used but, as this is not always the case, the depth of material used in the test shall always be stated. 17 Lecture: 3 Role of Consistency and Viscosity in Food Quality Introduction High-quality food is becoming increasingly important to consumers. In this industrial sector, manufacturing products that meet the high demands of the end users poses a challenge to analysts. Therefore, related measurements must be quick and accurate and should not be too expensive. This particularly applies to physical measuring variables like viscosity. Knowing the viscosity plays an important part in any industrial sector where liquid media are involved. For instance, viscosity plays a role in nearly all production stages in the food sector. For example, lots of liquid media must be carefully pumped through pipelines. The viscosities in this sector range from aqueous to pasty. In industrial food processing, different types of sugar are used frequently, such as glucose syrup to sweeten food and beverages. Many types of syrup are obtained from enzymatic degradation of starch and are important products for the starch industry. Since syrups are sticky, they are often used as binders in the production of food, e. g. of chocolate cereal mixes or sauces. The viscosity and the flow properties highly depend on the adhesive properties of the starch contained in the food. Starch has varying characteristics, depending on the temperature and the environment. For example, when the temperature increases, it has a solidifying effect. However, when boiled, it has a liquefying effect. When it cools down again, it has a solidifying effect again. These conditions are characterized by viscosity. Even for soups, the right consistency is achieved by adding thickeners. When determining the flow properties of sauces, dips, mayonnaises and liquid additives for quality control, the temperature- dependent viscosity plays an important role. 18 As viscosity changes the flow properties of a liquid food and influences the appearance and the consistency of a product, this measuring variable is important in most production stages. In the quality control of incoming liquid raw materials, viscosity is also an important control variable when it comes to differentiating between different qualities of raw materials and eliminating problems when further processing them. Depending on the application, random measurements in the laboratory are sufficient for the production of raw materials but in some cases, it is necessary to measure selectively on site or continuously (inline measurement). In many cases, it is necessary to save and transfer measured values. Therefore, some companies offer viscometers with an RS-232 interface and PC software. PCE Instruments, for example, offer a model which is suitable for the food, chemical and the cosmetics industry and measures viscosities between 3 and 13,000,000 mPas, at an accuracy of ±1 %. How can you measure viscosity? Viscometers are devices which measure the toughness (viscosity) of a liquid and define it as a physical measuring variable to make it comparable. Viscometers vary in the measuring principle and in the type of viscosity measured (dynamic or kinematic viscosity). Roughly, there are the following types of viscometers: Capillary viscometers Rotational viscometers Falling body viscometer Process viscometer Viscosity flow cup. These different types of viscometers are used depending on the application, quantity and measurement range of a sample. For most viscosity measurements in quality control, samples are taken on a random basis and the dynamic viscosity is then measured precisely and quickly by means of a rotational viscometer. 19 The rotational viscometer does this by measuring the mechanical resistance of a liquid which acts against the rotational movement of a spindle (as a rotational solid). The viscosity value arises from the resulting torque as referred to the spindle geometry. A rotational viscometer also measures the temperature of the sample liquid and shows it in an LC display along with some more parameters such as the spindle speed, the chosen spindle or the set measurement range. The rotational viscometers PCE-RVI 1, PCE-RVI 2 and PCE-RVI 3 are small but robust devices which can be used for almost any liquid medium. The stainless steel sensor is immersed into the liquid to be measured and the measurement result is immediately available. The probe tip must be completely covered in liquid. The size of the container and the volume of the liquid do not matter. 20 Lecture 4 Physical Properties: Size and shape, weight, volume, weight volume ratio, length, width, diameter, symmetry, curvature and area Introduction The study of food engineering focuses on the analysis of equipment and systems used to process food on a commercial production scale. Engineering of systems for food materials can be more thorough if there is an understanding of the changes that occur in food as it is processed by the system. Raw food materials are biological in nature and as such have certain unique characteristics which distinguish them from other manufactured products. Because food materials are mainly of biological origin they have (a) Irregular shapes commonly found in naturally occurring raw materials; (b) Properties with a non-normal frequency distribution; (c) Heterogeneous composition; (d) Composition that varies with variety, growing conditions, maturity and other factors; and they are (e) Affected by chemical changes, moisture, respiration, and enzymatic activity. Dealing with materials that have these unique characteristics requires additional consideration, mostly indirectly, in that there are additional sources or causes of variation. People unfamiliar with this natural variability of biological materials may overlook these factors or be frustrated by lack of control over the input parameters. The characteristics of a food material that are independent of the observer, measurable, can be quantified, and define the state of the material (but not how it attained that state) are considered as its physical properties. Physical properties describe the unique, characteristic way a food material responds to physical treatments involving mechanical, thermal, electrical, optical, sonic, and electromagnetic processes. A better understanding of the way food materials respond to physical and chemical 21 treatments allows for optimum design of food equipment and processes to insure food quality and safety. Knowledge of a food’s physical properties is necessary for: Defining and quantifying a description of the food material, Providing basic data for food engineering and unit operations, and Predicting behavior of new food materials. It is common for the physical properties of a food to change during processing operations. Not recognizing these changes can lead to potential processing failures. Physical properties are an important aspect of food quality and relate to food safety. They are the basis for instruments and sensors. A few examples of select physical properties of foods are presented in this unit. Physical Characteristics 1. Shape 2. Size 3. Weight 4. Volume 5. Surface area 6. Density 7. Porosity 8. Color 9. Appearance 10. Drag coefficient 11. Center of gravity Mechanical Properties 1. Hardness 2. Compressive strength 3. Tensile strength 4. Impact resistance 5. Shear resistance 6. Compressibility 7. Sliding coefficient of friction 8. Static coefficient of friction 9. Coefficient of expansion 10. Elasticity 11. Plasticity 12. Bending strength 13. Aerodynamic properties 14. Hydrodynamic properties Size and Shape Physical characteristics of raw, unprocessed, as well as processed food materials include particle size and shape, particle and bulk density, porosity, and surface area. The size and shape of a raw food material can vary widely. The variation in shape of a product may require additional parameters to define its size. The size of spherical particles like peas is 22 easily defined by a single characteristic such as its diameter. The size of non-spherical objects like wheat kernels, bananas, pears, or potatoes may be described by multiple length measurements. The longest diameter (major) and shortest diameter (minor) will adequately describe the size of an ellipsoidal object such as grain kernel or potato. The two dimensions are usually measured perpendicular to one another. The size of pear-shaped objects such as pears, carrots, or beets can be expressed by diameter or circumference of the largest part and an overall length in the direction of the stem. The size of irregular-shaped materials like bananas, or okra requires more extensive considerations. Particle size is used in sieve separation of foreign materials or grading (i.e., grouping into size categories). Particle size is particularly important in grinding operations to determine the condition of the final product and determines the required power to reduce the particle’s size. Small irregular-shaped objects can be sized with sieves by expressing particle size as the smallest sieve opening through which the particle passes. The size of larger objects may be expressed only in terms of its largest diameter or circumference. The size of a banana might be given only in overall length. Precise methods incorporating optical, light, or lasers in machine vision systems exist to define shape and size of irregular-shape objects. These systems are costly; their use is warranted in applications of high value materials more commonly found in highly processed, final products rather than raw, unprocessed materials. Ultimate use will dictate which physical characteristic properly represents size. Size of a carrot may be expressed only in length or in diameter of its large end. Size may be indicated by weight since it is so easily determined by simply placing on a scale. Thus, the physical property size is actually related or correlated to the property weight. In practice, there is often a compromise between ease or cost of measurement and usefulness or value of that property in the market channel. 23 Shape affects the grade given to fresh fruit. To make the highest grade a fruit or vegetable must have the commonly recognized expected shape of that particular fruit/vegetable. Misshapen fruit and vegetables will be down- graded and may sell at a lower price in high volume markets. The shape of an irregular object can be described by terms such as the following: Shape Description Round Approaching spheroid Oblate Flattened at the stem end and apex Oblong Vertical diameter greater than the horizontal Diameter Conic Tapered toward the apex Ovate Egg-shaped and broad at the stem end Oblate Inverted oblate Lopsided Axis connecting stem and apex slanted Elliptical Approaching ellipsoid Truncate Having both ends squared or flattened Unequal One half larger than the other Ribbed In cross section, sides are more or less angular Regular Horizontal section approaches a circle Irregular Horizontal cross section departs materially from a circle Various methods are used to measure or characterize the shape and size characteristics of foods and food products. In several cases, actual measurements are made to estimate the major dimensions and cross sections of the product. Tracings or projections are made to compare the shapes to listed standards. Various formulas and methods have been devised to estimate cross sections and other characteristics of the materials. Volume Volume of a sample can be measured by direct measurement of the volume of the liquid displaced. The difference of the initial volume of liquid in a measuring cylinder and the volume of the liquid with immersed material (coated) is the volume of the material. A non-wetting fluid such as mercury 24 is used for displacement. The use of a specific gravity bottle and toluene has been in practice for many years. A small-necked specific gravity bottle is not suitable for large objects, thus a special design is required. The volume of a specific gravity bottle can be measured using distilled water. Toluene has many advantages when used as reference liquid: 1) Little tendency to soak into the sample, 2) Smooth flow over the surface due to surface tension, 3) Low solvent action on constituents, especially fats and oils, 4) Fairly high boiling point, 5) Stable specific gravity and viscosity when exposed to the atmosphere, and 6) Low specific gravity. Toluene is carcinogenic, thus adequate precautions need to be taken. It is recommended that the experiment be performed inside a fume chamber. Roundness, as defined by Mohsenin (1970), “is a measure of the sharpness of the corners of the solid.” Curray (1951) and Mohsenin (1970) provided the following equations for estimating roundness under different conditions of geometry and application: where: Ap = largest projected area of object in natural rest position Ac = area of smallest circumscribing circle where: r = radius of curvature as defined in figure 2.01 R = radius of maximum inscribed circle N = total number of corners summed in numerator 25 where R in this case is the mean radius of the object and r is the radius of curvature of he sharpest corner. It should be noted that, in the last definition (roundness ratio), the use of the radius of curvature of a single corner determines the roundness or flatness of an object. Roundness values will differ for each of the above methods. Thus, the method for roundness determination should always be noted. Sphericity expresses the characteristic shape of a solid object relative to that of a sphere of the same volume (Mohsenin, 1970). Curray (1951) suggested the following equation for estimating the sphericity of an object: where: Di = diameter of largest inscribed circle Dc = diameter of smallest circumscribed circle Density (ñ ) of a material is the amount of that material occupying a certain space and is expressed in units of mass per unit volume. Materials consisting of particles or grains with interstitial air spaces have different values of particle density and bulk density. Materials without internal air spaces, such as fluids and solids, have equal particle and bulk density. Particle density is the mass divided by the volume of the particle alone. Bulk density is the mass of a group of individual particles divided by the space occupied by the entire mass, including the air space. Density of food materials is useful in mathematical conversion of mass to volume. Porosity is the percentage of air between the particles compared to a unit volume of particles. Porosity allows gases, such as air, and liquids to flow through a mass of particles referred to as a packed bed in drying and 26 distillation operations. Beds with low porosity (low percentage air space) are more resistant to fluid flow and thus are more difficult to dry, heat, or cool. With high porosity, air flows easily through the bed, drying is fast, and the power required by fans and pumps is low. A frequently used method of measuring the volume of non-porous objects such as vegetables and fruits is the use of platform scales or a top loading balance to determine the volume of a displaced liquid such as water. The liquid volume is computed by determining the mass of the displaced water and dividing by the known density of the water. The mass of the displaced water is the scale’s reading with the object submerged minus the mass of the container and water. For objects that float, it is necessary to force the object entirely into the water with a thin stiff rod. If the object is heavier than water, it must be suspended in the water by a rod or other support to insure that the added mass of the object is not measured. The following expression is used to calculate the volume of displaced water: The specific gravity is defined as the ratio of the mass of that product to the mass of an equal volume of water at 4°C, the temperature at which water density is greatest. A reference temperature other than 4°C may be used if that temperature is explicitly specified with the specific gravity value. Specific gravity may be calculated from the following expression Size Size is an important physical attribute of foods used in screening solids to separate foreign materials, grading of fruits and vegetables, and evaluating the quality of food materials. In fluid flow, and heat and mass 27 transfer calculations, it is necessary to know the size of the sample. Size of the particulate foods is also critical. For example, particle size of powdered milk must be large enough to prevent agglomeration, but small enough to allow rapid dissolution during reconstitution. Particle size was found to be inversely proportional to dispersion of powder and water holding capacity of whey protein powders (Resch & Daubert, 2001). It is easy to specify size for regular particles, but for irregular particles the term size must be arbitrarily specified. Particle sizes are expressed in different units depending on the size range involved. Coarse particles are measured in millimeters, fine particles in terms of screen size, and very fine particles in micrometers or nanometers. Ultrafine particles are sometimes described in terms of their surface area per unit mass, usually in square meters per gram (McCabe, Smith & Harriot, 1993). Size can be determined using the projected area method. In this method, three characteristic dimensions are defined: 1. Major diameter, which is the longest dimension of the maximum projected area; 2. Intermediate diameter, which is the minimum diameter of the maximum projected area or the maximum diameter of the minimum projected area; and 3. Minor diameter, which is the shortest dimension of the minimum projected area. 28 Lecture 5 – 9 Defects – classification, genetic – physiological factors: structural, off color, character; entomological defects: holes, scars, lesions, off coloring, pathological defects, mechanical defects, extraneous or foreign materials defects. Measurement of defects: Improving visibility by dilution, white background, color differences, standardization of conditions, reference standards, counts and measures, isolation of defects by floatation, elution, electronic sorting and internal defects Introduction During crop growth and subsequently after harvest many imperfection and blemishes occur due various means. 29 Major Diseases and its remedies Diseases are often the most important constraint to the production of different fruit crops. They directly or indirectly reduce yields by debilitating the plant, and depleting the fruit quality. They range from aesthetic problems that lower the marketability of the harvested product to lethal problems that devastate the overall production. Virtually all fruit crops are affected by one or more serious diseases. Diseases determine how and where a crop is produced, what post- harvest treatments are utilized, in what markets the crops are sold, and whether production is sustainable and profitable. Hence, as a fruit crop student one should know have the knowledge of different diseases occurring on major fruit crops, their symptoms and management strategies; MANGO Anthracnose (Colletotrichum gloeosporioides) Symptoms Produces brown to dark brown leaf spots, blossom blight, wither tip, twigs blight and fruit rot. Small blister like spots develop on the leaves and twigs. Young leaves wither and dry. Affected branches ultimately dry up. Black prominent spots appear on fruits, the pulp of which become hard, crack and start to decay at ripening. Infected fruits drop. Management Spray Psuedomonas fluorescens at three weeks interval commencing from March @ 5 g/ l on flower branches. About 5-7 sprays one to be given on flowers and bunches. After harvest the fruits are treated with hot water (50-55°C) for 15 min. or dip in Benomyl solution (500 ppm) or Thiobendazole (1000 ppm) for 5 min. followed by air-drying. 30 Powdery Mildew (Oidium mangiferae) Symptoms It attacks the leaves, flowers, panicle stalks and fruits. Shedding of infected leaves occurs when the disease is severe. The affected fruits do not grow in size, turn dark and then drop before attaining pea size. Survives as dormant mycelium on affected leaves and cloudy weather along with cold favours it attack. Management Dusting the plants with sulphur powder (250-300 mesh) at the rate of 0.5 kg/ tree. The first application may be soon after flowering, second 15 days later (or) spray with wettable sulphur (0.2%), (or) karathane (0.1%). One prophylactic spray must before panicle emergence in north Indian plains to avoid the future attack. Stem end rot (Diplodia natalensis) Symptoms It appears on fruit as dark epicarp around the base of the pedicel as a circular, black patch. High humidity conditions lead to its rapid spread on the whole fruit within two or three days. The pulp becomes brown and somewhat soft and watery. Inoculum perpetuate on dead twigs and bark of the trees, spread rapidly by rains at full maturity. Management Prune and destroy infected twigs. Spray Carbendazim or Thiophanate Methyl (0.1%) or Chlorathalonil (0.2%) at fortnightly interval during rainy season at two to three times. 31 Red-rust (Cephaleuros virescens) Symptoms Caused by algal attack foliage and young twigs. Rusty spots appear on leaves, initially circular, slightly elevated, coalesce to form irregular spots. The spores mature fall off and leave cream to white velvet texture on the leaf surface. Management Spray Bordeaux mixture (0.6%) or copper oxychloride (0.25%). Scooty Mould (Capnodium mangiferae) Symptoms Black encrustation is formed which affect the photosynthetic activity. The fungi produce mycelium, which is superficial and dark. These growths take place on sugary secretions made by the plant hoppers, jassids, aphids and scale insects. Management Controlling the insects by spraying systemic insecticides like monocrotophos or methyl dematon 0.2% or 2 ml/l BANANA Panama disease (Fusarium oxysporum f.sp. cubense) Yellowing of the lower most leaves starting from margin to midrib of the leaves. Yellowing extends upwards and finally heart leaf alone remains green for some time and which eventually also get affected. The leaves break near the base and hang down around pseudostem. Longitudinal splitting of pseudostem. Discolouration of vascular vessels as red or brown streaks. Commonly spread through use of infected rhizomes. 32 Spread with flood irrigation. Management Avoid growing of susceptible cultivars viz., Rasthali, Monthan, Red banana and Virupakshi. Grow resistant cultivar Poovan, Grand Naine etc. Treatment of sword suckers with Carbofuran (3 g /rhizome) granules followed with dip slurry of 2% Carbendezim followed by air drying in shade for 2-3 h. Adopt tissue culture raised plants. Moko disease (Pseudomonas solanacearum) Symptoms Leaves become yellow and progress upwards. The petiole breaks and leaves hang. When it is cut open, there is discolouration in vascular region with pale yellow to dark brown colour. There is discolouration is in the central portion of the corm and pseudostem, when cut transversely give bacterial ooze. Internal rot of fruits with dark brown discoloration. Management Avoid collection of plant material from sick plantations. Practice soil solrozation during summer. Fallowing and crop rotation to be followed Disinfection of pruning tools. Providing good drainage after heavy flash rains. 33 Tip over or Heart rot (Erwinia carotovora subsp. carotovora) Symptoms The base of the pseudostem and upper portion of the corm are affected and leads to rotting. Young 1-3 month-old plantation susceptible during summer months. Management Plant disease free suckers. Immediate removal of infected plants and burn or burry in pit. Drench rhizosphere soil with methoxy ethyl mercuric chloride (Emisan-6) 0.1% or sodium hypochlorite (10% v/v) or bleaching powder (20 g/litre/tree). Sigatoka or leaf spot (Mycosphaerella musicola & Cercospora musae) Symptoms On leaves small light yellow or brownish green narrow streaks appear. They enlarge in size and become linear, oblong, brown to black spots with dark brown brand and yellow halo. Black specks of fungal fruitification appear on the affected leaves followed by drying and defoliation. Management Removal and destruction of the infected leaves. Spray propiconazole 0.1%+ carbendazim 0.1% or chlorothalonil 0.25% along with wetting agent such as Teepol @1ml/l water. Banana bunchy top (Banana bunchy top virus) Symptoms The infected plants are dwarfed, leaves have dark broken bands of green tissues on the The infected plants are dwarfed, leaves have dark broken bands of green tissues on the veins, leaves and 34 petioles, size is reduced along with marginal chlorosis and inward curling, growing upright and become brittle. Several leaves get crowded at the top with no shooting and bunch production. The disease is transmitted primarily by infected suckers and also by aphid vector Pentalonia nigronervosa Management Select suckers from disease-free areas/ plantations. Control of aphid vector by spraying methyl demoton 1 ml/l or monocrotophos 2 ml/l or phosphomidon 1 ml/ l or injection of monocrotophos 1 ml/plant (1 ml diluted in 4 ml). Infected plants are destroyed using 4 ml of 2,4-D (50 g in 400 ml of water). Banana streak virus Disease severity is very variable, and probably depends on environmental conditions, as well as on host and virus genotypes. The most characteristic foliar symptoms of infection are chlorotic streaks, which become necrotic with time. The leaf lamina may also be narrower, thicker and become torn. Stunting of the plant, constriction of the bunch on emergence (choking), altered phyllotaxis (leaves arranged in a single vertical plane instead of the normal spiral pattern), and detachment and splitting of the outer leaf sheaths of the pseudostem. Management The eradication of infected plants followed by burning. The use of BSV-free planting material. BSV can be carried in in vitro plantlets, hence indexed and certified plants should be procured. 35 Banana bract mosaic virus Symptoms The name is derived from the conspicuous discoloration and necrotic streaks that develop on the bracts of the male bud. Early symptoms take the form of greenish to brownish spindle- shaped streaks irregularly scattered along leaf petioles. As the disease progresses, similar discolorations become very marked on the bracts of the male inflorescence, the fruit bunch, and even on the fruits themselves. A diagnostic symptom of the disease is the spindle- shaped streak formed on the pseudostem after removal of dried leaf sheaths. Management Effective control of the disease is similar to that of other viral diseases. Use of virus-free propagules which are certified. GUAVA Anthracnose (Colletotrichum gloeosporioides) Symptoms Sunken, dark coloured, necrotic lesions appear on fruits. Under humid conditions, the necrotic lesions become covered with pinkish spore masses. As the disease progresses, the small sunken lesions coalesce to form large necrotic patches affecting the pulp. The fruit loose marketability. Management Spray Mancozeb (0.25%). PAPAYA Stem rot / Foot rot (Pythium aphanidermatum) Symptoms Water soaked spots on the stem at the ground level which enlarge and girddle the trunk turns brown or black and rot, 36 followed by terminal leaves turning yellow which later droop off. In later stages entire plant topples over and dies. Favoured by standing water or rain. Management Seed treatment with Thiram or Captan (4 g/kg) Soil drenching with chlorothalonil or copper oxychloride (0.25%) or Bordeaux mixture (1%) or Metalaxyl (0.1%). Powdery mildew (Oidium caricae) Symptoms White mycelial growth appears on the upper leaf surface, flower stalks and fruits. Severe attack leads to yellowing and defoliation. Management Spray wettable sulphur (0.25%) or Dinocap (0.05%) or Chinomethionate (0.1%) or Tridemorph (0.1%). Papaya ring spot (Papaya ring spot virus) Symptoms Vein clearing, puckering and lobbing of leaf tissues. Margin and distal parts of leaves roll downward and inwards, mosaic mottling, dark green blisters, leaf distortion, which result in shoe string formation, stunting of plants. On fruit surface circular concentric rings are produced. If affected at early stage no fruit formation takes place. Spread by vector Aphis gossypii and A. craccivora. Management Raise papaya seedlings under insect-proof net houses. 37 Raising sorghum / maize as barrier crop before planting papaya. Rogue out affected plants immediately. Avoid growing cucurbits around the field. Leaf curl (Papaya leaf curl virus) Symptoms Curling, crinkling and distortion of leaves, reduction of leaf lamina, rolling of leaf margins inward and downward, thickening of veins. Leaves become leathery, brittle and distorted. Plants are stunted. Affected plant does not produce flowers and fruits. Spread by vector whitefly (Bemisia tabaci). Management Uproot and immediate burning of infected plants. Avoid growing tomato, tobacco near papaya plantations. Spraying with systemic insecticides to control the vector. Anthracnose (Colletotrichum gloeosporioides) Symptoms It appears as necrotic spots on leaf and stem. Initially brown superficial discoloration appear on the skin, which are circular and slightly sunken. Then they coalesce in which sparse mycelial growth appear on the margin of a spot. Under humid condition salmon pink spores are released and the fruits get mummified and deformed. Management Spray with carbendazim (0.1%) or chlorothalonil (0.2%) or Mancozeb (0.2%). 38 CITRUS Gummosis (Phytophthora parasitica, P. palmivora, P. citrophthora) Symptoms Initial symptoms are dark staining of bark which progresses into wood formation. Bark at the base of the trunk is destroyed resulting in girdling and finally death. Bark in infected areas dries, shrinks, cracks and shreds lengthwise in vertical strips resulting in profuse exudation of gum. Infection extends to crown roots. Spread rapidly with standing water when applied as flood irrigation in water logged areas and heavy soils. Sporangia spread by splashing rain water, irrigation water and wind. Management Mechanical injuries to crown roots or base of the stem during cultural operations should be avoided. If lesion has girdled less than half the girth, remove the diseased bark with a knife along with half an inch of the healthy bark. Bark of trunk should be coated with Bordeaux paste. Disinfection of tools used in cultural operations. Scab/Verucosis (Elsinoe fawcetti) Symptoms Attacks leaves, twigs and fruits of mandarin. Sour orange, lemon, mandarin, tangelos extremely susceptible; grapefruit, sweet orange and acid lime highly resistant. Severe in rainy seasons. On the leaves the disease starts as small pale orange coloured spots followed by distortion into firm hollow conical growth with lesion at the apex. The crest of this growth becomes covered with scabby corky tissue colour at first but later becomes dark olive with age. 39 Lesions also appear on undersurface of leaf. They penetrate leaf and are later visible on both sides. Infected areas run together and cover large area. Leaves wrinkled, distorted and stunted. On twigs also similar lesions are produced. They form corky outgrowths. On fruits irregular scab spots or caked masses produced. Cream colour in young fruits; dark olive grey on old fruits. Fruits attacked when young become misshapen with prominent warty projections. They drop prematurely. Management Spray carbendazim (0.1%) at fifteen day interval for at least three times. Canker (Xanthomonas campestris pv. citri) Symptoms Acid lime, lemon and grapefruit are most affected. Rare occurance on sweet oranges and mandarins. Affects leaf, twig and fruits. Lesions are typically circular with yellow halo; appear on both sides of leaf, severe in acid lime. When lesions are produced on twigs, they are girdled and die. On fruits, canker lesions reduce appearance quality. Management Streptomycin sulphate (500-1000 ppm); or Phytomycin (2500 ppm) or copper oxychloride (0.2%) at fortnight intervals. Control leaf miner when young flush is produced. Prune badly infected twigs before the onset of monsoon. 40 Tristeza or quick decline (Citrus tristeza virus -CTV) Symptoms Lime is most susceptible both as seedling or buddling on any rootstock. But mandarin and sweet orange seedlings on rough lemon, trifoliate orange, citrange; Rangpur lime rootstocks tolerant; susceptible root stocks are grapefruit and sour orange. In sweet orange or mandarin on susceptible rootstocks, leaves develop deficiency symptoms and abscise. Roots decay, twigs die back. Fruit set diminishes; only skeleton remains. Fine pitting of inner face of bark of sour orange stock. Grapefruit and acid lime are susceptible irrespective of rootstock. Acid lime leaves show large number of vein flecks (elongated translucent area). Tree stunted and dies yield very much reduced. Fruits are small in size. Use of infected bud wood and Toxoptera citricida (aphid) is the important vector. Management For sweet orange and mandarin, avoid susceptible rootstocks. For acid lime, use seedlings pre-immunized with mild strain of tristeza. Exocortis of scaly butt (Viroid) Symptoms Affects mostly the Rangpur lime, trifoliate orange and citrange rootstocks. Vertical cracking and scaling of bark on the entire rootstock along with stunting of plant. 41 Management Spray of systemic insecticide like monocrotophos (o.2%) to control the aphid vector. Use virus-free certified budwood and tolerant rootstocks like rough lemon Periodically cleaning of budding knife with 0.1% disodium phosphate solution. Greening (Liberobactor asiaticum) Symptoms Stunting of leaf, sparse foliation, twig die back, poor crop of predominantly greened, useless fruits. Foliar chlorosis, mottling resembling zinc deficiency often seen. Young leaves appear normal but soon assume on outright position, become leathery and develop prominent veins and dull olive green colour. Green circular dots appear on leaves with twigs becoming upright and produce smaller leaves. Fruits small, lopsided with curved columella. The side exposed to direct sunlight develops full orange colour but the other side remain dull olive green. Fruits with low juice and soluble solids, high in acid unfit for processing. Seeds poorly developed, dark coloured and aborted. Spread through infected budwood and psyllid vector -Diaphorina citri. Management Control of vectors with insecticides. Use pathogen-free bud wood for propagation. 500 ppm tetracycline sulphate sprays at 15 day intervals. GRAPE Downy mildew (Plasmopara viticola) Symptoms Irregular, yellowish, translucent spots on the upper leaf surface and powdery growth on lower surface. Affected leaves become yellow, brown, dry and cause premature 42 defoliation. Dwarfing of tender shoots, with brown, sunken lesions on the stem. White growth of fungus on berries, which subsequently becomes leathery and shrivels. Infection of berries results in soft rot formation with no cracking. Optimum conditions for occurrence as 20-22°C temp and relative humidity of 80-100 per cent. Management Spray Bordeaux mixture (1%) or Ridomil (Metalaxyl + Mancozeb) 0.4%. Powdery mildew (Uncinula necator) Symptoms Formation powder like powdery like growth on upper surface of the leaves followed by malformation and discolouration. Discolouration of stem to dark brown. Floral infection cause shedding of flowers and poor fruit set. Early berry infection results in shedding of affected berries. At later stages appear as powdery growth and cracking of skin. Occurrence is almost certain during sultry warm conditions with dull cloudy weather. Management Spray wettable sulphur (0.25%) or Chinomethionate (0.1%) or Dinocap (0.05%). Bird’s Eye Spot/Anthracnose (Gloeosporium ampelophagum Elsinoe amphelina) Symptoms It appears first as dark red spots on the berry, which then become circular, sunken, ashy-gray and in later stages get surrounded by a dark margin. 43 The fungus also attacks shoots, tendrils, petioles, leaf veins and the fruit stems. The spots gradually unite and girdle the stem, causing death of the tips. Commonly appear on warm wet weather in low lying and badly drained soils. Management Clipping of infected twigs. Spray of copper oxychloride (0.2%) or Mancozeb (0.25%) Fruit Spot (Cercospora sp.) Symptoms The affected fruits show small irregular black spots, which later on coalesce, into big spots. Management The diseased panicles should be collected and destroyed. Two to three spray at 15 days interval with Mancozeb (0.25%). Pomegranate Fruit Blight (Colletotrichum gloesporioides; Pseudocercospora punicae & Cercospora punicae) Symptoms The disease is characterized by appearance of small, irregular and water-soaked spots on leaves and developing fruitlets. Affected leaves fall off. Management Spraying Mancozeb (0.25%) at 15 days interval gives good control of the disease. 44 Fruit spot (Alternaria alternata) Symptoms Small reddish brown circular spots appear on the fruits. As the disease advances these spots, coalesce to form larger patches and the fruits start rotting. The arils get affected which become pale and become unfit for consumption. Management The affected fruits should be collected and destroyed. Spraying Mancozeb (0.25%) effectively control the disease. BER Powdery mildew (Oidium erysiphoides f.sp. zizyphi) Symptoms The developing young leaves show a white powdery mass causing them to shrink and defoliate. On fruitlets small, white powdery growth appears which later enlarge and coalesce and finally turn brown to dark brown. Affected young fruits drop off prematurely or become corky, cracked, mis-shapen and underdeveloped. Matured fruits turn rusty and are rendered unmarketable. Management Spray dinocap (0.05%) or wettable sulphur (0.25%) during first and third weeks of November or when the fruit attains pea size. Alternaria leaf spot (Alternaria chartarum) Symptoms Formation of small irregular brown spot on the upper surface of the leaves and dark brown to black spots on lower surface. The spots coalesce to form big patches. The diseased leaves later drop. 45 Management The disease can be controlled effectively by spraying mancozeb (0.25%). Rust (Phakopsora zizyphi-vulgaris) Symptoms On the lower surface of the leaves small, irregular, reddish- brown pustules appear which may cover the entire area The infected leaves dry and defoliate. Management Spray Mancozeb (0.2%) or Zineb (0.2%) or wettable sulphur (0.2%). Soft rot (Phomopsis natsume) Symptoms Appearance of light russet vinaceous coloured, irregular spots on the fruits, which increase in size and make the whole fruit into pulpy, brown to black in colour with soft and loose outer skin. Management Spray carbendazim (0.05%). APPLE Scab (Venturia inaequalis) Symptoms On lower side of the leaf lesions appear as olivaceous spots which turn dark brown to black and become velvety. On young foliage, the spots have a radiating appearance with a feathery edge. On older leaves the lesions are more definite in outline forming convex surface with corresponding concave area on the opposite side. In severe infection, the leaf blade curved, dwarfed and distorted. Fruits show small, rough, black circular lesions. The centre of the spots becomes corky with yellowish halo around the 46 lesions. Management Follow clean cultivation practices. Collection and destruction of fallen leaves. Spray Tridemorph (0.1%) before flowering; Mancozeb (0.25%) at bearing stage; 5% urea prior to leaf fall in autumn and 2% before bud break to hasten the decomposition of leaves. The fungicidal spray is as given below; S.N Tree stage Fungicide per 100 litre water o. 1 Silver tip to given tip Captafol 200 g (or) Captan 300 g or Mancozeb 400 g 2 Pink bud or 15 days Captan 250 g or Mancozeb 300 g after 1st spray 3 Petal fall Carbendazim 50 g 4 10 days later Captan 200 g or Mancozeb 300g 5 14 days after fruit set Captofol 150 g Powdery mildew (Podosphaera leucotricha) Symptoms Small patches of white powdery growth appear on upper side of leaves, which may spread to both the sides. Twigs are also infected. Affected leaves fall off in severe infection. Fruit buds are also affected and deformed or remain small. Management Spray Dinocap (0.05%) or Chinomethionate (0.1%). 47 Fire blight (Erwinia amylovora) Symptoms The initial symptom usually occurs on leaves, which become water soaked, then shrivel turn brownish to black in colour and fall or remain hanging on the tree. The symptom spread to twigs. Terminal twigs wilt from tip to downward and also spread to branches. Fruits become water soaked, turn brown, shrivel and finally becomes black with oozing of water. Management Removal and destruction of affected plant parts. Removal of blighted twigs Spray 500 ppm streptomycin sulphate. Soft rot (Penicillium expansum) Symptoms Young spots start from stem end of fruit as light brown watery rot, which increases further. Skin becomes wrinkled and the fruit emit a peculiar musty odour. Under humid conditions a bluish-green sporulating growth appears. Infection take place from wounds on the surface caused by insects and during handing in storage and transport. Management Careful handling of fruits after harvest. Dipping the fruits aureofunginsol @ 500 ppm for 20 min. Bitter rot (Glomerella cingulata) Symptoms Faint, light brown discolouration beneath the skin develops. The discoloration expands in a cone shape. The circular, rough lesions become depressed. The lesions increased and cover the entire 48 surface. Management Spray Mancozeb (0.25%) in field just before maturity. PEAR Fire Blight (Erwinia amylovora) Symptoms Cankers are formed on twigs and branches in the previous season. In the spring the bacteria begins to multiply at the same time growth starts. As the bacterium increases, ooze is formed at the margin of the canker. Insects are attracted to the ooze and it is carried to the open blossoms. Blossoms are blighted within 7-10 days after infection. After blossom infection, bacteria spread into the fruit peduncle and finally into the twig. Ooze is continually being produced which can add to secondary infection. Management Adopt tolerant varieties like Kieffer, Orient, Garber or Douglas. Maintain balanced fertilizer level. Do not use excess N levels. Prune during dormant months. Avoid summer pruning. Prune 8 to 12 inches below visible sign of disease. Apply bactericides at five day intervals between early and late blooms. Leaf Blight and Fruit Spot (Entomosporium maculatum) Symptoms Spots appear as small purple marks which with age develop into purple margins with brown centres. Fruit spots are one-fourth inch in diameter, black, and slightly depressed. They coalesce to cover a large portion of the 49 fruit surface. Secondary infection can occur during the spring and summer when the temperature is near 750F. and surface moisture is on the leaves. Management Fungicides should be applied three to four times at full leaf development and continued further. PEACH Peach leaf curl (Taphrina deformans) Symptoms It attacks the leaves, causing curling and blister formation. The leaves start turning yellowish or reddish and fall off prematurely. The infected portion develops a pink or reddish bronze colour. Growth of the tree is affected with a reduction in yield. Management Pruning of and burning of infected shoots. Spray the plants with Bordeaux mixture 1% or 0.1% carbendazim. Spray Mancozeb 0.25% at 20 days before harvesting. Powdery mildew (Sphaerotheca pannosa) Symptoms Small superficial white powdery mass appear on leaves. And spread on entire plant parts. Fruits turn pinkish and finally dark brown in colour. Management Spraying wettable sulphur (0.3%) or carbendazim (0.1%). 50 Lecture 10 Flavor: Definition and Its role in Food Quality Definition of Flavor 1. “Flavor is the sensation produced by a material taken in the mouth, perceived principally by the senses of taste and smell, and also by the general pain, tactile, and temperature receptors in the mouth. Flavor also denotes the sum of the characteristics of the material which produces that sensation.” 2. “ Flavor is one of the three main sensory properties which are decisive in the selection, acceptance, and ingestion of a food. 3. “A mingled but unitary experience which includes sensations of taste, smell, and pressure, and often cutaneous sensations such as warmth, color, or mild pain”. How do we recognize flavor: The five basic taste sensations are mediated by specialized epithelial cells, the taste receptor cells, that are located within the taste buds of the papillae on the surface of the tongue. These elongated taste receptors cells are deeply embedded in the surrounding epithelium and just contact the outside world in the gustatory porus of the taste buds. Thus, the porus is the place where tastants interact with the taste receptor molecules that are located at the apical site of the taste receptor cells. 51 In contrast to obsolete textbook knowledge, humans can perceive all taste qualities on any area of the tongue that contains papillae. Only the perceived intensities of the taste qualities differ depending on the tongue region and papilla type. Sweet taste saccharin for instance is highest at the tip of the tongue whereas the bitter taste of quinine is best perceived at the back of the tongue. Interestingly, the anterior part of the tongue is innervated by the VII cranial nerve whereas the posterior part of the tongue is innervated by the IX cranial nerve. These innervations are also reflected by the distribution of the taste papilla types. The fungiform papillae are located at the anterior part of the tongue and thus are innervated by VII cranial nerve. In contrast, the foliate and vallate papillae that is located at the back of the tongue that is innervated by the IX cranial nerve. This nerve also innervates isolated taste buds in the palate and epiglottis. 52 Fig. Human Olfactory system Flavor is typically described by aroma (odor) and taste. Aroma compounds are volatile—they are perceived primarily with the nose, while taste receptors exist in the mouth and are impacted when the food is chewed. While color and appearance may be the initial quality attributes that attract us to a food product, the flavor may have the largest impact on acceptability and desire to consume it again. The five basic taste qualities are exclusively mediated by specialized epithelial receptor cells that are located in taste buds. Most taste buds lie within taste papillae on the human tongue, but some of them are also distributed on the palate and epiglottis. The taste buds in the oral cavity are innervated by gustatory fibres of the VII, IX and X cranial nerve. Thus, the perception of Taste has been divided into five primary tastes: Sweet: Sweet taste is predominantly elicited by carbohydrates and indicates energy-rich food sources. Sour: Strong sour taste is also repulsive and prevents the ingestion of unripe fruits and spoiled food, which often contain acids. 53 Salty: Salt taste is elicited by sodium chloride and other salts and contributes to electrolyte homeostasis, salt taste is attractive at low concentrations and repulsive at high concentrations. Bitter: Bitter taste is evoked by many compounds that belong to multiple chemical classes. The common denominator of most bitter compounds is their pharmacological activity or toxicity. Therefore, due to its task to avoid harmful compounds strong bitter taste is aversive. Nevertheless humans can accept moderate bitter taste or even find it attractive. A reasonable explanation for this observation is that bitter and sour tastes should not deter us from advantageous food containing low concentrations of harmful compounds. Umami(a taste associated with salts of amino acids and nucleotides): The broth-like umami taste, that is mainly triggered by glutamate and enhanced by ribonucleotides such as inositol monophosphate (IMP), identifies protein-rich food. Odors are much more diverse and classified as: Spicy: Flowery: Fruity: Resinous or balsamic: Burnt: Foul: Flavors in food: Desirable flavor: orange juice, potato chip, roast beef Undesirable flavors: oxidized, stale, rancid, warmed-over 54 Classification of flavors: Flavor Subdivision Representative sample class Fruit Citrus type flavor (terpeny) Grape fruit , orange flavour Berry type flavor (non- terpeny) Apple, banana Vegetable Lettuce, celery flavour Aromatic Cinnamon, peppermint Spice flavor Lachrymogenic Onion, garlic hot Pepper, ginger Unfermented flavor Juices, milk Beverage Fermented flavor Wine, beer, tea flavor Compounded flavor Soft drinks Mammal flavor Lean beef Meat flavor Sea food flavor Fish, clams Olive oil, coconut fat, pork Fat flavor fat, butter fat Broth Beef bouillon Cooked Vegetable Legume, potatoes flavor Fruit marmalade Ham smoky flavor Processed Processed meat products Broiled, fried flavor flavor Coffee, snack foods, Roasted , toasted, baked flavor processed cereals Stench cheese flavor 55 Other Factors That Affect Flavor Perception Temperature Consistency Presence of contrasting tastes Presence of fats Color Sources of flavors Natural flavors Herbs and spices (Reaction after cutting) Fruit (Biosynthesis during ripening) Process flavors Browning Lipid oxidation Fermentations Artificial flavors Character impact compounds Food Flavor Profiles: Top notes or high notes: The sharpest first flavors or aromas Middle notes: The second wave of flavor, more subtle Low notes: The most dominant lingering flavor Aftertaste or finish: The final flavor Roundness: The unity of a dish’s various flavors Depth of flavor: A broad range of flavors Mechanism of flavor development: Enzymatic reaction: Volatile flavors developed in most food plants mainly at the ripening stage - the result of plant metabolism through enzymatic reaction. 56 Non-enzymatic reaction: Raw meat must be heated before it develops any organoleptically acceptable flavor, flavor development in baked cereals, nuts, coffee etc. Some terms in flavor: 1) Seasoning: An item added to enhance the natural flavors of a food without changing its taste, eg. Salt is the most common seasoning. 2) Flavoring: An item that adds a new taste to food and alters its natural flavors, eg. Herbs (Any of a large group of aromatic plants whose leaves, stems or flowers are used as a flavoring, used either dry or fresh), spices (Any of a large group of aromatic plants whose bark, roots, seeds, buds or berries are used as flavoring. Usually used in dry form, whole or ground), vinegars and condiments (Any item added to a dish for flavor, including herbs, spices and vinegars. Also refers to cooked or prepared flavorings such as prepared mustards, relishes, bottled sauces and pickles). 57 Lecture 11 Taste: Classification, taste qualities, relative intensity, reaction time, effect of disease, temperature and taste medium on taste, basic tastes, interaction of tastes Classification of Tastes Sweet taste Substances, which elicit the sweet sensation, are primarily organic compounds. Alcohol (glycerol), salts (lead acetate), sugars, complex aromatics (saccharine), organometallic compounds (cyclamates) aldehyde (cinnamic aldehyde) etc. taste sweet. Not all sugars are equally sweet; Fructose gives the most intensely sweet taste, followed by sucrose, galactose and lactose. Sweetness appears to be associated with hydroxyl (-OH) radicals on the sugar molecules. Lower sweet taste of some sugars attributed to the crumpling of the molecule, putting -OH groups so close that they get attracted to each other by H bonds, therefore not free to elicit sweet tastes. Sweetening agents used in food are toxic on long use and can be considered health hazardous. Saccharine - 300 times, sucramine - 700 times, cyclamates - 30 times sweeter than sugar. Sweetness is particularly important in soft drinks, fruits and fruit juices, in honey and in many baked foods. Sour taste Sourness or the tart taste of acids, is also important in fruits and fruit juices, and in fermented products. Lack of a certain amount of acidity results in flat & unpalatable taste in many foods. It is doubtful, if the acid taste has much protective value for man in food selection; even the most acid foods are not strong enough in acidity to be injurious to health. The sour taste is associated with hydrogen ions supplied by acids like vinegar, those found in fruits, in acid salts. The intensity of sensation depends more on H ion concentration than the total acidity, but sourness and H-ion concentration do not run exactly parallel. 58 At equimolar concentration acetic acid tastes more acid than hydrochloric, although pH of the latter is lower, may be due to interactions of saliva and the acid compound. Organic acids compared with inorganic acids at same pH will have a greater taste effect. Also, weak acids, which taste more acid than they should based on H ion concentration, may influence taste mechanisms other than the simple sour taste. Buffering action (of saliva) appears to play a role in determining the sourness of various acids. Salty taste Saltiness is much appreciated taste. It is due to ions of salts. Table salt is the most common salty taste in foods. Sodium chloride is said to be the only salty with pure salt sensation, even so, in dilute concentration it is frequently identified as sweet. The taste of salt is dependent on the nature of both cation (Na+) and anion (CI-). As the molecular weight of either cation/anion/both increases the salts are likely to taste bitter. KCI and CaCl2 have a salty taste, but different from NaCI. Similar is the case is with Sodium Fluoride and Iodide. The 'differences' may depend partially on other sensations - bitterness, feel, sweetness etc. The lead and beryllium salts of acetic acid have a sweet taste but are extremely toxic. Bitter taste The bitter taste is appreciated in beer, wines, and in some foods. It has little protective value to man in his selection of food, which is safe to eat. Bitter taste is widely distributed & can be attributed by variety of inorganic & organic compounds. Alkaloids (basic N containing organic compounds) -caffeine, theobromine, nicotine, and quinine are bitter. Glycosides of Phenolic compounds 'Naringin' -in grape fruit, Inorganic Salts - CsCI, CsBr, KI, and MgSO4 -bitter in taste Amino acids -phenylalanine, leucine, valine, and 59 histidine -bitter. Bitter peptides -partial enzyme hydrolysis of proteins -are formed during cheese ripening. Although, bitter taste by itself is usually considered as unpleasant, it is a common component of taste of many foods usually in combination with sweet and sour. Quinine is often used as a standard for bitter taste. Other aspects of taste In addition to the individual tastes, there is important interrelationship between them. The sugar to acid ratio - important role in fruits. Alkaline taste - attributed to OH ions, an irritating effect on general nerves endings in the mouth. Astringency - not taste but aspect of flavor, Borax is known for its astringency. Coolness - Characteristic of menthol, a part of mint flavor complex. Hotness - associated with spices, also known as pungency, non- volatile amides are responsible for heat effects. Metallic taste - no receptor sites, but is real. It appears to be modality of common chemical sense like irritation & pain. It is generated by salts of metals like Hg, Ag, Fe, Cu, and tin. The lead salt of saccharin- intense sweet - gives metallic after taste. It is frequently associated with oxidized products. 'Oct-1-en-3-one' -responsible for metallic flavor in dairy products. A drug 'gymneric acid' - renders taste bud insensitive to sweet & bitter, but no to salt and sour. A berry grown in Africa, known as 'miracle fruit' when eaten sour food (lemon) - tastes sweet. The active substance coats the taste buds. Salts reduces sourness of acids, certain acids increases saltiness. Salt on one side of tongue, cause distilled water on other side to taste sweet or insipid (tasteless). 60 Salt on one side, sub threshold concentration of sucrose to the other - easily recognized as sweet/very sweet. A sugar solution on one side - enhances saltiness. A salt also sensitizes to salt. Taste Threshold Thousands of threshold are reported in the literature. The data are not always comparable, because of differences in technique, impurities/type of Chemical used, inadequate number of tests, insufficient statistical analysis of their validity, plus undetermined factors such as order presentation, temp., time, experience, physical condition, age, sex and area stimulated. Taste -Interaction Since foods contain mixture of substances, which elicit all four-taste sensations, the subject of taste interaction is of great interest to food technologist. In most of the cases, there is probably desensitizing effects i.e. an increase in threshold. Salt reduces sourness of acids, sprinkling of salt on fruits increases the apparent sweetness of sucrose. A pinch of sugar may improve over salted soup. Sugar reduces bitterness of caffeine, sourness of acid. At higher concentration, the effect of second taste is generally to reduce the sensitivity of frost. Not all the people react the same. Taste - blindness Individuals may exhibit varied responses to taste stimuli of certain chemicals e.g. 1/4th of population is said to be 'taste-blind' to PTC (Phenyl- theo-carbamide), which contain -N- C" group. Being blind to a certain taste should not cause undue concern for the novice evaluator, since other factors play important role in judging dairy products. Most expert judges possess no special taste acuity. Factors Affecting Taste Threshold / Sensations (1) Diseases: Disease and Accident may result into loss of, decreased or altered, temporary/permanent, and taste sensations. Irritating tongue of patient with X-rays or cobalt source reduced taste sensitivity of all tastes 61 except sour. In case diabetes, sweet taste -in the absence of stimuli, bitter in the case of jaundice. Patients with adrenal insufficiency -increase sensitivity to all tastes. (2) Effect of sleep and hunger: Lack of sleep, up to 72 hours, did not affect the thresholds to salt & sweet, but raised the sour threshold significantly. Sensitivity to 4 basic tastes - maximum at II :30 a.m., significant decrease for about 1 hr. after meal, followed by an increase in 3-4 hr. Little influence on preference. Fasting from breakfast until 4:30 p.m - no effect. (3) Age: New born to 40 days -no/little taste differentiation. Higher sweet threshold - 52 to 85 yr. group than 15 to 19 yr. A decrease in taste sensitivity after 60-yr. Age, may be because of degenerative changes in taste receptors, particularly for sweet & sour, no change for salt & bitter. Differential sensitivity - less in children 7-11 yr. (4) Smoking: Smoking affect taste preferences via taste mechanism. No effect on threshold for sweet, sour, slat but for bitter was higher in smokers. Nicotine & other alkaloids plus smoke -fatigue the perception mechanism. No significant effects on receptors have also been reported. (5) Other factors: Chronic alcoholism, excessive smoking, allergy, hay fever, badly infected germs, marked tooth decay did not affect the sensitivity to sucrose. Water unless purified is a factor. Practice is another factor- increased familiarity. Related to threshold is the ability to distinguish intermediate concentrations. At lower concentration the solution chosen, was greater than half concentration, Quinine Sulphate was an exception. (6) Effect of temperature on taste: It is difficult to separate taste, temp. & pain effects. Moreover, temp. of receptor may be more important than temperature. of sapid substance. Fluids of extreme temperature. (especially extreme cold) cause temporary 62 insensitivity. Optimum sensitivity to taste producing substance occurs at 30-40°C. The sapid substance should be neither so cold nor so warm as to distract attention from the taste reaction. For judging milk-a temp of about 60°F (15.5°C) is more preferred which is not cold enough to have distracting influence and not warm enough to volatative completely all the odors, that may be present. Further, volatilization may occur as the temperature. of the milk is brought upto the body temperature (98.6°F). (7) Effect of taste medium: The intensity of the taste medium is greater in aqueous media than in paraffin oil/mineral oil. This is supposed to be due to: combined effects of viscosity and solubility of the compounds in oil and of the oil in saliva. (8) Chemical configuration/structure and taste: The relationship between the chemical structure of a compound and a taste is more easily established than between structure and smell. All acids are sour, NaCI and other salts are salty, but as the constituent atoms get bigger, bitter taste develops. Taste responses are related to chemical specificity, therefore, ortho, meta or para positions of different groups in compound alter these tastes. Minor changes in the chemical structure may change the taste of a compound from sweet to bitter or tasteless. Stereo structure, optical relation (levo or dextro) etc. may also alter tastes, because these behave differently on taste receptors. Taste Qualities There are four basic taste -sweet, salt, sour and bitter. There is a regional distribution of the four types of the receptors to create area of sensitivity on the tongue as shown in Fig. below. 63 Fig. Regional distribution of the four basic tastes on tongue Some sensory authorities believe that there may be several other taste reactions, namely alkaline, metallic, watery and/or meaty. Feelings in the mouth such as common chemical/pain sense, warmth, coolness, astringency, smoothness, anesthesia and other feelings are not taste reactions, but are sensations of touch/pressure. The true basic tastes may be sensed with the nose obstructed. Relative Intensity: It is the comparison of the taste intensity of the different tastes, by constructing psychological scales of taste intensity. It is measured in the unit called "Gust"- the concentration of different tastes (relative strength) that matched I % sucrose was called "a Gust". Relative intensity of Sucrose: NaCI: Citric acid: Quinine hydrochloride is 1: 14: 220: 2300. Reaction Time: The reaction time to taste i.e. "interval between initial stimulation of the receptor and the report of reaction". It can also be defined as "the interval of time between the application of the solution being tasted on the tongue and the appearance of the sensation. In electro-physiological studies, the reaction time was estimated at 0.02 -0.06 seconds whereas oral reaction time was estimated to be: 0.307 sec. for salt, 0.536 sec. for sour, 0.446 sec. for sweet and 1.082 sec. for bitter. Thus, reaction time is not identical for all basic tastes. In comparison to other senses, tastes have the slowest reaction, hence, maximum reaction 64 time. Taste Sensitivity Taste sensitivity varies with individuals and with temperature. Salt & quinine Sulphate - threshold increases with temperature, that of HCI remains constant from 62.6 - 107.6°F, for dulcin decreases from 17° - 35°C and rises slightly at 42°C. The concentration of a substance (in saliva) required to triggered the taste, is higher than the concentration (in air) required for odor. Taste - Interaction Since foods contain mixture of substances, which elicit all four-taste sensations, the subject of taste interaction is of great interest to food technologist. In most of the cases, there is probably desensitizing effects i.e. an increase in threshold. Salt reduces sourness of acids, sprinkling of salt on fruits increases the apparent sweetness of sucrose. A pinch of sugar may improve over salted soup. Sugar reduces bitterness of caffeine, sourness of acid. At higher concentration, th

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