Food Technology: Food Preservation and Storage - PDF

Food technology Yanal ALbawarshi 1  What is Food Science and food technology? Food Science is the discipline in which biology, physical sciences, and engineering are used to study the nature of foods, the causes of their deterioration, and the principles underlying food processing....

Food technology Yanal ALbawarshi 1  What is Food Science and food technology? Food Science is the discipline in which biology, physical sciences, and engineering are used to study the nature of foods, the causes of their deterioration, and the principles underlying food processing. Food Technology is the application of food science to the selection, preservation, processing, packaging, distribution, and use of safe, nutritious, and wholesome food. Yanal ALbawarshi 2  QUALITY people choose foods based on a number of factors which can in sum be thought of as "quality.“ Quality has been defined as degree of excellence and includes such things as taste, appearance, and nutritional content. Quality and price need not go together Yanal ALbawarshi 3  "value" is thought of as a composite of cost and quality. More expensive foods can be a good value if their quality is very high. The nutrient value of the different grades of canned fruits and vegetables is similar for all practical purposes, yet the price can vary as much as threefold depending on other attributes of quality. This is why processors will go to extremes to control quality. Yanal ALbawarshi 4  When we select foods and when we eat, we use all of our physical senses, including sight, touch, smell, taste, and even hearing. The snap of a potato chip, the crackle of a breakfast cereal, and crunch of celery are textural characteristics, but we also hear them. Food quality detectable by our senses can be divided into three main categories: 1- appearance factors, 2- textural factors, and 3- flavor factors. Yanal ALbawarshi 5  ADDITIONAL QUALITY FACTORS Three very important quality factors that may not always be apparent by sensory observation are nutritional quality, sanitary quality, and keeping quality. 1- Nutritional quality frequently can be assessed by chemical or instrumental analyses for specific nutrients. 2- Sanitary quality usually is measured by counts of bacteria, yeast, mold, and insect fragments, as well as by sediment levels. Yanal ALbawarshi 6 3- Keeping quality or storage stability is measured under storage and handling conditions that are set up to simulate or somewhat exceed the conditions the product is expected to encounter in normal distribution and use. Yanal ALbawarshi 7  Food Preservation and Storage Introduction Food is the basic necessity of life and is invaluable for healthy existence of human beings. Most of our food consists of agricultural and livestock products, which are usually seasonal and spoil quickly. Foods gradually undergo deterioration or spoilage from the time they are harvested, caught, slaughtered or manufactured unless it is preserved. Deterioration of food in some cases is accompanied by production of toxic substances while in other cases it results in losses of nutritional value. Yanal ALbawarshi 8  it is essential to possess knowledge of processing and preservation methods that produce/ preserve best possible foods over a long period of time with minimum loss of nutritive value. Yanal ALbawarshi 9  Definition of Food Storage Food storage is the process in which both cooked and raw materials are stored in appropriate conditions for future use without any entry or multiplication of microorganisms. Types of Storage Different foods need different types of storage. There are basically two types of storage, 1-dry storage and 2- low temperature. These are further classified on the basis of storage temperature required for different foods. Yanal ALbawarshi 10 1- Dry storage is meant for longer holding of non- and semi-perishable foods, the latter being stored for a shorter time. It is the space designed for the storage of foods usually at room temperatures ranging between 20-25°C with the relative humidity maintained at 60-65 percent. 2- Low temperature storage is further divided into three types based on temperature requirement. – Refrigerated storage is a storage space maintained at temperature between 3 to 10°C. It is used to store perishable foods for short term say 3-5 days. Milk, meat, fish, poultry and eggs are generally stored under refrigerated storage. – Cold storage is one in which temperature is maintained between 0 and 3°C. Such storage spaces are also called as chill rooms. These can hold perishables over a week and in the case of fruits and vegetables, even up to a month depending upon variety and stage of maturity. Fruits and vegetables are usually stored in this type of storage. – Freezer storage is apt for long term storage of perishable foods and the temperature ranges from -20°C to 0°C. Pretreatments like blanching, quick cooling to freezing temperature and packing in air tight containers are necessary for successful freezing.. Yanal ALbawarshi 11  Essential features of food Storage Areas The proper storage of preprocessed as well as post-processed foods is a key factor in the shelf-life of the food. The essential features of any food storage areas are as follows: It should be fit for purpose (dry store, chill, frozen etc.) i.e. it must provide proper temperatures and humidity for prolonging shelf life of foods The separate area could be designated for different types of food. For example raw and cooked should be stored separately. It should be able to provide protection from contamination/ infestation It should be weatherproof It should be able to keep out direct sunlight/ heat It should have suitable space and structural arrangement for providing sufficient light and ventilation. It should be easily cleanable. It should provide easy access to materials It should be accessible for transport of food Yanal ALbawarshi 12  Table 1: Storage life of some foods Food product Storage life (days) at 21oC Raw beef and mutton 1-2 Raw fish 1-2 Raw poultry 1-2 Dried salted or smoked 360 or more meat and fish Fresh fruits 1-7 Dried fruits 360 or more Leafy vegetables 1-2 Root crops 1-20 Dried seeds 360 or more Yanal ALbawarshi 13  Definition of Food Preservation Food preservation can be defined as the science that deals with the process of prevention of decay or spoilage of food thus, allowing it to be stored in a fit condition for future use. Microorganisms are responsible for causing or accelerating spoilage but also in some cases, use of benign bacteria and yeasts add specific qualities and preserve food e.g. cheese, wine. Spoilage results in loss of quality, edibility or nutritive value of food. Preservation usually involves the process of treating and handling food to stop or greatly slow down spoilage as well as maintaining or creating nutritional value, texture and flavor of food. Yanal ALbawarshi 14  Importance of Food Preservation Food preservation activities are as old as human race. It had an important role in the spread of civilization. Delay in the consumption or processing of fresh foods alters its freshness, color, texture, palatability and nutritive value, organoleptic desirability, aesthetic appeal and safety. Yanal ALbawarshi 15  Need for Food Preservation Eat what you can and CAN what you can’t. Preservation of fresh produce is needed for following reasons: - For increasing availability of certain foods which have a short growing season such as fruits and vegetables, for use throughout the year. - For utilization of surplus crops and prevent wastage. - For saving money by preserving foods when they are most plentiful, cheaper and are of good quality. - For producing food which is easier to store, distribute and transport and that can be made available in all places at all times. - For meeting the needs of the people for food in secluded and difficult areas. - For ensuring supply of protective foods in homes, hotels and other such places. Yanal ALbawarshi 16  It also includes process preservation mainly prevents the growth of bacteria, fungi, and other microorganisms. the oxidation of fats which causes "Rancidification"rancidity and to inhibit natural ageing and discolouration due to enzymatic browning. In some cases, preservation also includes sealing of food materials after heat treatment to avoid recontamination with microbes, such as canning. Methods like drying, allow food to be stored without any special control for long periods. A number of preservation methods include drying, spray drying, freeze drying, freezing, vacuum-packing, canning, food irradiation, and adding preservatives or inert "Gas“ gases such as carbon dioxide. Other methods that not only help to preserve food, but also add flavor, include pickling, salting, smoking, preserving in sugar syrup and curing. Yanal ALbawarshi 17  Food Spoilage Introduction Healthy tissues inside foods and foods in their natural form resist infection and they do not harbour microorganisms. It is a gradual process occurring because of poor sanitation, enzymatic or chemical reactions, improper temperature controls, microbial growth or physical abuse starting from the time food is harvested, slaughtered or manufactured till it is consumed. Physical changes, such as bruising or puncturing of tissue and water loss and chemical changes, such as those caused by enzymes; or the effects of microbial growth can make food unappealing. Spoilage of food refers to the undesirable alterations in foods or the food undergoes some physiological, chemical and biological changes, which reduces it inedible or hazardous to eat Yanal ALbawarshi 18  Major reasons for a food being rejected as spoiled 1. Organoleptic changes brought about by the growth of microorganisms. 2. Chemical changes in a food e.g. oxidative rancidity of fats, browning of fruits and vegetables. 3. Physical changes e.g. burning, drying, pressure, freezer burn etc. 4. Staling due to changes in H2O content giving a change in texture e.g. stale baked products. 5. Over Ripening overripe fruits are considered spoiled. 6. Contamination with chemical agents e.g. sanitizers that give rise to unacceptable odors and flavors. 7. Microorganisms and Insects. Yanal ALbawarshi 19  Factors Affecting food Spoilage The types of spoilage of a particular food item depend to a great extent on the following: The composition of food: The composition of food influences its susceptibility to spoilage. For example- presence of proteins and carbohydrates especially sugars are preferred by microorganisms for energy source. Very few utilize fat for energy production. Structure of the food item: Whole healthy tissues of food from inside are sterile or low in microbial content. Skin, rind or shell on food works as its protective covering from spoilage microorganisms. Types of microorganisms involved: The types of microorganisms present in food depend on its composition of food. Conditions of storage of the food: Conditions of storage of food affect the growth of microorganisms. Even if the proper storage of food is done, the food loses its freshness and nutritive value if it is stored for too long. Yanal ALbawarshi 20  Classification of Foods by ease of Spoilage (Perishability) Foods are classified into three groups based on ease of their spoilage. 1- Relatively stable or non-perishable foods: Foods that do not spoil unless handled carefully. E.g. grains, flour, sugar, pulses etc. 2- Protectable or semi-perishable foods: Foods those remain unspoiled for a fairly long period if properly handled and stored. E.g. potatoes, apples, onions etc. 3- Perishable foods: Foods that spoil readily unless special preservative methods are used. E.g. milk, eggs, meat, fish, poultry, most fruits and vegetables. Perishable foods can be kept at room temperature for only few hours or 1 or 2 days before spoiling. For example- milk and milk products, meat, fish, poultry, fruits, leafy vegetables and cooked food. Yanal ALbawarshi 21 1- Non- perishable foods will keep for months or years without spoiling unless handled and stored carelessly. Examples of such foods are all preserved food products (canned, dried, pickled etc.), whole cereal, pulse and millet grains, oil seeds, nuts, fats and oils, honey, sugar, jaggery, salt, some spices and essence. 2- Semi -perishable foods can be stored for a couple of weeks or even a month or two without any detectable signs of spoilage. Temperature and humidity of the environment again affects the shelf stability of such foods. Proper handling and storage can result in fairly long storage without spoilage. Examples are all cereal and pulse products like wheat flour, semolina, vermicelli, broken wheat, and some fruits and vegetables like citrus fruits, apples, roots and tubers, potatoes, onions, garlic etc. Yanal ALbawarshi 22 3- Perishable foods can be kept at room temperature for only few hours or 1 or 2 days before spoiling. For example- milk and milk products, meat, fish, poultry, fruits, leafy vegetables and cooked food.. The rate of spoilage varies with the temperature, moisture and or dryness of the environment. Yanal ALbawarshi 23  Causes of Food Spoilage There are mainly three types of causes of food spoilage 1 - Biological causes comprise of growth and activity of microorganisms such as bacteria, yeast and moulds; activity of food enzymes and damage due to pests, insects and rodents etc. 2-Chemical causes include reaction with oxygen and light and chemical reactions within food constituents. 3 -Physical causes consist of temperature and physical abuse, changes caused by freezing, burning, drying, pressure, etc.. Yanal ALbawarshi 24  All of these factors can act together. For example, bacteria, insects, and light, all can be operating concurrently to spoil food in a field or in a warehouse. Similarly, heat, moisture, and air at the same time affect the multiplication and activities of bacteria and chemical activities of food enzymes. Yanal ALbawarshi 25  The major types of spoilage that occur in foods are due to microbiological, biochemical, physical and chemical changes. These include: - Growth and activity of microorganisms such as bacteria, yeast and moulds - Activities of food enzymes, present in all raw foods, promote chemical reactions within the food affecting especially the food color, texture and flavor - Inappropriate holding temperatures (heat and cold) for a given food - Gain or loss of moisture - Reaction with oxygen and light causing rancidity and colour changes due to oxidative reactions - Physical stress or abuse - Damage due to pests, insects and rodents etc. - Non-enzymatic reactions in food such as oxidation and mechanical damage Yanal ALbawarshi 26 Causes of Food Spoilage 1- biological causes Yanal ALbawarshi 27  Spoilage due to growth and activity of microorganisms: Most significant deteriorative changes occur in foods due to microorganisms present in air, soil, water and on foods. They use our food supply as a source of nutrients for their own growth, which results in deterioration of food and render our food supply unfit for consumption. Microbes spoil any food in many ways viz. by increasing their number; by utilizing nutrients; by producing enzymatic changes; by contributing off-flavours; by breakdown of a product; and by synthesis of new compounds. The three major types of microorganisms which cause food spoilage are bacteria, yeasts and moulds. Yanal ALbawarshi 28  Bacteria Yeasts Moulds Factors affecting growth of microorganisms Spoilage due to enzymatic activity Factors affecting enzymatic activity Spoilage due to insects, pests and rodents Spoilage due to chemical reactions Spoilage due to physical factors Yanal ALbawarshi 29  Sources of microorganisms in food The primary sources of microorganisms in food include: 1. Soil and water 2. Plant and plant products 3. Food utensils 4. Intestinal tract of man and animals 5. Food handlers 6. Animal hides and skins 7. Air and dust Yanal ALbawarshi 30 Yanal ALbawarshi 31  How does food processing influence the spoilage rate and the type of spoilage that occurs? 1. Increase in the number of microorganisms during processing. 2. Destruction of the normal spoilage flora and the introduction of a new microflora. 3. Changes in the intrinsic and extrinsic parameters of the food. Yanal ALbawarshi 32  Bacteria Bacteria are much more difficult to kill than moulds and yeast and are the most common causes of food spoilage. They are present in two forms viz. vegetative and spore, The vegetative forms of bacteria are easily destroyed at boiling temperature whereas spores require harsh treatments like application of heat (100°C) for a long time (six hours) or at 121°C under 15 psi pressure for 30 min. Yanal ALbawarshi 33  Bacteria are classified as aerobic, anaerobic and facultative when they require free oxygen for growth, no oxygen and can grow with or without free oxygen, respectively. On the basis of temperature required for growth, bacteria can be grouped into four types viz. 1- mesophiles, requiring temperature below 38°C 2- obligate thermophiles, requiring temperature 38 to 82°C 3- facultative thermophiles requiring temperature below 38 to 82°C 4- psychrophiles, requiring temperature and at refrigeration temperatures. Yanal ALbawarshi 34  The most common bacteria causing significant reductions in shelf life of fruits and vegetables is the soft rotting species of the genus Erwinia. Under suitable conditions they produce large quantities of extracellular enzymes which rapidly macerate the tissue which gives unpleasant off-odours. Some bacteria are also useful particularly in food processing. For example- aerobic bacteria like Acetobacter aceti used in vinegar production and lactic acid bacteria like Lactobacillus plantarum, Pediococcus cerevisiae, Leuconostoc mesenteroides etc. produce lactic acid by fermentation of carbohydrates. Yanal ALbawarshi 35  yeasts Yeasts require less moisture and acidic pH to grow and do not grow in alkaline medium. Yeasts grow under moderate temperature (25-30°C) in sugar solution of low concentration. Most of the yeasts usually do not grow in media containing more than 65 percent of sugar or 0.5 percent acetic acid. Heating at 60°C for a few minutes is sufficient to destroy most species of yeasts. Boiling destroys yeast cells and spores effectively. Yanal ALbawarshi 36  Some yeasts are very useful in making bread, beer, wine, vinegar and many other fermented products. Yeasts are responsible for fermentation of fruits and fruit products. During active fermentation, yeast can be recognized by formation of bubbles of carbon dioxide gas on the surface of the product. Some of yeasts which grow on fruits are Saccharomyces, Candida etc. Saccharomyces generally spoils low sugar products whereas Candida is responsible for spoilage of high acid foods, salty foods and butter etc. Some yeasts which are like true yeast but do not form spores are known as pseudo-yeasts. This type of yeast is not suitable for fermentation as they produce off-flavours and cloudiness. Yanal ALbawarshi 37  Moulds Moulds are multicellular filamentous fungi. They grow on foods with their fuzzy or cottony appearance, sometimes colored. Moulds are made up of mycelium and spores. They grow in a network of hair like fibres called mycelia and send up fruiting bodies that yield spores. Some of common moulds are Aspergillus, Penicillium, Rhizopus and Heliminthosporium. Yanal ALbawarshi 38  They are strictly aerobic in nature and require less available moisture than yeast and bacteria and can grow well at 25-30°C. Their growth can be seen only on the surface of food. Moulds prefer sugar containing substances like jam, jelly, preserves and other sweet products. They can grow at wide range of pH (2 to 8.5) but majority grow well at acidic pH. Therefore, they grow nicely on pickles, juices etc. Majority of moulds are sensitive to heat and are destroyed at 60°C when heated for 30 minutes. Boiling quickly destroys both moulds and their spores. Some moulds produce toxic substances known as mycotoxins. For example Aspergillus flavus produces aflatoxins in moist groundnuts Yanal ALbawarshi 39  degradation processes by MO includes: Putrefaction: Protein foods proteolytic M.O. a.a+amines+ ammonia+ H2S. Fermentation: Carbohydrate foods saccharolytic M.O. organic acids + alcohol + gases. Rancidity: Fatty foods lipolytic M.O. fatty acids + glycerol. Yanal ALbawarshi 40 Table : Types of food spoilage with some examples of casual organisms Yanal ALbawarshi 41  Food Poisoning vs Food Spoilage Food poisoning and spoilage are two different things, which affect the final quality and safety of foods. What is Food Poisoning (as food borne illness)? It is a result of consumption of contaminated food. The major contaminations can be microbial or chemical. Microbial contaminations are classified 1- intoxicationIngestion of toxins produced by microorganisms; 2- toxicoinfection refers to the production of toxins after ingestion of harmful microorganisms. 3- Food infection is due to colonization of a host organism by the microorganism, and is the source of the symptoms. Microorganisms responsible for these reactions can be commonly called as pathogenic microbes Yanal ALbawarshi 42  What is the difference between food poisoning and food spoilage? Both processes are related to food and microbial activity on them. Spoiled food items will affect the quality of food, while the poisoned food affects the safety of food. Finally, both negatively affect human health and reduce the economic profit to the industry. Yanal ALbawarshi 43 Table 1: Factors affecting the development of microorganisms in foods Yanal ALbawarshi 44  Factors affecting microbial growth in food (a) Intrinsic factors: These are inherent in the food. They include:  Hydrogen ion concentration (pH), moisture content, nutrient content of the food, antimicrobial substances ad biological structures. oxidation-reduction potential (Eh), Yanal ALbawarshi 45  1. Hydrogen ion concentration (PH) The pH, or hydrogen ion concentration, [H+], Relationship Between pH & Acid The lower the pH, the higher the acid The higher the pH, the lower the acid A food with pH greater than 4.6 is considered ‘low acid’ A food with pH 4.6 or lower is ‘high acid’ Yanal ALbawarshi 46  The range of pH over which an organism grows is defined by three cardinal points: 1- the minimum pH, below which the organism cannot grow, 2- the maximum pH, above which the organism cannot grow, and 3- the optimum pH, at which the organism grows the best. Microorganisms which grow at an optimum pH well below neutrality (7.0) are called acidophiles. Those which grow best at neutral pH are called neutrophiles and those that grow best under alkaline conditions are called alkalophiles. Yanal ALbawarshi 47 Table 5: Approximate pH ranges of different microbial groups Yanal ALbawarshi 48  Foods can be classified according to their pH as follows: High-acid foods -- products that have a natural pH of 4.6 or below. Low-acid foods -- foods (other than alcoholic beverages) that have a pH greater than 4.6 and less than 7.0. (Low-acid does not mean low pH, but relates to the pH values above 4.6.) Acidified foods -- low-acid foods that have their pH lowered to 4.6 or less by the addition of acids or acid foods. In food pH is used to control microorganisms by: (1) directly inhibiting microbial growth, and (2) reducing the heat resistance of the microbes. Yanal ALbawarshi 49 Table 6: Approximate pH ranges of some common food commodities Yanal ALbawarshi 50  In general, bacteria grow faster in the pH range of 6.0- 8.0, yeasts 4.5-6.5 and filamentous fungi 3.5-6.8, with the exception of lactobacilli and acetic acid bacteria with optima between pH 5.0 and 6.0 The acidity of a product can have important implications for its microbial ecology, and the rate and character of its spoilage. For example, vegetables generally have a moderately acidic pH and thus are spoiled by soft-rot producing bacteria such as Erwinia carotovora and pseudomonads, while in fruits, a lower pH prevents bacterial growth and spoilage is caused by yeasts and molds. Yanal ALbawarshi 51  Also, fish spoil more rapidly as compared to meat under chill conditions. The pH of meat (5.6) is lower than that of fish (6.2-6.6) and this contributes to the longer storage life of meat. The pH-sensitive genus Shewanella plays an important role in fish spoilage but has not been reported in normal meat (pH