Non-thermal Food Processing and Preservation Lecture Notes PDF

Non-food processing and food preservations 10th lecture Dr. Mohamed Elsaadany  Outline Introduction. Types of thermal heat processing PRINCIPLES OF FOOD PRESERVATI...

Non-food processing and food preservations 10th lecture Dr. Mohamed Elsaadany  Outline Introduction. Types of thermal heat processing PRINCIPLES OF FOOD PRESERVATION An Introduction to Non-thermal processing METHODS OF FOOD PRESERVATION Types of Non-thermal heat ASEPSIS processing Maintenance of anaerobic Benefits and applications of Non- condition. thermal processioning Use of high temperatures. Use of low temperatures. Drying Smoking. Use of chemical preservatives. Irradiation. Others Dr. Mohamed Elsaadany 2  Types of thermal heat processing Heat processing using steam or water Boiling, Blanching, Pasteurisation, Heat sterilization, Evaporation & Distillation Heat processing using hot air Dehydration | Baking and roasting Heat processing using hot oils Frying Heat processing by direct and radiated energy Infrared, Dielectric, Ohmic Processing by The Removal of Heat Chilling, Freezing, Freeze drying Dr. Mohamed Elsaadany 3  Non thermal processing an Introduction The traditional food technologies, such as pasteurization, high temperature sterilization, drying and evaporation, can guarantee the microbiological safety or stability of their products, but can destroy some of the food ingredients, especially the heat sensitive vitamins and polyphenols, Higher processing temperatures and longer process times during food processing also produce some potentially harmful components that threaten human To overcome these problems non thermal methods came into food industries to increase the production rate and profit. The non thermal processing is used for all foods for its better quality, acceptance, and for its shelf life. Dr. Mohamed Elsaadany 4 Non-thermal processing methods Pulsed electrical field method (PEF) Pulsed Ultraviolet method Irradiation method Cold plasma Super critical carbon dioxide Pulsed light High hydrostatic pressure processing Radio frequency and microwave Ultrasound Dr. Mohamed Elsaadany 5  1. Pulsed electric field (PEF) PEF is a non-thermal food preservation technology that involves the discharge of high voltage electric pulses (20 - 80 kV/cm) into the food product, which is placed between two electrodes for a few microsec. widely applied for sterilizing foods, such as vegetable and fruit juices, milk and liquid egg. PEF can also be used to inactivate enzymes in the food industry in order to prolong the shelf life It enhance extraction of intracellular compounds from fruits and vegetables such as plant oil, polyphenols and pigments It improves drying rates of food such as potatoes and meat products Accelerating the ageing process of wine and chelating reactions Dr. Mohamed Elsaadany 6  Pulsed electric field (PEF) If combined with mild heating, it enhances the effectiveness of microbial inactivation and extends shelf life of foods. The pathogens are destroyed through destruction of the cell membranes and oxidation of macromolecule. https://www.youtube.com/watch?v=2z0uLS8oQ_I https://www.youtube.com/watch?v=-doPfIKimNY Dr. Mohamed Elsaadany 7  2.Ultraviolet Pulsed UV-light is a technique used to inactivate surface microorganisms using short pulses of an intense light in the spectral band between 200 and 280 nm for only microsecond. UV applications include disinfection of water supplies and food contact surfaces. It also used effectively kill the salmonella on the surface of unpackaged and vacuum packaged chicken, cooked meat products, freshly cut mushrooms. It improve the safety and extend the shelf life of some juices and milk while maintaining more of the fresh-like qualities of the cider compared to thermal processing. Dr. Mohamed Elsaadany 8  2.Ultraviolet Pulsed UV light can affect the colour and the texture of food stuffs depending on the energy dose and the distance between the lamp and surface of the samples The germicidal properties of UV irradiation are mainly due to DNA mutations induced through absorption of UV light by DNA molecules. Due to shadow effect it is necessary to combine other methods such as PEF, ultrasound or packaging or in combination with ozone and hydrogen peroxide. https://www.youtube.com/watch? v=GjHSJT90Omw Dr. Mohamed Elsaadany 9  3.Irradiation Three types of ionizing radiation are authorized to be used in the food irradiation applications, which include the high-energy gamma rays, X-rays and accelerated electrons. The mechanism by which ionizing radiation inactivates microorganisms is mainly due to the direct damage or indirect damage of the nucleic acids (DNA) of microbial Decontamination of spices, herbs and condiments remains the single largest application of irradiation It can be used for ready to-eat meat products, and fresh mushrooms useful sterilization method for its potential role for prolonging shelf-life. irradiation treatment can change the colour of fresh meat and cause a characteristic unpleasant odour as well as could affect the functional properties of the food matrix, such as whole wheat flour and rice The development of irradiation technology application in the food industry is limited because of nuclear technology, consumer perception, needs for safer and more reliable equipment https://www.youtube.com/watch?v=1rR1UsZkS74 Dr. Mohamed Elsaadany 10  4.Cold plasma Cold plasma is a method of ionizing gas with neutral molecules, electrons and positive and negative ions, leading to generating various highly reactive species that destroyed microorganisms There are many methods to ionize gases into plasma, such as heating, electricity and the use of lasers. Cold plasma used to inactivate contaminating microbes on meats, poultry, fruits, and vegetables. It was also used to sterilize cherry tomatoes, strawberries, almonds and food package materials The possible mechanism inactivating microorganisms using cold plasma is that the generated various reactive oxygen free radical affect the macromolecules of microbial cell Key limitations for cold plasma are the relatively necessary equipment, and the largely unexplored impacts of cold plasma treatment on the sensory and nutritional qualities of treated foods. https://www.youtube.com/watch?v=4lcMe7SNpvs https://www.youtube.com/watch?v=tmtTuHDmTuk Dr. Mohamed Elsaadany 11  Supercritical carbon dioxide (sCO2) 5.Supercritical Carbon Dioxide Supercritical carbon dioxide (sCO2) is a fluid state of carbon dioxide where it is held at or above its critical temperature(31C) and critical pressure (1071pci). Supercritical carbon dioxide (SCCO2) has been found to be a valuable technology for processing and preservation of fruit and vegetables. It has been employed for the inactivation of microorganisms and enzymes in fruit and vegetable products such as juices, purees, and smoothies. SCCO2 is also an effective and green technology for the extraction of bioactive compounds (carotenoids, flavonoids, phenols, etc.) from fruit and vegetables, owing to the relatively low temperature used and the production of extracts without organic solvents. Dr. Mohamed Elsaadany 12  6.Pulsed Light Pulsed light is a surface irradiation system and not a penetration system. It is primarily useful for surface kill of microorganisms, or for liquids if you can run liquids through as a very thin film. Pulsed light consists of very intense and short flashes of light with wavelengths from UV to NIR, emitted by Xenon discharge lamps. Despite its approval for surface microorganism control in foods by FDA, is not yet commercially used, mostly due to the lack of knowledge regarding the critical factors of influence and the inactivation mechanisms. https://www.youtube.com/watch?v=pFGYTcubGnw Dr. Mohamed Elsaadany 14  7. High Hydrostatic Pressure Processing (HPP) High hydrostatic pressure processing (also known as high pressure processing (HPP) and ultra-high-pressure processing (UHP) is a method of food processing in which foods are treated under high pressure (300-600 MPa) to achieve microbial inactivation. Typically, the food product is packaged into flexible containers which are then placed into a high pressure chamber filled with a pressure- transmitting medium (usually water). The fluid filled chamber is then pressurized with the pressure being transmitted through the package and into the food itself. The effectiveness of inactivation depends on the pressure, holding time and resistance of the microorganism and the food matrix under the HPP processing. The main mechanism for the sterilization effect is the irreversible destruction of cellular structure(cell membranes and cell walls) Dr. Mohamed Elsaadany 15  7. High Hydrostatic Pressure Processing (HPP) HPP technology is applied in the commercial processing of seafood, cooked products such as emulsion-type meat and poultry products, ready-to eat products and plant-based foods such as various fruit juices reduce the rennet coagulation time, promote the rate of curd formation and also increase the yield of cheese improve the content of bioactive components, such phenolic compounds and soluble dietary fiber and enhancing the antioxidant properties of grape pomace. Because HPP causes minimal changes in the freshness characteristics of foods by eliminating thermal degradation, HPP results in foods with a fresher flavor profile and better appearance, texture, and nutrition compared to thermally processed products. https://www.youtube.com/watch?v=o7CQLBkym4A Dr. Mohamed Elsaadany 16  8. Radio Frequency and Microwave Microwave and radio frequency heating refers to the use of electromagnetic waves of certain frequencies to generate heat in a material. Mechanism Dipolar interaction: polar molecules such as water molecules(dipole) inside the food will rotate according to the alternating electromagnetic field. The rotation of water molecules would generate heat for cooking Ionic interaction: Ionic compounds (i.e. dissolved salts) in food can also be accelerated by the electromagnetic field and collided with other molecules to produce heat Microwave and radio frequency heating for pasteurization and sterilization are preferred to the conventional heating because they are rapid Dr. Mohamed Elsaadany 17  8. Radio Frequency and Microwave They can approach the benefits of high temperature-short time processing whereby bacterial destruction is achieved, but thermal degradation of the desired components is reduced. Other advantages of microwave and radio frequency heating systems are that they can be turned on or off instantly and the product can be pasteurized after being packaged. Microwave and radio frequency processing systems can also be more energy efficient. Dr. Mohamed Elsaadany 18  Ultrasound method 9.Ultrasound Ultrasound is mechanical waves at a frequency exceeding the threshold of human hearing about 20 kHz Used for degassing, defoaming, filtration and emulsification, food preservation and extraction of active ingredients from the food stuffs promote protein hydrolysis, and accelerate mass transfer and heat exchange in food processing Used for preserving vegetable and fruits and their juices Used to extract phenolic compounds, pigments and prebiotic oligosaccharides from fruits and vegetables Sounds results from moving continues waves resulted in intracellular cavitation and break down and dislodge particles, destroy the cell membrane Dr. Mohamed Elsaadany 19 FOOD PRESERVATION Dr. Mohamed Elsaadany 3  foodPRESERVATION PRINCIPLES OF FOOD preparation PRINCIPLES OF FOOD PRESERVATION. 1. Prevention or delay or microbial decomposition. By keeping out microorganisms (asepsis) By removal of microorganisms (filtration) By hindering the growth and activity of microorganisms (drying, anaerobic condition, lowering the temperature, etc) By killing the microorganisms (heat or radiation) 2. Prevention or delay of self-decomposition of the food. By destruction or inactivation of food enzymes By prevention or delay of purely chemical reactions (E.g. prevention of oxidation) 3. Prevention of damage because of insects, animals, mechanical causes etc. Dr. Mohamed Elsaadany 21  METHODS OF FOOD PRESERVATION METHODS OF FOOD PRESERVATION. Asepsis- keeping out microorganisms. Removal of microorganisms. Maintenance of anaerobic condition. Use of high temperatures. Use of low temperatures. Drying Smoking. Use of chemical preservatives. Irradiation. Mechanical destruction of microorganisms. Combinations of two or more of the above methods. Dr. Mohamed Elsaadany 22  1. ASEPSIS food preparation 1. ASEPSIS Natural protection - outer layer of animal and plant tissue protects the inner layer free from microorganisms. e.g. shells of nuts, skins of fruits and vegetables etc. Packaging of foods - such as wrapping and sealed containers. This methods prevents primarily contamination during handling. Sanitary methods during handling and processing to avoided as much as possible the contamination e.g dairy industry. In Food industries- attention is given to prevent contamination of foods by of microorganisms(from raw material finished products) Dr. Mohamed Elsaadany 23  food preparation 2. REMOVAL OF MICROORGANISMS 2. REMOVAL OF MICROORGANISMS (a) Filtration The only successful method for the complete removal by using a pre-sterilized filters e.g. in fruit juices, soft drinks and water. (b) Centrifugation Not very effective because not all microorganisms are removed, examples: Treatment of drinking water. (c) Washing Especially helpful in removing soil microorganisms from fresh fruits and vegetables that may be resistant to heat process during canning. (d) Trimming Trim away spoiled portions of a food. Dr. Mohamed Elsaadany 24  food 3. MAINTENANCE OF preparation ANAEROBIC CONDITIONS 3. MAINTENANCE OF ANAEROBIC CONDITIONS Anaerobic conditions can be achieved by a complete fill, evacuation of the unfilled space, replacement of air by C02 or N2 and others. Spores are resistant to heat and may survive in canned food but they unable to germinate in the absence of oxygen. Dr. Mohamed Elsaadany 25  food preparation 4. USE OF HIGH TEMPERATURES 4. USE OF HIGH TEMPERATURES Temperature and time used in heat processing will depend on: The effect of heat on the food Other preservative methods employed Heat Treatment Microorganisms Classification of heat treatments used on foods: (a) Pasteurization (b) Heat at 100°C (c) Heat > 100°C Dr. Mohamed Elsaadany 26  food preparation 4. USE OF HIGH TEMPERATURES A. Pasteurization Heat treatments able to kills most but not all microorganisms. The pasteurized products are cooled promptly after the heat treatment. Pasteurization is important when: Heat treatment will not harm the quality of product Main spoilage microbes are not very heat resistant e.g. yeast in fruit juices Kill pathogens will be treated with other preservative methods Competing organisms are to be killed, allowing a desired fermentation Preservative methods used to supplement pasteurization: Refrigeration. Packaging. Maintenance of anaerobic conditions. Addition of high concentration of sugar. Presence of chemical preservatives Dr. Mohamed Elsaadany 27  food preparation 4. USE OF HIGH TEMPERATURES B. Heating at about 100oC Sufficient to kill all microbes but not spores, Many acid foods are successfully preserved at100°C. Methods: Boiled, Immersion, Baking, Simmering, Roasting, Frying, Blanching, Exposure to flowing steam Dr. Mohamed Elsaadany 28  food preparation 4. USE OF HIGH TEMPERATURES C. Heating above 100oC Obtained by means of steam under pressure (as Steam pressure Temp. Kill spoilage and pathogenic microorganisms. E.x high, ultra temperature for a short time (milk is heated at 150°C by steam injection followed by 'flash evaporation' of condensed steam and rapid colling All commercially sterile foods should be stored in cool, dry, place to prevent any viable thermophilic spores from germinating Objective of heating foods: Destroy pathogens and spoilage microorganisms Destroy toxin present in foods Destroy spores of yeast, bacteria and moulds Destroy undesirable enzymes this can affect the quality of foods. To control the growth of surviving microorganisms To retain the acceptance and nutritional quality of foods Dr. Mohamed Elsaadany 29  food preparation 4. USE OF HIGH TEMPERATURES Canning Process Preservation of foods in sealed containers followed by application of heat treatment. Canning is done in tin cans, glass containers, aluminum and plastic pouches. Canning Process: Raw food Prepare, inspect, sorting, grading Washing Filled in the can Brine added Evacuated by heating the headspace (vacuuming) Sealing Heat processing In general, microbial spoilage can occur due to under processing and/or leakage after processing. Dr. Mohamed Elsaadany 30  food preparation 5. USE OF LOW TEMPERATURES 5. USE OF LOW TEMPERATURES Low temperature reduces the activity of microorganisms by reducing the chemical reaction and action of enzymes. A. Chilling temperature Temperature of 6°C can prevent the growth of food poisoning microorganisms except the Clostridium botulinum type E Chilling temperature is the main method for temporary preservation of food. Psychrotroph are microorganisms which can grow at low temp. e.g. Flavobacterium spp. & Pseud. alcaligenes but they have a low growth rate. Dr. Mohamed Elsaadany 31  food preparation 5. USE OF LOW TEMPERATURES B. Freezing temperature Cause reduction in number of viable microorganism but does not sterilize the food. The percentage of microorganisms killed during freezing and storage varies depending on: Substrate (kind of food) Type of freezing Substrate: protein, fat and other substance can have protective effect, High moisture and low pH can increase killing rate. Type of freezing : Slow ~ temp. lowered to -20°C (3 - 72 hrs) Fast ~ temp. lowered to -20°C (30 mins) Advantages of fast freezing Smaller ice crystal form - less mechanical destruction to food sudden death to microorganisms and quick inactivation of the enzymes. Food quality after thawing is better Dr. Mohamed Elsaadany 32  food preparation 6. DRYING AND SMOKING 6. DRYING AND SMOKING A. Drying Methods which lower the water content of food to a point where the activities of enzymes and food spoilage and food poisoning microorganisms are destroyed / inhibited. The lower the water activity of food, the greater is the inhibition. If Aw is between 0.75 - 0.70, the spoilage is delayed. If Aw is 0.65, the spoilage is most unlikely to occur up to 2 years. Molds and yeasts are more important in spoilage dried foods since bacteria require higher water content for growth. Dr. Mohamed Elsaadany 33  food preparation 6. DRYING AND SMOKING Types of drying: Sun drying Freeze drying Spray drying Smoking Treatment before drying (to reduce number of microorganisms): Washing Dipping food in alkaline solution such as sodium carbonate for prunes. Treatment with SO2 to maintain the food's color as well as conserve the vitamin content. It will also prevent storage changes such as browning of vegetables and fruits. Blanching / scalding. The heat kills most of the microorganisms and destroys the enzymes that may become active Addition of sugar before evaporation e.g. sweetened condensed milk. The sugar will tie up the water and make them unavailable for microbial growth. In any drying method, the total count of coliforms and food poisoning microorganisms should be zero. Dr. Mohamed Elsaadany 34  food preparation 6. DRYING AND SMOKING Effects of drying upon foods. (Undesirable changes): Dried food that contains fat and oxygen can cause oxidative rancidity Dried food which contains reducing sugar can undergo a color change called Maillard reaction. The browning is undesirable because of the unnatural color and bitter taste Loss of vitamin C Toughness Methods of minimizing the chemical changes in dried food: Keep moisture content as low as possible Reduce the level of reducing sugar as low as possible Reduce serial blanching in the same water Use SO2 to retain vitamin C and avoid browning Dr. Mohamed Elsaadany 35  food preparation 6. DRYING AND SMOKING B. Smoking Heating foods using smoke from various types of wood to preserve foods. The smoke produces heat which kills some microorganisms on the surface Heat also reduces the Aw. It also has an antimicrobial compounds e.g. formaldehyde which can inhibit the growth of some microorganisms. The presence of aromatic compounds will also give a distinctive flavor and around to the food. This will make the foods taste better and more tender e.g. smoked fish. Woodsmoke is less effective against bacterial spores. Dr. Mohamed Elsaadany 36  food preparation 7. CHEMICAL PRESERVATIVES CHEMICAL PRESERVATIVES Food additives / preservatives: "A substance or a mixture of substance which are specifically added to prevent deterioration or decomposition of a food" Chemical preservatives are used mainly to inhibit activity of microorganisms by: Interfering with their cell membranes Their enzymes activity Their genetic mechanisms They can also be used as: Antioxidants to prevent oxidation of unsaturated fats. Neutralizers of ‘acidity. Stabilizers to prevent physical changes. Firming agents. Coating to keep out microorganisms. Prevent loss of water. Dr. Mohamed Elsaadany 37  food preparation 7. CHEMICAL PRESERVATIVES 7. CHEMICAL PRESERVATIVES An ideal chemical preservative should have: A wide range of antimicrobial activity Non toxic to human beings and animals Economical No effect on the flavour, taste or aroma of the original food Should not be inactivated by the food Should not encourage the development of resistant strains Should rather kill than inhibit microorganisms Propionates Used in bakery, cheese food & spreads Sodium or calcium propionates used in the prevention of mold growth and rope development Benzoates Used in jam, jellies, margarine, carbonated drinks, fruits etc. Sorbates Sorbic acids and sorbate salts are used as a direct antimicrobial additive in foods as a spray, dip or coating on packaging materials. Used in cheese, dried fruit, bakery etc. Dr. Mohamed Elsaadany 38  food preparation 7. CHEMICAL PRESERVATIVES Acetates Dehydroacetic acid has been used to impregnate wrappers for disease to inhibit mold growth. Acetic acid (vinegar) is used in mayonnaise, ketchup, sausages etc. Nitrites and nitrates Used in meats because nitrites can give a stable red color. Nitrites are shown to have an inhibitory effect toward C. botulinum. The use of nitrates is being restricted because it can react to amines and form nitrosamines which is carcinogenic. Sulfur dioxide and sulfites Used in the wine industry to sanitize equipment and to reduce normal flora of the grape must. In aqueous solution, they form sulfurous acid, the active antimicrobial compound. Ethylene and propylene oxide Powerful sterilant which kills almost all microorganisms Useful for fumigation, packaging materials, dried fruits, eggs, cereals and spices. Dr. Mohamed Elsaadany 39  food preparation 8. OTHER PRESERVATIVE METHODS 8. OTHER PRESERVATIVE METHODS A. Filtration Fruit juices are subjected to filters with steam sterilize methods for 10-20 minutes. The sterile products are filled aseptically in sterile bottles or cartons. B. Radiation Gamma ray is the cheapest form of radiation for food preservation. X-rays essentially has the same character like gamma rays but produced differently. Dr. Mohamed Elsaadany 40  food preparation CHEMICAL PRESERVATIVES C. Antibiotics Antibiotics such as aureomycin, terramysin and chloromycetin were found to be effective in lengthen the storage time of raw food especially meats, fish and poultry at chilling temperature. Natamycin has been tested in orange juice, fresh fruits, sausage and cheese. Niacin has been used to suppress anaerobes in cheese and cheese products. Some problems in the use of antibiotics: Effect of antibiotic on microorganisms vary with the species. Organisms ' may be adapted to increasing concentrations of an antibiotic so that resistant strains finally develop Effect of antibiotic to consumer. Dr. Mohamed Elsaadany 41 THANKS! Any questions? Dr. Mohamed Elsaadany 42