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Chapter 8

Chapter 8- Understanding Food Processing and Preservation - animal products.docx

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University of Guelph
Food Science
FOOD 2010
Massimo Marcone

Chapter 8: Understanding Food Processing and Preservation : animal products -Food processing : conversion of raw animal and plant tissue into forms that are convenient and practical to consume. Accomplished through mechanical action, heating, extrusion, and other manipulations - Food preservation: use of specific thermal and nonthermal processing techniques to minimize the number of spoilage microorgs. in foods, making them safe and giving them an extended shelf life. Techniques include canning, refrigeration, freezing, dehydration, high pressure, irradiation, and the use of certain additives. 8.1 Food Processing - From field and farm to consumers -definition above -foods are processed for one of 2 reasons 1) preserve them so that they remain fresh, wholesome, nutritious, safe and free from the effects of spoilage for a certain length of time 2) to manufacture specific desirable food products that exhibit a certain shelf life -one prime cause of spoilage is the amount of biologically active water in the tissue -high = deteriorate in a couple days -dry = contain more structural water, stored for years -major causes -microbial growth -enzymatic reactions -chemical changes (esp. oxidation) -spoilage occurs at -high aw -optimal conditions of temperature -optimal pH -other optimal enviro conditions -unit operations of food processing -multiple operating steps -unit operations are the broad categories of common food processing ops -about a dozen categories of unit operations EXAMPLES BELOW -material handling : -manner in which raw commodities are harvested and transported -separating: -isolates desirable part of food raw material from another part -ie liquid from solid (etc) -cleaning -implies removal of dirt, debris, and associated bacteria by washing with water and detergent (when practical) -debris: chemical residue/organic material that serves as food for bact. -cleaners -amphiphilic compounds having hydrophilic and hydrophobic structure -interact with water and dirt/debris by suspending particles in solution -sanitizers -chemical compounds that are bacteriostatic and bactericidal agents Chapter 8: Understanding Food Processing and Preservation : animal products -bacteriostatic: inhibiting growth of microorgs -bactericidal destroys microorgs -varying degrees of effectiveness against gram - and + bacteria -disintegrating -particle size reduction of foods -pumping -moving food material from point A to point B during processing -mixing -blending of food ingredients to create a food product -heat exchange -application or removal of heat from a food -evaporation -removal of moisture from a food to concentrate its solid contents -drying -product moisture is reduced to a mere few %. -forming -formed into specific shapes during processing -packaging -protects food from enviro and offers convenience for retailers and consumers -primary concern of prevention: contamination, presence O2, moisture, light, unwanted flavor and odor transfer, and pet access -newer strategies for food preservation, see 8.3 -basic principles of food processing -6 basic principles of food processing to achieve preservation -moisture removal -reduces moisture, rates enzyme activity and chemical reaction -achieved through drying, dehydration, evaporative concentration, and intermediate moisture processing -drying (sun drying, drum drying, spray drying, freeze-drying) -dried foods reduce moisture, but not necessarily w (warning) -heat treatment -pasteurization, blanching, baking, canning (to achieve sterility extrusion cooking and microwave cooking) -sterilization = complete destruction of microorgs -commercially sterile = degree of sterilization at which all pathogenic and toxin-producing orgs are destroyed, as well as spoilage orgs -pasteurization = involves low-heat treatment (below BP of water) -destroy orgs -extend product shelf life -flash pasteurization (high temp, short time) -blanching (foods 2700 notes) -canning (food 2700 notes) -low-temperature treatment Chapter 8: Understanding Food Processing and Preservation : animal products -refers to cold storage (refrigeration, freezing) -goal of freezing is to cool quickly (get out of danger zone) then freeze o -all detectable water in food is converted to ice when food = -60 C -direct expansion refrigeration = gaseous refrigerant pumped through a coil. Air cools coil, then coil cools food prodcut. (gases ammonia, CO2, liquid nitrogen) -IFQ (individual, quick, frozen) = uses CO2 cryogenic equipment to quickly cool foods -acidity control -controlling pH (use of acidulants etc) -acidification to kill microorgs makes food gross, so combination of acid, heat, and refrigeration are usually used -high-acid foods = pH < 4.6 -when canned high-acid foods need lower temp -traditional nonthermal processing -packaging, chemical additives with antimicrobial, antioxidative, or other key functional properties -antimicrobial chemcial preserves -function to maintain/preserve a food product's freshness -see page 217-218 for list -packaging -see chapter 13 -offer protection from biological, chemical, and physical factors -modified gas atmosphere -low gas permeable packaging -etc -innovative nonthermal processing -see 8.3 and challenge -ex : irradiation 8.2 What Is Heat Transfer -heat transfer = refers to the manner in which heat energy is transferred from a heat source to food particles in a container -heat transfer in a retort canner -heat energy is transferred from the heating source to the food inside -retort processing is the procedure used to heat sealed cans in order to destroy bacteria and spores -steam is injected in (steam is a better heat transferor than regular air so lower temp o is needed = steam at 100 C) -heat transfer within a can -conduction = heat transferred between food molecules inside the can via molecular collisions -convection = occurs when heat is transferred through a liquid according to density differences, and is unique to liquid foods, or foods packed in liquid Chapter 8: Understanding Food Processing and Preservation : animal products -conduction heat process is begun, the cold point is toward the center of the can because heat would have been conducted equally inward from all sides. -convection heat process, cold point is below the center of the can due to the movement of fluid from the bottom to the top -vacuum canning -all air is removed from inside the can -first removal of the air prevents the cans from swelling and bursting open if they are stored at reduced pressure -can stored in hot climates would swell as air inside would expand in volume -second canning under vacuum removes a source of oxygen that is potentially damaging to foods by producing off-colour and off-flavour -foods packaged into cans may cause a hermetic seal, which is airtight, meaning that no gases are able to enter or exit from the can 8.3 Food Preservation - Preventing Food Spoilage -biological changes in food stem from the action of microorganisms fermenting carbs into smaller organic molecules -chemical changes in food refers to the action of microbial enzymes called proteases and lipases on food protein and lipid molecules -physical changes in foods include loss of moisture due to evaporation and separation of phases -thermal processing for food preservation -goal = delay food perishability and inhibit food spoilage -both wet and dry heat can be applied -must cause cell death thus failure to grow and reproduce -heat resistance
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