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NHM 253 2/9

by: Regan Dougherty
Regan Dougherty
GPA 4.0

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About this Document

In class lecture notes for Tuesday 2/9
Food Science
Dr. Crowe
Class Notes
25 ?




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This 6 page Class Notes was uploaded by Regan Dougherty on Tuesday February 9, 2016. The Class Notes belongs to NHM 253 at University of Alabama - Tuscaloosa taught by Dr. Crowe in Fall. Since its upload, it has received 36 views. For similar materials see Food Science in Nutrition and Food Sciences at University of Alabama - Tuscaloosa.

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Date Created: 02/09/16
Tuesday, February 9, 2016 NHM 253 2/9/16 Food Preservation - The difference between jelly and jam: • Jelly starts with fruit juice. Jelly is just sugar. • Jam starts with fruit. Jam has fiber. - Food Spoilage • Food ingredients have a limited shelf life. • Highly perishable foods contain increased amounts of protein and water. • Three Major Types of Changes in Foods: - Biological - microorganisms - Chemical - enzyme-based reactions - Physical - obvious to the senses • Spoilage vs. Contamination - Spoilage - detectable changes occurring in food that affect the quality of food (appearance, taste, texture, odor) - Contamination - commonly undetected growth of microorganisms in food which affects the safety of food • Changes Affecting Spoilage - Biological Changes - the growth of microorganisms (bacteria, yeast, mold, viruses, parasites) in or on food • These microorganisms are consuming our food as their food. - Chemical Changes - brought about by the presence of enzymes • Suffix for all enzymes: -ase - Physical Changes - detectable by the senses (loss of color, separation of ingredients, loss of texture) - Biological Hazards 1 Tuesday, February 9, 2016 • Most bacteria have a reproductive rate of 20 minutes (doubling by binary fission every 20 minutes). • Temperature danger zone - 41 F - 135 F - Temperature conditions in which bacteria grow best. • FAT TOM (conditions for microbial growth) - food - acidity (bacteria flourish between a pH of 4.6 and 7) • Acids can be used to decrease microbial growth and lengthen the shelf-life of foods. - time - temperature (temperature danger zone) - oxygen • anaerobic - do not need oxygen to grow - moisture - Food and moisture are a must for growth, everything else simply enhances the rate of growth. - Potentially Hazardous Foods (PHF - high protein and water content) • Microorganisms thrive on these foods. • Low temperature storage is the best line of defense against microbial growth. - Foodborne Infection - illnesses occurring from ingestion and growth of causative bacteria in the intestinal tract • The bacteria growing inside you makes you sick. • Symptom onset: 12 hours to 2 days (depending of number of cells ingested) - Foodborne Intoxication - illnesses involving ingestion of toxins produced as by- products of microbial growth • The toxin produced by the bacteria growing on the food you ate makes you sick. • Symptom onset: within hours of ingestion 2 Tuesday, February 9, 2016 - Foodborne Intoxification - illnesses occurring when causative bacteria are ingested, grow, and produce toxins within the small intestine • The toxin produced by the bacteria growing inside of you makes you sick. • Symptom onset: 2-9 days - Chemical Hazards Associated with Food • Found in the Code of Federal Regulations (in Title 21) • Example of an unavoidable contaminant in food: maggots, fruit flies - Food Allergens as Hazards (MEMORIZE these 8 - most common) • milk • eggs fish • • shellfish • tree nuts • peanuts • wheat • All allergens are proteins. • The FDA requires labeling of foods that contain or have been processed in a facility with one of these allergens. • *know about IGA and IGG - Factors to Consider in Food Preservation • Water activity (water that is ready to engage in reactions) • pH (make sure that the food still tastes good) • Thermal or non-thermal techniques - The exposure of heat can cause food to lose its nutritive value. - Drying - decreasing water content of food (microorganisms are unable to grow) • Drying does not kill microorganisms, but rather causes microorganisms to enter a dormant state. 3 Tuesday, February 9, 2016 • Slows biological change. • Water activity required for preservation is usually below 0.6. • If something is dried above 110 F, it is destroying enzymes. - Slows chemical change. - Refrigeration - slows the rate of ripening by slowing enzyme reactions involved in ripening • Slows chemical change. • When fruits and vegetables are harvested, they continue to ripen and respire. • Low temperatures also slow the rate of microbial growth. - Slows biological change. Also slows physical changes. • - Freezing - moisture is bound within ice, rendering it unavailable to microorganisms • Slows biological change. • Also slows chemical and physical changes (but these changes do still occur). - For this reason, vegetables are typically blanched before freezing to destroy ripening enzymes. - Frozen vegetables are picked at peak maturity. Frozen vegetables are more nutritive then fresh vegetables. - Pickling - addition of acids to lower pH (below 4.6) and limit microbial growth Ex. vinegar, lemon juice • • Many fruits are acidic enough to discourage bacterial growth. • Slows biological changes. • Lactobacillus and Bifidobacteria produce lactic acid as they grow, lowering the pH of the food (ex. lowering the pH of milk to form yogurt). - Fermentation - limited to no available oxygen • Ethanol, carbon dioxide, and lactic acid decrease the ability of microorganisms to grow. 4 Tuesday, February 9, 2016 - The organisms that produce it can grow, but other organisms cannot grow. • Commonly fermented foods: pickles, olives, sauerkraut • Lowers pH - Canning - food is sealed in cans or jars and heated to high temperatures • removes oxygen, as well as exposes organisms to extreme temperatures • At 15 psi, water boils at 252 F Heat destroys microorganisms and enzymes but it does not destroy bacterial • spores. - Ex. Clostridium botulinum • Children under the age of 1 and older adults should not consume home-canned food. They have weaker immune systems. - Irraditaion - ionizing radiation destroys chemical bonds within enzyme systems and DNA in microorganisms • exposure of gamma rays • AKA cold sterilization • Considered a food additive by the FDA • Irradiation is the only non thermal method listed in these notes. • Common foods that are irradiated: spices, meats/poultry, nuts, sprouts, eggs • radura - symbol that must be present on first generation products that are irradiated - first generation: products that we would buy directly - Edible Coatings - commodities are dipped in a wax before they go to market • ex. bell peppers, winter squash, cucumbers • barrier to oxygen, gases, and moisture loss • vehicle for added flavors, antioxidants, antimicrobials • types: lipid, CHO, and protein-based. Waxes are most common. - Other Preservation Methods: • Curing - adding salt to bind to water in foods 5 Tuesday, February 9, 2016 • Pasteurization - high levels of heat - Packaging as Preservation • common materials: plastic, cardboard, styrofoam, glass • Modified Atmospheric Packaging (MAP) - slows the exchange of gases between the food and its environment and the external environment • Intelligent Packaging - food is packaged with a radio frequency indicator (indicates when the food has been in an environment with a too low or too high temperature) Active Packaging - takes MAP one step further. Something in the package (sashay) • absorbs any excess oxygen, nitrogen, or carbon dioxide. 6


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