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Published byChristopher Morgan Modified over 9 years ago
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Who’d want to spend life on a shelf anyway?
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Try this first…
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A food reaches its shelf life when it no longer maintains the expected quality desired by the consumer because of changes in Flavour Smell Texture Appearance (colour, mass) or because of Microbial spoilage
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Water content pH Light Temperature Oxygen contact More water= more microbial growth Low/High pH= less microbial growth Light exposure= rancidity, color change, loss of nutrients Higher temp= higher rate of spoilage… but cooking temps can kill microbes Oxygen= oxidation which spoils food
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What does “rancid” mean? Chemical decomposition of a fat which creates an unpleasant smell and/or taste Hydrolytic= breaking a fat back into glycerol and its component fatty acids Also called ester hydrolysis Fatty acids can taste bitter, sour, or even soapy Oxidative= oxygen breaks the double bonds, creating aldehydes or ketones Can be catalyzed by light Can be suppressed with antioxidants
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Putrefaction= usually anaerobic microbial decomposition of proteins into amino acids, ammonia (yuck-o) and hydrogen sulfide (super yuck-o) Fermentation= decomposition of sugars into acid, alcohol, and CO 2
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Processing, Packaging, Additives See Examples...
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Storing at low temperatures refrigeration + freezing High temperature processing Pasteurization= heating food to kill bacteria Cooking Storing with reduced light Opaque packaging Colored glass Keeping moisture low Drying Salting Sugaring Smoking Irradiation
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Low Oxygen Packaging with an inert gas Vacuum seal (with or without inert gas) Special Permeable Packaging Little Headspace Jams, canned goods, oils Packaging with Modified Atmosphere
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Ethanoic acid (vinegar) Pickling delays mold + adds flavor Sulfites or citric acid Delay browning Nitrates or nitrites Keep color Sodium benzoate or benzoic acid Antimicrobial (in juices) Propanoates or propanoic acid Delay mold + bacteria growth (in breads + cheeses) BHA, BHT, ascorbates Antioxidants Find any of these in the food packages at your table? Supersize Me Part 1 Supersize Me Part 1 Supersize Me Part 2 Supersize Me Part 2
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An antioxidant a substance that delays the onset or slows the rate of oxidation. It is used to extend the shelf life of food. Antioxidants are added to foods such as oils, fats and butter as they react with oxygen-containing free radicals and so prevent oxidative rancidity. Can reduce the formation of free radicals which can lead to cancer or heart disease. Synergists, so they form complexes with metals, preventing them from catalyzing oxidation Natural: vitamins E & C, Se, beta-carotene, flavonoids Synthetic: often have phenols (benzene with a – OH) or tertiary butyls (3 –CH 3 on 1 C) (see data booklet for more structures)
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Pemmican (Native American) Haggis (Scotland) Hangikjöt (Iceland) Century eggs (China) Lutefisk (Norway) Beer Kishke (Russia) Stinkhead (Alaskan Indian) Kimchi (Korea)
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