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Shelf Life

Shelf Life. Who’d want to spend life on a shelf anyway?. Try this first…. Look at the shelf life list. What changes seem to increase a food’s shelf life?. What is Shelf Life?.

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Shelf Life

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  1. Shelf Life Who’d want to spend life on a shelf anyway?

  2. Try this first… Look at the shelf life list. What changes seem to increase a food’s shelf life?

  3. What is Shelf Life? • 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

  4. Factors that affect S.L. • Water content • pH • Light • Temperature • Oxygen contact • More water= more microbial growth • Lower 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

  5. Rancidity • 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

  6. Side note… • 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 CO2

  7. Processing, Packaging, Additives See Examples... How is Rancidity Prevented?

  8. Traditional Foods… • Pemmican (Native American) • Haggis (Scotland) • Hangikjöt (Iceland) • Century eggs (China) • Lutefisk (Norway) • Beer • Kishke (Russia) • Stinkhead (Alaskan Indian)

  9. Processing • Storing at low temperatures • refrigeration + freezing • Storing with reduced light • Opaque packaging • Colored glass • Keeping moisture low • Drying • Salting • Sugaring • Smoking • Irradiation

  10. Packaging • Low Oxygen • Packaging with an inert gas • Vacuum seal (with or without inert gas) • Special Permeable Packaging • Little Headspace • Jams, canned goods, oils

  11. Additives • 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

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