Who’d want to spend life on a shelf anyway?

Try this first…

 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

 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

 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

 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

Processing, Packaging, Additives See Examples...

 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

 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

 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

 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)

 Pemmican (Native American)  Haggis (Scotland)  Hangikjöt (Iceland)  Century eggs (China)  Lutefisk (Norway)  Beer  Kishke (Russia)  Stinkhead (Alaskan Indian)  Kimchi (Korea)