Preservatives Flashcards
food preservation is the process of…
treating and handling food to stop or slow down food spoilage, loss of quality, edibility or nutritional value and thus allow for longer food storage
preservation usually involves preventing the growth of __,__ and other m-o as well as retarding the ____
bacteria, fungi, oxidation of fats which cause rancidity
what is ADI?
highest dose without adverse effects tested on animals, usually multiplied by 100 for humans
additives should be declared with a
function name (antioxidant, emulgator, preservative etc) followed by E-number or name
why can even freezing to -30 deg C not be enough to prevent food going bad?
at -30 only 90% of all water is frozen, which means enzymatic activity and microbial growth and metabolism can still take place!
what are common preservation techniques based on the control of water activity?
drying, salting, smoking, freeze-drying, water binding humectants. removing or binding water in some way will decrease aw
why can salting be used as preservative method?
most bacteria, fungi and other potentially pathogenic organisms cannot survive in a highly salty environment. any living cell in such an environment will become dehydrated through osmosis and die or become inactivated
phenolic substances from the smoke in smoking have…
antibacterial and antioxidative capacities. both antioxidants which slow rancidification of fats and antimicrobials which slow down bacterial growth
dried fish combines salting and drying, how?
it is first salted and then dried. before it can be eaten salt cod must be rehydrated and desalinated!
how is liquid smoke produced?
controlled burning of wood chips condensed into solids or liquids and then dissolved in water. toxic and unhealthy smoke condensates are removed from the solution.
what is the preservative action of pickling/marinating?
vinegar lowers pH and thereby retards bacterial growth. 15% acid is needed to completely stop bacterial growth, in vinegar 6% means most fish products are only temporally preserved. pickled products with 3% acetic acid can be stored chilled several months.
how is irradiation used for preservation?
in sweden only herbs can be irradiated. gamma-rays kill vegetative bacteria. unsaturated FA are vulnerable, irradiation can initiate autooxidation. if oxygen is present high levels of hydroperoxides are formed.
how is nitrite used for preservation?
pork is injected with pickling brine containing salt and sodium nitrate, stored in brine and smoked. salt will eventually get evenly distributed in the muscles
how does nitrite inhibit clostridium?
inhibits enzyme in energy metabolism of anaerobes such as clostridium
when are cancerous substances formed in cured meat?
amines react with nitrite to form N-nitroso compounds. secondary amines from m.o. activity, primary amines in protein a.a. removes available nitrite. N-nitroso compounds when heated forms volatile compounds linked to increased risk of colorectal cancer. ascorbic acid inhibits nitriso compound formation.
