preservation

1Destroying or inactivating some/all microorganisms/enzymes

aHeat processing-effectiveness depends of pH >4.7 5hours,4.5-3.7 short,<3.7 very short

iSterilisation-kill everything.Inpack&ultrahigh t.(UHT)

For fruit 80C 3min for enzymes,food into clean containers,heated by steam.Long,microwaves cannot go through metal.UHT only for liquid.140C 5sec,costly

iiPasteurisation-kill most pathogenic high temp short time(HTST)72 15sec to avoid cooked flavour

birradiation-reduces nutritional value,no radiation for food

cchemical techniques-preservatives with E

dhigh pressure-acid food,5000atm,fresh taste

eAcid-either by microorganisms or ethanoic acid added(vinegar)weakly dissociated acids are better preservatives(sorbic,benzoic)

fSalt(curing)-meat in 25% NaCl,0.001%NaNO2 1%NaNO3 12 days,also smoked

gAntibiotics-bacteria might get resistant,only nisin allowed

hAntioxidants-reduce oxidation of fatty acids,vitamin E,C,propyl gallate.Synergists(citric acid)improves action by forming complexes with metals catalysing oxidation

2Creatin conditions that limit deterioration

aFreezing-reduces rate of growth,makes H2O unavailable

iBlast-30-40C,fast less cell damage

iiImmersion-cold salt+glycerol.cyrogenic when liquid N2 used

iiiFreezing by contact(plate freezer)-costly,only for fish etc

bDehydration-removal of 90% H2O,popular,freeze dried&heat dried

cPackaging-protects against accidents,physical changes(dehydration),uptake of moisture,oxidation of fats.Material can be impermeable.Modified atmosphere(25%CO2)keeps meat red