Food preservation Flashcards
The binding ability of sugars, salt and starches
High
The binding ability of cellulose
weak
The binding ability of proteins and lipids
low
Aw that bacteria needs to grow
> 0.91
Aw that moulds need to grow
> 0.61
What does decreasing the Aw do
decreases/inhibits growth rate
increases the lag phase
two mthods of drying
physcial removal
binding of water using sugars and salts
how does pH effect microrganisms
effects growth and metabolism
pH range of bacteria grow
3-9
pH range of yeast growth
1.5-8.5
pH range of mould growth
1.5-11
name of micro-organism that requires O2
aerobes
name of micro-organisms that don’t require O2
anaerobes
what are facultative micro-organisms
can grow in the presence or absence of O2
Intrinsic factors that affect microbe growth
nutrients, water activity and pH
extrinsic factors that affect microbe growth
Temperature, humidity and gaseous atmosphere
example of aerobe
most common bacteria
example of anaerobe
clostridium Botulinum
why does a dried apricot have high shelf stability even though it has 20% moisture content compared to salami which is 10%
water is bound to sugars so it cant be utilised by bacteria
objectives of preservatives
extend shelf
retain nutritive value
ensure safety
3 classes of preservatives
traditional
synthetic
bio preservatives
sugar, salt, organic acids, alcohol and wood smoke are all examples of what kind of preservatives
traditional
examples of synthetic preservatives
sorbic acid, lactic acid, benzoic acid all of which can be natural
nitrites, hydrogen peroxide, sulphites
What are bio preservatives
chemical produce by a micro-organism that can prevent the growth of other micro-organisms
(chemical warfare)
nisin and Pimaricin are examples of what kind of preservative
Bio Preservatives
