food spoilage Flashcards
temperature ranges for micro organisms
mesophiles
psychrophiles
thermophiles
mesophiles
25-45º
psychrophiles
-5-20º
thermophiles
above 45º
microaerophilic
grow in a reduced oxygen environment
conditions necessary for the growth of mould
food: most are saprophytes
warmth: most are mesophiles, inactivated by freezing, stunted growth below 15º
oxygen: aerobic
pH: slightly acidic 4-6
asperigillus
saprophytic mould
black or green
reproduces asexually by:
mycelium spread out and establish on food source
hyphae grow upwards out of mycelium
conidia develops at head of hyphae
when ripe, conidia burst, releasing spores into the air to find suitable conditions for new mould growth
main causes of food spoilage
loss of moisture
micro organisms
enzyme action
toxic food poisoning bacteria
clostridium botulinum
clostridium botulinum
characteristics:
rod shaped
gram positive
forms spores
sources:
soil, decaying fruit/veg, untreated water
environmental factors:
anaerobic
20-27º
destroyed at 121º for 15mins
high risk foods:
low acid canned foods
vacuum packed foods
incubation:
12-36hrs
symptoms:
blurred vision, diarrhoea, paralysis, death
infectious food poisoning bacteria
salmonella
salmonella
characteristics:
rod shaped
gram negative
non spore forming
sources:
gut of humans and animals
unwashed hands
environmental factors:
facultative
37º
neutral pH
high risk foods:
poultry
eggs
symptoms:
nausea and vomiting
abdominal pains
fever
incubation:
12-36hours
duration of poisoning:
1-7days
toxic food poisoning
caused by eating food contaminated with waste products, exotoxins, released by bacterial cells
difficult to destroy
eg clostridium botulinum
infectious food poisoning
caused by eating foods contaminated with pathogenic bacteria which produce endotoxins within their cells, released when they die
easily destroyed with correct cooking and reheating
eg salmonella
