Processes applied to foods Effect on microorganisms Impact on food safety Impact on length of shelf life due to
spoilage
Vegetative bacteria (either
spoilage or pathogenic), and
mould spores and yeasts
Bacterial spores (cause spoilage or
food poisoning depending on type)
Washing of raw materials e.g.
plant material
Numbers present are reduced Numbers present are reduced May improve food safety by physically reducing
pathogenic bacteria present but levels may increase
if the water is poor quality, not changed frequently,
or if too great a volume of fresh produce is washed
at the same time
Variable. Washing may damage surfaces
which would allow microbial growth and
decrease shelf life
Cooking – includes baking Numbers present are reduced to
very low levels
No decrease in numbers and the process
may activate germination of the spores
Vegetative pathogenic bacteria inactivated using a
validated process
Spores will survive and may germinate to make the
food unsafe if it is not consumed or cooled
immediately
Some but not all pre-formed bacterial toxins will be
inactivated
Extended (providing that cooling is
managed), unless spores are able to
germinate and grow post-cooking or baking
Cooling of cooked foods Minimal reduction in numbers Potential for spores to germinate and grow
if cooling is slow or uncontrolled
Spore-forming pathogenic bacteria will germinate if
cooling is not managed correctly and the food may
become unsafe
Decreased if cooling is not managed
correctly and any spore-forming bacteria
present germinate
Pasteurisation of liquids or
solids
Numbers are reduced to low levels No decrease in the number of spores and
may be activated
Significant improvement provided that the time and
temperature applied is appropriate and cooling
managed correctly
Extended provided that cooling is managed
correctly
UHT / aseptic processing Inactivates most vegetative
bacteria and yeasts/moulds
Inactivates most spores except for a few
heat resistant spoilage types (however
these are usually unable to grow in the
anaerobic environment at ambient
temperatures in the container)
Foods become low risk Significant extension
Canning and retorting Inactivates most vegetative
bacteria and yeasts/moulds
Inactivates most spores except for a few
heat resistant spoilage types (however
these are usually unable to grow in the
anaerobic environment at ambient
temperatures)
Foods become low risk Significant extension