Tuesday, April 24, 2007
Pathogens Significance in dairy products
Salmonella
Salmonella is destroyed by pasteurisation, however it can be present in the
environment and can gain access to product after heat treatment. Initial source is
often birds and rodents, although occasionally present in the raw milk. Non-dairy
ingredients can be an important source of contamination.
Listeria
monocytogenes
L. monocytogenes is destroyed by pasteurisation. Its presence in heat-treated
products is due to post-pasteurisation contamination. L. monocytogenes is a
concern to the dairy industry as it can grow at 0ºC (refrigeration temperatures).
Staphylococcus.
aureus
S. aureus is destroyed by heat-treatment, however its toxins are heat stable, thus
control of growth of this organism prior to heat treatment is essential. However, S.
aureus does not grow well at low temperatures (i.e. refrigeration).
Bacillus cereus
Vegetative cells of B. cereus do not survive pasteurisation, however spores will
survive heat treatments. B. cereus is rapidly outgrown by gram-negative
psychrotrophs at refrigeration temperatures, but in their absence, B. cereus, if
present, may then be able to grow to high levels. This is a concern with extended
shelf-life chilled products, such as desserts.
Escherichia coli
E. coli is found in cattle and may enter milk through faecal contamination, however
E. coli is heat-sensitive and does not survive pasteurisation.
Campylobacter
spp.
Campylobacter spp. is destroyed by pasteurisation and its presence in milk
products is due to environmental contamination after heat treatment.
Campylobacter spp. are fragile organisms unable to grow in foods.
Yersinia
enterocolitica
Y. enterocolitica is destroyed by pasteurisation and its presence in heat-treated
milk products is due to environmental contamination after heat treatment. Y.
enterocolitica is able to grow in dairy products held at refrigeration temperatures
and therefore may be considered as a hazard in prolonged shelf-life products.
Enterobacter
sakazakii
E. sakazakii will not survive pasteurisation. Recontamination of powdered infant
formulae during manufacture is a risk. E. sakazakii cannot grow in a dry substrate,
but it can survive a long period of time and is a potential hazard when the powder
is reconstituted and held for long periods of time at favourable temperatures.
Contamination and subsequent growth may occur during reconstitution and
preparation.
I loved you at Tuesday, April 24, 2007
