Inactivation of Bacillus spores in reconstituted skim milk by combined high pressure and heat treatment.
OBJECTIVE
To determine the resistance of a variety of Bacillus species spores to a combined high pressure and heat treatment; and to determine the affect of varying sporulation and treatment conditions on the level of inactivation achieved.


RESULTS
Spores from eight Bacillus species (40 isolates) were high pressure-heat treated at 600 MPa, 1 min, initial temperature 72 degrees C. The level of inactivation was broad (no inactivation to 6 log10 spores ml(-1) reduction) and it varied within species. Different sporulation agar, high pressure equipment and pressure-transmitting fluid significantly affected the response of some isolates. Varying the initial treatment temperature (75, 85 or 95 degrees C) shifted the relative order of isolate high pressure-heat resistance.


CONCLUSIONS
The response of Bacillus spores to combined high pressure-heat treatment is variable and can be attributed to both intrinsic and extrinsic factors. The combined process resulted in a high level of spore inactivation for several Bacillus species and is a potential alternative treatment to traditional heat-only processes.


CONCLUSIONS
Sporulation conditions, processing conditions and treatment temperature all affect the response of Bacillus spores to the combined treatment of high pressure and heat. High levels of spore inactivation can be achieved but the response is variable both within and between species.
Scurrah
K J
KJ
Food Science Australia, North Ryde, NSW, Australia. katherine.scurrah@csiro.au
Robertson
R E
RE
Craven
H M
HM
Pearce
L E
LE
Szabo
E A
EA
D000818:Animals; D001407:Bacillus / Q000502:physiology*; D002417:Cattle; D005516:Food Microbiology; D005519:Food Preservation; D006358:Hot Temperature; D007218:Industrial Microbiology; D008892:Milk; D011312:Pressure; D013171:Spores, Bacterial; D013242:Sterilization