Abstract:
The presence of Bacillus sporothermodurans in retail UHT milk along with milk from
different points of a processing line was determined. The effect of chilling, preheating,
UHT, reprocessing and H2O2 individually and in combination on the survival
of B. sporothermodurans was also investigated in broth.
Design/methodology/approach - Standard plate counts were conducted for all milk
samples and isolates from UHT milk were characterised using PCR. BS vegetative
cells and spores in broth were subjected to various stresses encountered during UHT
processing of milk. Survival counts were conducted after all treatments.
Findings - B. sporothermodurans was detected in retail UHT milk packs from only
one processor. UHT treatment at 140 oC for 4s eliminated B. sporothermodurans in
broth. The combination of chilling and UHT was more effective in eliminating sporothermodurans spores than UHT treatment alone. H2O2 was also effective in
eliminating B. sporothermodurans spores after 15 min of exposure. The adopted real
time (RT) PCR with SYBR Green method was effective for the confirmation of B.
sporothermodurans.
Originality/Value - This research is the first to be conducted with regards to the
detection of B. sporothermodurans in UHT milk in South Africa and determining the
effect of UHT processing stresses on their survival. These results can be used to
design processing parameters so as to effectively eliminate B. sporothermodurans
spores during UHT processing. This research is the first in which RT PCR with
SYBR Green has been used to characterise B. sporothermodurans.
