Natasha Barrett1, Alistair S. Grandison2, Michael Lewis2
1Department of Food Science and Technology, University of Reading, UK
2Department of Food Science and Technology, The University of Reading, PO Box 226, Reading, RG6 6AP, UK
Tóm tắt
The lactoperoxidase system is a naturally occurring antimicrobial
system
found in milk, with lactoperoxidase, thiocyanate and hydrogen peroxide
as its
components. The keeping quality of milk pasteurized at 72°C for 15
s was found to
be better than that of milk heated at 80°C for 15 s. This agrees with
previous findings
and is usually attributed to heat shocking of spores. However, complete
deactivation
of lactoperoxidase occurred at 80°C–15 s, whereas at 72°C–15
s residual lactoperoxidase
activity was ∼70%, which may provide an alternative explanation.
Higher levels of hypothiocyanite (the major antimicrobial agent produced
by the
lactoperoxidase system) were also detected in milk processed at 72 than
at 80°C,
which supports the theory that the lactoperoxidase system has a role in
the keeping
quality of pasteurized milk. Of all the methods evaluated, titratable acidity
and
alcohol stability gave the most consistent estimates of keeping quality,
while
dissolved oxygen was a good indication of the onset of spoilage. Lactoperoxidase
activity decreased with temperature more rapidly between 70 and 80°C
than is usual
for an enzyme over a 10 deg C range.
