PPI Spring Meeting 2001 - Abstract
Microbiology of Pickled Vegetables
Fred Breidt, Jr.
Department of Food Science, North Carolina State University
We have investigated the use of microbial interference (biocontrol)
to prevent the growth of bacterial pathogens in non-acidified
refrigerated pickles (NARPs). The use of a biocontrol culture
may be needed to ensure safety of NARPs with an extended shelf
life. Extended shelf life for NARPs was achieved by blanching
fresh cucumbers and with the use of ingredients (garlic oil, irradiated
spices) that have reduced microbial cell counts compared to typical
ingredients. Using this procedure, the shelf life of NARPs was
more than doubled.
A culture of Lactococcus lactis, previously isolated from sauerkraut,
was tested to determine the ability of this microorganism to grow
and become the predominant bacterial culture in NARPs during temperature
abuse or spoilage. This culture produces a bacteriocin, which
is an antimicrobial agent active against the human pathogen, Listeria
monocytogenes. Growth rate measurements have shown that salt
(NaCl) concentration is an important factor limiting the ability
of the L. lactis culture to predominate over indigenous
NARP microflora, including potential pathogenic cultures. We have
isolated and characterized more than 80 lactic acid bacteria naturally
present in NARPs, which may also serve as biocontrol agents for
this product. We have also investigated how bacteriophage (viruses
attacking bacteria) can affect lactic acid bacteria, such as the
microorganisms used for biocontrol, as well as starter cultures
for vegetable fermentations.
Understanding the microbial ecology of lactic acid bacteria in
fermenting vegetables, including the effects of bacteriophage,
may lead to safe, high quality, processed and fermented vegetable
products.
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