This study was designed to determine the survival of Vibrio
parahaemolyticus in salted oysters as prepared in Korea. Three
levels of salt concentration were included; 3.0%, 6.8%, and 10.6%
of the weight of the raw oysters. Two methods were used to inoculate
the products, surface-inoculation and injection into the oysters,
which were then held at 18°C. Multiplication of V. parahaemolyticus
(Japanese strain T-3765-1) did not occur in the salted oysters, except
for a slight increase in numbers after 24 hours from surface-inoculated
samples with 3.0% salt and all samples of injected
oysters. The samples with the higher salt concentrations showed
longer survival of the organisms. Numbers of survivors in surface-inoculated
oysters were markedly reduced within three days; the
samples of injected oysters did not show reduced numbers in this
period. There were more survivors from the injected samples over the storage period than from the surface-inoculated samples. No viable
cells were observed after seven days from the surface-inoculated
samples with 3.0% salt and the injected samples with 3.0% salt, after
eight days from the surface-inoculated samples with 6.8% salt, after
nine days from the injected samples with 6.8% salt, and after 11 days
from the injected samples with 10.6% salt. A small number of V.
parahaemolyticus were recovered from the surface-inoculated samples
with 10.6% salt after eight days, the last testing period for these
samples. The results of pH measurement suggested that the samples
with higher salt concentration may have prolonged survival of V. parahaemolyticus
through the effect of the higher pH value. An analysis
of variance revealed a significant difference (5% level) in recovery
between a modified isolation medium (Twedt and Novelli) and
thiosulfate-citrate-bile salts-sucrose agar. Salt concentrations of
3.0%, 6.8%, and 10.6% slightly reduced the total bacterial counts
after three days from the two lots of oysters used for the surfaceinoculated
samples and further reduction was observed after seven
days; reduction in numbers was not detected within 8 or 11 days from
the two lots used for the injected samples. The latter two lots had
much lower plate counts at the beginning of the experiment. No
relationship was found between pH and total bacterial counts on the
salted oysters. / Graduation date: 1973
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/26940 |
| Date | 07 May 1973 |
| Creators | Ro, Sookja Lim |
| Contributors | Woodburn, Margy |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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