Parasitological and selected microbiological safety aspects
of Nham (Thai-style fermented pork sausage) were evaluated. Pork
meat from pigs experimentally infected with Trichinella spiralis
was divided into 4 portions; 3 portions were frozen at -23°C for
12, 18 and 24 hours before they were made into Nham. The formula
for fermented sausage included 3% w/w NaCl and garlic, 0.015% each
of NaN0₂ and NaNO₃, and either 1.0 or 1.5% w/w commercial starter
culture. Fermentation was at 30°C for 96 hours. The higher level
of starter culture resulted in faster acid production but no
difference in the maximum number of lactic acid bacteria attained.
Infected pork, after being frozen for 24 hours, was still found to
cause a low level of parasitism. However, the corresponding
fermented samples were noninfective. Use of 1.0% starter culture
and 12 hours freezing of meat prior to grinding rendered trichinae
larvae noninfective after 2 days of sausage fermentation.
Staphylococcus aureus (10³ cells per g) and Escherichia coli
(10⁴ cells per g) were introduced into the ground pork in a series of experiments. Starter culture levels used were 0.75% and 1.5%
by weight. Fermentation without starter culture stabilized the
numbers of E. coli but permitted slow multiplication of S. aureus.
Adding starter culture at either level increased the rate of acid
production during the initial days, resulting in a faster drop in
pH and a decline in numbers of both S. aureus and E. coli. After
36 and 48 hours, viable S. aureus were not recovered from products
with 1.5% and 0.75% starter culture, respectively. E. coli disappeared
from sausages with 1.5% starter culture after 96 hours but
persisted at low numbers when the lower level of starter culture
was used.
The rapid direct plating technique (RPT) for enumeration of
E. coli was compared to the two standard methods generally used:
plating on Violet Red Bile Agar (VRBA) and Host Probable Number
(MPN). Total coliforms from 43 fermented pork sausages were
enumerated. The RPT gave data highly correlated to those from VRBA
but with a significantly lower correlation to MPN. The regression
line of loglO coliform counts from the RPT and VRBA had a slope of
0.76 and an intercept of 0.98. The MPN assay gave significantly
higher (P=0.05) numbers than either the VRBA or the RPT. / Graduation date: 1986
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27229 |
| Date | 29 April 1986 |
| Creators | Petchsing, Urairatana |
| Contributors | Woodburn, Margy |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
Page generated in 0.0018 seconds