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S K Tamminga

Publications and source records attributed to S K Tamminga.

8 recordsLinked to original sources
PubMed1982

[Microbiological studies of beef tartar].

Two hundred lots of 'filet américain' (a mixture of minced meat, acid sauce, condiments, salt, etc., meant to be eaten raw) were sampled from retailers and examined for several types of micro-organism; 185 lots had been prepared by the retailer, fifteen on an 'industrial' scale. Pork had been used in seventy-three lots (including fourteen 'industrial' lots); beef was present in all lots, horse meat in none of them. On the whole, the bacterial state of the meats in which pork had been used was found to be considerably inferior to that of samples not containing this ingredient. The aerobic bacterial count and number of yeasts, as well as Enterobacteriaceae and group D. streptococci were at least 10 times higher on an average in this case than they were in lots not containing pork. In the case of Lactobacillus, Staphylococcus aureus and Clostridium perfringens the picture was similar, though the counts of the two lastnamed species were smaller. Salmonella was detected in 84 per cent of the pork-containing lots and in 13 per cent of the other lots. For Yersinia enterocolitica, these figures were 44 per cent and 5 per cent, and for Campylobacter fetus, subsp, jejuni 18 per cent and 6 per cent. The pH varied from 5 to 6. Lots containing pork averaged a higher pH. Addition of acid sauce had only a slight effect on pH levels. A number of these results were related to each other. It is concluded that the use of raw pork in meat products meant for raw consumption should be avoided.

Animals↗
PubMed1982

Microbiological studies on hamburgers.

One hundred and eighty-two raw, 112 pre-cooked and 750 cooked hamburgers composed mainly of beef or beef and pork were subjected to microbiological examination.Raw hamburgers gave total bacterial counts from 10(6) to 10(8) per g, counts of Enterobacteriaceae from 10(4) to 10(6) per g, of Escherichia coli from 10(3) to 10(5), of group D streptococci from 10(2) to 10(4), of Staphylococcus aureus from 3 to 10(2) and of Clostridium perfringens less than 10 bacteria per g. Of the samples, 32% contained salmonellas; the highest most probable number was 10(2) per g but most estimates were below 1 per g. Corresponding figures for the pre-cooked samples were 2-3 log cycles lower, and only one sample contained salmonella. Yersinia enterocolitica was not isolated from any raw or pre-cooked sample.Three hundred and ninety-five of the cooked hamburgers were prepared by grilling raw hamburgers for between 2 and 5.5 min. These gave total bacterial counts from 10(5) to 10(7) per g, and counts of Enterobacteriaceae from 10(2) to 10(5) per g. Of the samples, 9.4% contained salmonellas, always in numbers below 1 per g. The remaining 355 cooked hamburgers were prepared from samples pre-cooked for 10 min at 80 degrees C. Some were grilled and some fat fried. The total bacterial counts were from 10(3) to 10(5) per g, and counts of Enterobacteriaceae below 10(2) per g. Salmonellae, again in small numbers only, were recovered from 3.5% of samples.When hamburgers were artificially contaminated with Salmonella typhimurium it took 5.5 min on a commercial grill, 2.25 min frying in a frying pan and 1.75 min on a household grill to reliably reduce the salmonella count one hundredfold. This means that at many vending places hamburgers are often cooked for too short a time.D-values were determined for S. typhimurium in hamburger meat at 50, 55, 60, 65 and 70 degrees C, these values were 7.1, 5.1, 1.2, 0.9 and 0.6 min respectively. It can be concluded that the heating action in the centre of the hamburgers will take place more slowly than in the hamburger as a whole, and that the time between cooking and consumption is very important in reducing the microbial load to acceptable levels.Pre-cooking (10 min at 80 degrees C in a water bath) gives a reduction in the numbers of salmonella of about 4 x 10(3), after which cooking gives a further reduction as mentioned above.

Animals↗
PubMed1982

Microbiological sampling of towels: comparison of 7 methods.

Pull-out roller towels were infected with bacteria and examined with 5 non-destructive methods. In addition to three traditional methods, the agar contact method (A), the swab method (S) and the tape method (T), two lesser known methods have been applied: the rinsing box method (R), new developed in the laboratory, and the filter method (F). In the first (R), the towel is fixed between the lid and the cup of a metal box containing a rinsing liquid; shaking the box completes the test. In the second (F) the liquid is forced through the towel by vacuum. In both experiments the rinsing liquid is tested for contamination. Destructive methods, mainly with a peristaltic blender ("stomacher") (P) or rotary mixer (M), were used as reference for calculating ratios of recovery. With the methods A, S and T, a low ratio of recovery, resp. 5, 10 and 2%, was obtained for Escherichia coli and Staphylococcus aureus. With method R, ratios for the two species were 60-90%, and also for a Micrococcus species and for spores of Bacillus subtilis. With method F the ratio for E. coli and Micrococcus sp. was even slightly higher than 100%. Recovery with method M was about the same as with P. It is concluded that the rinsing box method as well as the filter method are well suited to the purpose of microbiologically testing towels; the lower recovery of the first is compensated by its simplicity.

Bacteria↗
PubMed1978

The hygienic quality of vegetables grown in or imported into the Netherlands: a tentative survey.

Samples of 61 home grown and 199 imported vegetables of different varieties were examined for Escherichia coli, faecal streptococci and, when E. coli was present, for salmonellas. Eleven per cent of samples contained greater than 10(4) E. coli per 100 g, and 14% greater than 10(6) faecal streptococci per 100 g. Salmonellas were isolated from 23 out of 103 samples examined. Salmonellas were isolated from 8% of 76 samples with E. coli less than 10(4)/100 g, but from 63% of 27 samples with E. coli exceeding 10(4)/100 g; from 6% of 65 samples containing less than 10(6) faecal streptococci/100 g but from 51% of 37 samples containing more than 10(6)/100 g. S. typhi was isolated from one sample of vegetables imported from the tropics. To our knowledge this is the first isolation of S. typhi from food in the Netherlands. Products from tropical countries were found to present the highest level of contamination. The hygienic quality of Dutch products is sometimes inferior to that of similar imported products, although the different seasons of sampling may have influenced the result. For the prevention of risk to the consumer of vegetables, good kitchen hygiene would appear to be the most important factor.

Escherichia coli↗
PubMed1977

Survival of Salmonella eastbourne and Salmonella typhimurium in milk chocolate prepared with artificially contaminated milk powder.

Milk chocolate mass containing salmonellas was prepared by mixing artificially contaminated milk powder with the other ingredients at a temperature of about 40 degrees C. From this mass bars were made. Two series were prepared, with S. eastbourne and S. typhimurium respectively. The number of surviving salmonellas was counted after various periods of storage, up to 19 months. S. eastbourne was reduced in numbers during 19 months from an initial count of ca. 3 x 10(4) to ca. 3 x 10(2) per 100 g of chocolate. S. typhimurium died off more rapidly, and was not detectable in about 55 g after 15 months, in spite of an initial count of ca. 10(5) per 100 g.In these experiments the salmonellas in the milk powder had had to survive the spraying procedure and the adverse conditions in the dried powder. This may be the reason why S. eastbourne showed a distinctly better survival on storage than the same serotype showed in previous experiments in which the organism was added as a broth culture to the chocolate mix. With S. typhimurium, however, such a difference was hardly detectable.Possible explanations of these results are discussed.

Animals↗
PubMed1976

Survival of Salmonella east bourne and Salmonella typhimurium in chocolate.

Experiments were carried out to assess the reduction rate of two salmonella strains (S. eastbourne and S. typhimurium) in chocolate bars. After artificial contamination of chocolate, after 'conching', with about 10(6) S. eastbourne/g. this organism was still recovered after 9 months storage. The strain of S. typhimurium was less resistant. Both serotypes died off more rapidly in bitter chocolate than in milk chocolate. After contamination with a smaller dose (about 10(3)/g.) with these two serotypes, similar differences were observed.

Cacao↗