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At least 19 recordsLinked to original sources
PubMed1962

Quantitation of Clostridium perfringens in foods.

A procedure is described for identifying and enumerating Clostridium perfringens in foods by means of a simplified agar plating method, followed by confirmation of black colonies in tubes of motility-nitrate medium and sporulation broth. The test is routinely completed within 48 hr. Under experimental conditions, the procedure has been used to quantitatively recover various levels of C. perfringens contamination in a variety of foods and has recovered as few as ten C. perfringens per g without interference from food constituents and associated flora. Under practical conditions of field application, the method has been used to investigate five food-poisoning outbreaks, and C. perfringens was implicated as the etiological agent in two of these outbreaks.

Agar↗
PubMed1962

Thermophilic aerobacillus from banana puree.

Bacillus licheniformis was isolated from spoiled cans of banana purée. The isolate proved to be a thermophilic gas former which causes soft swell in cans of nonacidic food. Thermal resistance of the spores was examined. Heat treatment for at least 90 to 100 sec at 230 F was found necessary to assure commercial sterility of canned banana purée at pH 4.5.

Bacillus↗
PubMed1962

Psychrophilic and mesophilic fungi in fruit-filled pastries.

Surveys of the mold flora of frozen blueberry and cherry pastries were undertaken. Molds were enumerated by preparing pour plates of the blended product and incubating the plates at 0, 5, 10, and 20 C. In this manner, the total fungal content of the product could be ascertained from the 10 and 20 C plates, and the psychrophilic fungal population was represented by those fungi which grew at 0 and 5 C. The pastry portion, or crust, of the blueberry material was sampled separately from the filling portion. Certain differences in fungal flora were apparent. Aureobasidium pullulans was the dominant fungus in crust at all temperatures of isolation. However, Penicillium thomii proved to be the most common mesophilic fungus in the filling portion, and A. pullulans was the most common psychrophile in the filling. Aspergilli were quite common in the crust, but, in general, were absent from the fruit filling. Cherry pastries had a much smaller total fungal flora than did the blueberry product. However, A. pullulans again was the most prevalent fungus in cherry pastries at all temperatures of isolation. Certain differences in fungal flora were apparent in the two fruit products. Phoma spp. were almost completely absent in blueberries, but represented the second most common fungus in cherry pastries. Blueberry filling had 440 psychrophilic fungi per gram of sample (at 0 C), blueberry crust had 65 per gram, and cherry pastries had 77 per gram.

Ascomycota↗
PubMed1961

Detection and enumeration of fecal indicator organisms in frozen sea foods. II. Enterococci.

Consistently high recoveries of enterococci as compared to the low numbers of coliforms obtained from the same samples of frozen sea foods are indirect evidence that enterococci are better indicators of contamination in such foods. The use of azide dextrose broth, modified by the incorporation of bromthymol blue, and of ethyl violet azide broth as presumptive and confirmation tests, respectively, were found to be highly specific for the detection and enumeration of enterococci in these samples. Tetrazolium agar medium, when used as a third step after the confirmation test, provides a reliable differentiation of Streplococcus faecalis types from other group D streptococci. A simple procedure is described for further identification of S. faecalis varieties and other enterococcal species. Incidence of biotypes within certain species is noted and relationships of these subgroups to the organisms described by other workers is discussed. The striking resistance of all group D streptococci to dihydrostreptomycin and polymyxin B seems to offer promise for evolving a new selective medium for these organisms.

Culture Media↗
PubMed1961

Time-temperature effects on Salmonellae and Staphylococci in foods. III. Thermal death time studies.

Thermal death time studies were conducted at 5 F intervals from 130 to 150 F with strains of salmonellae and enterotoxigenic staphylococci. Heat-resistant Salmonella senftenberg strain 775W, Staphylococcus aureus strains 196E and Ms149, and non-heat-resistant Salmonella manhattan were studied in custard, chicken à la king, and ham salad. The F(140) values (minutes of exposure at 140 F required to effect 100% destruction) were as follows: S. senftenberg 775W in custard 78, and chicken à la king 81.5; S. manhattan in custard 19, and chicken à la king 3.1; S. aureus 196E in custard 59, and chicken à la king 47; S. aureus Ms149 in custard 53, and chicken à la king 40. The end points of survival-kill at all the test temperatures for both salmonellae and staphylococci in ham salad were considerably less than for the other foods studied.D(140) values (minutes of exposure at 140 F required to effect a 90% reduction in numbers) were also calculated from the data and presented. Values for z(F) and z(D) (slope of the thermal-death-time and decimal-reduction-time curves) are also presented and discussed in relation to type of food, organism, and temperature. These data indicate that heating perishable foods of the type studied to 150 F and holding every particle of food at this temperature for at least 12 min reduces 10 million or less salmonellae or staphylococci per gram to nondetectable levels. The same degree of destruction is achieved in similarly contaminated foods when held at 140 F for 78 to 83 min. On the basis of the calculation procedures employed, it is estimated that 45-min exposure at 140 F would be necessary to reduce 1,000 organisms per gram to nondetectable levels.

Animals↗
PubMed1961

Isolation of Salmonellae from food samples. IV. Comparison of methods of enrichment.

A comparison of various methods of enhancing frequency of Salmonella isolations revealed that inoculation of a second enrichment broth, with culture from the first, was no improvement over the single direct enrichment method. It was inferior to centrifugation. Selenite was observed to produce more positive isolations at 48 hr than at 24. No change occurred in tetrathionate. Reconstitution of dried albumen with water produced a significant increase in isolations over direct inoculation of enrichment broth in the case of tetrathionate but not selenite broth.Pre-enrichment in lactose broth before inoculation of enrichment media was vastly superior to reconstitution in water for both enrichment broths. A comparison of results obtained using dulcitol, mannitol, lactose and carbohydrate-free purple broths in pre-enrichment indicated that the carbohydrate added was immaterial.

Culture Media↗