An Improved Procedure for the Enumeration of Campylobacter Jejuni and Campylobacter Coli in Foods

VARIABILITY OF MPN COUNTS FOR ESCHERICHIA COLI IN VACUUM PACKAGED MEATS. L.J. Harris· and M.E. Stiles, Department of Food Science, University of Alberta, Edmonton, Alberta. Escherichia coli was inoculated into irradiated ground beef, vacuum packaged and stored at 4°C for 7 days. Samples were taken at various time intervals and MPN counts were determined in EC broth (gas production from lactose) at 35 and 45°C. Colony counts were determined on Tryptic Soy Agar (TSA) and a range of selective media including Violet Red Bile Agar (VRBA) and Tryptone Bile Agar (TBA, for production of indole) also at 35 and 45°C. Consistent counts were obtained at 35 and 45°C on solid media compared with highly unreliable counts by MPN technique which differed by as much as 4 log cycles. Marked differences in the background microflora growing in the irradiated meats were noted. USE OF DNA PROBES IN ANALYTICALFOOD MICROBIOLOGY: CLONING AND CHARACTERIZATION OF LISTERIA MONOCYTOGENES-SPECIFIC SEQUENCES. P.I. Peterkin**, Bureau of Microbial Hazards, Health and Welfare Canada, Ottawa, Ontario, and E.S. Idziak, Deptartment of Microbiology, Macdonald College, Ste. Anne de Bellevue, Quebec. A Listeria monocytogenes genomic library was constructed and screened to determine which regions of the genome do not share sequence homology with the DNA of other Listeria spp. L. mOlJocytogenes DNA digested with restriction endonuclease BamHI was cloned into the plasmid pBR322 which was then used to transform Escherichia coli C600. Transformants grown and replicated on hydrophobic grid membrane filters were screened with L. monocytogenes DNA and with the DNA of other Listeria spp. The application of this work to the development of a DNA probe for the presence of L. monocytogenes in food will be discussed. AN IMPROVED PROCEDURE FOR THE ENUMERATION OF CAMPYLOBACTER JEJUNI AND CAMPYLOBACTER COLI IN FOODS. C.E. Park· and Z.K. Stankiewicz. Microbiology Research Division, Health Protection Branch, Health and Welfare Canada, Ottawa, Ontario. We searched for an efficient procedure of the enumeration of Campylobacter in foods. The study was carried out by comparing the following media for a three-tube MPN system: (a) Blaser's, (b) Butzler's, (c) Doyle's, (d) Preston, and (e) Modified Skirrow's. Each medium was used in four different states: (I) semisolid with lysed horse blood (5070), (2) semisolid without blood, (3) broth with blood, and (4) broth without blood. Various food samples were blended in Brucella-FBP broth and serially diluted in the same broth. One mL of each dilution was inoculated to the top of an MPN tube. The tubes were incubated at 42°C for 24, 48 and 72 h under the microaerobic condition. Modified Skirrow's agar was used for isolation. The highest counts of Campylobacter were obtained when Preston medium was used in semisolid form with blood after incubation at 42°C for 48 h. For raw milk, cysteine (50 mmoles IL) had to be added to inactivate the lactoperoxidase system which destroyed Campylobacter during the storage period. STUDIES ON THE EDIBLE MUSHROOM PLEUROTUS OSTREATUS. A.M. Martin and W. Manu-Tawiah. Department of Biochemistry. Memorial University of Newfoundland. St. John's, Newfoundland. Sphagnum peat moss was used as substrate in the growth of Pleurotus ostreatus mushroom in solid media. Untreated peat and treated peat, the treatment consisting in acid-hydrolysis with H 2S0 4 at 120°C, were used in the preparation of the spawn and in the actual production of mushroom fruit bodies. The acid-hydrolysed peat produced a better substrate for the mushroom growth. The results of these experiments are reported and compared with those reported for the growth of P. ostreatus in other solid media composition. EFFECT OF MEDIUM ON FERMENTATION PATTERNS OF COMMERCIAL WINE YEASTS. Jeff Anderson·· and Charles W. Nagel, Department of Food Science and Human Nutrition, Washington State University, Pullman, Washington. Studies were made of the growth response of six yeast strains in relation to ethanol, pH, and glucose in synthetic media (Yeast Nitrogen Base). Waedensville (Swiz.) and EC-I 118 strains were most tolerant to ethanol (8-10070) while pH (2.8-3.6) had no effect on growth. Chardonnay juice (25, 30, 35 Brix) was fermented with the yeasts Can. [nSf. Food Sci. Technol. J. Vol. 19, No.4, 1986

while following growth, viability, carbohydrate depletion and ethanol accumulation. Least growth and ethanol production was observed with the Chanson and Epernay strains. After 25 days, EC-lll8 and Waedensville strains had greater than 107 and less than 105 viable cells/mL respectively. IMPROVEMENT OF CANOLA SAUCE QUALITY WITH PURE CULTURE INOCULATION OF MOROMI. Araba A. Coleman· and B. Ooraikul, Department of Food Science, University of Alberta, Edmonton, Alberta. Quality of canola sauce produced in four weeks was improved by inoculation of pure cultures of Pediococcus halophilus, Torulopsis versatilis and Saccharomyces rouxii into moromi. The cultures were trained to grow at 30°C in media containing 18070 NaCl to produce cell counts of 107_10 8 CFU/mL before inoculation. P. halophilus was statically cultured in sodium acetate medium at pH 6.9, while S. rouxii and T. versatilis were grown by shaken culture in YM broth at pH 4.5. P. halophilus produced lactic acid in moromi which reduced its pH from 7 to 5, thereby stimulating ethanol production by S. rouxii. T. versatilis dominated latter stages of fermentation and produced 4-ethylguaiacol, 4-ethylphenol and 2-phenylethanol, principal aromas of mature sauce. SENSORY EVALUATION OF FROZEN CHICKEN. Sonia Campos, M.A.C. Moraes, Iracema O. Moraes·, C.A. Gasparetto, Adilma P. Scamparini, School of Food Engineering UNICAMP, Campinas, Brazil. Brazil has become a big exporter of frozen chicken and it is now important to establish a detailed sensory evaluation of this product. Frozen chickens at - 18°C, 20 from each of three different abattoirs were evaluated and analysed 30 days after slaughter. Samples were cooked in a microwave oven. Tests and measurements were performed with breast and leg muscles. Colour was measured on the muscle surface under skin and texture was measured with cubes of 1 cm. A panel specially trained was used for testing odor, flavor, juiciness and acceptance. Results for colour showed a wide scatter for red from one of the abattoirs. Flavour was classified as moderate either for white and dark meat. Texture showed a marked difference for the three abattoirs. Juiciness was excellent. SENSORY EVALUATION AND CHARACTERIZATION OF IMPORTED AND DOMESTIC HAVARTI AND SWISS CHEESES. C.M. Wilhelm·· and T.A. Watts, Department of Consumer Studies, University of Guelph, Guelph, Ontario. Sensory properties of two varieties of domestic and imported specialty cheese (Havarti and Swiss) were characterized by trained sensory panelists. Sensory attributes included aroma, appearance, colour, texture and flavour. Selected physical and chemical measurements were also made. For each variety of cheese consumer panels were conducted in Ontario and Quebec. Untrained panelists rated each of the sensory properties, including acceptance, for each variety of cheese. Relationships between sensory properties, objective analyses, and consumer acceptance of each cheese variety were examined. EFFECTS OF TERTIARY BUTYLHYDROQUINONE ON THE ACCELERATED STORAGE STABILITY OF CANOLA OILS. Zenia J. Hawrysh·, and Phyllis J. Shand, Department of Foods and Nutrition. University of Alberta, Edmonton, Alberta. The sensory (odor and flavor) and chemical characteristics of antioxidant treated canola oils subjected to accelerated storage conditions were determined. In Schaal storage tests, tertiary butylhydroquinone (TBHQ), at 100 and 200 ppm, was effective in retarding oxidative randicity. Addition of butylated hydroxyanisolel butylated hydroxytoluene, at 100 ppm each to oils did not improve storage stability. In fluorescent light tests (700 ft-c), all antioxidant treated canola oils were equally sensitive to light-induced oxidation. However, oils with 200 ppm TBHQ had diminished peroxide development following exposure to light. Correlation coefficients between odor and flavor intensity scores and chemical data were highly significant (p < .001). EFFECT OF DIET, SLAUGHTER WEIGHT AND OVEN TYPE ON THE QUALITY OF BEEF FROM BULLS. Zenia J. Hawrysh and Phyllis J. Shand·, Department of Foods and Nutrition, University of Alberta, Edmonton, Alberta. The effects of diet, slaughter weight and oven type on the cookInstitute Affairs / xliii