Multiple species cultures, including 2 strains of Streptococcus thermophilus and Lactobacillus acidophilus NCFM plus 1 strain each of Bifidobacterium longum and Lactobacillus casei, were used to make yogurt-like products. The lactobacilli and bifidobacteria were tested for growth in the products and subsequent viability during refrigerated storage. During fermentation, L. casei Com-5 actually declined in numbers, while L. casei E5 and E10 increased about 2 fold. Numbers of B. longum S9 increased about 3 fold while B. longum Com-4 did not increase. During storage, L. acidophilus NCFM appeared stable in all mixtures and both strains of bifidobacteria decreased. Lactobacillus casei E5 and E10 were more stable than was L. casei Com-5.

Cells of a strain of Lactobacillus lactis selected for ability to produce hydrogen peroxide were added to Trypticase soy broth (TSB) containing Escherichia coli O157:H7 to determine if L. lactis was antagonistic towards the E. coli during storage at 7 degrees C for 7 days. E. coli was enumerated on violet red bile agar. Three strains of E. coli O157:H7 (43894, 43890, and 35150) were evaluated. Control samples containing no L. lactis did not show significant declines in numbers of E. coli during the 7 days of storage. however, samples inoculated with at least 5.0 x 10(7) L. lactis per ml exhibited significant declines in numbers of E. coli after only 3 days of storage for all strains. Samples inoculated with fewer L. lactis displayed vary effects on E. coli O157:H7 depending on the strain E. coli O157:H7 strain 43894 appeared to be the most resistant to the antagonistic action of the L. lactis. Interaction experiments in the presence of catalase indicated that hydrogen peroxide was the main factor responsible for the inhibitory action produced by the lactobacilli. Raw chicken breast meat inoculated with E. coli O157:H7 strain 43894 plus the cells of L. lactis and stored at 5 degrees C exhibited declines in numbers of the pathogen, whereas those inoculated only with the E. coli exhibited no declines during storage at 5 degrees C.

Improved techniques for culturing and enumerating Campylobacter jejuni were developed. Parameters included (1) growth vessel type, (2) growth atmosphere, (3) incubation time, and (4) frequency of subculturing. Improved growth and consistent morphology were obtained using a tissue culture flask compared with an Erlenmeyer flask or a test tube as well as exposure to modified atmosphere (10% CO 2 , 85% N 2 , and 5% O 2 ). When cultures of C. jejuni were incubated more than 24 h, transformation to the coccoid increased, and fewer colony-forming units were detected. Excessive subculturing (>2 times) resulted in increased formation of coccoid forms. Decreased concentrations of colony-forming units of C. jejuni commonly attributed to the production of a viable, nonculturable form also may be due to cellular clumping. These techniques should alleviate difficulty and reduce variation when working with Campylobacter.

Four strains of Bifidobacterium longum were grown at pH 5.5, 6.0, 6.5 and 7.0 and evaluated for survival and bile tolerance during frozen and subsequent refrigerated storage in milk. There were no reductions in cell numbers following initial freezing. There were effects for strain, pH and storage for three of the four strains of B. longum during storage at 58C in milk. Bifidobacterium longum S9 was more stable than other strains in that no losses occurred, regardless of pH during growth. Results were variable for strains II, III, and ATCC 15707 grown at the various pH levels. Bifidobacterium longum S9 did not lose bile resistance during refrigerated storage as the other three strains did.

Whole watermelons were dipped in water or hypochlorite solution, and then cut with a knife or water jet. Cut melons were stored at 4C for up to 14 days and tested for color, texture, pH, soluble solids, weight loss, and bacterial counts. Sanitizing dip and cutting method had no @ect on pH or soluble solids. Sanitizing dip had no @ect on color, texture, or weight. Water jet-cut melon pieces were darker, knife-cut pieces were sofrer and showed higher weight loss. Aerobic plate counts for all treatments increased by up to 5 log cycles during storage. A precut sanitizing dip resulted in about a two log cycle reduction in initial aerobic and about a one log cycle reduction in inirial colifom bacterial counts. ' Approved for Publication by the Director, Oklahoma Agricultural Experiment Station. This ' Contact information for the corresponding author. TEL: 405-744-7573; FAX: 405-744-6313; research was supported in part under project H-02369. EM AIL: mcglynn@okstate . edu Journal of Food Quality 26 (