The efficacy of warm (20°C) and hot (55°C) acetic, citric and lactic acid sprays on survival of Escherichia coli O157:H7 on raw beef was determined. Fresh, raw beef sirloin tips were sliced into ca. 1-cm slices with a sanitized slicer. Discs (5-cm diameter, ca. 25-g) were then taken from internal areas of each slice and inoculated with a 5-strain mixture of E. coli O157:H7 such that final populations on beef samples were 103 or 106 CFU/g. After standing for 15 min, each inoculated disc was sprayed with 1 mi of 0, 0.5, 1.0 and 1.5% of each acid at 20 or 55°C using an atomizer. Acid-treated meat samples were allowed to dry for 15 min and held at 5°C for up to 13 days in sterile plastic pouches. Escherichia coli O157:H7 was acid tolerant, and acids did not differ appreciably in their lack of antimicrobial activity on E. coli O157:H7. For example, reductions in populations differed by <0.3 logl0 CFU/g immediately after treatment and < 0.5 logl0 CFU/g after 13 days incubation, compared to untreated Controls. None of the acid treatments appreciably reduced E. coli O157:H7 on beef samples nor were any of the acid treatments judged effective for practical uses.

Refrigerated ready-to-eat foods are becoming increasingly popular but are often vulnerable to contamination and subsequent growth by psychrotrophic foodborne pathogens. Consequently, there is a need for additional methods to assure the safety of these foods. Beef slices prepared from roasted whole sirloin tips were used in the study. Nine plant extracts were evaluated for ability to inhibit the growth of two psychrotrophic pathogens (Aeromonas hydrophila and Listeria monocytogenes) in refrigerated cooked beef. Results indicated that only eugenol (clove extract) and pimento extract significantly inhibited the growth of A. hydrophila and L. monocytogenes. However, L. monocytogenes was not as sensitive as was A. hydrophila to both treatments, especially to pimento extracts. These results suggest that plant extracts might be useful as an antimicrobial in cooked ready-to-eat meat.

No abstract

The ability of F. auruntiacum to reduce the aflatoxin B1 (AFBJ concentration was determined by inoculating about lo9 stationary phase cells in AFB,-contaminated phosphate buffer (PB). non-defatted peanut milk (NDPM) and partially defatted peanut milk (PDPM). The AFBl concentration and cell populations were determined periodically throughout the incubation (30°C). After 24 hr, the concentration of AFB, decreased about 40% in PB, 23% in NDPM and 74% in PDPM. Viable cell population decreased less than one log,, CFU/mL in all liquids but increased about 0.8 log,0 unit in control PDPM. AFB, recovery increased about 30% in proteolysed PDPM but proteolysis had no effect on recovery from NDPM.both non-defatted and partially defatted peanut milks were subjected to proteolysis to determine the effect of intact proteins on efficiency of AFB, removal. All experiments which involved AFBl were done in a dark environment.Maintenance of culture and APB, Flavobactetium aurantiacum NRRL B-184 was used throughtout this study. Cultures were maintained on trypticase soy agar (TSA, Difco) at 4°C. Cells were activated by two successive transfers in tryptictise soy broth (TSB, Difco) incubated at 30°C.Aflatoxin l3, (Sigma, St. Louis, MO) was prepared as a stock chloroform solution (5 mg/mL) and stored at -20°C until use.

This study was conducted to determine the influence of temperature and modified atmosphere appropriate for use with fresh produce on growth of Escherichia coli O157:H7. None of the gas mixtures tested (CO2/O2/N2: 0/5/95, 0/10/90, 5/10/85, 5/20/75, 10/5/85, and 10/20/70) significantly affected growth of this bacterium at 5, 10, and 20°C. Similarly, modified atmosphere did not significantly affect the tolerance of E. coli O157:H7 to 3% NaCl. E. coli grew at 10 and 20°C and survived at 5°C.