The effect of pH reduction with acetic (pH 5.2), citric (pH 4.0), lactic (pH 4.7), malic (pH 4.0), mandelic (pH 5.0), or tartaric (pH 4.1) acid on growth and survival of Escherichia coli O157:H7 in tryptic soy broth with 0.6% yeast extract held at 25, 10, or 4؇C for 56 days was determined. Triplicate flasks were prepared for each acid treatment at each temperature. At 25؇C, populations increased 2 to 4 log 10 CFU/ml in all treatments except that with mandelic acid, whereas no growth occurred at 10 or 4؇C in any treatments except the control. However, at all sampling times, higher (P < 0.05) populations were recovered from treatments held at 4؇C than from those held at 10؇C. At 10؇C, E. coli O157:H7 was inactivated at higher rates in citric, malic, and mandelic acid treatments than in the other treatments. At the pH values tested, the presence of the organic acids enhanced survival of the pathogen at 4؇C compared with the unacidified control. E. coli O157:H7 has the ability to survive in acidic conditions (pH, Ն4.0) for up to 56 days, but survival is affected by type of acidulant and temperature.
The purpose of this research was to determine the survival of Escherichia coli O157:H7 when heated in ground turkey containing various additives and fat levels. D values and z values were determined for low (3%)- and high (11 %)- fat ground turkey with or without one of three additives: 8% NaCl, 4% sodium lactate, or a mixture of 8% NaCl, 4% sodium lactate, and 0.5% polyphosphate. Products inoculated with E. coli O157:H7 strain 204P were mixed, aseptically placed into thermal-death-time (TDT) tubes which were sealed and heated at 52, 55, 57 and 60°C. Survival was determined by enumeration on phenol red sorbitol agar, and D values were calculated by two methods. Mean D52 values ranged from 46.8 to 104.8 min; mean D55 values ranged from 7.7 to 27.2 min; mean D57 values ranged from 2.7 to 13.0 min; and mean D60 values ranged from 0.7 to 4.8 min. The greatest survival, as evidenced by higher (P < 0.001) D values, occurred in turkey containing the mixture of additives. The z values ranged from 6.09 to 4.08°C, and higher z values were obtained in turkey meat containing the additive mixture versus other turkey additive formulations. The additives evaluated enhanced survival of E. coli O157:H7 in cooked turkey meat as compared to turkey meat with no additives. In contrast to earlier reports, added fat did not enhance survival (P > 0.05). Product formulation should be a critical consideration when safe cooking processes are developed for ready-to-eat turkey products.
A steam pasteurization process (patent pending) has been shown to effectively reduce pathogenic bacterial populations on beef tissue and to significantly reduce naturally occurring bacterial populations on commercially slaughtered beef carcasses. The objective of this study was to determine the effectiveness of the steam pasteurization treatment for reducing bacterial populations at several anatomical locations on commerically slaughtered carcasses. Before and after pasteurization treatment (82.2 degrees C, 6.5-s exposure time), a sterile sponge was used to sample 300 cm2 at one of five locations (inside round, loin, midline, brisket, or neck). Eighty carcasses (40 before treatment and 40 after treatment) were sampled per anatomical location over 2 processing days. Before treatment, aerobic plate counts (APCs) were found to be highest (P < or = 0.01) at the midline (4.5 log10 CFU/100 cm2), intermediate at the inside round, brisket, and neck (ca. 3.8 log10 CFU/100 cm2), and lowest at the loin (3.4 log10 CFU/100 cm2). After treatment, APCs at all locations were reduced significantly (P < or = 0.01). The inside round, loin, and brisket had the lowest (P < or = 0.01) APCs (ca. 2.6 log10 CFU/100 cm2), whereas the midline and neck had APCs of 3.1 and 3.3 log10 CFU/100 cm2, respectively. The lower reduction in APCs at the neck area indicated that the treatment may not be as effective there, possibly because of the design of the pasteurization equipment. Generic Escherichia coli populations were low at all locations before treatment, with populations on 32% of all carcasses sampled being less than the detection limit of the study (5.0 CFU/100 cm2). After treatment, E. coli populations were significantly lower (P < or = 0.01) than populations before treatment and 85% of all carcasses sampled had E. coli populations below the detection limit. The maximum E. coli population detected after treatment was 25 CFU/100 cm2. For enteric bacterial populations, no differences were observed in the effectiveness of the treatment among the five carcass locations.
The efficacy of organic acid sprays for eliminating Escherichia coli O157:H7 and Listeria monocytogenes from beef trim used in a model ground beef production scheme was determined. Beef trim pieces with ca. 20% fat inoculated with E. coli O157:H7 or L. monocytogenes (ca. 3 log10 CFU/g) were utilized as controls or treated by spraying with 2 or 4% acetic and lactic acids. Propylene glycol (20%) was the carrier for each treatment. Following acid treatment, intact pieces were stored at 4°C for 12 or 24 h, ground, divided into 4 100-g retail packages and stored at 4°C for 0, 1, 2, or 4 days, at which time surviving populations of E. coli O157:H7 or L. monocytogenes were enumerated. High populations (>2.6 log10 CFU/g) of the pathogens persisted in all treatments. The 2% acid spray reduced (P < 0.01) the E. coli O157:H7 population by only 0.1 log10 CFU/g. The 2 and 4% acid sprays reduced (P < 0.001) the L. monocytogenes populations by 0.36 and 0.44 log10 CFU/g, respectively. Storing beef trim intact prior to grinding resulted in lower populations of E. coli O157:H7, and storage following grinding did not affect populations of either pathogen. The acid treatments tested were only slightly effective as sanitizers for beef trim destined for ground beef production.
Survival of Escherichia coli O157:H7 when heated in commercial‐type turkey products was determined. Thermal death times (TDT) were determined at 52–60°C in ground turkey with no additives, 3% fat; ground turkey with no additives, 11% fat; turkey ham batter, 11% fat; turkey frank batter, 17% fat; and turkey sausage batter, 31% fat. Mean D52‐values ranged from 44.9 to 116 min; D55‐values from 6.63 to 39.4 min; D57‐values from 2.20 to 11.7 min; D60‐values from 0.68 to 5.86 min. At all temperatures, survival of E. coli O157:H7 was greater in formulated products than in turkey meat with no additives. Greatest survival occurred in the turkey frank batter. Using our z‐value data, times to provide a 5 D kill of E. coli O157:H7 in turkey franks cooked at 60°C, 65.6°C, or 71°C would be 26, 3.1, or 0.37 min, respectively.
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