Effect of meat ingredients (sodium nitrite and erythorbate) and processing (vacuum storage and packaging atmosphere) on germination and outgrowth of Clostridium perfringens spores in ham during abusive cooling.

The effect of nitrite and erythorbate on Clostridium perfringens spore germination and outgrowth in ham during abusive cooling (15 h) was evaluated. Ham was formulated with ground pork, NaNO2 (0, 50, 100, 150 or 200 ppm) and sodium erythorbate (0 or 547 ppm). Ten grams of meat (stored at 5 °C for 3 or 24 h after preparation) were transferred to a vacuum bag and inoculated with a three-strain C. perfringens spore cocktail to obtain an inoculum of ca. 2.5 log spores/g. The bags were vacuum-sealed, and the meat was heat treated (75 °C, 20 min) and cooled within 15 h from 54.4 to 7.2 °C. Residual nitrite was determined before and after heat treatment using ion chromatography with colorimetric detection. Cooling of ham (control) stored for 3 and 24 h, resulted in C. perfringens population increases of 1.46 and 4.20 log CFU/g, respectively. For samples that contained low NaNO2 concentrations and were stored for 3 h, C. perfringens populations of 5.22 and 2.83 log CFU/g were observed with or without sodium erythorbate, respectively. Residual nitrite was stable (p > 0.05) for both storage times. Meat processing ingredients (sodium nitrite and sodium erythorbate) and their concentrations, and storage time subsequent to preparation of meat (oxygen content) affect C. perfringens spore germination and outgrowth during abusive cooling of ham.

Inhibition of Clostridium perfringens spore germination and outgrowth by buffered vinegar and lemon juice concentrate during chilling of ground turkey roast containing minimal ingredients.

Inhibition of Clostridium perfringens spore germination and outgrowth in ground turkey roast containing minimal ingredients (salt and sugar), by buffered vinegar (MOstatin V) and a blend (buffered) of lemon juice concentrate and vinegar (MOstatin LV) was evaluated. Ground turkey roast was formulated to contain sea salt (1.5%), turbinado sugar (0.5%), and various concentrations of MOstatin V (0.75, 1.25, or 2.5%) or MOstatin LV (1.5, 2.5, or 3.5%), along with a control (without MOstatins). The product was inoculated with a three-strain spore cocktail of C. perfringens to obtain initial spore levels of ca. 2.0 to 0.5 log CFU/g. Inoculated products were vacuum packaged, heat shocked for 20 min at 75 degrees C, and cooled exponentially from 54.4 to 4.0 degrees C in 6.5, 9, 12, 15, 18, or 21 h. In control samples without MOstatin V or MOstatin LV, C. perfringens populations reached 2.98, 4.50, 5.78, 7.05, 7.88, and 8.19 log CFU/g (corresponding increases of 0.51, 2.29, 3.51, 4.79, 5.55, and 5.93 log CFU/g) in 6.5, 9, 12, 15, 18, and 21 h of chilling, respectively. MOstatin V (2.5%) and MOstatin LV (3.5%) were effective in inhibiting C. perfringens spore germination and outgrowth in ground turkey roast to <1.0 log CFU/g during abusive chilling of the product within 21 h. Buffered vinegar and a blend (buffered) of lemon juice concentrate and vinegar were effective in controlling germination and outgrowth of C. perfringens spores in turkey roast containing minimal ingredients.

Validation of a Sequential Hide-On Bob Veal Carcass Antimicrobial Intervention Composed of a Hot Water Wash and Lactic Acid Spray in Combination with Scalding To Control Shiga Toxin-Producing Escherichia coli Surrogates†.

Scalding of hide-on bob veal carcasses with or without standard scalding chemical agents typically used for hogs, followed by an 82.2°C hot water wash and lactic acid spray (applied at ambient temperature) before chilling, was evaluated to determine its effectiveness in reducing Shiga toxin-producing Escherichia coli surrogate populations. A five-strain cocktail of rifampin-resistant, nonpathogenic E. coli surrogates was used to inoculate hides of veal carcasses immediately after exsanguination (target inoculation level of 7.0 log CFU/100 cm2). For carcasses receiving no scalding treatments, spraying with 82.2°C water as a final wash resulted in a 4.5-log CFU/100 cm2 surrogate reduction, and an additional 1.2-log CFU/100 cm2 reduction was achieved by spraying with 4.5% lactic acid before chilling. Scalding hide-on carcasses in 60°C water (no chemicals added) for 4 min in a traditional hog scalding tank resulted in a 2.1-log CFU/100 cm2 reduction in surrogate levels, and a subsequent preevisceration 82.2°C water wash provided an additional 2.9-log CFU/100 cm2 reduction. Spraying a 4.5% solution of lactic acid onto scalded, hide-on carcasses (after the 82.2°C water wash) resulted in a minimal additional reduction of 0.4 log CFU/100 cm2. Incorporation of scalding chemicals into the scald water resulted in a 4.1-log CFU/100 cm2 reduction (1.9 log CFU/100 cm2 greater than scalding without chemicals) in the surrogate population, and the first 82.2°C wash provided an additional 2.5-log CFU/100 cm2 reduction. Application of antimicrobial interventions did not affect the carcass temperature decline during chilling, the pH decline, or the color characteristics of the ribeye or the flank of the bob veal carcasses.

Thermal Resistance of Clostridium difficile Spores in Peptone Water and Pork Meat.

The thermal resistance of four strains of Clostridium difficile spores (three hypervirulent and one nonhypervirulent) in peptone water (PW) and pork meat was evaluated individually at 70, 75, 80, 85, and 90°C using two recovery methods (taurocholate and lysozyme). PW or meat was inoculated with C. difficile spores and mixed to obtain ca. 5.0 log CFU/ml or 4.0 log CFU/g, respectively. The D-values of C. difficile spores in PW ranged from 7.07 to 22.14 h, 1.42 to 3.82 h, 0.35 to 0.59 h, 4.93 to 5.95 min, and 1.16 to 1.76 min at 70, 75, 80, 85, and 90°C, respectively, for the four strains using the taurocholate method. The D-values of the respective C. difficile spores were greater (P ≤ 0.05) using the lysozyme method, especially at higher temperatures (85 and 90°C). Greater thermal resistance of C. difficile spores was observed in meat than in PW using the lysozyme method. Hypervirulence of the C. difficile strains was not associated with greater thermal resistance in meat. The z-values for C. difficile spores in meat were between 6.21 and 7.21°C, and they were 11.24 and 12.12°C using the taurocholate and the lysozyme recovery methods, respectively. The D- and z-values of C. difficile spores were greater in both PW and pork than the values reported in the literature. C. difficile spores can survive traditional cooking or thermal processing practices and potentially grow in cooked, ready-to-eat products. The use of effective methods to recover heat-injured spores is necessary to obtain accurate thermal destruction parameters for C. difficile spores.

Predictive model for Clostridium perfringens growth in roast beef during cooling and inhibition of spore germination and outgrowth by organic acid salts.

Spores of foodborne pathogens can survive traditional thermal processing schedules used in the manufacturing of processed meat products. Heat-activated spores can germinate and grow to hazardous levels when these products are improperly chilled. Germination and outgrowth of Clostridium perfringens spores in roast beef during chilling was studied following simulated cooling schedules normally used in the processed-meat industry. Inhibitory effects of organic acid salts on germination and outgrowth of C. perfringens spores during chilling and the survival of vegetative cells and spores under abusive refrigerated storage was also evaluated. Beef top rounds were formulated to contain a marinade (finished product concentrations: 1% salt, 0.2% potassium tetrapyrophosphate, and 0.2% starch) and then ground and mixed with antimicrobials (sodium lactate and sodium lactate plus 2.5% sodium diacetate and buffered sodium citrate and buffered sodium citrate plus 1.3% sodium diacetate). The ground product was inoculated with a three-strain cocktail of C. perfringens spores (NCTC 8238, NCTC 8239, and ATCC 10388), mixed, vacuum packaged, heat shocked for 20 min at 75 degrees C, and chilled exponentially from 54.5 to 7.2 degrees C in 9, 12, 15, 18, or 21 h. C. perfringens populations (total and spore) were enumerated after heat shock, during chilling, and during storage for up to 60 days at 10 degrees C using tryptose-sulfite-cycloserine agar. C. perfringens spores were able to germinate and grow in roast beef (control, without any antimicrobials) from an initial population of ca. 3.1 log CFU/g by 2.00, 3.44, 4.04, 4.86, and 5.72 log CFU/g after 9, 12, 15, 18, and 21 h of exponential chilling. A predictive model was developed to describe sigmoidal C. perfringens growth curves during cooling of roast beef from 54.5 to 7.2 degrees C within 9, 12, 15, 18, and 21 h. Addition of antimicrobials prevented germination and outgrowth of C. perfringens regardless of the chill times. C. perfringens spores could be recovered from samples containing organic acid salts that were stored up to 60 days at 10 degrees C. Extension of chilling time to > or =9 h resulted in >1 log CFU/g growth of C. perfringens under anaerobic conditions in roast beef. Organic acid salts inhibited outgrowth of C. perfringens spores during chilling of roast beef when extended chill rates were followed. Although C. perfringens spore germination is inhibited by the antimicrobials, this inhibition may represent a hazard when such products are incorporated into new products, such as soups and chili, that do not contain these antimicrobials, thus allowing spore germination and outgrowth under conditions of temperature abuse.

Inhibition of Clostridium perfringens spore germination and outgrowth by lemon juice and vinegar product in reduced NaCl roast beef.

UNLABELLED: Inhibition of Clostridium perfringens spore germination and outgrowth in reduced sodium roast beef by a blend of buffered lemon juice concentrate and vinegar (MoStatin LV1) during abusive exponential cooling was evaluated. Roast beef containing salt (NaCl; 1%, 1.5%, or 2%, w/w), blend of sodium pyro- and poly-phosphates (0.3%), and MoStatin LV1 (0%, 2%, or 2.5%) was inoculated with a 3-strain C. perfringens spore cocktail to achieve final spore population of 2.5 to 3.0 log CFU/g. The inoculated products were heat treated and cooled exponentially from 54.4 to 4.4 °C within 6.5, 9, 12, 15, 18, or 21 h. Cooling of roast beef (2.0% NaCl) within 6.5 and 9 h resulted in <1.0 log CFU/g increase in C. perfringens spore germination and outgrowth, whereas reducing the salt concentration to 1.5% and 1.0% resulted in >1.0 log CFU/g increase for cooling times longer than 9 h (1.1 and 2.2 log CFU/g, respectively). Incorporation of MoStatin LV1 into the roast beef formulation minimized the C. perfringens spore germination and outgrowth to <1.0 log CFU/g, regardless of the salt concentration and the cooling time. PRACTICAL APPLICATION: Cooked, ready-to-eat meat products should be cooled rapidly to reduce the risk of Clostridium perfringens spore germination and outgrowth. Meat processors are reducing the sodium chloride content of the processed meats as a consequence of the dietary recommendations. Sodium chloride reduces the risk of C. perfringens spore germination and outgrowth in meat products. Antimicrobials that contribute minimally to the sodium content of the product should be incorporated into processed meats to assure food safety. Buffered lemon juice and vinegar can be incorporated into meat product formulations to reduce the risk of C. perfringens spore germination and outgrowth during abusive cooling.