Control of Clostridium perfringens in cooked ground beef by carvacrol, cinnamaldehyde, thymol, or oregano oil during chilling

Inhibition of Clostridium perfringens spore germination and outgrowth by carvacrol, cinnamaldehyde, thymol, and oregano oil was evaluated during abusive chilling of cooked ground beef (75% lean) obtained from a local grocery store. Test substances were mixed into thawed ground beef at concentrations of 0.1, 0.5, 1.0, or 2.0% (wt/wt) along with a heat-activated three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.8 log spores per g. Aliquots (5 g) of the ground beef mixtures were vacuum-packaged and then cooked in a water bath, the temperature of which was raised to 60 degrees C in 1 h. The products were cooled from 54.4 to 7.2 degrees C in 12, 15, 18, or 21 h, resulting in 3.18, 4.64, 4.76, and 5.04 log CFU/ g increases, respectively, in C. perfringens populations. Incorporation of test compounds (> or = 0.1%) into the beef completely inhibited C. perfringens spore germination and outgrowth (P < or = 0.05) during exponential cooling of the cooked beef in 12 h. Longer chilling times (15, 18, and 21 h) required greater concentrations to inhibit spore germination and outgrowth. Cinnamaldehyde was significantly (P < 0.05) more effective (< 1.0 log CFU/g growth) at a lower concentration (0.5%) at the most abusive chilling rate evaluated (21 h) than the other compounds. Incorporation of lower levels of these test compounds with other antimicrobials used in meat product formulations may reduce the potential risk of C. perfringens germination and outgrowth during abusive cooling regimes.     

Inhibitory effects of organic acid salts on growth of Clostridium perfringens from spore inocula during chilling of marinated ground turkey breast

Inhibition of Clostridium perfringens germination and outgrowth by salts of organic acids such as sodium lactate, sodium acetate, buffered sodium citrate and buffered sodium citrate supplemented with sodium diacetate was evaluated during continuous chilling of ground turkey. Turkey breast meat was injected with a brine-containing NaCl, potato starch and potassium tetra pyrophosphate to yield final in-product concentrations of 0.85%, 0.25% and 0.20%, respectively. The meat was ground, mixed with either sodium lactate (1%, 2%, 3% or 4%), sodium acetate (1% or 2%), buffered sodium citrate (Ional, 1%) or buffered sodium citrate supplemented with sodium diacetate (Ional Plus trade mark, 1%), in addition to a control that did not contain added antimicrobials. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.8 log10 spores/g. Inoculated products (10 g) were packaged into cook-in-bags (2 x 3 in.), vacuum sealed, cooked at 60 degrees C for 1 h, and subsequently chilled from 54.4 to 7.2 degrees C in 15, 18 and 21 h following exponential chilling rates. Products were sampled immediately after cooking and then after chilling. Chilling of cooked turkey following 15, 18 and 21 h chill rates resulted in germination and outgrowth of C. perfringens spores to 6.6, 7.58 and 7.95 log10 CFU/g populations, respectively, from initial spore populations of ca. 2.80 log10 CFU/g. Incorporation of sodium lactate (1%), sodium acetate (1%), Ional or Ional Plus (1%) substantially inhibited germination and outgrowth of C. perfringens spores compared to controls. Final C. perfringens total populations of 3.12, 3.10, 2.38 and 2.92 log10 CFU/g, respectively, were observed following a 15-h exponential chill rate. Similar inhibitory effects were observed for 18 and 21 chill rates with the antimicrobials at 1% concentrations. While sodium lactate and sodium acetate concentrations of 1% were sufficient to control C. perfringens germination and outgrowth (<1.0 log10 CFU/g growth) following 15 h chill rates, higher concentrations were required for 18 and 21 h chill rates. Ional at 1% concentration was effective in inhibiting germination and outgrowth to <1.0 log10 CFU/g of C. perfringens for all three chill rates (15, 18 and 21 h) tested. Use of sodium salts of organic acids in formulation of ready-to-eat meat products can reduce the risk of C. perfringens spore germination and outgrowth during chilling.     

Inhibition of germination and outgrowth of Clostridium perfringens spores by lactic acid salts during cooling of injected turkey

Inhibition of Clostridium perfringens spore germination and outgrowth by lactic acid salts (calcium, potassium, and sodium) during exponential cooling of injected turkey product was evaluated. Injected turkey samples containing calcium lactate, potassium lactate, or sodium lactate (1.0, 2.0, 3.0, or 4.8% [w/w]), along with a control (product without lactate), were inoculated with a three-strain cocktail of C. perfringens spores to achieve a final spore population of 2.5 to 3.0 log CFU/g. The inoculated product was heat treated and exponentially cooled from 54.5 to 7.2 degrees C within 21, 18, 15, 12, 9, or 6.5 h. Cooling of injected turkey (containing no antimicrobials) resulted in C. perfringens germination and an outgrowth of 0.5, 2.4, 3.4, 5.1, 5.8, and 5.8 log CFU/g when exponentially cooled from 54.4 to 7.2 degrees C in 6.5, 12, 15, 18, and 21 h, respectively. The incorporation of antimicrobials (lactates), regardless of the type (Ca, Na, or K salts), inhibited the germination and outgrowth of C. perfringens spores at all the concentrations evaluated (1.0, 2.0, 3.0, and 4.8%) compared to the injected turkey without acetate (control). Increasing the concentrations of the antimicrobials resulted in a greater inhibition of the spore germination and outgrowth in the products. In general, calcium lactate was more effective in inhibiting the germination and outgrowth of C. perfringens spores at > or = 1.0% concentration than were sodium and potassium lactates. Incorporation of these antimicrobials in cooked, ready-to-eat turkey products can provide additionalprotection in controlling the germination and outgrowth of C. perfringens spores during cooling (stabilization).     

Control of Clostridium perfringens germination and outgrowth by buffered sodium citrate during chilling of roast beef and injected pork

Inhibition of the germination and outgrowth of Clostridium perfringens by buffered sodium citrate (Ional) and buffered sodium citrate supplemented with sodium diacetate (Ional Plus) during the abusive chilling of roast beef and injected pork was evaluated. Beef top rounds or pork loins were injected with a brine containing NaCl, potato starch, and potassium tetrapyrophosphate to yield final in-product concentrations of 0.85, 0.25, and 0.20%, respectively. Products were ground and mixed with Ional or Ional Plus at 0, 0.5, 1.0, and 2.0%. Each product was mixed with a three-strain C. perfringens spore cocktail to obtain final spore concentrations of ca. 2.5 log10 spores per g. Chilling of roast beef from 54.4 to 7.2 degrees C resulted in C. perfringens population increases of 1.51 and 5.27 log10 CFU/g for 18- and 21-h exponential chill rates, respectively, while chilling of injected pork resulted in increases of 3.70 and 4.41 log10 CFU/g. The incorporation of Ional into the roast beef formulation resulted in C. perfringens population reductions of 0.98, 1.87, and 2.47 log10 CFU/g with 0.5, 1.0, and 2.0% Ional, respectively, over 18 h of chilling, while > or = 1.0% Ional Plus was required to achieve similar reductions (reductions of 0.91 and 2.07 log10 CFU/g were obtained with 1.0 and 2.0% Ional Plus, respectively). An Ional or Ional Plus concentration of > or = 1.0% was required to reduce C. perfringens populations in roast beef or injected pork chilled from 54.4 to 7.2 degrees C in 21 h. Cooling times for roast beef or injected pork products after heat processing can be extended to 21 h through the incorporation of > or = 1.0% Ional or Ional Plus into the formulation to reduce the potential risk of C. perfringens germination and outgrowth.     

Use of calcium, potassium, and sodium lactates to control germination and outgrowth of Clostridium perfringens spores during chilling of injected pork

Inhibition of Clostridium perfringens spore germination and outgrowth during abusive chilling regimes was investigated by the incorporation of lactates of calcium (CaL), potassium (KL) and sodium (NaL) in injected pork. Lactates (Ca, K, or Na) were incorporated into injected pork samples at four different concentrations (1.0%, 2.0%, 3.0%, and 4.8%), along with a no-lactate control. A three-strain cocktail of C. perfringens spores was inoculated into the product (injected pork) to obtain a final spore population of ca. 2.0-2.5 log(10)CFU/g. Chilling of injected pork (control) from 54.4 to 7.2 degrees C within 6.5, 9, 12, 15, 18, and 21 h exponential chill rates resulted in C. perfringens population increases of 0.49, 2.40, 4.02, 5.03, 6.24, and 6.30 log(10)CFU/g, respectively. Addition of CaL at 1.0% or KL and NaL > or = 2.0% to injected pork was able to control C. perfringens germination and outgrowth to <1 logCFU/g, meeting the USDA-FSIS performance standard. However, extension of chilling rates beyond 9.0 h (up to 21 h) required addition of CaL ( > or = 2.0%), KL or NaL ( > or = 3.0%) to meet the stabilization performance standard. In general, CaL was more effective compared to KL or NaL for all the chilling regimes, in reducing the potential risk of C. perfringens germination and outgrowth.     

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.     

Inhibitory effects of polyphosphates on Clostridium perfringens growth, sporulation and spore outgrowth

This study evaluated the effects of various polyphosphates (SPP, STPP, SAPP and TSPP) on growth, sporulation and spore germination of Clostridium perfringens, and germination and outgrowth of C. perfrinegns spores in poultry meat. We have found that the requirements of polyP (0.8–1.0%) to inhibit C. perfringens bacterial growth were higher than those reported for other bacteria. Sub-lethal concentrations of polyP significantly (p<0.01) inhibited sporulation of C. perfringens by reducing sporulating cells (heat-resistant cells) 5–6 log₁₀. While C. perfringens spores were able to germinate in the presence of 1% STPP, their outgrowth was significantly (p<0.01) inhibited. Finally, a significant (p<0.01) reduction of survival of C. perfringens was observed when meat samples contaminated with a cocktail of spores of C. perfringens isolates carrying enterotoxin gene on the chromosome were treated with 1% STPP. Collectively, this study demonstrated the inhibitory effects of polyP on growth, sporulation and spore outgrowth of C. perfringens, and suggests that polyP can be used not only as an enhancer of the functional properties of meat products, but also as a promising C. perfringens antimicrobial agent.     

Survival and germination of Clostridium perfringens spores during heating and cooling of ground pork

The effect of heating rate on the heat resistance, germination, and outgrowth of Clostridium perfringens spores during cooking of cured ground pork was investigated. Inoculated cured ground pork portions were heated from 20 to 75°C at a rate of 4, 8, or 12°C/h and then held at 75°C for 48 h. No significant differences (P > 0.05) in the heat resistance of C. perfringens spores were observed in cured ground pork heated at 4, 8, or 12°C/h. At heating rates of 8 and 12°C/h, no significant differences in the germination and outgrowth of spores were observed (P > 0.05). However, when pork was heated at 4°C/h, growth of C. perfringens occurred when the temperature of the product was between 44 and 56°C. In another set of experiments, the behavior of C. perfringens spores under temperature abuse conditions was studied in cured and noncured ground pork heated at 4°C/h and then cooled from 54.4 to 7.2°C within 20 h. Temperature abuse during cooling of noncured ground pork resulted in a 2.8-log CFU/g increase in C. perfringens. In cured ground pork, C. perfringens decreased by 1.1 log CFU/g during cooling from 54.4 to 36.3°C and then increased by 0.9 log CFU/g until the product reached 7.2°C. Even when the initial level of C. perfringens spores in cured ground pork was 5 log CFU/g, the final counts after abusive cooling did not exceed 3.4 log CFU/g. These results suggest that there is no risk associated with C. perfringens in cured pork products under the tested conditions.     

牛至油、香芹酚、柠檬醛和肉桂醛抗真菌研究

采用纸片扩散法以及双倍稀释法研究牛至油、香芹酚、柠檬醛和肉桂醛对面包酵母和黑曲霉的抑菌效果、最小抑菌浓度(CMIC)和最小杀菌浓度(CMFC)。结果表明,牛至油、香芹酚、柠檬醛和肉桂醛对面包酵母和黑曲霉均有明显的抑制作用。抑菌效力相比较,对面包酵母的抑制效果:肉桂醛>香芹酚>牛至油>柠檬醛;对黑曲霉的抑制效果:香芹酚>牛至油>肉桂醛>柠檬醛。因此,牛至油、香芹酚、柠檬醛和肉桂醛可以作为天然抑菌剂应用于食品加工中。     

Effects of chilling rate on outgrowth of Clostridium perfringens spores in vacuum-packaged cooked beef and pork

Cooked, chilled beef and cooked, chilled pork were inoculated with three strains of Clostridium perfringens (NCTC 8238 [Hobbs serotype 2], NCTC 8239 [Hobbs serotype 3], and NCTC 10240). Inoculated products were heated to 75 degrees C, held for 10 min in a circulating water bath to heat activate the spores, and then chilled by circulating chilled brine through the water bath. Samples were chilled from 54.4 to 26.6 degrees C in 2 h and from 26.6 to 4.4 degrees C in 5 h. Differences in initial C. perfringens log counts and log counts after chilling were determined and compared with the U.S. Department of Agriculture (USDA) stabilization guidelines requiring that the chilling process allow no more than 1 log total growth of C. perfringens in the finished product. This chilling method resulted in average C. perfringens increases of 0.52 and 0.68 log units in cooked beef and cooked pork, respectively. These log increases were well within the maximum 1-log increase permitted by the USDA, thus meeting the USDA compliance guidelines for the cooling of heat-treated meat and poultry products.     

Carvacrol and cinnamaldehyde facilitate thermal destruction of Escherichia coli O157:H7 in raw ground beef

The heat resistance of a four-strain mixture of Escherichia coli O157:H7 in raw ground beef in both the absence and presence of the antimicrobials carvacrol and cinnamaldehyde was tested at temperatures ranging from 55 to 62.5 degrees C. Inoculated meat packaged in bags was completely immersed in a circulating water bath, cooked for 1 h to an internal temperature of 55, 58, 60, or 62.5 degrees C, and then held for predetermined lengths of time ranging from 210 min at 55 degrees C to 5 min at 62.5 degrees C. The surviving bacteria were enumerated by spiral plating onto tryptic soy agar overlaid with sorbitol MacConkey agar. Inactivation kinetics of the pathogens deviated from first-order kinetics. D-values (time for the bacteria to decrease by 90%) in the control beef ranged from 63.90 min at 55 degrees C to 1.79 min at 62.5 degrees C. D-values determined by a logistic model ranged from 43.18 min (D1, the D-value of a major population of surviving cells) and 89.84 min (D2, the D-value of a minor subpopulation) at 55 degrees C to 1.77 (D1) and 0.78 min (D2) at 62.5 degrees C. The thermal death times suggested that to achieve a 4-D reduction, contaminated processed ground beef should be heated to an internal temperature of 60 degrees C for at least 30.32 min. Significantly increased sensitivity to heat (P < 0.05) was observed with the addition and/or increasing levels of carvacrol or cinnamaldehyde from 0.5 to 1.0%. The observed thermal death times may facilitate the design of acceptance limits at critical control points for ground beef at lower times and temperatures of heating.     

Evaluation of the microbial quality of Tajik sambusa and control of Clostridium perfringens germination and outgrowth by buffered sodium citrate and potassium lactate

Clostridium perfringens spore destruction, aerobic plate counts (APCs), and counts of Enterobacteriaceae, coliforms, and Escherichia coli during baking of sambusa (a traditional Tajik food) were evaluated. Control of germination and outgrowth of C. perfringens spores in sambusa during cooling at room or refrigerated temperatures was evaluated using organic acid salts (buffered sodium citrate [Ional] and 1 and 2% potassium lactate, wt/wt). Sambusa were prepared with 40 g of either inoculated or noninoculated meat and baked for 45 min at 180 degrees C. For evaluation of destruction of C. perfringens spores during heating and germination and outgrowth of spores during cooling, ground beef was inoculated and mixed with a three-strain cocktail of C. perfringens spores. Aerobic bacteria, Enterobacteriaceae, coliforms, and E. coli were enumerated in noninoculated sambusa before and after baking and after cooling at room or refrigeration temperatures. After baking, APCs and Enterobacteriaceae and coliform counts were reduced by 4.32, 2.55, and 1.96 log CFU/g, respectively. E. coli counts were below detectable levels in ground beef and sambusa samples. Enterobacteriaceae, coliform, and E. coli counts were below detectable levels (< 0.04 log CFU/g) in sambusa after cooling by both methods. Total C. perfringens populations increased (4.67 log CFU/g) during cooling at room temperature, but minimal increases (0.31 log CFU/g) were observed during cooling under refrigeration. Incorporation of 2% (wt/wt) buffered sodium citrate controlled C. perfringens spore germination and outgrowth (0.25 log CFU/g), whereas incorporation of up to 2% (wt/wt) potassium lactate did not prevent C. perfringens spore germination and outgrowth. Incorporation of organic acid salts at appropriate concentrations can prevent germination and outgrowth of C. perfringens in improperly cooled sambusa.     

Role of small, acid-soluble spore proteins in the resistance of Clostridium perfringens spores to chemicals

Previous work showed that C. perfringens spores lacking the majority of alpha/beta-type small, acid-soluble spore proteins (SASPs) (termed alpha(-) beta(-) spores) exhibit greatly decreased resistance to moist heat and UV radiation. The current study demonstrated that these alpha(-) beta(-) spores had reduced resistance to hydrogen peroxide, hydrochloric acid, nitrous acid and formaldehyde. These results clearly demonstrate the important role of alpha/beta-type SASPs in the resistance of C. perfringens spores to chemicals.     

Inhibition of growth,enterotoxin production,and spore formation of Clostridium perfringens by extracts of medicinal plants

The extracts of 14 plants used in the traditional medicine of Mexico were evaluated for their effects on the growth, spore formation, and enterotoxin production of Clostridium perfringens type A. The extracts of Psidium guajava L., Haemotoxylon brasiletto, and Euphobia prostata were the most effective inhibitors of growth, spore formation, and enterotoxin production. No enterotoxins were detected when extracts were added to the media at less than the MIC for growth.     

Control of Clostridium perfringens spores by green tea leaf extracts during cooling of cooked ground beef, chicken, and pork

We investigated the inhibition of Clostridium perfringens spore germination and outgrowth by two green tea extracts with low (green tea leaf powder [GTL]; 141 mg of total catechins per g of green tea extract) and high (green tea leaf extract [GTE]; 697 mg of total catechins per g of extract) catechin levels during abusive chilling of retail cooked ground beef, chicken, and pork. Green tea extracts were mixed into the thawed beef, chicken, and pork at concentrations of 0.5, 1.0, and 2.0% (wt/ wt), along with a heat-activated (75 degrees C for 20 min) three-strain spore cocktail to obtain a final concentration of approximately 3 log spores per g. Samples (5 g) of the ground beef, chicken, and pork were then vacuum packaged and cooked to 71 degrees C for 1 h in a temperature-controlled water bath. Thereafter, the products were cooled from 54.4 to 7.2 degrees C in 12, 15, 18, or 21 h, resulting in significant increases (P < 0.05) in the germination and outgrowth of C. perfringens populations in the ground beef, chicken, and pork control samples without GTL or GTE. Supplementation with 0.5 to 2% levels of GTL did not inhibit C. perfringens growth from spores. In contrast, the addition of 0.5 to 2% levels of GTE to beef, chicken, and pork resulted in a concentration-and time-dependent inhibition of C. perfringens growth from spores. At a 2% level of GTE, a significant (P < 0.05) inhibition of growth occurred at all chill rates for cooked ground beef, chicken, and pork. These results suggest that widely consumed catechins from green tea can reduce the potential risk of C. perfringens spore germination and outgrowth during abusive cooling from 54.4 to 7.2 degrees C in 12, 15, 18, or 21 h of cooling for ground beef, chicken, and pork.     

Incidence of Clostridium perfringens in commercially produced cured raw meat product mixtures and behavior in cooked products during chilling and refrigerated storage

A total of 445 whole-muscle and ground or emulsified raw pork, beef, and chicken product mixtures acquired from industry sources were monitored over a 10-month period for vegetative and spore forms of Clostridium perfringens. Black colonies that formed on Shahidi-Ferguson perfringens (SFP) agar after 24 h at 37 degrees C were considered presumptive positive. Samples that were positive after a 15-min heat shock at 75 degrees C were considered presumptive positive for spores. Of 194 cured whole-muscle samples, 1.6% were positive; spores were not detected from those samples. Populations of vegetative cells did not exceed 1.70 log10 CFU/g and averaged 1.56 log10 CFU/g. Of 152 cured ground or emulsified samples, 48.7% were positive, and 5.3% were positive for spores. Populations of vegetative cells did not exceed 2.72 log10 CFU/g and averaged 1.98 log10 CFU/g; spores did not exceed 2.00 log10 CFU/g and averaged 1.56 log10 CFU/g. Raw bologna (70% chicken), chunked ham with emulsion, and whole-muscle ham product mixtures were inoculated with C. perfringens spores (ATCC 12916, ATCC 3624, FD1041, and two product isolates) to ca. 3.0 log10 CFU/g before being subjected either to thermal processes mimicking cooking and chilling regimes determined by in-plant temperature probing or to cooking and extended chilling regimes. Populations of C. perfringens were recovered on SFP from each product at the peak cook temperatures, at 54.4, 26.7, and 7.2 degrees C, and after up to 14 days of storage under vacuum at 4.4 degrees C. In each product, populations remained relatively unchanged during chilling from 54.4 to 7.2 degrees C and declined slightly during refrigerated storage. These findings indicate processed meat products cured with sodium nitrite are not at risk for the growth of C. perfringens during extended chilling and cold storage.     

The prevalence and molecular typing of Clostridium perfringens in ground beef and sheep meats

This study was aimed at the investigation of the prevalence of Clostridium perfringens in ground beef and sheep meats and to detect the cpa, cpb, etx, iA, cpe and cpb2 toxin genes by multiplex PCR. Obtained from retail markets and butchers, 100 ground meat samples, 50 of which were beef and 50 of which were sheep meat samples, were examined. Out of the 50 ground beef samples 48 (96 %) and out of the 50 ground sheep meat samples 44 (88 %) were contaminated with C. perfringens. According to microscopic examination and the results of biochemical tests, 262 positive isolates obtained from these samples were identified as C. perfringens. Multiplex PCR results demonstrated that, out of the 262 isolates, 203 (77.4 %) possessed only the cpa gene (type A), while 20 (7.6 %) carried the cpa and cpb2 toxin genes (type A-cpb2), and 6 (2.2 %) the cpa and cpe toxin genes (type A-cpe). Furthermore, it was determined that, out of the 262 C. perfringens isolates, 4 (1.5 %), 10 (3.8 %) and 19 (7.2 %) were of the types B, C and D, respectively.     

Effect of spices and organic acids on the growth of Clostridium perfringens during cooling of cooked ground beef

This study evaluated the effect of organic acids and spices, alone or combined, on Clostridium perfringens growth in cooked ground beef during alternative cooling procedures. Ground beef was inoculated with a three-strain cocktail of C. perfringens (ATCC 10388, NCTC 8238, and NCTC 8239) at 2 log spores per g and prepared following an industrial recipe (10% water, 1.5% sodium chloride, and 0.5% sodium triphosphate [wt/wt]). Treatments consisted of the base meat plus combinations of commercial solutions of sodium lactate or sodium citrate (0 or 2%, wt/wt) with chili, garlic and herbs, curry, oregano, or clove in commercial powder form (0 or 1%, wt/wt). Untreated meat was used as a control. Vacuum-packaged samples of each treatment were cooked (75 degrees C for 20 min) and cooled from 54.4 to 7.2 degrees C in 15, 18, or 21 h. Spore counts were estimated after inoculation, cooking, and cooling. All treatments containing sodium citrate reduced the population of C. perfringens about 0.38 to 1.14 log units during each of the three cooling procedures. No sodium citrate and spice treatment combinations showed antagonisms or synergisms. Regardless of the cooling time, the control ground beef or treatments with any of the five spices alone supported C. perfringens growth above the U.S. Department of Agriculture stabilization guidelines of 1 log unit. Except for the 21-h cooling period, addition of sodium lactate prevented C. perfringens growth over 1 log unit. Depending on the cooling time and spice, some combinations of sodium lactate and spice kept C. perfringens growth below 1 log unit.     

Changes in the lipids of turkey muscle during storage at chilling and freezing temperatures

Diced turkey leg and breast muscle stored for 22 days at 0° and —3°, and for up to one year at —10°, —20° and —60° was examined at intervals for lipid composition. Free fatty acids increased at all temperatures except —60°, with a Q₁₀ of 3-4 between 0° and —20° 90% of the fatty acids liberated were unsaturated, matching in composition the unsaturated acids of the muscle glycerophospholipids. Demonstration of linear relationships between increase in free fatty acids and decrease in phosphatidylethanolamine or increase in lysophosphatidylcholine confirmed phospholipase A₂ as the enzyme mainly responsible. The composition of the fatty acids liberated during storage at 0° and —3° showed that both lipase and phospholipase were active. A slight decrease in extractability, resulting in an apparent loss of phospholipid-P, was observed after storage at low temperatures.