Heat-Resistance of Escherichia Coli O157:H7 in Meat and Poultry as Affected by Product Composition

The effects of fat level and low fat formulation on survival of Escherichia coli O157:H7 isolate 204P heated in ground beef [7%, 10% and 20% fat], pork sausage [7%, 10%, and 30% fat], chicken (3% and 11% fat), and turkey (3% and 11% fat) were determined by D- and z-values. D-values for E. coli 0157:H7 in lowest fat products were lower than in traditional beef and pork products (P < 0.05). Overall, higher fat levels in all products resulted in higher D-values. D₆₀ values (min) ranged from 0.45–0.47 in beef, 0.37–0.55 in pork sausage, 0.38–0.55 in chicken and 0.55–0.58 in turkey. D₅₅ and D₅₀ values were respectively longer. Z-values ranged from 4.4–4.8°C. Product composition affected lethality of heat to E. coli O157:H7.     

Heat resistance in Escherichia coli and its implications on ground beef cooking recommendations in Canada

This study assessed the adequacy of the current cooking recommendations in relation to heat resistant Escherichia coli by evaluating eight potentially heat resistant E. coli strains (four generic and four E. coli O157:H7) along with AW1.7. The D_60°C-values for these strains varied from 1.3 to 9.0 min, with J3 and AW1.7 being the least and most heat resistant strains, respectively. The D_60°C-values for E. coli 62 and 68 were similar and were not affected by growth medium, while the heat resistance of C37, J3, and AW1.7 varied with the growth medium. When heated in extra lean ground beef (100 g) in vacuum pouches, the mean D_54°C, D_57°C, and D_60°C-values were 44.8, 18.6, and 2.9 min for C37, 13.8, 6.9, and 0.9 min for J3, and 40.5, 9.1, and 6.1 min for AW1.7. Burger temperatures continued to rise after being removed from heat when the target temperature was reached, by 3–5°C, and resting of 1 min would result in a destruction of 133, 374 and 14 log C37, J3 and AW1.7. These findings along with the very low occurrence of heat resistant E. coli expected in ground beef show that cooking ground beef to 71°C should be adequate.     

Changes in heat tolerance of Escherichia coli O157:H7 after exposure to acidic environments

Acid-adapted bacterial cells are known to have enhanced tolerance to various secondary stresses. However, a comparison of heat tolerance of acid-adapted and acid-shocked cells of Escherichia coli O157:H7 has not been reported. D - and z -values of acid-adapted, acid-shocked, and control cells of an unusually heat-resistant strain (E0139) of E. coli O157:H7, as well as two other strains of E. coli O157:H7, were determined based upon the number of cells surviving heat treatment at 52, 54 or 56°C in tryptic soy broth (pH 7·2) for 0, 10, 20 or 30 min. The unusual heat tolerance of E. coli O157:H7 strain E0139 was confirmed. D -values for cells from 24-h cultures were 100·2, 28·3, and 6·1 min at 52, 54 and 56°C, respectively, with a z -value of 3·3°C. The highest D -values of other E. coli O157:H7 strains were 13·6 and 9·2 min at 52 and 54°C, respectively, whereas highest D -values of non-O157:H7 strains were 78·3 and 29·7 min at 52 and 54°C. D -values of acid-adapted cells were significantly higher than those of unadapted and acid-shocked cells at all temperatures tested. In a previous study, we observed that both acid-adapted cells and acid-shocked cells of strain E0139 had enhanced acid tolerance. This suggests that different mechanisms protect acid-adapted and acid-shocked cells against subsequent exposure to heat or an acidic environment. The two types of cells should be considered separately when evaluating survival and growth characteristics upon subsequent exposure to different secondary stress conditions.     

Differences in thermotolerance of variousEscherichia coliO157:H7 strains in a salami matrix

Three strains ofEscherichia coliO157:H7 (ATCC 43895, Ent C9490 and 380–94) were inoculated into salami and heated in water baths at 50, 55 or 60°C. At intervals between 1 and 360 min, salami samples were removed from the water bath and examined for the presence of survivingE. coliO157:H7. Samples were directly plated onto sorbitol MacConkey (SMAC) agar, and onto tryptone soya agar (TSA) with SMAC overlay. The number of sub-lethally damaged cells in each sample was estimated from the differences between the resultant direct (uninjured cells only) and overlay (total recovery) counts. In samples heated at 50°C, the percentage of cell injury ranged from 71·8–88% for all strains. In samples heated at 55°C the percentage of sub-lethally damaged cells in strains ATCC 43895 and Ent C9490 was significantly higher (P< 0·001) at 97% than that observed in strain 380–94 (64%). Cell injury was not measured at 60°C. There were significant differences between the derived decimal reduction times (D-values) related to the different strains ofE. coliO157:H7, the heat treatment applied and the recovery/enumeration agars used. Significant interstrain differences (P< 0·05) in thermotolerance were noted. Strain Ent C9490 was significantly more heat resistant at 50°C and 60°C (D-values of 116·9 and 2·2 min, respectively), while at 55°C strain 380–94 was more thermotolerant (D-value of 21·9 min). The implications of these findings for the design of studies investigating the heat resistance ofE. coliO157:H7 in fermented meat environments are discussed.     

Thermal Inactivation of Escherichia coli O157:H7 in Strawberry Puree and Its Effect on Anthocyanins and Color

Raw whole strawberries, if contaminated with pathogens, such as Escherichia coli O157:H7, must be pasteurized prior to consumption. Therefore, the objective of this research was to investigate the thermal inactivation kinetics of E. coli O157:H7 in strawberry puree (SP), and evaluate the changes in anthocyanins and color, and the survival of yeasts and molds (YM) after thermal processing. Inoculated with a 5‐strain cocktail, fresh SP, with or without added sugar (20 and 40 °Brix), was heated at 50, 52, 54, 57.5, 60, and 62.5 °C to determine the thermal resistance of E. coli O157:H7. In raw SP, the average D‐values of E. coli O157:H7 were 909.1, 454.6, 212.8, 46.1, and 20.2 s at 50, 52, 54, 57.5, and 60 °C, respectively, with a z‐value of 5.9 °C. While linearly decreasing with temperature, the log D‐values of E. coli O157:H7 increased slightly with sugar concentration. The log degradation rates of anthocyanins increased linearly with temperature, but decreased slightly with sugar concentrations. These results suggest that sugar may provide some protection to both E. coli O157: H7 and anthocyanins in SP. The browning index was not affected by heating at 50 and 52 ºC at low sugar concentrations, but increased by an average of 1.28%, 2.21%, and 10.1% per min when SP was exposed to heating at 54, 57.5, and 60 °C, respectively. YM was also inactivated by heating. This study demonstrated that properly designed thermal processes can effectively inactivate E. coli O157:H7 and YM in contaminated SP, while minimizing the changes in anthocyanins and color.     

Lethality of heat to Escherichia coli O157:H7: D- and z-value determinations in turkey,lamb and pork

Thermal inactivation of a four-strain mixture of E. coli O157:H7 was determined in lean ground turkey, lamb and pork. Inoculated meat was packaged in bags completely immersed in a circulating water bath and held at 55, 57.5, 60, 62.5, and 65°C for predetermined lengths of time. The surviving cell population was enumerated by spiral plating meat samples on tryptic soy agar overlaid with Sorbitol MacConkey agar. D-values, determined by linear regression, in turkey were 11.51, 3.59, 1.89, 0.81 and 0.29 min at 55, 57.5, 60, 62.5 and 65°C, respectively (z=6.5°C). When a survival model was fitted to the non-linear survival curves, D-values in turkey ranged from 11.26 min at 55°C to 0.23 min at 65°C (z=6°C). When the E. coli O157:H7 four-strain cocktail was heated in ground pork or lamb, D-values calculated by both approaches were similar at all temperatures. Thermal-death-times from this study will assist the retail food industry to design cooking regimes that ensure safety of ground muscle foods contaminated with E. coli O157:H7.     

Determination of the effect of sodium lactate on the survival and heat resistance of Escherichia coli O157:H7 in two commercial beef patty formulations

The effect of 4% sodium lactate (NaL) in beefburger patty formulations on the survival and heat resistance of Escherichia coli O157:H7 was investigated. Fresh beef trimmings were inoculated with E. coli O157:H7 to a concentration of 6·0–7·0 log₁₀ cfu g⁻¹ and subjected to the processing stages of beefburger patty production. Two commercial beefburger patty formulations were produced: a ‘quality’ patty (100% beef) and an ‘economy’ patty (70% beef, 30% other ingredients, including onion, water, salt, seasoning, rusk and soya concentrate). Sodium lactate (4% w/v) was added to the beefburger patties during mincing and the formed patties were frozen and stored for 1 month. Beefburger patties without added NaL were used as controls. After frozen storage for 1 month, patties were examined for E. coli O157:H7 counts. There was a synergistic effect between freezing and NaL, which resulted in a small but significant reduction (P<0·05) (approximately 0·5 log₁₀ cfu g⁻¹) in E. coli O157:H7 numbers. The frozen beefburger patties were also heat-treated at 50, 55 and 60°C and the data analysed to derive D -values for E. coli O157:H7 cells. At each temperature treatment, theD -values of the quality and economy beefburger patties with 4% NaL were significantly lower (P<0·001) than the D -values of the patty formulations without NaL. The study demonstrates that the presence of 4% NaL in beefburger patty formulations can reduce the overall risks posed to consumers by the presence ofE. coli O157:H7 by, first; reducing pathogen survival during freezing and frozen storage of the uncooked product; and, second, by increasing the susceptibility of the pathogen to heat during normal cooking processes.     

Growth and thermal inactivation of Listeria monocytogenes and Escherichia coli O157:H7 in four kinds of traditionally non-fermented soya bean products

This study evaluated growth and thermal inactivation of Listeria monocytogenes and Escherichia coli O157:H7 inoculated in tofu, dougan, qianzhang and doupi which were stored at 4, 25 and 37 °C and heated at 55, 60, 65 and 70 °C. Growth of the two pathogens in four soya bean products increased with temperature or A_w of soya bean products increasing. At the same temperature, lag time (LT) values of L. monocytogenes (16.32–0.94 h) and E. coli O157:H7 (2.66–0.98 h) in tofu which has the highest A_w were the lowest. When inoculated soya bean products were stored at 4 °C, L. monocytogenes grew slowly, while E. coli O157:H7 did not grow but survived for 14 days. With temperature increasing, δ-values of L. monocytogenes and E. coli O157:H7 in the four soya bean products were decreased. With A_w of soya bean products increasing, thermal resistance of L. monocytogenes decreased, while that of E. coli O157:H7 increased. This study could assist retail soya bean products processors and food industry to enhance safety of soya bean products and design thermal processing regimes.     

Thermal inactivation ofClostridium perfringensvegetative cells in ground beef and turkey as affected by sodium pyrophosphate

The heat resistance (55–65°C) ofClostridium perfringensvegetative cells in ground beef and turkey that included 0, 0.15 or 0.3% (w/w) sodium pyrophosphate (SPP) was assessed in bags heated using a water bath. The surviving cell population was assayed on tryptose–sulfite– cycloserine agar. The decimal reduction (D)-values in beef that included no SPP were 21.6, 10.2, 5.3, and 1.6min at 55, 57.5, 60, 62.5°C, respectively; the values in turkey ranged from 17.5min at 55°C to 1.3min at 62.5°C. Addition of 0.15% SPP resulted in concomitant decrease in heat resistance as evidenced by reduced bacterialD-values. TheD-values in beef that included 0.15% SPP were 17.9, 9.4, 3.5, and 1.2min at 55, 57.5, 60, and 62.5°C, respectively; the values in turkey ranged from 16.2min at 55°C to 1.1min at 62.5°C. The heat resistance was further decreased when the SPP level in beef and turkey was increased to 0.3%. Heating such products to an internal temperature of 65°C for 1min killed >8log₁₀cfug^-1. The z-values in beef and turkey for all treatments were similar, ranging from 6.22 to 6.77°C. Thermal death time values from this study should assist institutional food service settings in the design of thermal processes that ensure safety againstC. perfringensin cooked beef and turkey.     

Influence of gamma irradiation on growth and survival of Escherichia coli O157:H7 and quality of cig kofte, a traditional raw meat product

Cig kofte is a traditional Turkish food containing raw ground meat. Samples inoculated with Escherichia coli O157:H7 were irradiated at 0.5–6 kGy with a ⁶⁰Co source and stored at 4 and 25 °C. Total aerobic mesophilic count decreased with increasing irradiation doses, D₁₀ value was 0.83 kGy. Escherichia coli O157:H7 count decreased from 5.1 log₁₀ CFU g^?1 to an undetectable level (<1 log₁₀ CFU g^?1) after 1‐day storage at 4 °C following irradiation at 2 kGy, D₁₀‐value was 0.29 kGy. Irradiation doses up to 2 kGy did not affect sensory quality after 1 day. There was colour loss in samples irradiated at 2 kGy or above and stored for longer periods. Storage of the irradiated products at abused temperature must be avoided for safety assurance. Irradiation at 2 kGy has a great potential for extending the shelf‐life of cig kofte and assuring safety by decreasing the number of E. coli O157:H7 and other bacteria, but further studies with suitable package designs are needed to decrease quality degradation during extended storage.     

Trisodium Phosptiate (TSP) Treatment of Beef Surfaces to Reduce Escherichia coli O157:H7 and Salmonella typhimurium

Trisodium phosphate (TSP) was evaluated for removing attached E. coli O157:H7 and S. typhimurium from beef surfaces using microbiological plating and scanning electron microscopy (SEM). Both fat and fascia surfaces were exposed to 10⁹ CFU/mL of each inoculum for 15 min and rinsed with 10% TSP solution (10°C) for 15 sec. Compared to controls, the level of E. coli O157:H7 was 1.35 and 0.92-logs lower on TSP-treated fat and fascia surfaces, respectively by plating. .S. typhimurium was 0.91- and 0.51-logs lower, respectively. By SEM, TSP-treated fabcia surfaces showed 1.39-log and 0.86-log reductions in E. coli O157:H7 and S. typhimurium, respectively. Overall, TSP was more effective on removing E. coli O157:H7 than S. typhimutium and more efficient in removing both bacteria from fat surfaces than from fascia.     

Inactivation ofEscherichia coliO157:H7 by combinations of GRAS chemicals and temperature

Reported outbreaks of foodborne illness involvingEscherichia coliO157:H7 have increased in the United States during the last decade, with a variety of food products being implicated as vehicles of infection. Studies were carried out to determine the efficacy of combinations of various GRAS chemicals and moderate temperatures to killE. coliO157:H7. A five-strain mixture ofE. coliO157:H7 of approximately 10⁸cfu ml⁻¹was inoculated into 0·1% peptone solutions containing 1·0 or 1·5% lactic acid plus 0·1% hydrogen peroxide, 0·1% sodium benzoate or 0·005% glycerol monolaurate. The solutions were incubated at 8°C for 0, 15 and 30 min; at 22°C for 0, 10 and 20 min; or at 40°C for 0, 10 and 15 min; populations ofE. coliO157:H7 were determined at each sampling time. At 40°C, the pathogen was inactivated to undetectable levels within 10 min of incubation in the presence of 1·0 or 1·5% lactic acid plus hydrogen peroxide, and within 15 min of incubation in the presence of 1·5% lactic acid plus sodium benzoate or glycerol monolaurate. At 22°C, complete inactivation ofE. coliO157:H7 was observed after 20 min of exposure to 1·5% lactic acid plus 0·1% hydrogen peroxide, whereas a reduction of 5 log₁₀cfu ml⁻¹was observed with a treatment of 1·5% lactic acid plus glycerol monolaurate. None of the treatments resulted in total inactivation of the pathogen at 8°C. The aforementioned treatments could potentially be used to inactivate or reduceE. coliO157:H7 populations on raw produce.     

Enhancing the thermal destruction of Escherichia coli O157:H7 in ground beef patties by trans-cinnamaldehyde

The effect of trans-cinnamaldehyde (TC) on the inactivation of Escherichia coli O157:H7 in undercooked ground beef patties was investigated. A five-strain mixture of E. coli O157:H7 was inoculated into ground beef (7.0 log CFU/g), followed by addition of TC (0, 0.15, and 0.3%). The meat was formed into patties and stored at 4 °C for 5 days or at −18 °C for 7 days. The patties were cooked to an internal temperature of 60 or 65 °C, and E. coli O157:H7 was enumerated. The numbers of E. coli O157:H7 did not decline during storage of patties. However, cooking of patties containing TC significantly reduced (P < 0.05) E. coli O157:H7 counts, by >5.0 log CFU/g, relative to the reduction in controls cooked to the same temperatures. The D-values at 60 and 65 °C of E. coli O157:H7 in TC-treated patties (1.85 and 0.08 min, respectively) were significantly lower (P < 0.05) than the corresponding D-values for the organism in control patties (2.70 and 0.29 min, respectively). TC-treated patties were more color stable and showed significantly lower lipid oxidation (P < 0.05) than control samples. TC enhanced the heat sensitivity of E. coli O157:H7 and could potentially be used as an antimicrobial for ensuring pathogen inactivation in undercooked patties. However detailed sensory studies will be necessary to determine the acceptability to consumers of TC in ground beef patties.     

Predicting process lethality of Escherichia coli O157:H7, Salmonella,and Listeria monocytogenes in ground,formulated, and formed beef/turkey links cooked in an air impingement oven

The pathogen thermal lethality in ground and formulated beef/turkey was evaluated for a cocktail of E. coli O157:H7, Salmonella, and Listeria monocytogenes, respectively. At a temperature range of 55–70°C, the heat resistance of L. monocytogenes was not significantly (at α=0.05) different from those of Salmonella. The heat resistance of L. monocytogenes at 55–70°C was 45–81% higher than that of E. coli O157:H7. In this study, a practical approach was developed to predict log₁₀(CFU/g) reduction of E. coli O157:H7, Salmonella, or L. monocytogenes in ground, formulated, and formed beef/turkey links that were cooked in an air impingement oven. The predictions of pathogen thermal kills in the links were verified via the inoculation studies for at least a 7 log₁₀(CFU/g) reduction of E. coli O157:H7, Salmonella, and L. monocytogenes.     

Critical Factors Affecting the Destruction of Escherichia coli O157:H7 in Apple Cider Treated with Fumaric Acid and Sodium Benzoate

Destruction of Escherichia coli O157:H7 in apple cider treated with fumaric acid and sodium benzoate (0.15% and 0.05% w/v, respectively) was determined under pH and storage temperatures that commonly occur in apple cider. At 5°C storage, while destruction of E. coli O157:H7 in the presence of preservatives increased with time, there was little decline in E. coli O157:H7 populations in the absence of the preservatives. Increasing storage temperatures to 15°C and 25°C significantly increased the rate of destruction of E. coli O157:H7 in cider with the preservatives (P < 0.05). Increasing the pH of cider (from 3.2 to 4.7) decreased the rate of destruction of E. coli O157:H7.     

Thermal inactivation of Escherichia coli O157:H7 and Escherichia coli isolated from morcilla as affected by composition of the product

Morcilla is a link sausage quite similar to black pudding, consisting of an inert casing stuffed with a mixture of beef blood, fat, and seasonings. Thirty samples of morcilla showed total microbial counts (6.3×10³–2.1×10⁸ Cfu/g ), molds and yeasts (8.9×10¹–6.3×10⁴ Cfu/g), sulfite-reducing microorganism (2.0×10¹–2.1×10²MPN/g); total coliforms (1.4×10¹–1.1×10³ MPN/g); fecal coliforms (7.0–1.5×10²MPN/g); Enterobactereaceae (1.6×10²–5.0×10⁵ Cfu/g). S. aureus and B. cereus were not detected. E. coli was detected in 76.6% of the samples analyzed. The thermal resistance (D and z-values) of Escherichia coli O157:H7 and E. coli isolated from morcilla were determined in nutrient broth and in a heating menstruun prepared with ground morcilla (discarding the casing) and added fat or starch. Higher fat and starch levels resulted in higher D-values (min) at 54, 58 and 62 °C for both strains. The z-values (°C) for isolated E. coli in nutrient broth (M1), ground morcilla (M2), M2+10% fat (M3), M2+20% fat (M4), M2+10% starch (M5), and M2+20% starch (M6) were 7.9, 7.8, 10.5, 10.4, 10.3, and 10.4, respectively, and for E. coli O157:H7 were 7.8, 7.4, 9.8, 10.2, 10.3, and 10.7. The composition of product affected heat lethality of the two strains of E. coli.     

Survival of Escherichia coli O157:H7 in Apple Cider as Affected by Dimethyl Dicarbonate, Sodium Bisulfite, and Sodium Benzoate

Survival of Escherichia coli O157:H7 in apple cider containing no preservatives, 0.025% dimethyl dicarbonate (DMDC), 0.045% sodium benzoate (SB), 0.0046% sodium bisulfite (NaS; 65.5% sulfur dioxide), or a combination of NaS and SB (NaS/SB) and stored at 4, 10, and 25°C was evaluated. E. coli O157:H7 survived for up to 18 days at 4,10, and 25°C in unpreserved apple cider. At 4 and 10°C, DMDC was most efficient at inactivating E. coli O157:H7, generally followed by NaS/SB SB, and NaS (p<0.05). E coli O157:H7 was more resistant to preservatives at 4°C than at 25°C (P < 0.05). E. coli O157:H7 was sublethally injured in cider containing preservatives, and to a lesser extent, in unpreserved cider. Generally, injury was more pronounced in cider containing DMDC, followed by NaS/SB, SB, and NaS (p<0.05).     

Fate of Escherichia coli O157: H7 in Chinese-Style Sausage During the Drying Step of the Manufacturing Process as Affected by the Drying Condition and Curing Agent

In this study, Chinese-style sausage was subjected to three different air-blast drying conditions commonly employed during the manufacturing process. The fate of Escherichia coli O157: H7 during the drying period was determined and compared. The effect of curing agents on the survival of E coli O157: H7 was also identified. Results showed that populations of E coli O157: H7 decreased ca 1.51 Log CFU g^-1 in sausage containing curing agents after a 6-h drying period at 50°C. However, the number of viable cells of E coli O157: H7 increased slightly in sausage without curing agents. When subjected to air-blast drying at 55°C for 6 h or at 55°C for 2·5 h and then 60°C for 3·5 h, a reduction in the number of viable cells of E coli O157: H7 was observed in sausage with or without curing agents. The reduction was more significant in sausage containing curing agents than in those without curing agents. No viable E coli O157: H7 was detected after 6 h of drying in samples containing curing agents, while the control samples still contained a viable E coli O157: H7 population of ca 2·65–4·36 Log CFU g^-1. After drying the sausage at 55°C for 4 h, inactivation of E coli O157: H7 increased in the presence of 30·00 g kg^-1 sodium chloride or 1·50 g kg^-1 sodium sorbate. On the other hand, the presence of 0·07–0·15 g kg^-1 sodium nitrite did not increase the inactivation of E coli O157: H7 compared to that in the control. © 1997 SCI.     

Reduction of Pathogens Using Hot Water and Lactic Acid on Beef Trimmings

Beef trimmings from young or mature beef cattle were obtained commercially. Trimmings within age type then were inoculated with about 6.0 log₁₀ CFU/mL of rifampicin-resistant. Escherichia coli O157:H7 and Salmonella typhimurium (ATCC 13311) were randomly assigned to 1 of 3 treatments (control; 95 °C hot water alone, or with 2% L-lactic acid). After treatment, trimmings were ground, held for 0, 14, 28, or 42 d in chub packages at 4 °C, and total aerobic plat counts, E. coli O157:H7, and S. typhimurium counts were determined. Non-inoculated trimmings were also treated and samples were evaluated for pH, fat, moisture, TBA, meat color by colorimeter, and meat color, and odor by trained sensory panels. Trimmings treated with water or hot water plus lactic acid reduced levels of E. coli O157:H7 and S. typhimurium and tended to be darker after treatment. Meat odor in the final product was not affected by treatment.     

Fate of Escherichia coliO157: H7 in Chinese-style sausage subjected to different packaging and storage conditions

In this study, Chinese-style sausages were subjected to air, vacuum or nitrogen packaging and stored at either 5 or 25°C. The survival characteristics of Escherichia coli O157: H7 during the storage period were determined. Results revealed that, when stored at 5°C, the number of viable E coli O157: H7 in sausages decreased slowly as the storage period extended, regardless of packaging methods. E coli O157: H7 in sausages decreased from an initial population of ca 5·97 log CFU g⁻¹ to ca 4·42–4·81 log CFU g⁻¹ after 40 days of storage at 5°C. It was also found that viable cells of E coli O157: H7 declined more rapidly in sausage stored at 25°C than at 5°C. No viable E coli O157: H7 was detected in either vacuum-packed or nitrogen-packed sausage after 40 days of storage at 25°C. On the other hand, the population of E coli O157: H7 reduced to non-detectable levels in air-packed sausages after 20 days of storage. Refrigerated storage and vacuum or nitrogen packaging provided conditions that slowed down the death rate of E coli O157: H7 in sausage. Furthermore, it was noted that, among the curing agents tested, NaCl exerted the most significant lethal effect on E coli O157: H7 in sausage during the storage period. © 1998 Society of Chemical Industry.