Heat-Resistance of Escherichia Co/i 0157:H7 in Meat and Poultry as Affected by Product Composition NAHED M. AHMED, DONALD E. CONNER, and DALE L. HUFFMAN ABSTRACT The effects of fat level and low fat formulation on survival of Escheri- chiu coli 0157:H7 isolate 204P heated in ground beef [7%, 10% and 20% fat], pork sausage [7%, lo%, 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. D,, values (min) ranged from 0.4550.47 in beef, 0.37-0.55 in pork sausage, 0.38-0.55 in chicken and 0.5550.58 in turkey. D,, and D,, values were respectively longer. Z- values ranged from 4.44.8”C. Product composition affected lethality of heat to E. coli 0157:H7. Key Words: meat, poultry, E. cob, fat content, thermal death INTRODUCTION ESCHERICHIA COLI occur among natural bacteria of the intestinal tract of humans and other animals (Drasar and Hill, 1974) but a limited number of types of E. coli are pathogenic. E. coli 0157:H7 was established as a human pathogen in 1975 when it was isolated from a patient with perfuse diarrhea (Riley et al., 1983). Subsequentlythis pathogen was epidemiologically linked to consumption of contaminated food following outbreaks in Oregon and Michigan (Riley et al., 1983). Such outbreaks led to recognition of the enterohemorrhagic E. coli (EHEC) group of pathogenic E. coli (Padyhe and Doyle, 1991, 1992). Food is the primary route of transmission for E. coli 0157:H7. Cattle apparently have been a major reservoir of this patho- gen. Undercooked ground beef and raw milk have been the foods most often associated with diseaseoutbreaks (Padhye and Doyle, 1992). At least 16 documented foodbome disease out- breaks have been caused by E. coli 0157:H7, of which, six have been attributed to ground beef (Mermelstein, 1993). One out- break, from late 1992 to early 1993, received high news-media coverage and publicity. The cause of the outbreak was associated with undercooked hamburgers from a foodservice chain in several western states. Other outbreaks have been at- tributed to contaminated poultry (Ryan et al., 1986; Carter et al., 1987). E. coli 0157:H7 readily colonized the ceca of chick- ens and was shed in feces for several months (Beery et al., 1985). E. coli 0157:H7 was isolated from retail poultry in the U.S. (Doyle and Shoeni, 1987). However, the USDA indicated that of 6000 ready to cook poultry samples obtained directly from processing plants, none yielded the pathogen (Carosella, 1993). These findings indicate that poultry could be another res- ervoir for E. coli 0157:H7 and that poultry products become contaminated during further processing, distribution and/or han- dling. Undercooking or survival of the pathogen during cooking has been a contributing factor in most outbreaks (Mermelstein, 1993). Therefore, there is high interest in determining the heat Authors Conner and Huffman are with the Dept. of Poultry Sci- ence and Dept. of Animal & Dairy Science, Auburn Univ. Alabama Agricultural Experiment Station, Food Technology Institute, Au- burn, AL 36849-5476. Author Ahmed, formerly with the Dept. of Poultry Science, is now with the Dept. of Food Science, Univ. of Arkansas, Fayetteville, AR 72703. Address inquiries to Dr. D.E. Conner. Table l-Fresh pork sausage formulations Product 10% 30% Ingredient (%) Fat Fat Meat 94.60 94.60 Salt 1.630 1.630 Dextrose 0.250 0.250 Slack pepper 0.160 0.160 Ground red pepper 0.030 0.030 Crushed red pepper 0.125 0.125 Carrageenan 0.000 0.000 Water 3.000 3.000 a AU Lean” formulations. 7% Fata 76.90 2.030 0.313 0.200 0.038 0.156 0.350 20.00 Table 2-Proximate analysis of ground beef products Product 7% Fatd 10% Fat 20% Fat Moisture 1%) 72.6a 69.lb 61.gc Fat 1%) 7.2= lo.ob 19.v Protein (%) w.lb 20.7a 18.2c a,b,c Means within a row followed by different letters are different IP < 0.05). d AU Lean” formulation. Table 3-Proximate analysis of pork sausage products Product 7% Fat 10% Fat 30% Fat Moisture (%) 73.3a 70.9a 51.1” Fat (%) 6.3c 11.3” 32.7a Protein (%) 19.1a 16.8b 15.3c a5b.c Means within a row followed by different letters are different (P < 0.05) d AU Lean” formulations resistanceof E. coli 0157:H7. This serotype is similar in many characteristicsto other types of E. coli (Buchanan and Klawitter, 1992; Gibson and Roberts, 1986). However, it differs in its abil- ity to ferment sorbitol and produce the B-glucuronidase enzyme, and exhibits considerable resistance to environmental stresses including acidic conditions, freezing and low growth tempera- tures (Conner and Hall, 1992, 1993, 1994; Conner and Kotrola, 1994). Thus, other characteristics,including heat resistance, may not be similar for all E. coli types. Reportedly, E. coli 0157:H7 has shown no unusual heat re- sistance, with D-values at 5764°C ranging from 27s9.6 set (Padhye and Doyle, 1992; Line et al., 1991; Shipp et al., 1992). However, intrinsic and extrinsic factors that affect heat resis- tance of E. coli 0157:H7 have not been extensively studied. Isolates of E. coli 0157:H7 vary considerably in heat resistance (Ahmed, 1994; Ahmed and Conner, 1992) and environmental conditions can increase D-values (Murano and Pierson, 1993). Moreover, few data have related the effects of meat product composition to survival of E. coli 0157:H7 during cooking. Our objective was to determine the effects of species,fat content and low-fat formulation on heat resistance (survival) of E. coli 0157:H7 in meat and poultry products. MATERIALS & METHODS Inoculum preparation E. coli 0157:H7 strain 204P was obtained from M.P. Doyle, Univ. GA. and maintained on tryptic soy agar (TSA, Difco) at 4°C. Cell sus- 606-JOURNAL OF FOOD SCIENCE-Volume 60, No. 3, 1995