Survival and growth of Escherichia coli O157:H7 in ground, roasted beef as affected by pH, acidulants, and temperature

Abstract

A study was undertaken to determine the fate of Escherichia coli 0157:H7 in ground, roasted beef as influenced by the combined effects of pH, acidulants, temperature, and time. There was essentially no change in the viable population of E. coli 0157:H7 when beef salads (pH 5.40 to 6.07) containing up to 40%o mayonnaise were incubated at 5°C for up to 72 h. At 21 and 30°C, significant (P 5 0.05) increases in populations of the organism occurred in salads containing 16 to 32% mayonnaise (pH 5.94 to 5.55) between 10 and 24 h of incubation. Death was more rapid as the pH of acidified beef slurries incubated at 5°C was decreased from 5.98 to 4.70. E. coli 0157:H7 grew in control slurries (pH 5.98) and in slurries containing citric and lactic acids (pHs 5.00 and 5.40) incubated at 21°C for 24 h; decreases occurred in slurries acidified to pHs 4.70, 5.00, and 5.40 with acetic acid or pH 4.70 with citric or lactic acid. At 30°C, populations decreased in slurries acidified to pHs 4.70 and 5.00 with acetic acid. Citric and lactic acids failed to prevent significant increases in populations in slurries at pH 4.70 to 5.40 between 10 and 24 h of incubation. The order of effectiveness of acidulants in inhibiting growth was acetic acid > lactic acid. citric acid. The same order was observed for inactivation of E. coli 0157:H7 in acidified (pH 5.00) beef slurry heated at 54°C.

The survival and growth of acid-adapted mesophilic pathogens that contaminate meat after lactic acid decontamination

“…Buchanan and Klawitter (1991) demonstrated that at 12°C, E. coli O157 : H7 grew in Brain Heart Infusion broth adjusted to pH 5·5 with HCl. The resistance of E. coli O157 : H7 to acid is unexceptional for a Gram-negative organism, and has also been demonstrated by others (Brackett et al 1994 ;Podolak et al 1996) during storage after acid decontamination, in fermented meat at pH 4·5 (Glass et al 1992) and in lactic acid-acidified (pH 5·4-6·1) beef salads (Abdul-Raouf et al 1993).…”

Development of membrane filter holder (MFH) method for recovery of heat-injured Escherichia coli O157:H7 and Salmonella typhimurium

“…Foodborne pathogens such as Escherichia coli O157:H7 and Salmonella typhimurium are important micro-organisms (Andrew and Ray 1989;Karmal 1989;Dickson and Anderson 1991;Abdul-Raouf et al 1993;Dickson and Siragusa 1994;Clavero and Beuchat 1995;McCleer and Rowe 1995;Rochelle et al 1996). To control those foodborne pathogens, several interventions or chemicals have been used and applied (Abdul-Raouf et al 1993;Davey and Smith 1989;Dickson and Anderson 1991;Barkate et al 1993;Zhao et al 1993;Dickson and Siragusa 1994;Dorsa et al 1996).…”

“…Foodborne pathogens such as Escherichia coli O157:H7 and Salmonella typhimurium are important micro-organisms (Andrew and Ray 1989;Karmal 1989;Dickson and Anderson 1991;Abdul-Raouf et al 1993;Dickson and Siragusa 1994;Clavero and Beuchat 1995;McCleer and Rowe 1995;Rochelle et al 1996). To control those foodborne pathogens, several interventions or chemicals have been used and applied (Abdul-Raouf et al 1993;Davey and Smith 1989;Dickson and Anderson 1991;Barkate et al 1993;Zhao et al 1993;Dickson and Siragusa 1994;Dorsa et al 1996). These interventions include organic acid sprays (generally lactic or acetic acids), hot water/steam treatments and antimicrobial chemical applications such as chlorine, chlorine dioxide, and trisodium phosphate (Abdul-Raouf et al 1993;Davey and Smith 1989;Dickson and Anderson 1991;Barkate et al 1993;Zhao et al 1993;Dickson and Siragusa 1994;Siragusa 1995;Dorsa et al 1996;Rochelle et al 1996).…”

“…To control those foodborne pathogens, several interventions or chemicals have been used and applied (Abdul-Raouf et al 1993;Davey and Smith 1989;Dickson and Anderson 1991;Barkate et al 1993;Zhao et al 1993;Dickson and Siragusa 1994;Dorsa et al 1996). These interventions include organic acid sprays (generally lactic or acetic acids), hot water/steam treatments and antimicrobial chemical applications such as chlorine, chlorine dioxide, and trisodium phosphate (Abdul-Raouf et al 1993;Davey and Smith 1989;Dickson and Anderson 1991;Barkate et al 1993;Zhao et al 1993;Dickson and Siragusa 1994;Siragusa 1995;Dorsa et al 1996;Rochelle et al 1996). Heat-injured foodborne pathogens subjected to sublethal environmental stresses cannot survive on selective medium such as MacConkey Sorbitol Agar (SMAC for E. coli O157:H7) or XLD (Xylose Lysine Desoxycholate for S. typhimurium) (Andrews and Ray 1989;McCleer and Rowe 1995).…”

Development of a selective plating technique for the recovery of Escherichia coli O157: H7 after heat stress

“…1986;March and Ratnam 1986). However, this medium has been shown to perform poorly when heat-stressed, acidstressed (Abdul-Raouf et al 1993) or freeze-stressed (Conner and Hall 1994) cells of E. coli 0157: H7 are present. It is important that any detection method used for this organism takes account of injured cells not only because E. coli 0157 : H7 has a very low infective dose (Lior 1994) but also because injured cells, in general, retain their pathogenic traits and a proportion of the population in food is liable to be in the injured state as a result of processing operations or subsequent storage.…”