Submitted to: Journal of Food Protection
Publication Type: Research Notes
Publication Acceptance Date: June 26, 1995
Publication Date: N/A
Interpretive Summary: Nisin is a naturally occurring protein produced by bacteria responsible for the texture and flavor of cheddar cheese. While used extensively in Europe as a preservative of fresh, processed, and canned foods, nisin is only approved for use in the U.S. to inhibit bacterial growth in pasteurized, processed cheese spreads. It has been found that combinations of nisin and common food additives can reduce pathogenic bacteria in the laboratory. This study reports the first use of nisin and food additives against Escherichia coli 0157:H7 and Salmonella typhimurium attached to beef. Pieces of beef with approximately 100 million bacteria were treated with combinations of nisin and food additives (EDTA, sodium hexametaphosphate, citric acid, and lactic acid) and stored at 41 deg F for up to 3 days. Nisin and additive combinations did not reduce the pathogens greater than 1%. This study demonstrated that unlike previous experiments performed in the laboratory in which treatments with nisin and additives resulted in greater that 99% of the pathogens being killed, such reductions were not observed on meat.
Technical Abstract: Nisin and chelators were examined for inhibiting pathogens attached to red meat. Approximately 7 log**10 CFU/cm**2 of Salmonella typhimurium ATCC 14028 or Escherichia coli 0157:H7, attached to beef, were treated with citrate, lactate, sodium hexametaphosphate, EDTA, alone or in combination with nisin. Inoculated meat was submerged in 10 mL of solutions for 15 min, 25 deg C, and incubated at 4 deg C up to 3 days. Lactate and nisin maximally reduced S. typhimurium attached to beef by 0.40 log**10 CFU/cm**2, while EDTA and nisin maximally reduced E. coli 0157:H7 by 0.42 log**10 CFU/cm**2. Unlike earlier in vitro studies in which treatments with nisin and chelating agents resulted in reductions of >4 log**10 CFU/ml, such reductions were not observed in situ.