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Weekly UpdatesEfforts to control harmful pathogens by applying a variety of chemicals with proven bactericidal properties have not been adequately effective. Many of these chemicals might also adversely impact one's health through reactive effects from their residual presence on products.
So, scientists at North Carolina A&T State University wanted to determine the ability of L-ascorbic acid and propyl gallate, alone or in combination with lactic acid, to inhibit the growth of E. coli O157:H7 in tryptic soy broth. Their research indicates that 1% L-ascorbic acid and 0.1% propyl gallate, in combination with 0.3% lactic acid, may have the potential to control foodborne pathogens.
In experiments, five strains of E. coli O157:H7 with populations of approximately 3.5 log CFU per ml were individually inoculated into the broth. The broth had been supplemented with either L-ascorbic acid or propyl gallate alone or in combination with lactic acid.
During an 8-hour incubation period at 37 C, the researchers determined microorganism growth (turbidity via optical density) for each strain at 2-hour intervals using a spectrophotometer at 610 nm. At the end of the incubation period, the tryptic soy broth was also serially diluted in sterile 0.1% peptone water and then surface plated onto tryptic soy agar.
The scientists found that the concentrations required so that L-ascorbic acid, lactic acid and propyl gallate could have the strongest inhibitory effects against the growth of the microorganisms were 1%, 0.3% and 0.1%, respectively. Specifically, a combination of 0.25% L-ascorbic acid or 0.025% propyl gallate along with 0.2% lactic acid completely inhibited the growth of the E. coli O157:H7 strains.
Further information. S. A. Ibrahim, 171 Carver Hall, Food Microbiology and Safety Laboratory, Department of Human Environmental and Family Sciences, North Carolina A&T State University, Greensboro, NC 27411; phone: 336-334-7328; fax: 336-334-7239; email: ibrah001@ncat.edu.
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