29G-12 |
Molecular weight and concentration influences antimicrobial activity of chitosan in oil-in-water emulsions |
C. BASURTO, S. Zivanovic, P. M. Davidson, S. Chi, and J. Weiss. Dept. of Food Science & Technology, Univ. of Tennessee, 2605 River Dr., Knoxville, TN 37996-4591
Several studies have been conducted to assess the antimicrobial efficacy of chitosan against foodborne pathogens in microbiological model systems. However little is known about the influence of molecular properties of chitosans on their inhibitory activity in complex food systems such as oil-in-water emulsions. The objective of this study was to determine the antimicrobial activity of two chitosans in oil-in-water emulsions. Chitosan emulsions were prepared by adding acetic acid solutions of two chitosans (low molecular weight [LMW] with 150KDa and oligosaccharide lactate [OL]) to aseptic corn oil emulsions to give chitosan concentrations ranging from 0.1 to 0.7%. The pH of emulsions was adjusted to 4.5 using acetic acid. Controls consisted of chitosan-free emulsions. Aliquots were inoculated at ~7 logs CFU/mL with Salmonella Typhimurium DT104 2486 and 2576, Listeria monocytogenes Scott A and 310. Samples were incubated at 24±1ºC and 10±1ºC. Viable cells were enumerated at 0, 24, 48 and 96h Addition of the lowest concentration (0.1%) of LMW chitosan was sufficient to reduce number of viable cells of both Salmonella strains by ~7 logs CFU/ml within 48h at 24±1ºC. However, Salmonella 2586 and 2576 only decreased by ~4 logs at 10±1ºC after 48h. Adding more chitosan improved inactivation e.g. at 0.7wt% LMW chitosan, viable cells were reduced by ~5.5 logs. Similar trends were observed with both Listeria strains, however Scott A was slightly more resistant to chitosan than 310, e.g. 0.65% chitosan was needed to achieve complete deactivation within 48h at 24±1ºC. Molecular weight influenced antimicrobial efficacy of chitosan. Chitosan oligosaccharide lactate was only effective against the two Salmonella strains, not the two Listeria strains, and higher concentrations of OL were needed to inactive pathogens. Our results show that adding low molecular weight chitosan to food emulsions can significantly decrease the number of pathogens and increase the safety of such foods.
Session 29G, Food Microbiology: General
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