Enhanced antimicrobial effect of organic acid washing against foodborne pathogens on broccoli by vacuum impregnation.
This study was undertaken to evaluate the effect of vacuum impregnation applied to the washing process for removal of Salmonella Typhimurium and Listeria monocytogenes from broccoli surfaces. Broccoli was inoculated with the two foodborne pathogens and treated with simple dipping washing or with vacuum impregnation in 2% malic acid for 5, 10, 20, or 30 min. There were two methods of vacuum impregnation: continuous and intermittent. After 30 min of 101.3 kPa (=14.7 psi, simple dipping), 61.3 kPa (=8.9 psi), and 21.3 kPa (=3.1 psi) of continuous vacuum impregnation treatment, there were 1.6, 2.0, and 2.4 log 10 CFU/g reductions of S. Typhimurium and 1.5, 1.7, and 2.3 log 10 CFU/g reductions of L. monocytogenes, respectively. After 30 min of 101.3, 61.3, and 21.3 kPa of intermittent vacuum impregnation treatment, there were 1.5, 2.3, and 3.7 log 10 CFU/g reductions of S. Typhimurium and 1.6, 2.1, and 3.2 log 10 CFU/g reductions of L. monocytogenes, respectively. Scanning electron photomicrographs showed that bacteria tend to attach to or become entrapped in protective sites after simple wash processing (dipping). However, most bacteria were washed out of protective sites after intermittent treatment. Direct treatment of cell suspensions with vacuum impregnation showed that it had no inactivation capacity in itself since there were no significant differences (P ≥ 0.05) between the reduction rates of non- and vacuum impregnation treatment. These results demonstrate that the increased antimicrobial effect of vacuum impregnation can be attributed to increased accessibility of sanitizer and an enhanced washing effect in protected sites on produce. Color, texture and titratable acidity values of broccoli treated with intermittent vacuum impregnation in 2% malic acid for 30 min were not significantly (P ≥ 0.05) different from those of untreated samples even though a storage interval was needed for titratable acidity values to be reduced to levels comparable to those of untreated controls.
Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea; Institutes of Green Bio Science & Technology, Seoul National University, Pyeongchang-gun, Gangwon-do 232-916, Republic of Korea.
Jun-Won
JW
Kang
Department of Food and Animal Biotechnology, Department of Agricultural Biotechnology, Center for Food and Bioconvergence, Research Institute for Agricultural and Life Sciences, Seoul National University, Seoul 151-921, Republic of Korea; Institutes of Green Bio Science & Technology, Seoul National University, Pyeongchang-gun, Gangwon-do 232-916, Republic of Korea. Electronic address: kang7820@snu.ac.kr.
Dong-Hyun
DH
Kang
D001937:Brassica / Q000382:microbiology*; D015169:Colony Count, Microbial; D004202:Disinfectants / Q000494:pharmacology*; D005516:Food Microbiology; D005517:Foodborne Diseases / Q000382:microbiology / Q000517:prevention & control*; D008089:Listeria monocytogenes / Q000187:drug effects*; D008293:Malates / Q000494:pharmacology*; D008855:Microscopy, Electron, Scanning; D012486:Salmonella typhimurium / Q000187:drug effects*; D014618:Vacuum
D004202:Disinfectants; D008293:Malates; C030298:malic acid
Broccoli; Listeria monocytogenes; Organic acid; Salmonella Typhimurium; Sanitizer; Vacuum impregnation