title: Gastric Fluid and Heat Stress Response of Listeria monocytogenes Inoculated on Frankfurters Formulated with 10%, 20%, and 30% Fat Content.
abstract: This study evaluated the effects of frankfurter fat content on Listeria monocytogenes resistance to heat stress and gastric fluid, and the Caco-2 cell invasion efficiency of the pathogen. A 10-strain mixture of L. monocytogenes was inoculated on frankfurters formulated with 10%, 20%, and 30% fat content (10%: F10, 20%: F20, 30%: F30) and stored at 10℃ for 30 d. The samples were analyzed for L. monocytogenes resistance to heat stress and a simulated gastric fluid challenge. The total bacteria and L. monocytogenes survival rates were measured on tryptic soy agar plus 0.6% yeast extract and Palcam agar, respectively. L. monocytogenes colonies inoculated on F10, F20, and F30 samples were used for a Caco-2 cell invasion assay. In general, no obvious differences were observed between the survival rates of total bacteria and L. monocytogenes grown on different fat contents under heat stress and gastric fluid challenge. However, L. monocytogenes obtained from the F30 samples had a significantly higher Caco-2 cell invasion efficiency than those in the F10 and F20 samples (p<0.05). These results indicate that although high fat content in food may not be related to L. monocytogenes resistance to heat stress and gastric fluid, it may increase the Caco-2 cell invasion efficiency of the pathogen.
authors.affiliation: Department of Animal Resources Science, Kongju National University, Yesan 340-702, Korea.
authors.forename: Hack-Youn
authors.initials: HY
authors.lastname: Kim
authors.affiliation: Department of Food Science and Biotechnology of Animal Resources, Konkuk University, Seoul 143-701, Korea.
authors.forename: Cheon-Jei
authors.initials: CJ
authors.lastname: Kim
authors.affiliation: Department of Food Science and Biotechnology of Animal Resources, Konkuk University, Seoul 143-701, Korea.
authors.forename: Sung Gu
authors.initials: SG
authors.lastname: Han
authors.affiliation: Department of Food and Nutrition, Sookmyung Women's University, Seoul 140-742, Korea.
authors.forename: Sunah
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Oral Microbiology, College of Dentistry, Wonkwang University, Iksan 570-749, Korea.
authors.forename: Kyoung-Hee
authors.initials: KH
authors.lastname: Choi
authors.affiliation: Department of Food and Nutrition, Sookmyung Women's University, Seoul 140-742, Korea.
authors.forename: Yohan
authors.initials: Y
authors.lastname: Yoon
keywords: Listeria monocytogenes; caco-2 cell; fat; gastric fluid; heat resistance