Bacterial biofilms of foodborne pathogens pose the risk of secondary contamination in a food processing environment. Listeria monocytogenes is a Gram-positive, foodborne pathogen that contaminates various foods and environments. This bacterium can form biofilms on food-related surfaces. In this study, to inhibit biofilm formation by L. monocytogenes, we focused on suppressing the initial adhesion of the pathogen onto polystyrene dishes, which is the first step of biofilm formation. Screening of adhesion inhibitory materials using polystyrene dishes surface-treated with food-related materials demonstrated high inhibitory effects of nisin and whey powder against L. monocytogenes adhesion. Moreover, surface treatment with nisin was able to delay biofilm formation of L. monocytogenes and the dish surface showed bactericidal activity. To improve the adhesion inhibitory effects of nisin, we combined nisin and a sucrose fatty acid ester, sucrose palmitate, for surface treatment, and this combination markedly improved the adhesion inhibitory effects. Thus, combined surface treatment with nisin and sucrose palmitate may be an effective method to prevent biofilm formation by L. monocytogenes in food processing environments.

Two cured vanilla beans having different harvest maturities were compared by sensory evaluation and Aroma Extract Dilution Analysis (AEDA). Based on the sensory evaluation, the mature vanilla possessed sweeter, less sour, and less hay-like notes than the immature group. The AEDA result suggested the compounds contributing to each aroma characteristic, for example, vanillin, 2-methoxyphenol, isovaleric acid and 3-methyl-2,4-nonanedione. Among these, the flavor dilution (FD) factor of vanillin was the highest in each vanilla and significantly differed according to maturity. A further study of β-glucosidase in green vanilla, related to vanillin formation, revealed that the mature vanilla exhibited greater activity than the immature group. These results suggested that enzymatic activity is an important factor in differences in the aroma characteristics between mature and immature vanilla beans.

Yellowtail Seriola quinqueradiata raised on a diet supplemented with powdered olive leaves is a popularly cultured fish registered under the brand name “Olive Yellowtail” in Japan. Here the fat content in 1-year-old yellowtail and the taste of its muscles were compared between an experimental group raised on a diet supplemented with powdered olive leaves (OL-fish group) and a control group raised on a conventional diet. Crude lipid analyses showed that the dark muscles of the OL-fish group had 25% lower lipid content than those of the control group. Crude lipid content in dorsal ordinary muscles showed no between-group difference. In abdominal ordinary muscles, crude lipid content tended to be lower in the OL-fish group than in the control group. Free amino acid analyses of dorsal and abdominal ordinary muscles showed that the OL-fish group had 1.4- and 1.3-times higher alanine content, respectively, than the control group. Fatty acid content showed no between-group difference. Taste assessment of muscle extracts using a taste sensor indicated that saltiness and umami were higher in the OL-fish group than in the control group. These results suggested that the OL-fish group was different in fat content and primary taste compared with the control group.