76C-12 |
The effect of pH on inactivation of bacteria on fresh-cut lettuces by dipping treatment with electrochemical activated water |
H. YANG1, B. L. Swem2, and Y. Li2. (1) Department of Poultry Science, University of Arkansas, Poultry Science Center, O-420, Fayetteville, AR 72701, (2) Department of Biological and Agricultural Engineering, University of Arkansas, Poultry Science Center, O-420, Fayetteville, AR 72701 Fresh-cut and ready-to-eat lettuce has been identified as a vehicle of pathogens such as Escherichia coli O157:H7, Listeria monocytogenes, and Salmonella Typhimurium. Initial microbial load on fresh-cut lettuce was reported to have great influence on the product safety and the shelf-life of the products. Electrochemical Activated Water (ECAW) had shown a higher bactericidal efficacy than the chlorinated water with the same amount of chlorine, due to its fresher supply and more active agents. The purpose of this research was to determine the effect of pH in ECAW treatment on the bacterial reduction and the shelf-life of lettuce products. Six dipping treatments, each with pH of 4, 5, 6, 7, 8 or 9, were conducted with 300 ppm ECAW at 30°C for 5 min. To determine the reduction of pathogenic bacteria, six lettuce samples were inoculated with nalidixic acid (NA) resistant S. Typhimurium, E. coli O157:H7 and L. monocytogenes. Three samples were controls and three samples were treated with ECAW. To compare the shelf-life of lettuces with and without ECAW treatment, twelve non-inoculated lettuce samples, six treated and six untreated were placed into perforated bags and stored at 4°C for 7 days. Three treated and three untreated samples were collected in both days 1 and 7 for determination of Aerobic Plate Count and vegetable color. The pH of ECAW changed between 4 and 9 resulted in a variation of bacterial reduction within 0.5~1 log cycle. The most effective pH values for reduction of S. Typhimurium, E. coli O157:H7, L. monocytogenes and aerobic bacteria were 7, 4/8, 4/7 and 7, respectively. Including the consideration of the visual quality of vegetable, pH 7~8 is suggested. This research provides the fresh produce industry with valuable information needed for application of ECAW in control of product safety and quality.
Session 76C, Fruit & Vegetable Product: Fresh Fruits and Vegetables
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