Control of Food-Borne Pathogens in Pre-and Post-Harvest Environments

NON-TECHNICAL SUMMARY: Several outbreaks have been linked to the consumption of seafood with foodborne pathogens. This project will develop methods for controling foodborne pathogens on the surface of seafood.

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APPROACH: Inoculation of seafood and fish: Listeria monocytogenes or Salmonella spp. will be grown in BHI broth at 37degreeC for 24 h. The culture (5 ml) will then be added to a sterile dip cup and diluted in 45ml of PBS buffer. The seafood and smoked fish samples will be inoculated by dip method for 1 min. and allowed to sit for 1 h to ensure adhesiveness of cells to the sample surface. Following inoculation, each sample will be treated with either edible coatings containing antimicrobial agents, cetylpyridinium chloride (CPC) or acidified sodium chlorite (ASC). Samples will be stored at 4degreeC under simulated industry conditions and L. monocytogenes counts determined on modified Oxford (L. monocytogenes) or XLD (Salmonella spp.) media at day 0, 2, 4, 6, and 8. Preparation of sanitizers: Seven solutions of cetylpyridinium chloride (CPC) will be prepared in sterilized deionized water at concentration levels of 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0%. All solutions will be made fresh prior to conducting experiment and will be used at room temperature within 1 h. Sodium chlorite solution (Keeper Professional Bio-Cide International, Inc.) will be mixed with citric acid and sterile distilled water to form the acidified sodium chlorite solution. The mixing process will be done according to manufacturer's instructions with sterile distilled water. The sodium chlorite concentrate (Keeper Professional) will be mixed with citric acid and allowed to activate for 10 minutes. The solution concentrate (pH 2.62) will be then diluted with sterile distilled water to 250, 500, 750 and 1000 parts per million (ppm). The various treatments will be placed in sterile specimen cups and held for one hour at room temperature before being used. Cetylpyridinium chloride treatment will be analyzed at concentrations of 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0%. Edible coating treatment (LA): We will evaluate agar gels (0.75% or 1.25%), chitosan coatings, 15% whey protein films, 5% soy protein films or 0.5% calcium-alginate films with a combination of the most effective antimicrobial agents as determined above (Natrajan and Sheldon, 2000a-b). In addition, zein propylene glycol liquid film and zein prolamine powder preparations will be obtained from Freeman Industries, L.L.C., Tuckahoe, New York. The antimicrobial agents incorporated into the edible films will include nisin, lauric acid or lysozyme in combination with chelating agents needed to reduce the bacterial species inoculated onto the surface of food products. Nisin at a concentration of 500 IU/g, 1000 IU/g 1500 IU/g or 2000 IU/g of film solutions with and without added EDTA at 15 or 30 mM. Lysozyme will be tested at concentrations of 33, 66 and 99 mg/g of film solutions with and with out EDTA at 15 or 30 mM (Padgett et al., 2000). Lauric acid at concentrations of 4 and 8% (w/w) will be added to the test film solutions with and without added EDTA at 15 or 30 mM (Padgett et al., 2000).