Development of nisin-based treatments to control pathogenic and spoilage microorganisms associated with poultry products

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Title: Development of nisin-based treatments to control pathogenic and spoilage microorganisms associated with poultry products
Author: Shefet, Sarid Moshe
Advisors: Dr. Brian W. Sheldon, Chair of Advisory Committee, Member
Dr. Todd R. Klaenhammer, Member of Advisory Committee, Member
Dr. William H. Swallow, Minor Representative, Member
Abstract: More than 10% of the U.S. population experience at least one incident of foodborne disease annually (Todd, 1989). From 1983 to 1987, infections contribute to at least 1,000 deaths per year in the United States. Poultry products are considered to be the single most important food source of contamination rates for live chickens can vary from about 13% to 80% of the flock and are invariably higher after processing (Mead, 1976; Roberts, 1988; Budnik, 1990). In 1992, the U.S. was ranked first in the world in poultry consumption with 94.8 pounds per capita, followed by Israel with 83.7 pounds, and Hong Kong with 79.3 pounds (Brown, 1993). In 1993 over 27.6 billion pounds of ready-to-cook poultry products were produced in the U.S. Per capita consumption of poultry products has increased substantially over the last two decades relative to other meat products; therefore, exposure of the consumer to poultry product-associated microorganisms including pathogens has correspondingly increased and no doubt contributes to these foodborne disease statistics. Besides bacterial pathogens, poultry products are also contaminated with a variety of spoilage microorganisms which can contribute to the development of strong off odors and/or slime formation and shortened product shelf life. These organisms, however, are not generally associated with human illness. A reduction in the population of these microorganisms or suppression of their growth often results in increased product shelf life and greater consumer acceptability. Some reports have estimated that the presence of pathogenic and spoilage microorganisms on poultry may cost the American public over two billion dollars annually in foodborne disease-related expenditures and spoiled products (Roberts, 1988; Todd, 1989). The bacteriocin nisin was approved by the United States Food and Drug Administration in 1988 as a GRAS (general recognized as safe) substance for use in pasteurized cheese spreads to control outgrowth and toxin production by Clostridium botulinum. Blackburn when combined with chelating agents such as disodium ethylenediamine tetraacetate (EDTA) and citrate. Perturbation of the outer membrane of gram-negative bacteria via chelation of divalent cations located in the lipopolysaccharide layer is believed to sensitize the cells by providing access to the cytoplasmic membrane where nisin-mediated inactivation occurs. The initial focus of this study was to optimize the inhibitory activity of nisin against a NAR skin population, as observed with broiler drumstick skin, were detected following treatment with the four nisin-containing treatments. Experiments were also conducted to determine the efficacy of the nisin-based treatments against NAR-infected drumstick skin under varying exposure times and concentrations of nisin. Exposure time significantly influenced the lethality of the treatments and depending on the treatment, nisin concentrations could be reduced from 100 µg/ml to 50 or 25 µg/ml without loss of significant biocidal activity. In other studies, the refrigerated shelf life of broiler drumsticks was extended by 1.5 to 3 days following immersion for 30 minutes in one of the optimized nisin-containing treatments in comparison to drumsticks immersed in distilled, deionized water. These findings indicate that treatments containing nisin and varying concentrations of chelating agents and/or surfactant at an acidic pH are capable of significantly inhibiting the population of -free poultry products, the identification and implementation of effective preservation methods could result in several long term benefits including greater public confidence in poultry products, an increased market potential, and increased profits for the poultry industry.
Date: 1997-09-19
Degree: MS
Discipline: Food Science

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