Development of antimicrobial edible coatings to reduce microbial contamination of broiler carcasses (original) (raw)

Broiler carcasses are a significant source of pathogenic microorganisms which can cause food-borne illnesses if not properly cooked. The extent of broiler flock contamination varies, but normally increases by contact of birds with equipment, and by scalding, defeathering and chilling. The currently used on-line approved chernical antimicrobials vary in their activity and do not effectively inactivate contaminating microorganisms, presumably as a result of microbial cell entrapment inside the carcass skin. In this work, antimicrobial coatings were designed to be sprayed or coated on broiler carcasses during processing. The resistance of physical and mechanical properties of high amylose pea starch (PS) and rice starch (RS) films to high relative humidity (RH) and plasticizer addition was investigated in the first part of the thesis. PS films which contained higher amylose showed more desirable properties than the RS films which contained low amylose at the same RH. The addition of glycerol to the films helped to form a more continuous structure. Increasing the RH from 5l to 90 o/o reduced tensile strength and increased the elongation of both films with PS films being more resistant to deformation. Both films were excellent oxygen bariers at low RH (534 %) but had relatively low water vapor permeability compared to other edible f,ilms in the literature. The inhibitory activity of the most commonly used commercial antimicrobials was examined against E coli 0757:H7, Salmonella and Campylobacter spp. in the second part of the thesis. The commercial antimicrobials used were trisodium phosphate (TSP), Sanova (acidified sodium chlorite, ASC), Safe2O, Inspexx 100 and Cecure. Factors such as antimicrobial concentration, contact time, sequential use of two antimicrobials and the most appropriate stage of processing for use of the antimicrobials were studied. Results showed v that TSP (10 %) and acidified sodium chlorite (0.12 %) were the most effective for reducing viability of the pathogens and this was related to their effect on surface pH of the skin. Increasing the antimicrobial concentration and contact time up to 20 min enhanced the antimicrobial effectiveness. Sequential use of antimicrobials also increased activity especially for compounds used before cetylpyridinium chloride (CPC), with TSP being the most effective. Antimicrobials were also more effective on \¡/arm (before chilling) than on cold (after chilling) carcasses, indicating the use of antimicrobials in early stages of processing would be more efficient. When TSP (10 o/o) and ASC (0.12 %o) were stabilized by incorporation into coatings made of pea starch (3 %) or calcium alginate (l .0 %), respectively, their antimicrobial activity significantly (p < 0.05) increased. Salmonellct inoculated on the skin were reduced about 1.5 log cfu/g and < 1.0 log cfu/g by the stabilized and unstabtlized antimicrobials, respectively, after storage at 4 "C for 24h. Current Canadian standards require that carcasses be free of any additive before leaving the processing plant. This is why the third objective of the study was to formulate coatings ix TABLE OF CONTENTS