Effect of refrigeration on the quality of beef frankfurter and chicken pepperoni

Abstract

The present study was conducted to assess the microbial, physico- chemical and organoleptic qualities of beef frankfurter and chicken pepperoni at chilled and frozen storage. Effect of storage on these products was studied by estimating various microbial counts, assessing the presence of certain pathogenic and spoilage bacteria and studying the changes in pH and TBARS number and organoleptic qualities like color, odor and presence of sliminess. In chilled samples (4-7°C) the mean total viable count, faecal streptococcal count, psychrotrophic count and yeast and mold count were found to increase significantly as storage period progressed. In both the products, coliforms reached a detectable level by second day of chilled storage and thereafter the count increased. E. coli were detected only from samples of chilled beef frankfurter from fourth day onwards and the count remained at 101 cfu/g level. Aeromonas hydrophila, A. sobria and A. caviae were the three species of Aeromonas isolated from the chilled samples of both the products. Hemolytic and hemagglutination assays of these isolates were also carried out which is indicative of enteropathogenic effects. Escherichia coli were isolated from beef frankfurter samples. Among the isolates 84.62 per cent belonged to the serotype O2 ( Enterohaemorrhagic E. coli.). Salomonellae could not be detected from any of the samples. A number of samples revealed the presence of Pseudomonas aeruginosa. Important species of lactobacilli isolated were Lactobacillus brevis, Lactobacillus curvatus, Lactobacillus fermentum and Lactobacillus sake. The mean pH and TBARS values were increased during chilled storage, indicating the progress of development of acidity and rancidity. Color and odor scores gradually increased from fourth day onwards and slight discoloration was noticed on 10th day in both the products. Surface slime was developed on fourth day in beef frankfurter samples and from sixth day onwards in chicken pepperoni samples. Thus, the shelf life was found to be four days for beef frankfurter and less than six days for chicken pepperoni stored at 4-7° C. When samples were stored at –20°C, it was observed that mean total viable counts of fresh and frozen beef frankfurter samples did not differ significantly. Frozen samples of chicken pepperoni had the total viable count significantly (P<0.05) lower than that of fresh samples. Aeromonas hydrophila, A. sobria and A. caviae were isolated from frozen samples of both the products. Many of the isolates were hemolytic and hemagglutinating. Pseudomonas aeruginosa were also detected. E. coli , salmonellae, and lactobacilli were not isolated from any of the frozen samples. Frozen sausage samples had lower mean pH values when compared to fresh samples and mean TBARS values were found to decrease gradually during the frozen storage. Color and odor scores remained the same during frozen storage and slime formation was not observed in frozen samples. Study revealed that frozen samples of both products had a shelf-life of 90 days. In order to identify various critical points of bacterial contamination, samples of air, water, rinse samples from equipment, hand washing of personnel in the processing line and packaging material were examined for their hygienic quality. The mean total viable count and yeast and mold count of air samples were found to increase after processing. Among the water samples, the high microbial count was recorded for hand washings, reflecting unsanitary working practices. Among the equipment, sausage filler was found to contribute maximum to the total microbial load of the product. Among the raw ingredients, samples of beef used for preparation of beef frankfurter and samples of pork used for chicken pepperoni were found to possess high bacterial load. Coliforms were present at 2 log cfu/g level in all the ingredients. Faecal streptococci were detected in all the ingredients except beef. E. coli were present only in samples of spices. Study reflects the importance of quality assurance during every step of preparation of ready-to-cook meat products to avoid the early spoilage and to safe guard consumer health. Presence of pathogenic organisms in these products is of great public health significance as improper cooking can cause outbreaks of food borne diseases.