EFFECT OF FREEZING AND PACKAGING METHODS ON SURVIVAL AND BIOCHEMICAL ACTIVITY OF SPOILAGE ORGANISMS ON CHICKEN

Abstract

SUMMARY— A study was conducted to determine effects of freezing, thawing, and subsequent holding at about 5°C on survival or growth of aerobic bacteria on chicken packaged with various materials. Production of fluorescent pigment, and extracellular proteinase and lipase activities were used as indices of the ability of the organisms to produce spoilage. Growth of bacteria was determined by colony counts. Assays for proteolysis were made by means of a dye binding method; lipolysis of chicken fat was determined by titration of free fatty acids. Fluorescent pigment formation was evaluated by means of a photofluorometer. The influence of availability of oxygen on proteolytic and lipoytic spoilage of poultry was studied after chicken was packaged with materials having high or low oxygen permeability and by vacuum packaging. Fluorescent pigment production, proteofytic and lipolytic spoilage of chicken stored at 5°C was directly related to the availability of oxygen provided by the packaging procedure. Bacterial numbers paralleled increases in biochemical indices of deterioration. Freezing of chicken at −29°C for 35 days followed by defrosting and refrigerated storage increased the proportion of biochemically active psychrophiles on the surface of the meat. Vacuum packaging generally limited amount of spoilage as measured by the criteria specified. When samples were analyzed after alternate freezing and thawing, total aerobic bacterial counts were only slightly different from those on chicken frozen continuously for 22‐25 days.