Influence of Temperature and Gas Permeability of Packaging Film on Development and Composition of Microbial Flora in Vacuum-Packed Bologna-Type Sausage

Abstract

Studies were done on the influence of gas permeability of packaging film on microflora of vacuum-packed Bologna-type sausage at three storage temperatures, i.e., 2, 5 and lOoe. Great-est development of total aerobic plate count and Brochothrix ther-mosphacta was observed in film having the highest permeability. The packaging film influenced the maximum counts and growth rates of organisms. Growth of both gram-positive cocci and yeast were stimulated in packages having the greatest permeabilities, whereas the opposite occurred for the lactic acid bacteria. Large numbers of gram-negative bacteria were found in all series. These consisted of Enterobacteriaceae, MoraxellalMoraxella-like bac-teria and atypical Vibrio. Only Enterobacteriaceae were highly influenced by the nature of the packaging film. Organoleptic analyses showed a clear association among odor, the develop-ment of microflora and the gas permeability of packaging film. Many studies have been done concerning the develop-ment of the microflora in vacuum-packed, cured meat products. Results of some of these experiments are con-flicting with regard to the effect of vacuum packaging (l,15,20; J. C. Ayres, Proc. 18th Ann. Reciprocal Meat Conf. 1965, 18:40-52). While some authors observe no ef-fect of vacuum packaging, others find a reduced growth rate and/or a lower maximum count in vacuum-packed samples. Development of microflora in the package is in-fluenced by the availability of oxygen and the concentra-tion of carbon dioxide in the head space and dissolved in the water phase. Marked differences between the studie"s may, therefore, be associated with the permeability of oxy-gen and carbon dioxide through the packaging film used. This is particularly important in early studies where films with high gas permeabilities were used (15,20), but also in recent experiments where very permeable film has been used (7). In a recent study (23), the effect of using films with oxygen permeabilities of 11 and 87 mlim 2 /24 h at 24°C for inoculated packages of bacon was examined. The effect of packaging film on the bacterial flora was variable; however, increasing the initial vacuum level from 64-66 mm Hg to 71-73 mm Hg retarded growth. The present study was done to determine the influence of gas permea-bility of packaging film on the growth pattern and compo-sition of microflora during storage at different tempera-tures. Moreover, an organoleptic assessment of odor was done of content of the packages during storage.