MATHEMATICAL MODELING OF MICROBIAL GROWTH IN VACUUM-PACKAGED AND REFRIGERATED FRESH COW MEAT

Abstract

Fresh meat is a highly perishable product due to its biological composition. This study examined the effect of different storage time (24, 48, 72 hours), gaseous permeability of packaging film (Aluminum foil and Polyethylene) on the growth of microorganisms (Bacteria and fungi) isolated from the refrigerated cow meat at constant temperature of 0°C. Microbial growth was modeled using Gompertz and Linear Regression Models. The bacteria count was observed to decrease as the storage time increases. While fungi count was observed to increase with increasing storage time. Aluminum foil packaged cow meat samples recorded lower microbial growth when compared to polyethylene packaged samples. In Gompertz model, the specific growth rate (μ) of the test organisms was observed to increase significantly upon a shift of storage time. The transition from 24 hours to 48 hours resulted in large changes in the growth profile with increased maximum population density (MPD) of the test organisms. However, lag phase of approximately two hours for bacteria and five hours for fungi was observed. An increase of storage time from 48 hours to 72 hours, an accelerated μ, higher MPD with reduced lag phase duration (LPD) was observed. In the linear regression model, the  coefficient of determination (R²) values for aluminum foil packaged samples was 0.3 and polyethylene packaged samples was 0.1. Therefore, it can be concluded that varying storage time at constant temperature; μ and MPD of the test organisms significantly increased with decreasing LPD of both studied vacuum packaging films of the refrigerated fresh cow meat.