Tolerable limits of fecal coliforms in the conservation of vacuum-packed beef stored at 0° C

Abstract

pH and temperature are fundamental parameters for the storage and maintenance of beef quality. The purpose of the present work was to evaluate the shelf life of meat from 120 samples of 10 steers, during 3 months of storage at 0° C and vacuum packed. For this purpose, a measurement was made 48 h post mortem in 3 pH ranges: <5.8, 5.9 and 6 to 7 to quantify Escherichia coli and mesophilic aerobes. Regarding the sensory factor, flavour, colour, odour and texture of the meat were evaluated. Samples were evaluated monthly. The statistical analysis corresponded to the randomized block design, applying the Tukey test at 5 % and 1 %. The mesophiles, were 6.8x106 to 10x106 CFU/g, E. coli that developed between 1.75 to 2.5 CFU/g. Bacterial growth showed values of 5.9 and 6 to 7 pH, unfavourable values according to Bolivian standard 310017. In the evaluation of E. coli, there was no significant statistical difference (p>0.05), however, aerobic bacteria showed a significant difference in the months of study (p<0.01). The sensory analysis did not show variations until the 2nd month of conservation, deteriorating afterwards with pH higher than 5.9 in meat stored under vacuum for 3 months, which means that its sensory and microbiological characteristics are not within the normal parameters. It is concluded that meat with intermediate and high pH should not be vacuum packed or stored for more than 3 months, as it loses its organoleptic characteristics. However, meat with low pH and stored at low temperature maintained its quality for 3 months, therefore it is considered that pH and temperature are important factors to control microbial growth and maintain meat quality.