A SURVEY OF MINCED LAMB PACKAGED IN MODIFIED ATMOSPHERES

A survey of microbiological and physico-chemical parameters of minced lamb packed under modified atmosphere and sold by five major supermarkets nation-wide in the U.K. was made. Samples were analysed on the purchase and on the expiry day. Lactic acid bacteria (Carnobacterium piscicola, Carnobacterium divergens, Leuconostoc mesenteroides subsp. mesenteroides, Lactococcus raffinolactis), Brochothrix thermosphacta, pseudomonads (Pseudomonas fragi, Pseudomonas fluorescens, Pseudomonas lundensis), Enterobacteriaceae and yeats, given in order of numerical importance, were members of the microbial associations on the expiry day. Of the physico-chemical attributes pH decreased, glucose, glucose 6-phosphate, gluconate were catabolised, and, L-, D-lactic and acetic acid and ammonia were produced. Dominance of lactic acid bacteria was reflected in a decrease in pH, production of D-lactic and acetic acid and, following depletion of the carbohydrates, an oxidation of lactate isomers to acetate. When B. thermosphacta was dominant these changes were not detected to the same extent. When a large population of pseudomonads was present oxidation of glucose to gluconate occurred.