SUBSTRATE-MEDIATED ASSAY OF BACTERIAL PROTON EFFLUX INFLUX TO PREDICTTHE DEGREE OF SPOILAGE OF BEEF MINCE STORED AT CHILL TEMPERATURES/

A method was developed to predict spoilage of minced meat at chill tem peratures, based on the difference in proton efflux from and influx in to bacterial cells. This difference depends on the number of organisms present, the available glucose in the meat sample and the ability of the organisms to metabolize amino acids. The proton efflux/influx of a meat filtrate containing bacteria was measured at 25 degrees C with a pH/ion meter in the presence of peptone with or without glucose. Ther e was a noticeable rate of change of mV h(-1) of the meat filtrate pri or to the organoleptic detection of spoilage which may be used semi-pr edictively to determine the remaining shelf-life of meat at different storage temperatures. The method could be investigated further, encomp assing type and relative numbers of organisms, incubation temperature, meat type and composition (i.e. available glucose) to produce a spoil age prediction model. The method does not require sophisticated equipm ent, only a standard pH/ion meter, is cheap, needing only peptone and glucose, is relatively simple, and takes less than 2 h to perform.