Microbiological Studies on Gas-Packaged Crumpets

Abstract

English-style crumpets, a chemically leavened bakery product, had a shelf life of 14 d when packaged in a CO 2 :N 2 (3:2) gas atmosphere and stored at ambient temperature. Packages were visibly swollen after 14 d due to additional CO 2 production, and the product had a distinct fruity odor when opened. Initial microbiota of the product, isolated from anaerobic plates, consisted entirely of facultative anaerobic spore-forming strains of Bacillus licheniformis. After 7 d at 25°C the spoilage pattern changed, with lactic acid bacteria (LAB) accounting for almost 100% of the total anaerobic plate counts (TPC) on APT and MRS (pH 5.5) ~gar m~dia. Subsequently, the number of LAB declined slightly III relatIOn to the TPC, and B. licheniformis strains reappeared. As the LAB increased in numbers, there was a concomittant increase in CO 2 and lactic acid production and a drop in pH of the product. Metabolic activity continued even after the LAB were in the maximum stationary phase. Leuconostoc mesenteroides was subsequently identified as the major CO 2-producing isolate.