Hygienic status and biogenic amine content of mung bean sprouts

 Microbiological analyses of commercial mung bean sprouts showed the total, viable microbiological population to exceed 10⁸ cfu/g. Enterobacter cloacae, Klebsiella pneumoniae and Enterobacter agglomerans were found to be the dominant and most frequently isolated microbial species. Putrescine, cadaverine, spermidine and spermine were detected in all samples investigated. Formation of biogenic amines by pure culture isolates was studied in a modified decarboxylase medium at different temperatures, pH values and atmospheres. Highest activities were found under aerobic conditions at 20  °C. K. pneumoniae 861 produced 1.2 mg cadaverine/ml after an incubation period of 24 h and E. cloacae 862 produced 2 mg putrescine/ml after 48 h of incubation. For E. agglomerans 863, no biogenic amines were detected under these conditions. Production of cadaverine by E. cloacae 862 and K. pneumoniae 861 under aerobic conditions is presumably related to lysine decarboxylase activities. Although highest decarboxylase activities have usually been found at acidic pH values, amine production reached a maximum at pH 7. Under anaerobic conditions, E. cloacae 862 produced only about half the amount of putrescine as under aerobic conditions, whilst K. pneumoniae 861 produced significantly less cadaverine but was able to produce putrescine. Received: 10 October 1997 / Revised version: 21 January 1998