Growth of Listeria monocytogenes during germination of alfalfa sprouts

A large number of micro-organisms are able to proliferate on sprouts. The microflora may occasionally contain pathogenic bacteria that can be a source of outbreaks. Listeria monocytogenes has been detected from various vegetables and has been the source of foodborne outbreaks originating from vegetables. This study investigated the capacity of L. monocytogenes to grow on germinating alfalfa sprouts in a mini-sprouter. It also assessed the inhibitory activity of Lactococcus lactis against L. monocytogenes inoculated onto sprouts (approximately 2 x 10(2) cfu g(-1)). L. monocytogenes was able to proliferate during the germination of alfalfa sprouts, reaching levels of around. 10(6) cfu g(-1) within 48 h. The level of L. monocytogenes remained constant when the sprouts were subsequently stored at 4degreesC for 7 days, When Lact. lactis was co-inoculated onto the seeds at the beginning of the sprouting process, the maximum levels of L. monocytogenes were approximately 1 log lower than those observed with the control cultures. LAB counts increased rapidly, reaching almost 10(8) cfu g(-1) in 24 h, but by the end of the first 24h the total aerobic counts exceeded the LAB counts. The extent of the inhibitory effect of Lact, lactis was substantially less on alfalfa than that observed in a model system. Published by Elsevier Science Ltd.