Changes in microbial contamination levels and prevalence of foodborne pathogens in alfalfa (Medicago sativa) and rapeseed (Brassica napus) during sprout production in manufacturing plants

Samples were taken from three sprout processing plants at five different stages of production (a total of 20 investigations). Quantitative analyses comprised aerobic plate counts (APCs) and the measurement of coliforms and Bacillus cereus levels, whereas qualitative analyses involved assessing the levels of Escherichia coli and major foodborne pathogens (E. coli O157:H7, Listeria monocytogenes, Salmonella spp., and Staphylococcus aureus). The APC for alfalfa seeds (3·71-4·61 log CFU g^-1) and rapeseed (4·25-5·11 log CFU g^-1) increased by approximately 3 log CFU g^-1 during sprouting, reaching 7·17-7·61 and 7·33-8·28 log CFU g^-1, respectively, by the final stage of production. Similarly, increasing trends were noted in the level of coliforms (0·58-4·03 log CFU g^-1 at the seed stage, increasing to 5·52-6·99 log CFU g^-1 by the sprout stage). Bacillus cereus was detected in eight alfalfa (40%) and 14 rapeseed (70%) sprouts, and L. monocytogenes was isolated from one pregermination soaked alfalfa seed. A slight reduction in the level of bacterial contamination was noted after washing the sprouts with water prior to storage, indicating that improvements to the current washing protocol, or other efficient intervention methods, may be needed. Taken together, these results suggest that improved hygiene control during production and processing and a more sanitary environment are needed. The present study provides comprehensive information regarding the microbiological safety of seeds and sprouts during manufacturing. Significance and Impact of Study: The present study investigated the levels of microbial contamination present in alfalfa and rapeseed sprouts by examining the samples taken at different stages of the manufacturing process in three actual plants. The results provide detailed information regarding the levels of seed and sprout contamination during production. The results may be useful to those involved in the sprout industry and/or academic research in terms of developing hygienic control measures, efficient intervention methods and appropriate guidelines.