Characterizing the cultivation practices and microbiological quality of watercress

Watercress is an aquatic leafy vegetable widely consumed in Mauritius. However, the microbiological safety of watercress is a concern as it is typically consumed raw without cooking or any heat-treatment. The main aim of this study was to characterize the cultural practices of watercress in Mauritius and to assess the microbiological safety and sanitary quality of the leafy green. Information on cultivation practices of watercress was gathered through in-depth interviews with planters from different regions of the island as well as on-site observation. Samples of watercress and surrounding water were collected from different growers and subjected to microbiological analyses for mesophilic aerobic bacteria (MAB), generic E. coli, pathogenic E. coli, Salmonella spp., Listeria spp. and Clostridium perfringens for watercress; and MAB, total coliforms and E. coli for water. In addition, watercress samples were subjected to different washing treatments to compare their efficacy to reduce the microbial load. The study revealed that watercress was typically cultivated in river or spring water, on a medium comprising of soil or gravel bed, and propagated by vegetative fragments. Both watercress and growing water were found to have a relatively high population density of generic E. coli of up to 3.4 log cfu/g and 3.1 log cfu/ml respectively pointing to a high possibility of fecal contamination. Washing watercress leaves with 40% vinegar was found to be marginally effective achieving a reduction of 1.1 log cfu/g in MAB count. This study sheds light on the cultivation practices and the microbiological quality of watercress and also underscores the need for more research to devise effective sanitizers for leafy green vegetable such as raw watercress for enhanced quality and extended shelf-life.