Effectiveness of Common Sanitisers on the Microbial Load of Lettuce (Lactuca sativa) Produced in Bamako, Mali

Abstract

Raw lettuce may transmit foodborne microorganisms when produced or consumed without adequate hygienic control. This study evaluated bacterial contamination in field-fresh lettuce and the effectiveness of sanitising lettuce using the three-stage cleaning method recommended for vegetables in Mali with tap water and varying concentrations of commonly used sanitisers, including potassium permanganate (510, 340 and 170 ppm), vinegar and bleach (0.00855, 0.00570 and 0.00285 ppm), and ordinary salt (1500, 1000 and 500 ppm). Lettuce samples were randomly collected from smallholdings irrigated with natural well and river water in six communities in Bamako (old administrative division). The low-, intermediate- and high-level concentrations of sanitiser solutions were applied for 15, 10 and 5 min, respectively. Total microflora (TM), total coliforms (TC) and faecal coliforms (FC) were detected and counted as colony-forming units (CFU). Salmonella spp. and Escherichia coli were detected, isolated and identified using the API 20E gallery. All sanitisers, including tap water, reduced bacterial populations by 1.79–3.11 (TM), 2.37–3.65 (TC), 1.32–3.27 (FC) and 2.66–2.87 (E. coli) log CFU/100 g at 5, 10 and 15 min, respectively, below the undesirable ICMSF (2018) level. At all treatment contact times, all sanitisers eliminated Salmonella spp. All chemical sanitisers, including tap water at 15 min, reduced total microflora, total and faecal coliforms, and E. coli populations below the undesirable ICMSF (2018) level. These findings could help reduce the health risk associated with lettuce consumption in Mali.