Risk of food-borne illness in fresh vegetables

Abstract

Vegetable intake is widely recommended because of its high content of vitamins, minerals and fibres. However, the fields where vegetables are grown, are often fertilized with manure and irrigated with second-class water, which may cause unseen microbial pollution. This contamination by pathogens may lead to significant hazards to human health. These pathogens are microorganisms that can be found anywhere if they find ideal conditions for their survival. The vegetable chosen for analysis in this study is lettuce (‘Lactuca sativa’). This vegetable was analysed for the presence of coliforms, which were used as an indicator for the presence of other pathogens. This study involved the collection of representative samples of lettuce from different agricultural fields. The samples of lettuce taken were carried in sterile bags in cool boxes and then taken to the laboratory. These were analysed for total coliforms in three different conditions, which were : prior washing (straight from the field), just washed with water and finally sanitized with a chlorine-based solution. Results obtained showed that different types of cultivation give rise to different yields of total coliforms. With lettuce produced through hydroponics, tend to carry the least total coliform count (mean of 52 total coliform count), whilst lettuce grown through organic farming carried the highest of the total coliform counts (mean of 153 total coliform count). When samples from the three fields were washed with tap water for 30 minutes showed a similar percentage drop in total coliform counts, with the conventional samples having the highest drop of 94%, the organic samples showed an 86% drop and hydroponics samples lowering total coliform count to 76%. Sample treated with a chlorine-based solution as a disinfectant yielded an undetectable level of total coliform count.