Abstract: The number of total coliforms is widely used as indicator of the presence of pathogens. They coexist in the human large intestine and even after disposal to the environment. One useful application is in the determination of the presence of coliforms in food, specially those to be consumed by the public without further heat treatment or cooking. Such is the case with ready to eat (RTE) salads. In this study, the vegetable jarjeer (Eruca sativa), rocket in English, was the vegetable tested. Jarjeer is usually a component of green salads and there were reports that these vegetables were harbouring coliforms which could not be removed by washing. It was therefore appropriate to test some household common disinfection method such as microwaving if it would be effective in inactivating these coliforms present in jarjeer. Both the time of inactivation and the thickness of the jarjeer placed in the plate were varied in the experiment. At a thickness of 0.1 cm and inactivation time of 15 seconds a 58% reduction in coliform was obtained and at 30 seconds inactivation time 81 % reduction was obtained. At a thickness of 1 cm, no reduction of coliforms was obtained at 15 and 30 seconds inactivation time. Note that the thickness of 0.1 cm was equivalent to the single leaf of vegetable placed on the plate so that it is already the minimum thickness possible for the study. A 58 or 81 % inactivation of coliforms is not acceptable as far as health safety is concerned since there are still plenty of coliforms left in the leaves. Ideally there should be few or no coliforms present (99.9 % inactivation). We therefore conclude that microwaving is not an effective method to inactivate the coliforms in jarjeer.
Keywords: coliforms, vegetable salads, pathogen, microwave, inactivation.