A preliminary study of the microflora level of some fruits and vegetables pre and post-preservation

Abstract

Samples of 15 different fruit and vegetable types were purchased from five small groceries around Addis Ababa. Enumeration, isolation and identification processes were performed for the microbial flora of each sample before and after 15-30 days of preservation. Both direct and enrichment culture media were used to distinguish these microflora as members of the groups of normal contaminants, indicators, spoilage and foodborne disease causing organisms. The overall result of this work indicates that a total of 25 different organisms, comprising 3 (12%) indicators, 15 (60%) spoilage, 5 (20%) food-borne pathogens and 2 (8%) normal contaminants, were isolated. The predominant isolates of these groups were Escherishia coli type I, among the indicators Bacilli, molds and Enterobacter species among the spoilage and Staphylococcus aureus, Salmonella typhimurium and Bacillus cereus among the pathogens. The direct inoculation method revealed the isolation of more than one indicator organisms from each of 7 (46.7%) fresh or unpreserved fruit and vegetable samples, more than 3 spoilage organisms from each of 8 (53.3%) samples, and, at least, one pathogenic organism from each of another 8 (53.3%) samples. When enrichment culture method was applied, all these results were increased as: >1 indicators in 10 (67%), >3 spoilage organisms in 9 (60%), and pathogens in 9 (60%) of the unpreserved samples. The enumeration values of the indicator/organisms and the spoilage groups of mesophyllic aerobes/anaerobes, molds and/or yeasts were all above the accepted limits for such fruits and vegetable samples. This was shown to be true in 10 (66.7%), 4 (26.7%) and 6 (40%) samples for the indicators, spoilage mesopheles, and mold or yeasts respectively. The preservation processes have proved to be effective in eliminating or reducing the numbers and types of the organisms isolated from each fresh sample. The effectivity of the preservation methods is discussed and its applicability in a simplified and comprehensive manual for a small-scale (household level) preservation of fruits and vegetables has been recommended.