Thermobactebiology of Some Ghanaian Canned Foods

Abstract

The microbiological content and the thermal processes in use for s ix locally canned vegetables, Bambara Beans in sauce , Garden eggs in Brine, Okro in brine , Whole Tomato in tomato juice and Pepper puree were studied to establish causes of spoilage in the canned products, . Preliminary can examination and microbiological analysis of the canned product s showed that both leakage and under processing occur red widely in the products. Leakage occurred chiefly as a result of improper double seaming operation^. It was shown that the seaming process** es in use at the factories tended to produce cans with loose double seams ( i . e 0 large Free Space and small % Over laps ), , Side seam defects (due mainly to inadequate sold er in g ) were also considered significant as a cause of leakage, A procedure for predicting when leakage was likely to occur in the product s was evolved based on Free Space measurements ; and it was considered that Free Space measurement s could be used in the factories to prevent the occurrence of leakage, Heat processes in use at the Factories were evaluated and compared with recognized process in g standards for low acid food s . It was found that the heating processes in use were not adequate to prevent a residual population of thermophilic spores occurring in the end product s and al so to prevent the occurrence of Clostridium botul inium spores in the products, White this was shown to contribute to the high incidence of spoilage due to underprocessing the products were al so a potential health hazard to consumers . Some of the thermophilic spores isolated from the product s included Baci l lus polymyxa. Bacillus s tearo - th erm ophi lus and Clostridium therm osaccharolyticum . The isolation of relatively low heat resistant spores of Bacilluscereus and Clostridium histolyticum from the product s suggested a likely occurrence of high p reprocessing bacterial contamination. Investigation conducted on the raw vegetable product s prior to heat processing showed that delays which occur red between the cleaning of the vegetables and the heating process could result in a 10 - 100 fold increase of the initial bacterial load in the raw vegetables . While this could lead to pr e -processing spoilage , a residua l spore population could also remain in the end product after the heat processing. Based on the results obtained from the microbiological analysis and heat process evaluation new heating processes were defined f o r use in the factories to prevent the occurrence of underprocessing . Further work is however needed on the relative heat resistance of thermophilic spores isolated from tropical products. This information could be used to define minimum processing standards for tropical based products .