International Journal of Nutrition and Food Sciences 2014; 3(3): 6-14 Published online September 20, 2014 (http://www.sciencepublishinggroup.com/j/ijnfs) doi: 10.11648/j.ijnfs.s.20140303.12 ISSN: 2327-2694 (Print); ISSN: 2327-2716 (Online) An investigation on the causes of Escherichia coli and coliform contamination of cheddar cheese and how to reduce the problem (A case study at a cheese manufacturing firm in Harare, Zimbabwe) Amanda Kwenda, Moses Nyahada, Amos Musengi, Misheck Mudyiwa, Perkins Muredzi Department of Food Processing Technology, School of Industrial Sciences & Technology, Harare Institute of Technology, Ganges Rd, Box BE 277, Belvedere, Harare, Zimbabwe Email address: ammaragie@gmail.com (A. Kwenda), mnyahada@hit.ac.zw (M. Nyahada), amusengi@hit.ac.zw (A. Musengi), mmudyiwa@hit.ac.zw (M. Mudyiwa), pmuredzi@hit.ac.zw (P. Muredzi) To cite this article: Amanda Kwenda, Moses Nyahada, Amos Musengi, Misheck Mudyiwa, Perkins Muredzi. An Investigation on the Causes of Escherichia coli and Coliform Contamination of Cheddar Cheese and How to Reduce the Problem (A Case Study at a Cheese Manufacturing Firm in Harare, Zimbabwe). International Journal of Nutrition and Food Sciences. Special Issue: Optimizing Quality and Food Process Assessment. Vol. 3, No. 3, 2014, pp. 6-14. doi: 10.11648/j.ijnfs.s.20140303.12 Abstract: The aim of this study was to investigate the causes of E. coli contamination of Cheddar cheese through the application of Hazard Analysis Critical Control Points (HACCP) principles. Cheese samples were analyzed for E. coli and coliforms after production, during the validation stage, as well as at the verification stage. Average E. coli and coliform counts were analyzed statistically using the t-test. Results showed that after the implementation of the corrective measures there was a decrease in E. coli and coliform counts at the 5% level of significance. Results presented in this study also show that manufacturing Cheddar cheese whole observing high standards of hygiene improves the reduces E. coli and coliform contamination of the product, even though the problem is not completely eliminated. Keywords: Validation, Hazard Analysis Critical Points (HACCP), Pathogenic Microorganisms, Coliform Count 1. Introduction A company that specializes in the production of dairy products (cheese, ice cream and yoghurt) in Harare was selected for this study. Among the wide range of products that are produced at Kefalos, Cheddar cheese is one of the major income generating products. The production process is labour-intensive and human resources are used extensively for all major processes including raw material acquisition, conversion of raw materials into final product, packaging and dispatch. The bulk of Cheddar cheese is widely consumed in its natural state (Steffen et al., 1993) while smaller quantities are further processed and consumed as pasteurised process cheese. The cheese is packaged in different forms such as blocks, cuts, slices or shreds to suit the needs of customers. Cheese is a good substrate for the growth of certain adaptive fungal species and other bacteria due to its low pH, elevated salt concentration and low water activity [3]. Growth of microorganisms can occur on cheese during its ripening period or along the distribution chain under refrigerated storage and this can result in a safety and spoilage problem. Refrigeration alone cannot reduce the number of pathogens, as it has been proven that Listeria monocytogenes and other psychrotrophic pathogens are capable of growth at these temperatures. Therefore, lack of pathogen growth in fermented dairy foods may point to effective implementation of control factors such as diligence to good hygiene practices. During the manufacture of semi-soft, hard and very hard cheese, the cheese is subjected to relatively long exposure periods at temperatures that are ideal for the growth of bacteria [3] . For example, Cheddar and other related varieties are incubated at 31-39°C during manufacture and are hooped at temperatures in the 32-37°C range. Many