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.

Abstract:This research was a contribution on the optimization of extrusion process by determining the effects of feed properties on extrusion failures and implementing a solution. The objectives of the research were to increase the set soy meal to chunk conversion standard from 65% to 80%; to determine the effects of feed properties on extrusion failures; to determine the best conditions of the feed properties that promote an effective extrusion cooking process; and to determine a solution of optimizing these feed properties for successful extrusion. The research was company based and it followed the failures of extrusion experienced at Monmouth Path Investment (Pvt) Ltd in Waterfall, Harare. This research was limited to feed properties such as fat content, moisture content and particle size as the factors that cause extrusion failures. The determination of moisture content was done by using a moisture analyzer, fat content was determined through the Soxhlet method and the particle size of the feed was determined through sieve analysis. The results revealed that extrusion process was most successful when the soy meals fat content was greater than 6.0%, with a moisture content less than 6.0% and particle size range of 0.95-1.0mm. The process of optimization of extrusion process was solved by designing an extrusion calculator and blending ratio factors. The objective of determining the effects of feed properties on extrusion failures was achieved as well as that of implementing a solution. The objective of increasing Monmouth Path's standard soy meal/chunk conversion was partially achieved since the implemented solution is not yet measurable.