General hygiene of commercially available milk in the Bloemfontein area
Cawe, Nangamso Buntukazi
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From the extensive literature review given in Chapter 1, it is evident that milk is an important part of the diet and can also serve as a good medium for growth of microorganisms. These microorganisms can be either pathogenic or being undesired causing spoilage. The pathogenicity and incidence of undesired microorganisms were reviewed and as a result one of the aims of this study was to assess the hygienic quality of milk sold in and around Bloemfontein. The results obtained during this study proved interesting as it showed an alarming high percentage of these milk samples were of a poor microbial quality as they did not confirm to the National Legislation regarding milk sold to consumers. The importance of yeasts in the dairy industry has been highlighted on a number of occasions by various authors. Despite indications of yeasts associated with dairy products, especially in yoghurts and cheeses, and milk being the raw material of these products, surprisingly few studies have been conducted on the specific occurrence of yeasts in either raw or pasteurized milk. The results obtained showed an ability of these yeasts to survive and proliferate in both raw and pasteurized milk. However, the number of yeast cells was low and insignificant to cause major problems. A wide diversity, including 14 different species was isolated and characterized. The alarming effect remains that predominant species like Candida albicans was found, a severe human pathogen. Due to concerns that some potentially dangerous and high numbers of undesired microorganisms may derive from the dairy farm, the ability to efficiently control these populations at the farm level seemed desirable. Consequently, the effect of ultraviolet irradiation on the microbial loads and chemical composition of raw milk was investigated. The results showed a 90% reduction on the microbial populations, except yeast numbers showing more resistance being reduced by 73%. Chemical analysis compared from results performed before and after UV radiation showed no significant alterations in the milk composition. Based on the results obtained, it was suggested that the usage of UV radiation on the milk resulted in an enhanced shelf-life and better microbial quality.