Theses and Dissertations Collection

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    Evaluation of factors affecting keeping quality of raw milk under different production systems in Kilimanjaro And Coast regions
    (Sokoine University of Agriculture, 2001) Magesa, Rehema John
    study was carried out in Kilimanjaro and Coast region to evaluate factors affecting the keeping quality of raw milk under different production systems. General milking practices were studied including milking methods; place of milking, milking time. cleanliness of milking and storage vessels, milk preservation and also the time taken before milk reaches the collection or selling point. A total of 80 producers were interviewed using a questionnaire. From Kilimanjaro and Coast region, 40 milk samples each were collected for analysis. The samples were taken to Sokoine University laboratory where the samples were analysed for chemical composition and bacteriological quality. Visual appearance and smell were performed in the field, also the keeping quality was assessed in the laboratory on samples stored at 4°C and 20°C and then acidity and total plate count was determined at different storage time intervals. The General Linear Model (GLM) was used in analysing the laboratory results for differences between different categories of observations and regression analysis was done to asses the relationship between thiocyanate content in milk with bacterial count. From the data obtained it was observed that all samples collected had normal organoleptic characteristics. It was also noted that 85% of milk samples collected had a normal density of between 1.026 and 1.029g/cc. Tests for acidity indicates that most of the raw milk samples collected from Kilimanjaro and Coast region had an acidity range of 0.16% lactic acid to 0.2% lactic acid. Results on bacteriological quality showed that the LSMeans for total plate counts for raw milk samples ranged from 5x105 to 1.9x106 efu/ ml. The LSMeans for the thermoduric count performed, ranged from 6xl03 to 17.7xl03 efu/ ml. Also the coliform count was found to range from 9.2x10“ to 5.2x10 efu/ ml respectively. Chi square test wasIll also performed to test if there was any significant relationship between different milking practices and bacterial count in raw milk samples, from the %2 test performed it was observed that the practices had highly significant influence on bacterial count at 0.1% level of probability. For the compositional quality of milk it was found out that the LSMeans range for total solids from Kilimanjaro and Coast regions was 12.21 ±0.12 to 14.08±0.57. The LSMeans for butterfat content ranged from 3.94±0.38 to 6.32±0.63. Solids not fat content in milk samples from both regions did not differ significantly (P>0.05) and it ranged from 7.9±0.34 to 8.39±0.17. Lastly the crude protein content was high in milk samples from the traditional dairy cattle keepers from Coast region and low in the same production system in Kilimanjaro region. However, the cyanide content in feed samples was low as it ranged between 0.0012 to 1.7 pg CN/ kg of feed. Thiocyanate levels had an apparent bacteriostatic effect on bacterial multiplication at 4°C and 20°C in raw milk as samples with high thiocyanate content had lower total plate count with coefficient of determination R2 of 0.84 and 0.83 respectively. Therefore from the study it can be concluded that bacterial count was dependent on the production system in question as it was observed that milk from the traditional cattle keepers was having the highest bacterial counts compared to milk from the large scale producers and the smallholders. High bacterial counts obtained from different production systems in Kilimanjaro and Coast regions might have been contributed by type of milk containers used, milk hygiene level and time taken to deliver milk to collection/ selling point several milking practices carried out in those production systems.