The quality of raw milk obtained from Friesian (Holstein) cows at Neudamm dairy farm was investigated after the quality issue was raised by some milk consumers at the University of Namibia, Neudamm campus. Some consumers complained about the short shelf-life of the milk as it is sold untreated due to lack of processing facilities at the centre. Others were worried of their health as they usually ferment raw milk for home use. In addition, the farm has no proper records of the quality of its milk for dairy herd management. The Department of Food Science and Technology of the University of Namibia, Neudamm campus took an initiative to identify the cause of the problems and the consumers' health concerns in order to come up with some remedial solutions. Samples for proximate composition and microbiological analyses were collected during the winter and summer seasons and from morning and evenings' milk at Neudamm Dairy Farm for chemical and microbial analyses. The quality of raw milk sold to staff members was evaluated and the data were used to assist the farm with dairy herd management programme and quality assurance. The mean temperatures, chemical, microbiology and acidity tests were determined. The temperatures ranged from 35 to 37 o C. Titratable acidity expressed as lactic acid had a mean of 0.18%, total protein 3.2%, fat 3.63%, total solids (TS) 12.33%; solids-not-fat (SNF) 8.7% and pH varied from 6.0 to 6.7. There were some variations in composition between winter and summer and between morning and evening milk, which are well known and significant at p<0.05. Furthermore, large variations were noted in microbiological composition of raw milk with total aerobic counts ranging from 7.8x10 4-1.3x10 6 cfu/ml, coliforms from 2.4x10 2-2.3x10 3 cfu/ml and lactic acid bacteria (LAB) from 1.2x10 3-2.6x10 5 cfu/ml. Yeasts and moulds were less than 100 cfu/ml in all samples analyzed. From the bacteriological and chemical analysis, it is concluded that the university farm needs a processing unit to control the quality of milk, add value and for training purpose.
In this study, we have investigated the microbial diversity and stability in the Tibetan kefir during the primary cultivation and subcultivation processes via a combination of culture-independent and culturedependent methods. According to the culture-independent methods, the profiles of PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis) indicated that nine microbial species were predominant at different cultivation stages; seventy four isolates of seven predominant species were obtained and identified via the culture-dependent methods. PCR-DGGE further confirmed that Lactobacillus kefiranofaciens, Lactobacillus kefiri, Lactobacillus paracasei, Streptococcus thermophilus, Kazachstania unispora and Saccharomyces cerevisiae were the most dominant species in the Tibetan kefir during the process of primary cultivation, among which Lb. kefiri, Lb. paracasei and K. unispora showed relative strong stability during both the processes of primary cultivation and subcultivation. These findings suggested that some isolates of the three species possessed the potentiality of being used in the development of direct vat set (DVS) starters for the production of Tibetan kefir and the related products.
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