Compatative Study On Differences Of Fat And Protein In Goat And Bovine Milk

Goat milk and bovine milk are characteristics of dairy products that rich in protein, minerals, lactose, lipids and a variety of vitamins. They were all important source of protein for the human safety. It has been favored by the vast number of consumers. Therefore, the security of cow and goat milk and dairy draw universal attention. The protein and fat differences between bovine and goat milk were comparatively studied to lay a foundation for the development of goat milk quality standards and distinguishing inspection for the bovine and goat milk.Milk quality and safety index is mainly based on the protein and fatty acid. In this paper, we used the Kjeldahl method, biuret method, Coomassie brilliant blue method and ultraviolet absorption method comparison to research the protein content of milk. Compared types of the two milk’ proteins with the method of polyacrylamide gel electrophoresis. Milk α-LA and β-Lg were used as immunogen for rabbit then the sera was separated and purified, and antibodies, which have high titer and high specificity. All above were in preparation for the immunological detection technology for the goat milk incorporated with bovine milk. The fatty acid composition of bovine milk and its products were analyzed by GC-MS.1. The protein contents in goat and bovine milk were quantitatively detected. The protein contents were determinated by Kjeldahl nitrogen, biuret colorimetric, Coomassie brilliant blue and ultraviolet absorption method. The respectively protein contents were as follows:(31.15±0.08)g/L and(29.79±0.09) g/L,(32.77±0.07) g/L and(29.96±0.06) g/L,(32.40±0.46) g/L and(30.01±0.62) g/L,(33.37±0.07)g/L and(30.11±0.11)g/L. The protein content of goat milk measured by four different kinds of method were all higher than the content in bovine milk. The measurement of ultraviolet absorption spectrometry determination had the highest numerical, while the Kjeldahl Nitrogen determination had the minimum numerical. Every method had its advantages and disadvantages, so we should choose the most appropriate method to determinate the milk protein content in depends.2. The various types of milk proteins were determined by polyacrylamide gel electrophoresis. In SDS-PAGE, the main difference between them was that: the casein content is much larger in goat milk than bovine milk, but the molecular weight of protein in goat milk is larger than bovine milk. And the beta casein content and molecular weight of goat were both higher than that in bovine milk. So the alpha and beta casein could be regarded as the signature bands to separate the bovine milk from goat milk. In Native-PAGE, as for albumin components, in goat milk only appeared only alpha lactalbumin band, but in bovine milk alpha lactalbumin band and beta lactoglobulin strip. So beta lactoglobulin could be used to distinguish between goat and bovine milk specifically by Native-PAGE.3. The preparation of the specific polyclonal antibodies. This research established rabbit immunization program with milk α-LA and β-Lg. New Zealand rabbits were used as immunization animal, from which the Rabbit antibovine α-LA and β-Lg antibody in serum was obtained. The antiserum dealed with graded salting and then purified with the protein A affinity chromatography. The antibody titer was divided into 1:64000, 1:16000, while the protein concentrations were separately 2.733mg/m L and 6.400mg/m L, after using protein purification system, the titer of the purified α-LA-Ig G and β-Lg-Ig G, were respectively 1:16000, 1:8000, protein concentrations were 3.012mg/m L and 6.864mg/m L.4. The research for the difference between fatty acids in bovine and goat milk. The detection results of milk fatty acid were as follows: The average fat contents of goat and bovine milk were 3.90g/100 g,and 3.62g/100 g. Saturated fat acid content of goat and bovine milk were(74.25±1.40)% and(67.49±0.64)% by GC-MS. Saturated fat acids in the two types milk were composed of capric acid, lauric acid, myristic acid, palmitic acid, oleic acid and stearic acid. And the unsaturated fat acids mainly include oleic and linoleic fatty acids. The difference lies mainly in the short chain fatty acids(C6-C10), in addition the content of short chain fatty acids in goat milk was significantly higher than that in bovine milk, especially decanoic acid, decanoic acid content in milk were(9.44±0.26)% and(2.85±0.04)%. It was also the most important reason for the smell of mutton in goat milk. It was also the most important reason for the smell of mutton in goat milk. With the help of the value of C10:0/C6:0 and C16:0/C10:0 in bovine and goat milk the fresh bovine and goat milk, pure bovine and goat milk powder, infant formula bovine and goat milk powder could be clearly identified.From all the above, the conclusions provided theoretical basis to establish the quality and safety standards by comparative analysis of protein and fatty acid compositions in bovine and goat milk. Using bovine α-lactalbumin and β-lactoglobulin as antigens for polyclonal antibodies which could through immune method serve the quick distinctive detection for bovine and goat milk. The conclusions laid the foundation for the distinguishing test methods for bovine and goat milk.