Fatty acid compositions, vitamin A, and tocopherols in the butter lipid of the purebred of yak animal were determined by GLC and HPLC. The cholesterol content of yak butter and lipid oxidation kinetics were investigated by GLC and gravimetric methods. The butter produced from yak milk exhibited a strong flavor. This was caused due to the presence of a high concentration of short-chain saturated fatty acids in this butter. The major fatty acids in yak lipids were 16：0, 18：1, 14：0, 18：0, 4：0 and 8：0 in descending order. Retinol content in yak butter was 402.3 μg/100 gm fat. Alpha (α-) tocopherol in yak butter was higher (2.6 mg/100 gm fat) than in cow butter (1.9 mg/100 gm fat), although γ-tocopherol was significant in cow butter (440 μg/100 gm fat). Tocopherols (β- and δ-forms) were found in insignificant amounts in yak and cow butter. Cholesterol content in yak butter was pronounced (325 mg/100 gm fat) than in cow butter (223 mg/100 gm fat). The cow milk lipid oxidation rate was faster and higher compared to the yak milk lipid. Polar lipid content in yak butter lipid was higher than in cow butter lipid.

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 As the second step to constructing a new method for a series analysis of traditional milk processing system, “groups of milk processing elements” have been classified in this paper. A group of milk processing elements has been defined as one unit possessing a common goal-oriented technique among certain milk processing elements. The purpose for a class-structure analysis for the milk processing elements has been to clarify the central goal-oriented intentions of human beings in regards to milk processing. From the results of analysis, the milk processing elements has been classified into three central groups, namely, “a processing group for the utilization of milk components”, “a processing group for preservation”, and “a processing group for separation”. The “processing for utilization of milk components” is composed of three sub-groups for processing main milk elements. The “processing group for preservation” is a processing group mainly for long preservation under favorable condition. The “processing group for separation” is a processing group for physically separating the solids from the liquid in the milk. The traditional milk processing systems of all the tribes can essentially be explained using the above three central groups of milk processing elements.

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