Study on Extraction and Functional Properties of Different Casein in Yak Milk
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Abstract:
In this work, fresh yak milk was used as a raw material to separate and extract the different casein by adding calcium salt and employing its isoelectric point. Single factor experiments screened the extraction and separation parameters of α-, β-, κ-casein in yak milk. SDS-PAGE was applied to analyze the purity of different casein in yak milk. At the same time, the solubility, emulsification, and foamability of α-, β-, κ-casein in yak milk were analyzed and compared. The results showed that the optimum concentration of Ca2+ and the optimum temperature for casein components separation in yak milk were 0.08 mol/L and 2 ℃, respectively. At this point, the separation effect of α- and β-casein in yak milk was better compared to the other. When different casein in yak milk was close to isoelectric point (pI), the solubility, emulsification, and foaming ability were at the lowest. On the contrary, the foam stability was at its best. The solubility of the casein component which was close to the isoelectric point was the lowest, the solubility of α-, β-casein was at its highest at 2.1 (60%, 80%, respectively), while the κ-casein was at its highest at pH 6.22 (43%). In the range between 40 and 80 ℃, the solubility of κ-casein was significantly affected by temperature. In pH 2.1, the emulsification ability and foaming ability of α-, β-, κ-casein were at the largest, and the emulsion stability was gradually increased from the isoelectric point. This study aimed to provide ideas for the utilization and advanced processing of yak milk casein, as well as providing a scientific basis for the development and utilization of Yunnan’s unique dairy products.
