Distribution of Calcium, Phosphorus and Magnesium in Yak (<i>Bos grunniens</i>) Milk from the Qinghai Plateau in China

Abstract

This research was aimed to assess the distribution of calcium, phosphorus and magnesium within the casein micelles of yak milk. To this aim, nine bulk yak milk samples (Y-milk), collected in three yak farms located in the Chinese province of Qinghai, were compared to nine bulk cow milk samples used as a reference. A quite similar content of colloidal calcium (0.80 vs. 0.77 mmol/g of casein; p > 0.05), a higher content of magnesium (0.05 vs. 0.04 mmol/g of casein; p ≤ 0.01) and a lower content of colloidal phosphorus (0.48 vs. 0.56 mmol/g of casein; p ≤ 0.01) between yak and cow casein micelles were found. Moreover, the yak casein micelles showed a lower value of prosthetic phosphorus (0.20 vs. 0.26 mmol/g of casein; p ≤ 0.05) compared to the cow micelles. The lower values of colloidal and prosthetic phosphorus in yak casein micelles suggest that the yak casein is less phosphorylated than the cow one.

Keywords

• yak milk
• protein fractions
• mineral content
• salt equilibria
• casein micelles mineralisation