Characterization of fat globules and milk fat globule membrane proteins in milk of different yak breeds.

摘要

Milk fat globule and milk fat globule membrane (MFGM) proteins in whole yak milk from the 3 yak breeds Maiwa (n = 6), gannan (n = 4) and Zhongdian (n = 4) were characterized. Fat globule size distribution and specific fat surface area of whole yak milk were determined using a laser diffraction particle size analyser. The average specific fat surface area of Gannan yak milk (2.05 m2 mg-1) and Zhongdian yak milk (2.01 m2 mg-1) was higher (P < 0.05) than that of Maiwa yak milk (1.92 m2 mg-1). The total protein content of MFGM and surface protein coverage of fat globule in Maiwa yak milk (11.12 mg g-1 fat and 5.67 mg m-2, respectively) and Gannan yak milk (12.24 mg g-1 fat and 5.97 mg m-2, respectively) were higher (P < 0.05) than that of Zhongdian yak milk (9.72 mg g-1 fat and 4.81 mg m-2, respectively). Protein components in the MFGM of yak milk were analysed using an Ultrascan XL laser densitometer and LKB 2400 GelScanXL computer software. No major differences (P > 0.05%) in the protein patterns produced using SDS-PAGE were observed among the MFGM of Maiwa yak, Gannan yak and Zhongdian yak milk samples, with the exception of mucin 1 and butyrophilin which were significantly lower (P < 0.05) in the MFGM of Zhongdian yak milk.