西藏不同海拔牦牛奶渣营养、风味特性及抗氧化活性研究

Study on Nutrition,Flavor Characteristics and Antioxidant Activity of Yak Milk Dregs at Different Elevations in Tibet

本研究分析西藏海拔2500~2800 m奶渣N_(A)、海拔3500~4000 m奶渣N_(B)和海拔4300 m以上奶渣N_(C)的物理、营养、风味特性以及抗氧化活性。结果表明,海拔对牦牛奶渣物理、营养、风味以及抗氧化活性影响明显。相较于奶渣N_(A)和N_(B),高海拔奶渣N_(C)的平均蛋白质含量(71.00 g/100 g)、维生素A含量(3.52μg/100 g)、维生素E含量(0.33 mg/100 g)、维生素D_(3)含量(0.66μg/100 g)、铁元素含量(55.51 g/kg)、总氨基酸含量(79.32 g/100 g)和必需氨基酸含量(36.40 g/100 g)最高。相较于奶渣N_(A)和N_(C),奶渣N_(B)极值温度(129.68℃)最低,而tanδ最高,说明奶渣N_(B)流动性最佳。牦牛奶渣挥发性组成主要是醛类(最小相对百分含量V_(min)>30%),奶渣N_(A)和N_(B)主要挥发性成分是壬醛,呈现玫瑰花香,奶渣N_(C)主要挥发性成分是己醛,呈现青草花香,其它成分包括酸类、烯烃类和醇类等;牦牛奶渣具有较好抗氧化活性,奶渣N_(C)具有最强DPPH自由基清除能力,奶渣N_(A)具有最强过氧化氢清除能力。

The physical,nutritional,flavor and antioxidant characteristics of yak milk dregs(N_(A),N_(B),and N_(C))obtained from three different elevations(2500~2800 m;3500~4000 m;above 4300 m)in Tibet were analyzed in this study.The results showed that the elevation had obvious effects on the physical,nutritional,flavor characteristics and antioxidant activity of yak milk dregs.Among the three yak milk dregs,N_(C)had the highest contents of proteins(71.00 g/100 g),vitamin A(3.52μg/100 g),vitamin E(0.33 mg/100 g),vitamin D3(0.66μg/100 g),iron element(55.51 g/kg),total amino acid(79.32 g/100 g)and essential amino acid(36.40 g/100 g).The extreme temperature of N_(B)(129.68℃)was significantly lower than those of N_(A)and N_(C);its tanδwas higher than those of N_(A)and N_(C),which indicated that N_(B)had the strongest liquidity.The volatile components of yak milk residue were mainly aldehydes(V_(min)>30%).The main volatile component of both N_(A)and N_(B)was nonanal,which gave the scent of rose flowers of milk dregs;while the main volatile component of milk dregs N_(C)was hexanal,which led to the scent of grass of milk dregs.Other ingredients in Yak milk dregs include acids,olefins,alcohols,etc.Yak milk dregs had good antioxidant activity.Among the three yak milk dregs,N_(C)had the strongest DPPH free radical scavenging ability,and N_(A)had the strongest peroxide scavenging ability.