荔枝果干蛋白质组成及其抗氧化性研究

Composition and Antioxidant Activity of Proteins from Dried Litchi Fruit

分析荔枝干果肉蛋白组成并比较不同组份蛋白质的抗氧化性。采用等电点法提取不同组份蛋白质,利用氨基酸自动分析仪测定不同组份蛋白及总蛋白的氨基酸组成,用超高压液相质谱联用系统Q1扫描测定不同等电点组份中小分子蛋白分子量分布,用抗氧化试剂盒测定不同等电点组份蛋白质的抗氧化性。试验结果表明荔枝浆浸泡2 h为蛋白质的最佳提取时间,测得pH 3.5、pH 5.5、pH 6.5和pH 7.5为荔枝蛋白的4个等电点,且4个等电点组份蛋白含量分别占果肉总蛋白的12.03%、14.37%、17.18%、9.45%;不同组份蛋白氨基酸种类相同、含量不同;pI 3.5和pI 5.5组份中含量较高的小分子蛋白集中在5000 Da附近,pI6.5和pI7.5组份中含量较高的小分子蛋白主要集中在1000 Da和5000 Da附近。说明不同组份荔枝蛋白抗氧化性不同。荔枝蛋白四个等电点组份的蛋白氨基酸含量、分子量分布及抗氧化性不同。

The composition of proteins from dried litchi fruit was analyzed and the antioxidant activity of different protein fractions were compared. Different components of proteins were extracted with isoeleclric point （pI） method and amino acids of exWacted proteins were measured by an automatic amino acid analyzer. A preliminary analysis of different components of small molecular proteins （SMP） were studied by ullra performance liquid chromatography-mass spectrometer Q1 scan. The best extraction time was 2 h for litchi pulp static leaching. The contents of four components with pI values of 3.5, 5.5, 6.5 and 7.5 were 25.03%, 26.98%, 1.83% and 0.53%, respectively. The litchi proteins had the same amino acid composition but different amino acid contents. Molecular weights （Mw） of the mian component of SMP at pI 3.5 and 5.5 were near 5000 Da, while Mw of the main components of SMP at pI 6.5 and 7.5 were near 1000 Da and 5000 Da. The litchi proteins with different pI were different in antioxidant activity, amino acid contents, Mw distribution and antioxidant activity.