基于主成分分析法对不同杀青方式桑叶品质影响的综合评价

Comprehensive Evaluation of the Effects of Different Fixation Methods on Mulberry Leaf Quality Based on Principal Component Analysis

为系统评价不同杀青工艺对桑叶营养成分、功能性成分和抗氧化活性的影响,采用差异性分析、相关性分析和主成分分析等方法,分析漂烫、微波和蒸汽3种杀青方式对桑芽和霜桑叶品质的影响。结果表明,采用不同杀青方式处理获得的桑叶营养成分、功能性成分及其抗氧化活性均有显著差异(P<0.05),其中微波杀青处理获得的桑叶可溶性蛋白含量、游离氨基酸含量、可滴定酸含量、绿原酸含量、丙二醛含量(MDA)及清除DPPH自由基能力最高;蒸汽杀青的桑叶可溶性糖含量、白藜芦醇含量、黄酮含量、多酚含量、清除ABTS自由基能力和螯合金属离子能力最高。大部分叶片品质性状间存在显著相关性。将不同杀青方式对桑叶品质的影响进行综合评价分析,得到3个公因子,累计方差贡献率为81.508%,能较好地解释自变量。根据3个公因子及其方差贡献率,得出霜桑叶的品质显著高于桑芽,其中蒸汽杀青处理的白玉王霜桑叶、桂109号霜桑叶和微波杀青处理的白玉王霜桑叶的综合得分值位于前3。最终确定螯合金属离子能力、可溶性糖含量、铁还原能力、绿原酸含量、MDA含量、清除DPPH自由基能力等6项指标可作为评价不同杀青方式对桑叶品质影响的代表性指标。综合筛选得出,蒸汽杀青最适合作为桑叶茶开发的杀青方式,为桑叶提质加工和桑树资源综合开发利用提供了科学依据。

In order to systematically evaluate the influence of different fixation processes on the nutrient composition, functional composition and antioxidant activity of mulberry leaves, the effects of three fixation methods, namely blanching, microwaving and steaming, on the quality of mulberry buds and frost mulberry leaves were analyzed by means of differential analysis, correlation analysis and principal component analysis. The results showed that the nutrients, functional composition and antioxidant activity of mulberry leaves treated by different fixation methods had significant differences(P<0.05). Mulberry leaves treated by microwaving had the highest level of soluble protein, free amino acid, titratable acid, chlorogenic acid, malondialdehyde(MDA) and the ability to scavenge DPPH free radicals. While leaves treated by steaming had the highest level of soluble sugar, resveratrol, flavonoids, polyphenols, and the ability to scavenge ABTS free radicals and chelate metal ions. Significant correlations existed between most leaf quality traits. The effects of different fixation methods on the quality of mulberry leaves were comprehensively analyzed, yielding three public factors, with the cumulative variance contribution rate being 81.508%, which could well explain the independent variables. Based on the three public factors and their variance contribution rate, the leaf quality of frost mulberry leaves was significantly higher than that of mulberry buds. The comprehensive scores of Baiyuwang frost mulberry leaves and Gui 109 leaves treated by steaming and Baiyuwang frost mulberry leaves treated by microwave were in the top 3. In the end, six indicators, including metal-ions chelating ability, soluble sugar content, iron reduction ability, chlorogenic acid content, MDA content, and ability to scavenge DPPH free radicals, were selected as representative indicators to evaluate the effects of different fixation methods on mulberry leaf quality. Results of comprehensive screening shows that steaming is the best fixation method in mulberry leaf tea development, which provides a scientific basis for the quality improvement of mulberry leaf tea and for the comprehensive development and utilization of mulberry resources.