腐乳的聚类与相关分析

Cluster and correlation analysis of sufu

为从腐乳内在质量指标方面探讨不同腐乳品质的差异以及各质量指标之间的关系 ,对 2 6种有代表性的国产腐乳中与风味密切相关的理化指标总酸、氨基态氮、食盐和总酯含量进行了测定 ,利用SPSS 10 0统计分析软件进行了聚类分析和相关分析。聚类得到类别间差异显著的 5类腐乳样品 ,传统分类方法得到的各类腐乳的理化指标没有显著差异 ,辅料的组成对腐乳基本风味的形成有重要作用。相关分析结果表明 ,腐乳中氨基态氮与总酸含量的Pearson相关系数为 0 5 88,呈极显著正相关 ,表明腐乳中游离氨基酸对总酸含量有较大贡献 ;氨基态氮与总酯含量的Pearson相关系数为 - 0 4 0 2 ,呈显著负相关 ,表明部分游离氨基酸参与酯化反应形成了腐乳的香味物质 ;当盐的质量分数超过 8%时 ,对蛋白酶的活性有显著抑制作用 ,但后酵时间可以抵消其作用 ,且盐含量的增加可能会促进耐盐菌的生长 ,使氨基态氮含量增加。生产中应控制腐乳中上述理化指标之间的比例 ,以确保产品品质。

In order to study the relationship of sufu qualities of different species, the contents of main flavor components such as total acid, free amino nitrogen,NaCl and total ester of 26 representative sufu in China mainland were determined. The cluster and correlation analysis were made by statistic software of SPSS 10 0. The results showed that the 26 samples could be divided into five species with significant difference and some kinds of sufu in the same manufacture belonged to different species. There was no significant difference between sufu species classified by traditional method and the compositions in dressing mixture were crucial to the background flavor of sufu. The positive linear correlation between free amino nitrogen and total acid indicated that the free amino acid contributed much more to total acid. The negative linear correlation between free amino nitrogen and total ester suggested that some free amino acids would take part in the chemical reaction to form the ester in sufu. When the salt content reached to 8% (g·g -1 ), it would significantly reduce the activity of protease. However, the long time post fermentation would counteract the effect of reduction of protease activity. The samples with high content of salt were characteristic of higher free amino acid, which was benefit to halophilic organisms. To insure the good flavor of sufu, the control of chemical reaction during sufu fermentation should be made.