关键词: 牦牛曲拉, 品质指标, 主成分分析, 聚类分析

Abstract: In order to improve the quality consistency of Qula, the dried residue of naturally fermented skim yak milk, in pastoral areas of China, a comprehensive quality evaluation was conducted for Qula samples collected from some major producing areas in the country. A total of 95 Qula samples from 8 producing areas were analyzed for nutritional composition, antioxidant properties, color values and 5-hydroxymethylfurfural (5-HMF). The appropriate indicators to evaluate the quality of Qula were screened by principal component analysis (PCA) and the samples were classified by cluster analysis. At the same time, analysis of variance was used to comprehensively evaluate the quality of Qula samples. The results showed that majority indicators were extremely significant (P < 0.01) and significant (P < 0.05) correlation. The first and second principal components (PC1 and PC2) identified by PCA, accounting for 72.846% and 13.763% of the total variance, were interpreted as a ‘color component’ and a ‘nutritional quality component’, respectively. The PC1 loading factors for color L*, a* and b* values and 5-HMF content were all higher than 0.9, suggesting that the color could be considered the major indicator of Qula quality. Cluster analysis suggested that these Qula samples were classified into four categories, showing good consistency with the result from principal component analysis. There were extremely significant differences between four categories of Qula samples in terms of quality indicators (P < 0.01). Approximately 14.74% of Qula samples were bad in quality, 69.47% good and 15.79% excellent.

Key words: Qula, quality indicators, principal component analysis, cluster analysis