Characteristic Quality Evaluation of Nang from the Yili Region in Xinjiang Based on Principal Component and Cluster Analysis

This study determined 13 quality indexes (weight, transverse diameter, height, moisture content, water activity, L^*, a^*, b^*, hardness, cohesion, elasticity, adhesiveness, and chewability) in 55 different Nang samples from the Yili region in Xinjiang to examine their quality characteristics. The main indexes were selected for the Nang quality evaluation via principal component analysis, cluster analysis, and sensory quality assessment. The results showed an association between the 13 quality indexes of the 55 Nang samples. The height was highly significantly correlated with moisture content, water activity, elasticity, and chewiness (P<0.01), while the L^* value and adhesiveness were substantially related (P<0.05). Three principal components were extracted via principal component analysis, with a cumulative variance contribution rate of 76.856%. Cluster analysis showed that six quality indexes, namely elasticity, chewability, adhesiveness, hardness, L^* values, and b^* values, were crucial for evaluating Nang quality. Then, the 55 Nang samples were classified into three categories: Large Nang, thick Nang, and snack Nang. The sensory quality analysis revealed significant differences between the quality of the three Nang categories (P<0.05). The color, flavor, and hardness scores of the large Nang were the highest at 14.85, 13.52, and 14.37, respectively, with a golden color and rich flavor. The elasticity and chewability scores of the thick Nang were the highest at 14.82 and 14.54, respectively, while the crisp score of the snack Nang was the highest at 14.47. These results revealed the key indexes for assessing the quality characteristics of three types of Nang from the Yili region in Xinjiang, providing a scientific classification method for constructing a Xinjiang Nang quality evaluation system.