Quality evaluation of Lycium barbarum L. based on phenotypic characteristics and functional components

Lycium barbarum L. (LBL) has been used in China for more than 2,000 years as a traditional medicinal herb and food supplement. Nowadays, LBL has been cultivated in the Northwest of China like Ningxia, Qinghai, Inner Mongolia, Gansu and Xinjiang province. With the expanding of plantation areas and developing of new varieties, more and more factors affecting qualities of LBL. Establishing a quality evaluation method based on both commercial quality and effective components is very essential. The purpose of this study was to investigate the correlation between the phenotype and main nutritional & functional components of LBL, and to construct a comprehensive quality evaluation system for LBL, to provide reference for the quality evaluation of LBL for both medicinal and edible use. Taking 224 of LBL samples including different batches, grades, germplasm and producing area as research objects, several measurements were taken to obtain phenotypic indicators of the fruits, including longitudinal area, longitudinal diameter, transverse diameter, average single fruit weight, color values of L, a, b, and the content of nutritional and beneficial components including total sugar, polysaccharides, flavonoids, betaine, and carotenoids were also examined. The correlation between phenotypic characteristics and chemical composition of LBL was then studied, principal component analysis, hierarchical analysis and discriminant analysis were used to comprehensive quality evaluate of LBL to establish quality evaluation method. According to the variable coefficient, the variation coefficients for longitudinal area and average fruit weight of LBL were both higher than 30%, but less than 10% for L, a and b values, the variation coefficient of functional components was relatively high（19.27%～63.68%）, except total sugar content (9.63%), indicating that the color between different LBL samples was relatively low but the fruit size and component content was high. The results also showed that the content of nutritional & functional components of LBL was highly correlated with phenotypic characteristics. The smaller the LBL fruit was (i.e. the smaller the longitudinal area, longitudinal diameter, transverse diameter and average fruit weight), the higher the content of effective components such as Lycium barbarum polysaccharide, betaine and carotenoids were, but lower the total sugar content was. LBL for both medicinal and food use can be evaluated and classified into 3 types by four functional components including Lycium barbarum polysaccharide, flavonoid, betaine, carotenoid and two phenotypic indexes including longitudinal diameter and a value. Among them, the second type of sample showed the highest content of Lycium barbarum polysaccharides, carotenoids and betaine, and the fruit phenotype quality including longitudinal area, longitudinal diameter, transverse diameter and average fruit weight was better, which can be used as high-quality medicinal samples. The fruits of the third type can be regarded as the best edible samples because of the large longitudinal area, longitudinal diameter, transverse diameter and average fruit weight, the color of the fruit was redder and brighter, also the highest total sugar content making them the best edible tastes. The quality of the first type fruit was between the second and third types and can be used as secondary medicinal or edible samples. In conclusion, LBL fruit with smaller phenotypic indexes shows higher content of effective components but lower content of total sugar. LBL fruit can be evaluated and classified into 3 types by Lycium barbarum polysaccharide, flavonoid, betaine, carotenoid, longitudinal diameter and a value, to distingush medicinal and edible LBL samples.