Analysis of nutritive components of different types of Xinjiang wild walnuts

Abstract:【Objective】The Xinjiang wild walnut (Juglans regia L.) is a perennial deciduous nut tree. It is only distributed in the Yili area of Xinjiang. As a wild sibling species of cultivated walnut, Xinjiang wild walnut is of important value in walnut cultivation as well as its origin and evolution. Xinjiang wild walnut distribution area is located in the inversion layer of Yili River Valley, where the sunshine is abundant, the precipitation is rich, and the soil is fertile and loose. These conditions provide a good environment for the growth and development of Xinjiang wild walnuts, and also exert an important influence on the nut quality. Wang Lei divided Xinjiang wild walnuts into 14 different types through investigation and comparison. At present, the research on the nutrient composition of Xinjiang wild walnuts shows that Xinjiang wild walnut oil has the highest content of monounsaturated fatty acids, which is rich in protein, sugar and oil, but no other systematic analysis and research have been reported so far. In this experiment, 10 types of Xinjiang wild walnuts were used as experimental materials to determine the nutrient composition, to explore the nut quality, to screen the excellent resources with developing potential, and to provide a theoretical reference for the utilization of Xinjiang wild walnut germplasm resources.【Methods】According to 10 different types of Xinjiang wild walnuts, 15 quality indexes including protein, fatty acid, vitamin E and mineral elements in the nuts were determined. Through the analysis of variance, the nutrition of nuts was carried out. Differences in ingredientswere compared by using Excel 2010 and SPSS 20.0 software, and Duncan's multiple comparison in ANOVA was used for statistical analysis of the measurement indexes.【Results】The nutrients in wild walnut kernels mainly included fat, protein, soluble sugar, vitamin E, etc., and except for protein, there were extremely significant differences among them. The nutrients of kernel showed abundant variability. The variation coefficient of protein contents with different types was small, the average value was 18.995%. The contents of soluble sugar in wild walnut kernels ranged from 4.23% to 6.53%, which was much higher than the soluble sugar content of pecans (0.26%-0.68%) ; the contents of vitamin E ranged from 2.86 to 8.67 mg · kg^-1. The contents of nine mineral elements in the kernels were ranked as follows: potassium > phosphorus > magnesium > calcium > iron > sodium > zinc > copper > selenium. The highest total amount of mineral elements was 12 827.19 mg · kg^-1, which may have a great relationship with the soil organic matter, water and sunlight in the growing areas of Xinjiang wild walnuts. The average fat content in the kernels was656.4 g · kg^-1. Wild walnuts were rich in fat. The detection of five fatty acids in the kernels showed that the contents of fatty acid in different types were significantly different, with higher contents of linoleic acid, oleic acid and linolenic acid. The higher contents of linoleic acid and linolenic acid could exert certain effects on purifying blood and preventing cardiovascular diseases. The average content of linolenic acid in Xinjiang wild walnuts was 18.575%, which was much higher than that of common vegetable oil, such as rapeseed oil (8.04%) , sesame oil (0.45%) and soybean oil (0.85%) . Among the five fatty acid compositions, the content of unsaturated fatty acids accounted for 90.115% of the total fatty acids, which was similar to the results of Liu Huaying; but in this study, Xinjiang wild walnut kernels were heavy linoleic acid. The content of oleic acid was the highest, and Liu Huaying had the highest oleic acid content, showing the results were inconsistent. The reasons for this may be large area of wild walnut ditch, diverse topographical conditions, different sampling sites, and yearly difference in measurement.The climate difference of the year may cause differences in the composition of wild walnut kernels.【Conclusion】Compared with Xinjiang walnut cultivars, the nut nutrients of Xinjiang wild walnuts were rich in protein, fat, soluble sugar, fatty acids and trace elements. Theflat-bottom nuts had the highest fat content and the sharp nuts had the highest soluble sugar content. Among the trace elements in Xinjiang wild walnuts, the contents of potassium, phosphorus and magnesium were higher. Among the fatty acid compositions of Xinjiang wild walnuts, the ovale fatty acid had the highest mass fraction. In the development, utilization and breeding of Xinjiang wild walnut resources, Xinjiang wild walnuts can be used as a high-quality protein plant, and at the same time, the flat-bottom round and small round nuts can be chosen as the resources of edible vegetable oil. Different types of wild walnuts in Xinjiang had different excellent indicators. Therefore, when the nutrient composition of Xinjiang wild walnuts are evaluated, the comprehensive considerations are needed.