Comparative Analysis of Nutritional Components and Flavor Substances between Dali Yangpao and Purple Walnut Kernels

The aim of study was to analyze the differences in nutritional elements and flavor substances between the Dali Yangpao and purple walnut kernels, two kinds of walnut kernels were used as raw materials, the content of amino acids, fatty acids, essential nutrients and mineral elements were determined separately, and the volatile components between the two walnut kernels were detected by gas chromatography mass spectrometry (GC-MS). The results showed that compared to those of the Yangpao walnut kernels, the purple walnut kernels had a higher content of total amino acid, essential amino acid, and umami amino acid (P<0.05). Three kinds of saturated fatty acids were detected in both walnut kernels, the palmitic acid content of Yangpao walnut kernels (4.17%) was higher than that of purple walnut kernels (2.69%). Five kinds of unsaturated fatty acids were detected in both walnut kernels, compared to those of the Yangpao walnut kernels, the purple walnut kernels had a higher content of oleic acid, arachidonic acid, and linolenic acid, but purple walnut kernels had a lower content of palmitoleic acid and linoleic acid (P<0.05). Compared to those of the Yangpao walnut kernels, the purple walnut kernels had a higher content of fat, protein, and carbohydrate (P<0.05). A total of 9 mineral elements were detected in both walnut kernels, and the P, Zn, Fe, Cu, Na, and K elements content of Yangpao walnut kernels was higher than those of purple walnut kernels (P<0.05). 30 and 33 volatile flavor compounds were identified from Yangpao and purple walnut kernels, respectively. Alcohols, aldehydes, and ketones were the main flavor substances of purple walnut, while Yangpao walnut's main flavor substances were alcohols and olefin compounds (19.948%, 3.819%). The peak area of alcohol compounds, especially hexanol, accounted for the highest proportion in Yangpao and purple walnut kernels, respectively. The above results indicate that purple walnut kernels have higher nutritional value and flavor substances.