Evaluation of nutrition, aroma components and antioxidant activity of mulberry fruits from nine varieties

Abstract: 【Objective】Mulberry fruit (Fructus Mori) is one of the first batch of medicinal and edible homologous agricultural products approved by the Ministry of Health. It has high nutritional value and has extremely significant effect on improving memory, reducing blood lipids, regulating intestinal flora,and relieving fatigue. In recent years, the production and consumption of fruit mulberries have in-creased rapidly, and its processed products have also increased apparentally. Therefore, selection of high-yield and high-quality fruit mulberry varieties is very important for the development of the fruit mulberry industry by accurate evaluating the fruit properties, nutrition, aroma components and antioxi-dant capacity of the existing fruit mulberry varieties.【Methods】The 9 fruit mulberry varieties named Anshen, Qusang, Mengsang, 8632, Wu45, Luyou 7, Guihua, Baiyuwang, and Dongguang Dabai in He-bei Province were used as experimental materials, ultraviolet spectrophotometry, solid-phase microex-traction combined with gas chromatography-mass spectrometry and enzyme-labeled method were em-ployed to detect the nutrition, aroma components and antioxidant capacity of the each variety, and SPSS 23.0 software was used to perform difference analysis and principal component analysis of the measure ment results (principal component analysis, PCA).【Results】The juice yield of the white mulberries was generally higher than that of the black or red mulberries. The juice yield of Guihua was the highest (76.75%), and the juice yield of Anshen was the lowest (49.970%). There was no significant difference in the water content among the 9 varieties (p＞ 0.05). The soluble solid substance (TSS) content of all verieties distributed in 13%-20%, the veriety Mengsang had the highest content in the contents of the soluble solid substance (20.383%). the ascorbic acid (89.488 mg·g^-1), the total acid (21.365 mg·g^-1) and reducing sugar c (68.844 mg·g^-1). The hardness (4.503 N·cm^-2), the total flavonoid content (26.468 mg·g^-1), the total polyphenol content (23.097 mg · g^-1), the DPPH removal capacity (25.202 mg·g^-1 Vc equivalent) and the ABTS removal capacity ( 51.778 mg·g^-1 Vc equivalent) of Anshenare were significantly higher than those of the other varieties. The active ingredient content and antioxidant activity of the white varieties Guihua, Baiyuwang and Dongguang Dabai were significantly lower than those of the purple-black varieties. A total of 59 aroma compounds were identified from various mulberry varieties, and the aroma components were basically the same in big category, mainly including esters, ketones, al-dehydes, and alcoholsand acids. The types and contents of the components were significantly different (p ＜ 0.05). The relative contents of esters, aldehydes, acids, alcohols, and ketones in descending order were 35.71%, 28.57%, 14.29%, 7.14% and 7.14%, respectively. The variety with hiest content of aroma substances was Dongguang Dabai (36 kinds), followed by Guihua (34 kinds), Baiyuwang (33 kinds), Anshen (28 kinds), and Qusang (27 kinds). The contents of aroma substances of the remaining 4 variet-ies were very low. The PCA results showed that the cumulative variance contribution rate of the 7 prin-cipal components reached 97.187%, and the larger contribution rates were PC1 and PC2. The character-istic value of PC1 was 10.976, and its contribution rate was 37.847%. The characteristic value of PC2 was 6.592, and its contribution rate was 22.730% . The comprehensive principal component value F showed that Mengsang had the highest score, 1.611 points, followed by Baiyuwang and Anshen.【Conclusion】There were significant differences in nutrition, aroma components and antioxidant capacity of the different varieties of mulberry (p ＜ 0.05). Mengsang, Baiyuwang and Anshen had the best compre-hensive quality Baiyuwang had large fruit shape and high yield, low acidity and sweet taste; Mongolian mulberry was sweet and sour, but the fruit shape was small and the yield was low; Anshen was a new variety with significantly higher active substances content and antioxidant capacity than other varieties.These three varieties could be used as excellent germplasm resources for in-depth development for dif-ferent perspectives. Follow- up research should further explore the related factors affecting mulberry quality, and post-harvest treatment and quality control as well.