Characterization and Comparison of Unfermented and Fermented Seed-Watermelon Juice

Fermented juice was prepared with byproducts (pulp and rind) of seed watermelon (Citrullus lanatus sp. vulgaris var. megalaspermus) for the first time, and its radical scavenging capacity and aroma were compared with those of the corresponding unfermented juice. The 2,2-diphenyl-1-picryhydrazyl and hydroxyl radical scavenging capacities of the fermented juice were significantly stronger than those of the unfermented juice. The oxygen radical scavenging capacity of the fermented juice was 60 µM trolox equivalent/mL, which was 7.14% higher than that of the unfermented juice. Gas chromatography-mass spectrometer analysis showed a total of 26 and 29 volatiles in unfermented juice and fermented juice, respectively. The content of typical watermelon aroma, including 1-nonanol, 3,6-nonadien-1-ol, nonanal, trans-2-nonenal, and trans,cis-2,6-nonadienal, was reduced from 92.08 mg/L in the unfermented juice to 26.41 mg/L in the fermented juice. Furthermore, isoamylol, ethyl octanoate, ethyl acetate, and ethyl laurate contributed a typical grape-wine bouquet to the fermented juice. Sensory evaluation further confirmed the attractive appearance and watermelon aroma of the fermented juice. Therefore, the fermented seed-watermelon juice showed a strong radical scavenging capacity and presented the typical watermelon aroma with a grape-wine bouquet