Fruit Quality and Nutrient Dynamics during Fruit Maturation of Jujube (Ziziphus jujuba Mill.) in New Mexico

Jujube (Ziziphus jujuba Mill.) originated in China, and plays an important role in traditional Chinese medicine. Jujube is considered a functional food, and is believed to help improve sleep quality and regulate the digestive system. Jujube cultivars were imported to the United States in 1908, and are currently distributed widely across the country. Jujube is predicted to have a high potential as a crop in the southwestern United States because of this plant’s good environmental adaptation and drought tolerance. Interest in jujube is growing, and farmers are requesting more information on cultivar selections for different uses, vitamin C content, flavor (sweetness), and antioxidant capacity. Our objective is to study the nutrient dynamics during fruit maturation, including vitamin C content, titratable acid, soluble solids, moisture content, sugar composition, and total phenolic content. Fruits of 10 cultivars grown at New Mexico State University (NMSU) Sustainable Agriculture Science Center at Alcalde, NM, and 5 cultivars grown at Los Lunas were harvested on Aug. 25, Sept. 10, Sept. 25, and Oct. 7, 2014. Vitamin C content and moisture content decreased significantly during the ripening process. The vitamin C content of fully matured fruits ranged from 248–374 mg/100g fresh weight in this study, which is 5 times higher than in orange. Vitamin C content varied among cultivars. ‘Lang’, ‘So’, ‘Sugarcane’, and ‘Sherwood’ had higher vitamin C content. Titratable acid and soluble solids increased significantly during maturation. In fully mature jujubes among cultivars studied, the range for titratable acid was from 0.27% to 0.46%, and 19.9% to 33.7% for soluble solids. Glucose, fructose, and sucrose content increased during ripening. Matured fruits in this study contained 31–82 mg/g FW glucose, 32–101 mg/g FW fructose and 53–159 mg/g FW sucrose. Sucrose content increased rapidly during fruit development. Cultivars could be divided into two groups: "high-sucrose" group (more sucrose than glucose and fructose), which included ‘Dagua’, ‘Honeyjar’, ‘Lang’, ‘Li’, ‘Maya’, ‘Sugarcane’ and ‘Sherwood’ and "low-sucrose" group (less sucrose than glucose or fructose).Total phenolic content in fruit decreased during maturation. Mature fruits in this study contained 12–16 mg GAE/g DW total phenolic content.