Phenolic composition and nutritional attributes of diaphragma juglandis fructus and shell of walnut (Juglans regia L.)

Phenolic composition and nutritional attributes of diaphragma juglandis fructus (Djf) and walnut shells (Ws) were investigated. Phenolic acids, hydroxybenzoic acid, isoflavone, and flavone were identified in the free phenolic fractions (FPFs) of both Djf and Ws. Bound phenolic fractions were less than FPFs both in content and diversity. The soluble dietary fiber contents of Djf and Ws were 25.56 g/100 g and 9.5 g/100 g, respectively. The contents of unsaturated fatty acids (1912.28 mg/kg and 9137.56 mg/kg, respectively) were significantly higher than that of saturated fatty acid both in Djf and Ws. The content of essential amino acids in Djf (9.67 mg/g) was significantly higher than that in Ws. More than eight types of monosaccharides were detected in Djf and Ws. The monosaccharide content of Djf (314.16 mg/g) was significantly higher than that of Ws (60.97 mg/g). Trehalose was the predominant component both in Djf (71.2%) and Ws (78.6%).