The Effects of Altitude on Fruit Characteristics, Nutrient Chemicals, and Biochemical Properties of Walnut Fruits (Juglans regia L.)

This study aimed to investigate changes in fruit characteristics, total phenolics, total antioxidant capacity, organic acids, sugar content, and fatty acid composition in ten walnut genotypes and three cultivars grown at different altitudes under Mediterranean climate conditions. At altitudes of 500 m and 1200 m, total phenolics ranged between 237.51 and 412.96 mg GAE/100 g dw and 234.94 and 392.31 mg GAE/100 g dw, respectively. According to DPPH radical inhibition, the total antioxidant capacity varied between 47.65% and 64.99% at an altitude of 500 m and between 57.76% and 68.92% at an altitude of 1200 m. The oil content demonstrated variations between 53.44% and 76.17% at an elevation of 500 m and between 43.11% and 67.03% at an altitude of 1200 m. At both 500 m and 1200 m altitudes, linoleic acid emerged as the predominant fatty acid and ranged from 58.82% to 62.44% at 500 m altitude and from 57.33% to 59.38% at 1200 m altitude. Notably, malic acid was identified as the primary organic acid, with concentrations ranging from 1.35% to 7.33% at both altitudes. In conclusion, this study demonstrates that walnut seeds are abundant in oil, protein, total phenolics, antioxidants, and fatty acids, with variations influenced by the cultivar or genotype and notably affected by altitude