Nutrient composition of two varieties of wild Japanese walnut and Japanese stone oak

Abstract

We analyzed the nutrient composition of two varieties of wild Japanese walnut (Juglans mandshurica var. sachalinensis and Juglans mandshurica var. cordiformis) and Japanese stone oak (Lithocarpus edulis) to reappraise their values as food resources. We evaluated previously unreported mineral and vitamin contents, and compared those with that of other species within the same genus and family. The Japanese walnut varieties showed higher magnesium, phosphorus, iron, zinc, and manganese contents than the Persian walnut (Juglans regia), whereas L. edulis had higher manganese and copper contents than other Fagaceae species. J. mandshurica var. sachalinensis had higher gamma-tochopherol and vitamin B₁ contents than other walnut species. L. edulis presented higher vitamin K₁ and C contents than chestnut species (Castanea spp.). The proportions of inedible parts to the total weight (refuse proportion) for J. mandshurica var. sachalinensis, J. mandshurica var. cordiformis, and L. edulis were 73.6%, 72.1%, and 35.3%, respectively.