Abstract
Hazelnut (Corylus) is an important woody oil tree species in economic forests. China, as one of the original countries of native Corylus species, had 8 species and 2 varieties. However, little information is available on the hazelnut nutritional quality of these Chinese Corylus species. In this study, four main wild Corylus species (C. heterophylla Fisch., C. mandshurica Maxim., C. kweichowensis Hu., and C. yunnanensis Franch.) originating in China and one main cultivar of hybrid hazelnut (Corylus heterophylla Fisch. × C. avellana L.) cv. ‘Dawei’ from China were used to analyze the basic nutritional composition (content of oil, fatty acid, protein, saccharide, aminao acid, vitamin C, tocopherol, total phenols, and total flavonoids) and antioxidant ability. The results showed that oil content ranged from 52.97 to 60.88 g/100 g DW and highly unsaturated fatty acid (UFA) content was over 91%. Oleic was the most dominant UFA in these hazelnut kernels, and the relative content was ranging from 71.32 to 85.19%. Compared with other four hazelnut kernels, C. heterophylla Fisch. was the lowest oil content of hazelnut with lower oleic acid content and higher linoleic acid content, obviously. The total protein content ranged from 13.15 to 18.35 g/100 g DW, and all amino acids were detected as hydrate amino acids, but Tryptophan, an essential amino acid, was not detected as free amino acid in these hazelnut kernels. Kernel of C. heterophylla Fisch. was with the highest content of protein and amino acid. Saccharose was the most essential and abundant disaccharide in the hazelnut kernels. C. mandshurica Maxim. was the highest saccharide content among these hazelnut kernels. α-tocopherol was the main type of tocopherol found in the hazelnut kernels. Wild hazelnut kernels generally had higher bioactivity substance content (vitamin C, total tocopherol, total phenol and total flavonoid) and antioxidant capacity. Compared to the four wild hazelnut kernels, the hybrid hazelnut cv. ‘Dawei’ had higher content of oil, oleic acid, α-tocopherol and sugar. Overall, there were great differences in the nutritional composition of different hazelnut species. Wild species are a good source of breeding materials because of their own characteristics in nutrition composition, and the hybrid hazelnut cv. ‘Dawei’ with good quality has the value of commercial promotion.
Highlights
Hazelnut (Corylus), an important economic forest and nut tree, generally grows in temperate climate zones with a relatively high humidity and a high rainfall rate (Kole, 2011)
Nut oil is mostly unsaturated, and unsaturated fatty acid (UFA) have been associated with beneficial effects
Oil content is largely different among different hazelnut species and varieties and even in the same cultivar produced in different areas
Summary
Hazelnut (Corylus), an important economic forest and nut tree, generally grows in temperate climate zones with a relatively high humidity and a high rainfall rate (Kole, 2011). The distribution of these resources ranges from 24◦31’N to 51◦42’N covering 24 provinces in China (Zhang et al, 2005). Among these wild Corylus species in China, C. heterophylla has been the most valuable and widely utilized until recently and is distributed mainly over the north and northeast of China. C. mandshurica, which is distributed at higher altitudes and has a very fragrant flavor, C. kweichowensis, which grows in the middle and southern regions of China, and C. yunnanensis, a high shrub or a small arbor tree, which is distributed at higher altitudes from 2,000 to 3,700 m in the southwest of China, are the other three wild species that can be focused on due to the ease of collection relative to the rest of the wild Corylus species
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