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| Composition of walnut kernels from different varieties and effect of roasting on their oils quality and endogenous protease activities |
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| DOI： |
| KeyWord:walnut peeled walnut kernel roasting temperature walnut oil endogenous protease |
| FundProject:江苏省林业科技创新与推广项目（LYKJ-句容〔2020〕01） |
| Author Name | Affiliation | | WANG Luming1, HUANG Minmin2, CHEN Yeming1
(1.School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiang | (1.School of Food Science and Technology, Jiangnan University, Wuxi 214122, Jiangsu, China
2.Institute of Economic Forestry, Xinjiang Academy of Forestry Sciences, Urumqi 830092, China) |
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| Abstract: |
| In order to provide reference for roasting treatment conditions of industrial peeled walnut kernels, four varieties of walnut kernel cultivated in China were selected as samples, the protein and fat contents in the four walnut kernels were compared, and the amino acid and fatty acid compositions were analyzed, respectively. Then the effects of roasting (reducing the moisture of peeled kernels to below 5% by roasting for 1-3 h at 60-140 ℃) on the oil quality and endogenous protease activity of the four peeled walnut kernels were examined. The results showed that there were significant differences in the protein content (13.73%-17.54%), fat content (69.10%-72.77%) of the four walnut kernels and linolenic acid content (8.77%-1323%) in their oils (p<0.05). In the case of amino acid composition, the four walnut kernels did not show significant differences. With the increase of roasting temperature, the acid value and peroxide value of walnut oil in the four peeled walnut kernels showed a rising trend, but none of them exceeded the national standard. The endogenous protease activity of the four peeled walnut kernels (unroasted) showed significant differences (p<0.05). The roasting temperature had a significant effect on the protease activity of walnut kernel. Most of the endogenous protease activity was retained after roasting at 60-80 ℃, whereas after roasting at 100-140 ℃, the endogenous protease activity decreased substantially or even lost. In conclusion, the effect of roasting on oil and endogenous proteast of peeled walnut kernels does not differ according to walnut varieties, and roasting at 60-80 ℃ is suitable for the production of peeled walnut kernels with high endogenous protease activity (nut products). |
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