不同品种核桃仁成分及烘烤对其油脂品质 和内源性蛋白酶活性的影响Composition of walnut kernels from different varieties and effect of roasting on their oils quality and endogenous protease activities

Abstract

旨在为工业去衣核桃仁的烘烤处理条件提供参考，选择我国4个品种核桃仁作为研究对象，比较了4种核桃仁的蛋白质和脂肪含量，分析了其氨基酸和脂肪酸组成，并考察了烘烤（60~140 ℃烘烤1~3 h使水分含量降至5%以下）对这4种去衣核桃仁油脂品质及内源性蛋白酶活性的影响。结果表明：核桃仁蛋白质（13.73%~17.54%）、脂肪（69.10%~72.77%）含量及其油脂亚麻酸含量（8.77%~13.23%）在品种间存在显著性差异（p<0.05），而氨基酸组成未表现出明显差异；随着烘烤温度的升高，4种去衣核桃仁油脂的酸值及过氧化值均呈现不断上升的趋势，但均未超过国家标准要求；未烘烤核桃仁内源性蛋白酶活性在品种间也存在显著性差异（p<005）；烘烤温度对核桃仁内源性蛋白酶活性有显著影响，60~80 ℃烘烤尚且保留了大部分的内源性蛋白酶活性，而100~140 ℃烘烤核桃仁内源性蛋白酶活性大幅度下降甚至丧失。综上，烘烤对去衣核桃仁油脂及内源性蛋白酶的影响并不因核桃品种的不同而产生差异，60~80 ℃的烘烤适合生产高内源性蛋白酶活性的去衣核桃仁（坚果类产品）。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%-1323%) 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).

Keywords

• 核桃；去衣核桃仁；烘烤温度；核桃油；内源性蛋白酶
• walnut; peeled walnut kernel; roasting temperature; walnut oil; endogenous protease