内种皮色泽及其热烫脱除对压榨核桃油品质的影响

Effect of Walnut Skin Color and Its Removal by Blanching on the Quality of Pressed Walnut Oil

内种皮色泽是核桃仁等级划分的重要标准之一。本实验研究了内种皮色泽及其热烫脱除对压榨核桃油颜色、营养成分和稳定性的影响。结果表明:内种皮色泽对压榨油颜色的影响不显著(P>0.05),且去皮处理对压榨油颜色无影响。营养成分上,深色仁油与浅色仁油在不饱和脂肪酸、总酚及生育酚含量上均无显著性差异;去皮处理对两者的不饱和脂肪酸含量无明显影响,但会导致生育酚总量的显著下降,深色仁油、浅色仁油生育酚总量分别降低20.19%、16.33%。而去皮前后核桃油中总酚含量均很少,主要存在于压榨粕中。稳定性方面,深色仁油与浅色仁油无显著差异;去皮后,两者的氧化诱导期分别缩短0.68、0.53 h,60℃货架期分别缩短5.52、3.36 h。另外,研究还发现内种皮的存在可提高核桃仁的压榨出油率,去皮后深色仁与浅色仁的出油率分别降低5.43%、3.29%。

Walnut skin color is one of the most important quality parameters for walnut grading. In this paper, the effects of walnut skin color and its removal by blanching on the color, nutritional composition and stability of pressed walnut oil were studied. The results showed that oil color was not significantly affected by walnut skin color （P 〉 0.05） and was not affected at all by peeling treatment. In the case of nutritional composition, there were no significant differences in unsaturated fatty acids, total phenolics or tocopherols between dark-colored and light-colored walnut oils; although the peeling treatment had no obvious effect on unsaturated fatty acids, but it decreased total tocopherols by 20.19% and 16.33% in the darkcolored and light-colored oils, respectively. The content of total phenolics was quite low in dark-colored and light-colored oils obtained from unpeeled walnuts and most of the phenolics were remained in meals. With respect to stability, no significant difference was found between the two oils; after peeling, the oxidation induction periods of the dark-colored and light-colored oils decreased by 0.68 and 0.53 h, respectively, and the shelf lives of 60 ℃ decreased by 5.52 and 3.36 h, respectively. In addition, it was found that the oil yield during pressing was improved by the presence of walnut skin; after peeling, the oil yields from dark-colored and light-colored kernels decreased by 5.43% and 3.29%, respectively.