陇南清香核桃主要理化指标随生长期的动态变化

Dynamic changes of main physical and chemical indexes of walnut with growth period in Longnan

为深入了解核桃品种‘清香’的果实性状特点及其仁油的部分理化性质,以确定其最佳采摘时期,以甘肃省陇南市经济林研究院核桃示范基地种植的‘清香’核桃为研究对象,对不同日期采摘的‘清香’核桃果实部分形态特征指标(如鲜青果的质量、三径和去皮后鲜坚果的质量、三径等)和主要理化指标(含油率、出油率,酸价、皂化值、过氧化值)及核桃油的脂肪酸组成的动态变化特点进行了测定和分析。结果表明:其各形态特征随采摘期的推移而先增后减的变化趋势基本相同;核桃仁的含油率随采摘日期的推移而逐渐上升,其含油率较高且较平稳;在以其干仁所提核桃油的主要成分中,亚油酸的含量远高于其他成分的含量,随采摘期的推移亚油酸、十六酸、亚麻酸的含量均呈增加的趋势,油酸和硬脂酸的含量变化均较小;酸价、过氧化值、皂化值在整个采摘期的动态变化值都较低,均低于GB/22327-2008《核桃油》中的规定值。综合分析结果表明:陇南市‘清香’核桃的最佳采摘期为其采摘期后半阶段的8月30日至9月13日,此时采摘的核桃其油脂质量最好。

For the purpose of deep understanding of fruit phenotypic trait and partial physicochemical properties of oil of walnut variety of Qingxiang and further determining its optimum picking period, Qingxiang walnuts were studied, being planted in the walnut planting demonstration base of the Longnan economic forestry institute of Gansu province. The fruits morphological characteristics including quality and three diameters of fresh green fruits and fresh nuts after peeling, the main physical and chemical indicators including oil content, oil yieldl acid value, saponification value, peroxide value and the dynamic changes of the fatty acid composition of walnut oil of Qingxiang walnuts picked on different dates were measured and analyzed. The results showed that these different measured morphological characteristics had similar change trends from increase to decrease along with picking period; the oil content of walnut kernels gradually increased with the picking date, and the oil content was higher and more stable than other varieties; the content of linoleic acid in walnut oil is much higher than that of other components, and the contents of linoleic acid, palmitic acid and linolenic acid were increased with the time of picking. The content of oleic acid and stearic acid changed less. Dynamic change values of acidic value, peroxide value, and saponification value kept lower during the whole picking period, and these values were all lower than specified value in GB/22327-2008 of Walnut Oil. The analysis results above suggested that the optimum picking period for Qingxiang walnuts in Longnan was from August 30 to September 13 in the latter half of the picking period, when the walnuts had the best oil quality.