Abstract
To gain knowledge of the fat characteristics of walnut varieties in different production areas of Shanxi Province, kernel oil content and its fatty acid composition of 6 walnut varieties were analyzed by using soxhlet extraction method and gas chromatography. The experiment sites were Yicheng and Tunliu. Yicheng has 800 m of altitude and 11 ºC of annual mean temperature while Tunliu has 1100 m of altitude and 9.3 ºC of annual mean temperature. The results indicated between Yicheng and Tunliu County, the most variety’s oil content was increased with increasing of altitude, but had no significant difference (64.9% > 64.3%, P > 0.05). Both the content of oleic acid and linoleic acid showed a significant difference between Tunliu and Yicheng, and there is a negative relationship between the contents of oleic and linoleic acid. Annual mean temperature has an obvious influence on ?-linolenic acid (ALA) content of walnut. The content of ALA from Yicheng with higher annual mean temperature is higher than that from Tunliu with lower annual mean temperature. The nutrition analysis showed that Tunliu’ walnut kernel has a lower saturated fatty acids (SFA) (7.6% < 8.2%, P < 0.05) and a higher unsaturated fatty acids (UFA) (92.5% > 91.8%, P < 0.05) compared to Yicheng, respectively, but the polyunsaturated fatty acids (PUFA) content of Yicheng was higher than that of Tunliu (76.3% > 68.5%, P < 0.05), and its ratio of N-6/N-3 was also better compared to Tunliu (5.4:1 < 5.9:1). These results showed that with the different altitude and annual mean temperature, the walnut nutrition of fat is also different. Higher altitude and lower annual mean temperature can help to produce oleic-rich walnut while lower altitude and higher annual mean temperature is helpful for the higher content of ALA in walnut kernel.
Highlights
Walnut kernel contains around 60-70% of oil, and can be praised as “the oil store on the tree” (Li et al, 2009)
The nutrition analysis showed that Tunliu’ walnut kernel has a lower saturated fatty acids (SFA) (7.6% < 8.2%, P < 0.05) and a higher unsaturated fatty acids (UFA) (92.5% > 91.8%, P < 0.05) compared to Yicheng, respectively, but the polyunsaturated fatty acids (PUFA) content of Yicheng was higher than that of Tunliu (76.3% > 68.5%, P < 0.05), and its ratio of N-6/N-3 was better compared to Tunliu (5.4:1 < 5.9:1)
6 varieties of walnut were selected to inspect the effects of two different production areas (Tunliu and Yicheng) on walnut oil content and fatty acid content
Summary
Walnut kernel contains around 60-70% of oil, and can be praised as “the oil store on the tree” (Li et al, 2009). People prefer plant oils to animal fat due to concerning about animal cholesterol (Pyorala, 1987). Plant oils don’t contain any animal cholesterol; but it contains a large amount of unsaturated fatty acids (UFA) that benefit human health. To obtain the perfect nutrition characteristics of fatty acid composition of walnut, a lot of investigations have been done about variety (Wang et al, 2004; Chen et al, 2007; Wu et al, 2007). In order to gain knowledge of the fat characteristics of walnut in different production areas, the effect of production area on walnut oil quality is necessary to be investigated. Its total plant area of walnut is large (Cheng, 2011), so we selected Shanxi as experimental site to determine the effect of producing region of walnut on oil quality
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