Development of Breeding Method by Controlling Lipoxygenase Activity in Soybeans for Rising and Diversifying the Taste and Flavor of Tofu.

对日本各地大豆育种站生产的大豆品种的脂肪氧合酶(Lox)活性的测定表明，凉爽地区的大豆品种在pH 7.0和pH 9.0时的Lox活性明显高于温暖地区的品种。我们发现新丹巴郎的LOX活性水平很低。利用结构基因和启动子序列的单核苷酸多态性(SNPs)，开发了L2基因和L3基因的标记，以有效地培育缺乏各种类型脂肪氧合酶。分析了含有不同脂肪氧合酶同工酶的大豆品种铃谷(L-123)、玉米谷(L-1)、甘藤102(L-2)、九州119(L-3)的氧合代谢。和Ichihime(缺少L-0三种同工酶)。不同品种的…酯中氧化脂肪酸的含量更具体化的形式高于自由形式的。关东102形成的氧化脂含量最高，Yumeyutaka和Ishihime形成的最低。关东102和九州119形成了大量的酮脂肪酸，而Yumeyutaka和Ichihime检测不到它们。利用大豆正常品系(L-123)和低氧大豆品系(L-1、L-2、L-3、L-0)，对豆腐的香气成分进行了研究。与其他LOX缺陷系(LOX-1、LOX-3、LOX-0)相比，L-123和L-2制作的豆腐中的香气成分，特别是己醛、1-己醇和己酸的含量更高。与热榨豆腐相比，非热榨豆腐的己酸含量更高，口感更饱满，更甜美。在较高的温度和湿度条件下，储藏大豆制成的豆腐中己醛、己酸和麦芽酚的含量增加。这意味着大豆的采收和储存条件是影响豆腐风味的重要因素。从以上结果可以得出结论，控制大豆中的Lox活性使我们能够使豆腐的味道和风味多样化。较少

Examination of lipoxygenase (Lox) activity of soybean varieties produced in breeding stations throughout Japan showed that there is a marked tendency for higher Lox activities at the both of pH 7.0 and pH 9.0 in the varieties produced in cool regions than those produced in warm regions. We found that cv.Shintanbaguro has low levels of Lox activity. Genetic study revealed that the low Lox activity of cv.Shintanbaguro is due to genetic factor(s).By the use of single nucleotide polymorphisms (SNPs) of the DNA sequences of structural gene and of promoter region, we developed DNA marker of L2 gene and L3 gene to breed effectively the lipoxygenase lacking variety of various types.We analyzed oxylipin metabolism in soybean homogenates containing different set of lipoxygenase isozymes (L1, L2 and L3), namely, Suzuyutaka (L-123) ; Yumeyutaka (L-1) ; Kanto102 (L-2) ; Kyushu119 (L-3) ; and Ichihime (lacks all the three isozymes : L-0). With every cultivar, amounts of oxidized fatty acids in ester … More ified form were higher than those in free form. Kanto102 formed highest amounts of oxidized lipids, and Yumeyutaka and Ishihime formed the lowest. With Kanto102 and Kyushu119 high amounts of keto fatty acids were formed, while they were undetectable with Yumeyutaka and Ichihime. Lower amounts of oxidized lipids again made Yumeyutaka and Ichihime good cultivar for food processing.Using normal (L-123) and Lox-deficient (L-1, L-2, L-3, L-0) lines of soybeans, the aroma constituents of tofu were investigated. The aroma constituents, especially hexanal, 1-hexanol and hexanoic acid were contained more amounts in the tofus made from L-123 and L-2 compared with those of the other Lox-deficient lines (LOX-1, LOX-3, LOX-0). The tofu prepared by the non heat-squeezing method contained more hexanoic acid and tasted more mouthful (rich) and sweeter compared with that by the heat-squeezing method. The amounts of hexanal, hexanoic acid and maltol increased in the tofu made from the stored soybean under the condition of higher temperature and humidity. This means that the harvest and storage condition of soybeans is important factors affecting the flavor of tofu.From the above results it can be concluded that manipulation of Lox activity in soybeans enables us to diversify the taste and flavor of tofu. Less