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

对日本各地选育站生产的大豆品种脂氧合酶（Lox）活性的测定表明，在pH 7.0和pH 9.0时，冷区品种的Lox活性明显高于暖区品种。我们找到了cv。新檀巴uro的氧活性很低。遗传研究表明，cv。新檀巴uro是由遗传因素引起的。利用结构基因和启动子区DNA序列的单核苷酸多态性（snp），开发了L2基因和L3基因的DNA标记，有效地培育了各种类型的缺乏脂肪加氧酶的品种。我们分析了含有不同组脂氧合酶同工酶（L1， L2和L3）的大豆匀浆中的氧脂素代谢，即Suzuyutaka (L-123)；游丰（L-1）；Kanto102 (L-2)；九州119 (L-3)；和一姬（缺乏所有三种同工酶：L-0）。各品种中酯态、多态氧化脂肪酸含量均高于游离态。Kanto102形成的氧化脂质含量最高，yumyutaka和Ishihime形成的氧化脂质含量最低。Kanto102和Kyushu119形成了大量的酮脂肪酸，而Yumeyutaka和Ichihime则检测不到。较低的氧化脂质再次使游丰和一姬成为食品加工的好品种。以大豆正常系（L-123）和缺氧系（L-1、L-2、L-3、L-0）为材料，研究了豆腐的香气成分。与其他缺氧品系（LOX-1、LOX-3、LOX-0）相比，以L-123和L-2为原料的豆腐乳香气成分含量较高，其中以己醛、1-己醇和己酸含量最高。非热挤压法制得的豆腐比热挤压法制得的豆腐含有更多的己酸，口感更浓郁、更甜。在较高的温度和湿度条件下，以大豆为原料制成的豆腐中己醛、己酸和麦芽糖醇的含量有所增加。这说明大豆的收获和贮藏条件是影响豆腐风味的重要因素。综上所述，通过对大豆中Lox活性的调控，可以使豆腐的口感和风味更加多样化。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