鲜食玉米中脂氧合酶活力、脂肪酸与挥发性成分的相关性研究

Correlation Analysis of Lipoxygenase(LOX) Activity and Fatty Acids with Volatile Components in Fresh Corn

研究了晶甜5号和晶甜紫花糯2号两种鲜食玉米在早于适采期、适采期和晚于适采期三个采收期脂氧合酶（LOX）的活力、脂肪酸和挥发性成分的组成及变化情况。结果显示样品的LOX活力为2.63~4.28 U/g FW,脂肪酸均以亚油酸的含量最高（32.40%~46.68%）,而亚麻酸含量较低（0.97%~2.40%）。挥发性成分则以己醇或己醛的含量最高,早采和适采期的晶甜5号中己醇含量最高,晚采的晶甜5号和三个采收期的京甜紫花糯2号均以己醛含量最高。两种玉米的粗脂肪、脂氧合酶活力随采收期的延后而增加,但是亚油酸、己醛却表现为下降趋势。相关性分析表明LOX途径的底物脂肪酸亚油酸和亚麻酸与己醛呈现显著正相关关系,但与LOX活力的相关性未达显著水平。这说明鲜食玉米中来自LOX途径的挥发性成分可能主要取决于亚油酸或亚麻酸的量,而并非LOX活力的大小。另外,两种玉米挥发性成分尤其是C6醛醇含量的不同可能体现了样品间LOX途径上的差异。

The lipoxygenase（LOX） activities and the compositions of fatty acids and volatiles as well as their changes in sweet corn（var. Jingtian 5） and waxy corn（var. Jingtianzihuanuo 2）, harvested before, at, and after the favorable harvest time, were investigated. The LOX activities of the samples were in a range of 2.63~4.28 U/g FW, and the fatty acids in the highest and lowest amounts were linoleic acid（32.40%~46.68%） and linolenic acid（0.97%~2.40%）, respectively. The volatiles in the highest amount were hexanol and hexanal. Jingtian 5 samples harvested before and at the favorable harvest time showed the highest hexanol content, whereas Jingtian 5 harvested after the favorable harvest time and Jingtianzihuanuo 2 harvested in all three periods had the highest hexanal content. With prolonging of the harvest time, the LOX activities and crude fat content in both cultivars increased, but the contents of linoleic acid and hexanal exhibited a downward trend. Correlation analysis indicated that the substrates linoleic acid and linolenic acid in the LOX pathway had significant positive correlation with the hexanal contents but no significant correlation with LOX activity. These findings indicate that the volatiles from the LOX pathway in these fresh corns may depend on the level of linoleic acid or linolenic acid, rather than the level of LOX activity. In addition, the differences in the volatile contents between the two cultivars, especially of hexanol and hexanal, might reflect the differences in the LOX pathway between the two samples.