鲜食玉米发育过程中游离糖和氨基酸变化

Changes of Free Sugars and Amino Acids in Table Corn during Development

以晶甜5号超甜玉米和晶糯8号糯玉米2个鲜食玉米品种为研究对象,采用高效液相色谱法测定并分析玉米鲜穗由吐丝授粉至乳熟期发育过程中3种游离糖和18种氨基酸的含量变化。结果显示,晶甜5号和晶糯8号2个品种的蔗糖和丙氨酸含量随发育时间延长均表现为低-高-低的变化趋势,并分别与3种游离糖和18种氨基酸总量的变化一致。对这2种玉米发育中测定的上述21个指标进行了主成分分析(principal components analysis,PCA)和聚类分析。PCA法提取了3个主成分,其贡献率分别为39.9%、24.4%和13.3%,其中PC1与PC2主要提取了鲜食玉米不同发育阶段甜味氨基酸及糖含量的变化信息,PC3则主要体现了2个品种中天冬氨酸与谷氨酸2种鲜味氨基酸含量的不同;聚类分析结果则显示玉米样品因发育阶段接近而聚集。综上所述,发育程度是影响鲜食玉米游离糖和氨基酸含量差异的主要因素,其次为品种间的差异。研究结果为从原料角度调控鲜食玉米加工产品品质尤其是玉米汁风味有良好的借鉴作用。

Changes in the contents of 3 free sugars and 18 free amino acids in two table corn cultivars(Jingtian 5 sweet corn and Jingnuo 8 waxy corn)during development from pollination after silking to milky maturation were determined using high performance liquid chromatography(HPLC).The contents of sucrose and alanine,as well as total sugars and total amino acids in both cultivars showed low-high-low trends with development time.Principle component analysis(PCA)and cluster analysis(CA)were applied to analyze the changes of these 21 compounds in the two cultivars at different developmental stages.Three PCs were extracted which explained 39.9%,24.4%,and 13.3%of the total variance,respectively.Sweet amino acids and sugars presented high loadings on PC1 and PC2,illustrating that PC1 and PC2 are responsible to the sweet related informations.In addition,PC3 most correlated with the umami taste amino acids,aspartic acid and glutamic acid,and the samples from the different cultivars were separated on PC3.Moreover,CA showed that the samples were clustered into groups according to similar developmental stages.In conclusion,the PCA and CA performed on free amino acids and sugars clearly allowed to discriminate the developmental stages,and the cultivars to a lesser extent.These results would provide a practical reference for quality control of processed table corn products especially for corn juice flavor enhancement.