新收获小麦后熟过程中蛋白质和氨基酸含量的变化

分析了储存在4℃和室温条件下新收获的软麦和硬麦在后熟过程中的生理生化变化。新收获小麦在20℃的发芽率超过80%,在收获后3~4个月中呼吸有2次高峰,尤其第1个呼吸峰非常明显,室温条件较4℃提高第1个呼吸峰值。当呼吸速率趋于不变时,软麦硬度增大在第4个月,硬麦在第5个月。水溶蛋白、盐溶蛋白及谷蛋白各有2次合成高峰。硬麦醇溶蛋白在第60天有一个积累高峰,软麦至少有2个积累高峰,分别在第30天和60天。谷蛋白合成最高峰在第90天,与水溶蛋白类似,而醇溶蛋白合成最高峰在第60天,与盐溶蛋白类似。随着醇溶蛋白和游离巯基含量减少,谷蛋白迅速积累。常温条件下谷蛋白的氧化聚合较低温条件下迅速,积累量大。软麦谷蛋白氧化聚合过程较硬麦早。谷蛋白积累之前,绝大部分氨基酸急剧积累,在室温条件较4℃下积累明显。半胱氨酸含量在90~120天时增加到最大,之后迅速减少。

Content Changes of Proteins and Amino Acids in Newly Harvested Wheat Grains during Post-Maturation

The physiological change of newly harvested soft wheat and hard wheat variety grain samples stored at room temperature and 4 ℃ for 3～4 months were studied. Results : The germination rates at20 ℃ of seven newly harvest wheat varieties are over 80%. Both soft wheat and hard wheat grains present two peaks of respiration, and the first respiration peak is higher for storage at room temperature than at 4 ℃. When grain respiration trends stable, grain hardness increase occurs at the 5th month for hard wheat and at the 4th month for soft wheat. The accumulations of water-soluble protein, salt-soluble protein and glutenin exhibit two peaks. The peak accumulation of alcoholsoluble protein appears on the 60th day after harvest for hard wheat, while two peaks for soft wheat appear on the 30th day and 60th day, respectively. The highest peak for glutenin accumulation on the 90th day is similar to that of water-soluble protein. The highest accumulations for both alcohol-soluble protein and salt-soluble protein are on the 60th day. The glutenin content increases quickly when both alcohol-soluble protein and free SH contents decrease, especially at room temperature. The oxidative polymerization of glutenin for soft wheat is earlier than for hard wheat. Most amino acids accumulate before glutenin accumulation, and the amino acid accumulation is more evident at room temperature than at 4 ℃. Cysteine increases to a peak value during the 90～120 th day, and then decreases.