Changes Of Physiological Characteristics And Main Quality Of Maize During High Temperature Storage

Maize(Zea mays L.)is the most widely cultivated grain crop in the world,and is one of the three major reserve grain varieties in China,which provides an important source of raw materials for livestock and poultry feed production.During the storage process of harvested maize,due to the change of external temperature and humidity environment conditions,the seed embryo vitality and nutritional quality of maize are often reduced,and the edible value and seed use value of maize are lost or partially lost.At present,the molecular mechanism of maize deterioration under high temperature storage conditions is not completely clear,and the difference of storage characteristics between corneous maize and flour maize needs further study.In this paper,Zhengdan 958 and Qiule 368,the representative varieties of corneous maize and flour maize from Central China,were selected to accelerate their deterioration by simulated high-temperature storage method,and the changes of their physiological characteristics,nutrients and metabolic pathways during the deterioration process were studied,in order to provide theoretical reference for revealing the mechanism of maize grain storage deterioration.The main findings are as follows:1.ROS accumulation caused by respiration of maize seed embryo during deterioration is an important reason for the decrease of physiological activity of maize.ROS accumulation destroyed the intracellular antioxidant enzyme system,unbalanced ROS production and clearance,further led to protein carbonyl modification and membrane lipid peroxidation in embro cells,and accelerated germ cell death.The results showed that corneous maize was more storage tolerant than flour maize.With the deterioration,the activity of Zhengdan 958 embryos decreased less than that in Qiule 368 embryos.Zhengdan 958 showed better performance than Qiule 368 in ROS production rate,activity of antioxidant enzyme system,accumulation of toxic substances in cells and oxidative damage to membrane lipids.2.In the process of quality deterioration,the respiration rate of maize first increased and then decreased,and the consumption rate of fat,protein,starch and other storage substances was related to the intensity of respiration.The protein in maize grain was degraded to different degrees and the secondary structure was changed.The proportion of amylose and amylopectin in maize grains changed,and some amylopectin was decomposed into amylose.The rate of fat conversion to free fatty acid and the degree of starch hydrolysis in Zhengdan 958 were lower than Qiule368.The changes of fat and starch in maize had significant correlation with seed embryo activity.3.After quality deterioration,ROS accumulation and changes in storage substances affected several important metabolic pathways such as glycolysis and gluconogenesis,pentose phosphate pathway,TCA cycle,pyruvate metabolism,synthesis of secondary metabolites,glutathione and folic acid biosynthesis in maize cells,and cells could not carry out normal metabolic activities.The effect of high temperature storage on the metabolism of Zhengdan 958 is weaker than that of Qiule368,which may be the reason why corneous maize is more durable.In summary,this study concluded that high temperature storage was an important factor leading to ROS accumulation in maize.ROS accumulation disrupted the REDOX balance in cells,resulting in decreased physiological enzyme activity,increased membrane permeability,and changes in protein structure,and ultimately significantly affected many important metabolic pathways in maize grains,resulting in loss of kernel activity and deterioration of food quality.