Study On Mechanism Of Maize Timely Harvest And Technology Of Enzyme Activity Increase Based On Enzyme Activity Detection

Corn is one of the main food crops in China,its yield and quality are related to China’s growing grain demand,and it plays an important position in China’s agricultural production and national economy.Due to the high internal water of the newly harvested corn,it is easy to mold and deteriorate in the process of storage and transportation,which seriously affects the quality and brings great economic losses.Improper field harvest,failure to dry out in time,qualitative changes in the storage process are important reasons for corn production decreased.For the issue of timely corn harvest and improving the antioxidant enzymatic activities in the process of storage of corn grain.The growth curve of corn grain was measured and the antioxidant enzyme activity were also measured throughout the harvest process.The mathematical models of the change of water content,dry weight and antioxidant enzymatic activities were established and determined the optimal harvest period.Corn kernels were pretreated using glow discharge low-temperature plasma technology,and the effect of different plasma pretreatment conditions on the antioxidant enzymatic activities of corn kernels were investigated.On this basis,the response surface optimization experiment was designed and the optimal optimization process parameters were obtained.The main research contents and conclusions are as follows:（1）The water change of the corn grains of 4 varieties were determined using NMR（Nuclear Magnetic Resonance）,the change of the thousand grain weight and dry weight were calculated,and the maturity curve of the corn kernels were determined.The results showed that the moisture content of corn kernels were decreased with the increase of harvest time.The moisture content of Fumin 985 was decreased slowly than other varieties.The thousand grain weight of the corn grains were first increased slightly and then decreased,the thousand grain weight of Xianyu 335 was increased the most and the thousand grain weight of kx3564 was increased the least.With the increase of harvest period,the dry weight of corn grain accumulated.When the dry weight of corn kernels entered the ripening period on October 3rd,the accumulation of dry weight tended to be maximum and no longer increased.After that,there was even a decrease of dry weight which was called hidden loss.The trend of dry weight was different in the four varieties,the dry weight of Jidan 31 was increased the most and the dry weight of kx3564 was increased the least.The mathematical models of water content and dry weight of 4 maize varieties were established and ANOVA analyses were also performed.（2）The antioxidant enzymatic activities of corn kernels of 4 varieties at different harvest periods were analyzed,mainly the activity of peroxidase（POD）,the activity of catalase（CAT）,the activity of superoxide dismutase（SOD）.The results showed that the overall enzymatic activities of POD,CAT and SOD of corn grains were tended to rise first and then decline,and the difference between the different varieties was more significant.The enzymatic activity of POD of Jidan 31 was increased the most,with a maximum value of 442.2 U/g.The enzymatic activity of CAT of Xianyu 335 was increased the most,with a maximum value of 187.39 U/g.The enzymatic activity of SOD of Jidan 31 was increased the most,with a maximum value of439.20 U/g.The mathematical models of antioxidant enzyme activity of 4 maize varieties were established and ANOVA analyses were also performed.According to（1）and（2）,the optimal harvest period of each corn variety is determined.（3）Low temperature plasma technology was used as an efficient pretreatment method of corn kernels to pretreat corn kernels,and the effects of different low plasma pretreatment power,low plasma pretreatment time and air flow on enzymatic activities of POD,CAT and SOD of corn kernels were investigated.The results showed that the plasma pretreatment could significantly improved the enzymatic activities of POD,CAT and SOD of maize kernels.The enzymatic activities of POD,CAT and SOD of corn kernels were significantly higher than in control groups under different plasma pretreatment conditions.（4）On the basis of（3）,the response surface optimization experiment was designed.The enzymatic activity of POD,the enzymatic activity of CAT and the enzymatic activity of SOD were used as the response values.Within the experiment range,the optimal process parameters for the enzymatic activity of POD of corn kernels under plasma pretreatment conditions are plasma pretreatment power of 500 W,plasma pretreatment time of 30 s and air flow rate of 150m L·min^-1.The optimal process parameters for the enzymatic activity of CAT of corn kernels under plasma pretreatment conditions are plasma pretreatment power of 350 W,plasma pretreatment time of 30 s and air flow rate of 150 m L·min^-1.The optimal process parameters for the enzymatic activity of SOD of corn kernels under plasma pretreatment conditions are plasma pretreatment power of 400 W,plasma pretreatment time of 30 s and air flow rate of 200m L·min^-1.