Study On Quality Characteristics Of High Moisture Maize In Simulation Of Temperature And Humidity Dynamic Change

Corn had become a commodity with the rapid development of economic.In order to obtain higher profits,some grain traders will directly put high-moisture corn into the market without adequate drying.So,how to ensure the safe of high moisture corn is essential in transportation.Most of the previous studies are about static storage,but corn is affected by the external environment and it is dynamic.Therefore,it is of great significance to study the storage and transportation of corn in dynamic environment.In this paper,five moisture content corn(14%,18%,22%,26%and 30%)were stored for 40 days in the dynamic temperature and humidity environment based on the simulation of road transport,waterway transport and rail transport in the laboratory,and a static temperature and humidity environment group was set up.For simplicity,the four experimental groups are represented by A,B,C,D in turn.The quality indexes,gelatinization characteristics and microstructure of corn starch,volatile compounds were studied in the storage and transportation.(1)The germination rate and viability of corn decreased with prolonged time.The degree of declining was different in different water content and different groups.The higher water content,the faster the decline,and the change of germination rate was more obvious than the vitality.Fatty acid values increased with storage time.Aerobic plate count and the mold colonies increased first and then decreased,but the final number was increased.Color L increased first and then decreased,but the final number was decreased.Color a,Color b decreased with time.The quality indexes of 14%and 18%moisture content corn were more stable than other moisture content.The quality indexes of corn were affected highly significantly by moisture content and time(P<0.01).There was no significant difference between the experimental groups(P>0.05).The fatty acid value was negatively correlated with Color L and Color a(P<0.01).Aerobic plate count and the mold colonies were significantly negatively correlated with the germination rate of corn(P<0.01).Aerobic plate count was significantly positive correlated with the mold colonies(P<0.01).(2)Amylose content decreased with prolonged time.Peak viscosity,through viscosity,final viscosity,breakdown and setback were increased,and the higher initial moisture content,the more obvious change.Amylose content and through viscosity were affected significantly by initial moisture content and time(P<0.05).Peak viscosity,final viscosity,breakdown and setback were affected highly significantly by initial moisture content and time(P<0.01).There was no significant difference between the experimental groups(P>0.05).The microstructure of corn starch granules was damaged to a certain extent during storage and transportation.The surface of the starch granules gradually changed from smoothness to rough polygonal,even in the depressed state.The small starch granules increased,and the higher water content,the more significant the changes.(3)As a result of the GC-MC test,the relative contents and types of volatile compounds of corn were obvious difference in different water content and different groups.The volatile compounds could be divided into alkanes,olefins,benzene ring,alcohol ethers,acid esters,aldehydes,ketones and heterocycles.the species and relative content of volatile compounds were affected by moisture content of corn.After the analysis of the main components for of various volatile compounds,acid esters,aldehydes and ketones showed the largest contribution to the overall flavor,and Trichloroacetic acid,Octanoic acid,nonanoic acid,tetradecyl pentafluoropropionic acid,ethyl palmitate,Diisobutyl phthalate,9,12-Octadecadienoic acid ethyl ester,methyl trans-13-octadecenoic acid,Vanillin,benzaldehyde,2,4-nonadienal,hexanal,(E)-nonenal phenylacetaldehyde,nonanal were the main component,and this main component had a higher correlation with the storage time,viability,germination rate,fatty acid value and mold quantity.The initial moisture content of 14%to 18%of corn can be short-term transport(20 days or less),which can better maintain the quality of corn.