Study On Quality Change Of Fresh Waxy Corn During Freezing Storage

Corn is rich in nutrients and is an important food crop and feed crop in the world.It is also one of the main food crops in China.For a long time,fresh corn is difficult to keep fresh after harvesting,and the shelf life is short.After harvest,it is prone to quality deterioration such as yellow and dry of leaves,loss of water and atrophy of the grain,and production has strong seasonality.And it is often difficult to meet consumer demand in off-site and off-season.Therefore,it is of practical significance to study the storage and preservation of fresh corn.In this experiment,the optimal maturity of corn was selected,and the quality changes of corn under different storage temperatures were analyzed.The sensory and physicochemical properties of fresh corn during storage were examined.The chitosan and tea polyphenol composite coating film was applied to fresh corn storage.This study provide reference for fresh corn storage and preservation.The main conclusions are as follows:(1)The L~*,a~*,and b~* values of the old corn is higher than the tender corn during the ripening period.Fresh tender corn has higher moisture,soluble sugar content,and old corn has higher total starch content and ash.(2)With the increase in storage time,the L~*,b~* and ?E value of the corn during storage showed a downward trend,the a~* value showed an upward trend,the overall color became darker,and yellow became lighter,and water,soluble sugar,total starch,amylopectin content and ratio were all show the decline trend.The samples with high initial value maintain higher levels during storage compared to samples with lower initial values.There were differences in the content of nutrients between different varieties,but there was the same trend during storage.There is a large correlation between sensory score,soluble sugar content and branching ratio,but there are differences in the degree of correlation between different maturities and different varieties.Medium maturity corn has a higher sensory score thro ughout the storage period,and the overall sensory quality of the B variety is better than that of the A variety.(3)With the increase in storage time,the L~* and b~* value of corn decrease during storage,and the a~* value shows an upward trend.The higher the storage temperature,the more significant the change.Low temperature storage is beneficial to the cooking quality preservation of corn to a certain extent,but the temperature is too low.Compared with lower temperature,storage of corn at-18 ? can achieve better preservation effect.(4)Under the conditions of-4?,-18?,-40?,the water content,amylopectin content and the ratio of branching decreased with the increase of storage time,and the amylose content showed an upward trend obviously.The higher the temperature,the more obvious the change.Under the storage conditions of-4? and-18?,the soluble sugar content decreased with the prolongation of storage period,the total starch showed a downward trend,and the higher the storage temperature,the more obvious the change,while under the storage condition of-40 ?,soluble sugar The content first increased,the starch content decreased first,and both remained unchanged at the end of storage.In terms of correlation correlation between indicator s,there is a difference in correlation between the next indicators of different storage temperatures,but overall,sensory score,water content,soluble sugar content,total starch content,and amylopectin content are generally observed.(5)Using headspace-solid phase microextraction combined with gas chromatography-mass spectrometry,the types of volatile flavor components in corn during storage at-4°C,-18°C,and-40°C,respectively.The relative content was analyzed and a total of seven major types of hydrocarbons,alcohols,aldehydes,ketones,acids,esters and other small substances were detected.The effects of aldehydes,ketones and esters on the volatile components of the two maize varieties were compared.The main characteristic compounds of the volatile components common to A and B varieties are decane,geranylacetone,n-octadecane,ethyl 9-hexadecenoate,2-nonenal,3-octyl En-2-one,2-n-pentylfuran.The low temperature has little advantage in maintaining the volatile flavor component of the nail variety.The storage effect of the B variety is better at-40°C during storage for 60 days,and there is little difference in the longer storage period.(6)By comparing the three coating treatments with the non-coated control group,it was found that the coating treatment can better inhibit the color change during the preservation of waxy corn,effectively preserve the cooking quality characteristics,and delay the storage of corn kernels.Hard,significantly reduce post-harvest transpiration,reduce water loss,can preserve the soluble sugar and starch content of fresh waxy corn,and maintain the storage quality.The composite treatment of chitosan and tea polyphenols is better than single chitosan coating.There were strong correlations between the four processed corn samples during storage,such as moisture,soluble sugar content,total starch content,sensory score,and hardness change.