| This article studied the changes in corn quality under different storage conditions.The corn with the newly harvested initial moisture of 16% is naturally dried to four moisture gradients of moisture content of 12%,13%,14%,and 15%.Packed in a sealed box,set the oxygen and nitrogen ratio in the sealed box with a modified atmosphere packaging machine,adjusted the oxygen concentration of the 4 groups of sealed boxes to 2%,5%,8%,and 21%,respectively,and then depressurize and nitrogen.They were then placed in artificial climate chambers at 15?,20?,25?,and 30? to simulate storage.There were 64 storage conditions under three factors and four levels.The fatty acid,electrical conductivity,enzyme activity and other indicators were measured every 30 d,and the volatile substances were measured by electronic nose and gas chromatography mass spectrometer to determine the quality change of corn.The experimental analysis results concluded that:1.Storage time was a key factor affecting corn quality indicators,Under all conditions,fatty acids and surface color would change with storage time.Moisture,temperature and oxygen concentration all had a very significant effect on corn fatty acid changes(p<0.01),When the water content was 15%,the fatty acid growth rate was 76.93%±8.3% at medium and high temperature 25?.At the end of storage under high temperature and high moisture conditions,it would reach a slightly unsuitable state.The growth rate of fatty acid in corn samples with moisture below 14% was 63.24%±0.3% at high temperature of 30?,and the growth rate of fatty acid was 44.05%±3.74% when the temperature was lower than 25?.The growth rate was relatively small.The state should be kept.When the moisture temperature was high,adjusting the oxygen concentration had a greater impact on fatty acids,When corn with 14% moisture was stored at 25°C,when the oxygen concentration was less than 5%,the fatty acid growth rate was between 16.12 mg KOH/100 g and 20.99 mg KOH/100 g.When the oxygen concentration was higher than 8%,the fatty acid growth rate was between 30.02 mg KOH/100 g and 40.03 mg KOH/100 g.The higher the moisture and temperature were,the greater the change in corn L* was.The high temperature and high moisture conditions would make the corn darker during storage and cannot maintain the original color.Moisture and temperature had a very significant effect on corn L*(p<0.01),Oxygen concentration had no significant effect on L*(p>0.05),Temperature had a very significant effect on b*(p<0.01),moisture and oxygen concentration were not the key influencing factors(p>0.05).2.Moisture content,oxygen concentration and temperature conditions had a very significant effect on the change of corn electrical conductivity(p<0.01).Under the condition of low temperature storage at 15?,the increase rate of corn electrical conductivity was between 5.81 ?s/cm and 9.92 ?s/cm,and the growth rate was between 55.25% and 106.71%.As the temperature increased,the increase in conductivity increased,At 15?,20?,25? and 30?,the conductivity of 14% moisture corn increased by 4.72 ?s/cm,9.52 ?s/cm,13.19 ?s/cm,14.13 ?s/cm.At the same time,only F temperature>F time,the influence factors of moisture and oxygen concentration were less than the storage time.When the temperature was low,the effect of moisture content on the activity of corn polyphenol oxidase enzyme was not significant,When the temperature was higher than 20?,water only had a significant effect on enzyme activity,Temperature and oxygen concentration had a significant effect on enzyme activity,but the degree of influence was much lower than the effect of time on enzyme activity.3.When the moisture content was less than 15%,the response value to the electronic nose T30/1 and PA/2 sensors decreases with storage time.High temperature and high moisture samples were more sensitive to P10/2 response changes than low temperature and low moisture samples.On the principal component analysis chart,the samples with different conditions could be distinguished,The samples with moisture of 15% and temperature of 20? were distributed in four quadrants during the storage period of 6 months.The first 3 months and the next 3 months were distributed on the left and right sides of the Y axis,and the samples in the 6th month were distributed below the X axis.It showed that the odor change of corn was less within 3 months,and the odor change was bigger after 3 months,especially after 6 months.A total of 15 alcohols,25 aromatics,23 aldehydes,59 esters,18 ketones,53 alkanes,22 olefins,and 27 heterocycles were detected in the gas quality test.The esters,aromatic hydrocarbons and alcohols accounted for a large proportion,with a total of 43.158%,65.786%,and 80.657%.At the same time,use the material load map to find the characteristic volatiles under each storage condition,Determine whether the current storage status of corn was good by the presence or amount of characteristic volatiles.Under high temperature storage,1,4-dioxaspiro[4.5]decane-6-carboxylic acid,the volatile amount of dimethylamide was higher,N-methyl-4-chlorobenzenesulfonamide had higher volatile content in high-moisture corn,amides were more easily hydrolyzed under high temperature and high humidity conditions than low temperature and low humidity,generating carboxylic acids and amines,resulting in more ester volatiles.Vanillin had the fragrance of vanilla bean and rich milky fragrance.The volatilization of vanillin in samples with high temperature and high moisture was much lower than that of other samples.Unsaturated olefins and enols all increased with storage time. |
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