Study On The Correlation Of Low Temperature Hot Air Drying To The Formation Of Aroma Of Jujube Hami

In this study,Hami jujube was used as the experimental material,which was dried by natural sun and 45℃.The content of organic acids and β-D-glucosidase in Hami jujube during two different drying processes were studied.The changes of aroma components in free and bond states of Hami jujube during two different drying processes were analyzed The correlation can provide a scientific basis for further study on the release mechanism of aroma precursors of Hami jujube and the enhancement and retention of aroma of dried jujube products in industrial production.The main results are as follows:(1)A method for the determination of acid in Hami jujube was established.Chromatographic conditions:wondasil C18-WR column(4.6 mm×50 mm,5 μm)was used for separation,and the mobile phase KH2PO4 buffer solution of 0.05 mol/L:methanol=9:1;pH=2.3;flow rate of 0.8 ml/min;column temperature of 35℃;detection wavelength of 210 nm;injection volume of 20 μL.Under these conditions,six organic acids,oxalic acid,malic acid,tartaric acid,citric acid,fumaric acid and succinic acid,can be separated,and the content of organic acids in the drying process can be determined.The sequence of organic acid content change from high to low was malic acid>tartaric acid>citric acid>fumaric acid>oxalic acid,and succinic acid was not detected.At the end of drying,the content of malic acid and tartaric acid in hot air drying was higher than that in natural drying.(2)Response surface methodology was used to optimize the determination method ofβ-D-glucosidase in Hami jujube during the whole red period of crisp ripening:when the pH of buffer solution was 5.3,PVP was 3.00%,the temperature of enzymolysis was 36℃,and the reaction time was 94 min,and the wavelength of determination was 400 nm,the activity of β-D-glucosidase was the highest.The β-D-glucosidase activity of Hami jujube was measured in two different drying processes.Under natural drying conditions,the enzyme activity increased to the highest point 1700.32 U on the second day of drying,and disappeared on the sixth day.In the process of hot air drying at 45℃,the activity ofβ-D-glucosidase reached the highest point at 8 h and disappeared at 36 h.(3)The species and contents of aroma components in free and bond states in two different drying processes of Hami jujube were determined.According to the test,Natural drying process,theβ-D-glycosidase enzymes enzyme activity and bonding state ester aroma components were extremely significant positive correlation,and was significantly positively related to free acids aroma components,fumaric acid and aroma components of present negative correlation,the aroma with acids composition has significantly positive,enzymatic activity increasing,the content of free aroma components of the acids aroma substances increased significantly;The contents of esters in the bonded aroma components increased significantly.During the hot air drying process at 45℃,there are a total of 74 kinds of aroma components in the free state.The main aroma components are acids,most of which are myristic acid 267.07 μg/L,and 100 kinds of aroma components in the bonded state.The main group is esters,and the most abundant is methyl myristic acid 444.09μg/L.(4)The correlation analysis of organic acid content,β-D-glucosidase activity,free aroma components and bond aroma components of Hami jujube during natural drying and hot air drying at 45℃ was carried out.Through the analysis,we can find that there are more kinds and contents of free and bonded aroma components in the hot air drying process than in the natural drying process.In the process of natural drying,with the prolongation of drying time and the increase of β-D-glucosidase activity,the contents of ketones,acids,esters and alcohols in the free aroma components increased significantly,while the esters in the bonded aroma components increased significantly.In the process of 45℃ hot air drying,at the beginning of drying,when the content of oxalic acid is increasing,the content of the aroma components of the bonded acids is decreasing.When the content of fumaric acid is increasing with the drying time,the content of the aroma components of acids and esters is decreasing.When the activity of β-D-glucosidase increased,the aroma components of acids increased significantly;when the activity of free aroma components increased with the drying time,the content of ketones,acids,esters and alcohols increased significantly.