Effect Of Grape Drying Promoter Optimization And Packaging On Quality Of Seedless White Raisins

Seedless white grape has the characteristics of high yield,high sugar content and green color.The green raisins made from seedless white grape are well known at home and abroad for their green color and sour and sweet taste.In recent years,seedless white raisins have developed into a pillar industry of increasing farmers’ income and developing regional characteristic economy.The seedless white raisins are mainly dried in the air.There are many problems in the drying process,such as long drying time and browning.In order to solve these problems better,this paper optimizes the formulation of drier,studies the drying characteristics of seedless white grapes in the drying process,and studies the late storage of seedless white raisins,providing theoretical basis for production practice.The main results are as follows:1.Prepare five different drying agents(A1,A2,A3,A4,A5)and market-purchased drier T were dipped in seedless white at room temperature for 1 minute,then dried by air,and the moisture content was less than 15%.During the drying process of seedless white grapes,the drying rate gradually decreased,the content of vitamin C and titratable acid in grapes decreased,the activity of polyphenol oxidase,brown were observed and variability increased.The content of vitamin C,titratable acid and browning coefficient were 6.15-7.83 mg/100g·DW,1.02%-1.24%and 0.44-0.51 respectively.It was found that the drying rate of A3 and A4 treatments was faster,the browning degree was the lowest,and the content of vitamin C and titratable acid in grapes could be well maintained.2.By studying the drying characteristics of seedless white grapes treated with drier,it was found that the drying process of seedless white raisins was a slowdown process;the drying time of self-made drier formula was shorter,and the drying time was completed on the 14th day,which was 4 days shorter than that of T treatment group.In the whole drying process,the fastest drying rate was A4 treatment group.3.Formula A3,A4 and T were pretreated on the seedless white grape to study the browning of the seedless white grape during the natural drying and drying process in the drying room.The seedless white grape showed obvious browning after 3 days of drying.The browning degree increased with the drying process in the later stage,mainly showing red value(a*)rise,brightness value(L*),yellow green.The value of(b*)decreased,and the browning degree of the dried non-nuclear white raisins was positively correlated with a*,and the browning degree was significantly positively correlated with PPO activity.The browning degree of the seedless white of the A4 treatment group with faster drying rate was significantly lower than that of the other treatment groups.Rapid drying can effectively reduce the browning rate of raisins and have certain effects on the green preservation of seedless white raisins.4.The content of total phenols in grapes declined continuously during the drying process.The oxidation of phenols led to browning.The content of total phenols in fresh grapes was 0.109 mg/g·DW.At the end of drying,the content of total phenols in treatment A3,A4 and T decreased to 0.069,0.076 and 0.065 mg GAE/g·DW,respectively.5.Raisins were packaged in different ways and stored at different temperatures for 60 days.The results show that proper temperature reduction(5℃)and the addition of deoxidizers are more conducive to maintaining the original color and quality of the raisins.