Study On The Influence Of Drying Methods On Quality And Flavor Of Dehydrated Jujube Products

Red jujube is a kind of nutritious product with the reputation of "natural vitamin pill".As the largest main production area of red jujube,Xinjiang has the largest planting area and output in China,but there are few processed products related to red jujube.This paper further explores the high-quality utilization mode of red jujube,which can broaden the sales mode of red jujube products,promote the sales of red jujube products and promote the development of local characteristic agricultural product processing industry.At present,there is no relevant in-depth research on Xinjiang red jujube chips and jujube powder.Therefore,this paper takes gray jujube,Jun jujube and sour jujube unique in southern Xinjiang in different storage years as the main test materials,and determines the varieties suitable for making red jujube chips and red jujube powder according to the analysis of different morphological structure and nutritional value of different varieties of red jujube.On this basis,this paper analyzes the influence of drying methods on the quality and flavor of red jujube chips,The technology of spray drying wild jujube powder was optimized.The results are as follows:(1)The fruits of Grey jujube and Jun jujube are processed by vacuum frying and hot air drying because of their good anti browning and color retention at high temperature;The fruit shape of wild jujube is small,which is not convenient for the production of jujube slices.The content of flavonoid,total phenol and soluble proteins in the analysis of physical and chemical components is high.Compared with the processing methods of Grey jujube and Jun jujube,spray drying has certain advantages in preparing dry powder.(2)The quality of jujube chips was analyzed by comparing the methods of hot air drying,vacuum low-temperature frying and freeze-drying.The results showed that the total phenol content of jujube slices after frying was the highest among the five drying temperatures;The content of flavonoid in jujube slices dried at 90?was the highest and the browning degree was the lowest;The soluble protein content and Vc content of jujube slices dried at 80?were the highest;The content of carotenoid in jujube slices dried at 60?was the highest.Among them,the jujube slices dried at 90?show bright red and low browning degree,which can maintain the content of flavonoid and total phenol in the fruit.It can be seen that 80?drying is more suitable for the drying of jujube slices in terms of protein and VC nutrient content,but 90? drying has a better effect on the quality of dried products.(3)The rehydration ratio and soluble protein content of jujube chips under hot air drying are higher than those of the other two drying methods,but affected by hot air temperature and time,it is easy to cause the loss of ascorbic acid and flavonoid and serious browning.However,the jujube chips prepared by vacuum freeze drying have higher ascorbic acid,flavonoid and other nutrients and less browning degree.The total phenol content of jujube slices under vacuum frying drying method was the best,and the other nutrients were lower than the other two drying methods.(4)The PCA analysis of red jujube chips under different drying temperatures showed that the total contribution rate of the first two principal components accounted for 99.49%.When the drying temperature was 90?,hot air drying had the best retention of aroma components of red jujube;The PCA analysis of red jujube chips under different drying methods showed that the total contribution rate of the first two principal components accounted for 99.91%,and freeze-drying treatment had the best retention of aroma components of red jujube.(5)Taking wild jujube as raw material,the effect of different temperatures on water content,color difference,flour yield and other indicators of wild jujube were studied.The best processing technology suitable for wild jujube was selected.The effect of spray drying on the quality and flavor of different varieties of red jujube powder were analyzed.Firstly,the enzymatic hydrolysis process and the addition of maltodextrin were optimized,The most important three factors and three levels were selected to optimize the process of preparing jujube powder by spray drying.The best process is that the inlet air temperature is 140?,the results showed that the optimal process was pectinase 11.79%,and enzymatic hydrolysis temperature 50.12?,maltodextrin 7.95%.