Effects Of Pretreatment And Drying Methods On Drying Characteristics And Quality Of Hippophae Rhamnoides L

Hippophae rhamnoides L.is one of the varieties of Hippophae rhamnoides.Because of its few thorns and large fruit particles,it has been planted in a large area in Northeast and Northwest China in recent years.However,Hippophae rhamnoides belongs to berries,with more juice,soft texture,easy to break,and mature in high temperature season,not easy to long-distance transportation and storage,easy to rot and mildew after picking,resulting in a great waste of raw materials.Drying is mainly used in production,such as natural drying,natural shade drying and hot air drying,but there are some problems such as uneven color and decrease of nutrients after drying.Therefore,using Hippophae rhamnoides as raw material,the effects of different drying methods and pretreatment on the drying efficiency and quality of Hippophae rhamnoides were studied,and the best pretreatment method and drying process suitable for Hippophae rhamnoides were determined.The main conclusions are as follows:1.Among the five drying methods,the shortest hot air drying time is 118 h,followed by heat pump drying(124 h).The hot air drying time is 4.48%-89.97%shorter than other drying methods,while after vacuum freeze drying for 120 h,the drying rate is only 27.67%.Continue to increase the drying time,the drying efficiency remains basically unchanged,and the freeze-drying efficiency is low.However,vacuum freeze-dried Hippophae rhamnoides fruit has bright color,bright yellow,low browning,closer to fresh color,low volume shrinkage and high rehydration,which can maintain the appearance and structure of fruit,and maintain the quality of fruit,such as Vc,titratable acid,total phenols and total flavonoids.Considering the drying efficiency and quality,hot air and heat pump drying are the better drying methods for the processing of Hippophae rhamnoides.It is suggested that vacuum freeze drying and hot air or heat pump drying can be used in the follow-up study.2.Different pretreatments(distilled water(control),70? blanching,150 W ultrasound,2%Na2CO3,2%drying promoter and 2%NaHCO3)had different effects on the epidermis microstructure of Hippophae rhamnoides,and the 2%Na2CO3 pretreatment had the most obvious damage to the wax dissolution and stomatal structure of Hippophae rhamnoides.The hot air drying time of Hippophae rhamnoides could be significantly shortened by blanching at 70?,2%Na2CO3,2%drying agent and 2%NaHCO3,among which the pretreatment effect of 2%Na2CO3 was the most significant,which was only 44 h,which was 62.71%shorter than that of the control(118h).After 2%Na2CO3 pretreatment,the hot air drying quality of Hippophae rhamnoides is better,in which the content of Vc is 351.90 mg/100 g DW,the content of total flavonoids is 10.14 mg/g DW,the content of total phenol is 7.50 mg/kg DW,and the color is the most close to that of fresh fruit.It can be seen that 2%Na2CO3 soaking 1 min is a better pretreatment method for hot air drying,which can be applied and popularized in production.3.After the fresh big fruit seabuckthorn was pretreated by 2%Na2CO3 and then dried by vacuum freezing and hot air drying at 70?,the total drying time was shortened by 9.09%to 66.67%compared with other drying methods,and the drying rate was increased to 100%.At the same time,vacuum freezing-70 ? hot air combined drying can not only maintain the fruit color,but also keep the contents of Vc,total phenols and total flavonoids at a high level.Therefore,vacuum freezing-70? hot air combined drying can be used as a better combined drying process for big fruit Hippophae rhamnoides.