Study On Rehydration And Packaging Storage Characteristics Of Ginger Slices Based On Osmotic Pretreatment And Combined Drying

Ginger,as a seasoning vegetable used for both medicine and food in China,has high nutritional value and abundant yield,making it an indispensable seasoning in daily life.At present,the main processing method for ginger is dehydration.Ginger tissue contains a large amount of vascular structure,which to some extent affects the dehydration and rehydration rate.Therefore,it is meaningful to study its segmentation based on the vascular structure of ginger.Vacuum freeze-drying is a relatively advanced method for drying ginger slices,but the drying time is long,and the formation of aromatic substances in dehydrated ginger slices is limited.The color is pale,and the water-carrying capacity of rehydrated ginger slices is low.Joint drying is expected to leverage the advantages of different drying techniques,overcome the shortcomings of vacuum freeze-drying,achieve precise drying of ginger slices,and improve the drying rate and quality of ginger slices.This article explores the effects of cutting methods and drying techniques on the quality of rehydrated ginger slices,selects suitable drying methods to form combined drying,and then conducts pre-treatment before the combined drying to shorten drying time,increase rehydration rate,and further improve the quality of rehydrated ginger slices.To extend the shelf life of dried ginger slices,vacuum-laminated aluminum foil packaging was used,and a suitable processing method of "cutting + pre-treatment +drying + storage" for ginger slices was ultimately established.The main contents and results of the study are as follows:(1)A study was conducted on the effects of commonly used drying methods(Convective hot air drying,Catalytic infrared drying,Vacuum freeze-drying)combined with Transverse and Longitudinal cutting on the drying rate,polysaccharide structure,rehydration kinetics,and physicochemical properties of rehydrated ginger slices and ginger soup,in response to the current characteristics of ginger as a conduit structure.The results showed that the drying rate of the longitudinal cut sample was significantly higher than that of the transverse cut sample,while the transverse cut sample had a higher rehydration capacity(Longitudinal load capacity: 3.41～4.12 mg/g;longitudinal load capacity: 3.79～4.57 mg/g).Four rehydration kinetic models(Peleg model,firstorder rehydration kinetic model,exponential model,and polynomial model)were used to fit the rehydration process of dried ginger slices.It was found that the Peleg model had the best-fitting effect.The dehydrated ginger slices obtained by vacuum freezedrying reached the highest rehydration capacity within 30 minutes,with a relatively complete polysaccharide structure and high retention of nutrients.However,the drying time was up to 17 hours,and the formation of aroma was limited.The ginger slices obtained after convective hot air drying only reach the maximum rehydration capacity after 60 minutes,with a slower rehydration rate but a richer odor.Based on this,this study proposes a cross-cutting vacuum freezing combined convection hot air drying process,and pre-treatment is carried out before the combined drying to shorten the drying time and improve product quality.(2)In response to low efficiency and white color of vacuum freeze-drying,the application of osmotic pretreatment,ultrasonic-assisted osmotic pretreatment,and negative pressure ultrasonic-assisted osmotic pretreatment techniques in the study of combined drying of ginger slices was investigated.The effects of the "cross-cutting +pretreatment + combined drying" technology on the drying rate of ginger slices,the physical properties of dehydrated ginger slices,and the physicochemical properties of rehydrated ginger slices were investigated,and the effect of negative pressure ultrasonic osmotic pretreatment on microorganisms was also studied.The results showed that the water content of ginger slices decreased by 33% after negative pressure ultrasonic infiltration pretreatment,which was 1.9 times higher than that of conventional osmotic dehydration.It can also damage bacterial cell walls and achieve antibacterial effects.The combination of negative pressure ultrasonic infiltration pretreatment and drying effectively shortened the drying time,which was 53.7% shorter than the single vacuum freeze-drying method,and the rehydration rate increased by 1.35 times.Convective hot air drying promoted the Maillard reaction,and the total sulfur compounds in ginger slices increased by 220%.At the same time,the disadvantage of high whiteness value caused by vacuum freeze drying was improved.Therefore,negative pressure ultrasonic infiltration can be used as a pre-treatment method for ginger slices vacuum freezing combined with convective hot air drying.(3)Regarding the preservation characteristics of the developed process products,discussed the storage stability of dehydrated ginger slices in four types of packaging(vacuum-laminated aluminum foil packaging,laminated aluminum foil packaging,vacuum polyethylene packaging,and polyethylene packaging).The results showed that during storage,the color of dehydrated ginger slices became darker,the rehydration rate decreased,and the weight continued to increase.Vacuum laminated aluminum foil packaging has a good ability to isolate water vapor and oxygen,resulting in minimal color,rehydration rate,and weight changes in dehydrated ginger slices.During storage,the content of gingerol,total phenols,total flavonoids,and antioxidant activity in dehydrated ginger slices showed an overall trend of first increasing and then decreasing.The content of 6-gingerol in dehydrated ginger slices packaged with vacuum-laminated aluminum foil reached its maximum on the 14 th day,which was delayed by 7 days compared to polyethylene packaging.In summary,vacuum-laminated aluminum foil packaging can be used as an effective packaging method for the storage of dehydrated ginger slices.The above research results indicate that the combination of transverse negative pressure ultrasonic infiltration pretreatment and vacuum freezing with convective hot air drying greatly shortens the drying time of ginger slices,improves the rehydration rate of dehydrated ginger slices,and increases the production of aromatic compounds.Vacuum-laminated aluminum foil packaging can effectively isolate air and prevent the deterioration of dehydrated ginger slices during storage.Finally,a suitable processing method for ginger slices was explored,which included "cross-cutting,negative pressure ultrasonic infiltration pretreatment,vacuum freezing,combined with convective hot air drying,and vacuum laminated aluminum foil packaging".Compared with a single vacuum freeze-drying method,this processing method shortened the drying time by53.70%,increased the rehydration rate by 1.35 times,and increased the total sulfur compounds in ginger slices by 220%,with higher storage stability.