Effect Of Different Rehydration Models On The Quality、kinetics And Mechanism Of Osmunda Japonica

Osmunda japonica is known for the title of"Shanzhen"and"King of Wild Vegetables".The dehydrated products of O.japonica are very popular with consumers.Rehydration is an important step for the consumption or further processing of dried O.japonica.It is of great practical significance to study the rehydration characteristics of O.japonica.In this paper,the effects of different rehydration temperatures on the quality of O.japonica at constant-and variable-temperature rehydration were studied.The hydrodynamics and the mechanism of rehydration of O.japonica at different rehydration models were explored.Meanwhile,the effect of adding pectin on the quality of rehydrated O.japonica was studied.The research results were as follows:(1)The effect of rehydration models on the quality of the products was investigated in terms of the physical and chemical indexes and textural analysis.The results showed that water holding capacity(WHC),hardness,elasticity,chewiness,total phenol content and vitamin C content decreased with the increase of temperature,while the rehydration rate(RR)increased.However,the quality of O.japonica at variable rehydration was higher than that of constant temperature rehydration at the same temperature.(2)At constant temperature rehydration,the water absorption rate all increased with increasing temperature,and the Weibull’s model well fitted the rehydration process of O.japonica at 45 and 90℃;however,the Peleg’s model did well at 60 and 75℃.At variable temperature rehydration,the water absorption rate all increased first and then decreased with increasing temperature,and the Weibull’s model was suitable to fit the rehydration process of O.japonica.(3)At the constant-and variable-temperature rehydration models,the content of total pectin and soluble dietary fiber decreased with the increase of temperature,while the value of T_m increased slightly with the increase of temperature.It indicated that the cell interstitial space and matrix of O.japonica were destroyed,and the cell structure collapsed.LF-NMR showed the dynamic migration process of water from cell wall to cytoplasm to vacuole during rehydration.Scanning electron microscopy(SEM)was used to observe the structural changes of the samples.At the same temperature,the structure of O.japonica at variable rehydration was less than that at constant temperature rehydration.(4)Adding pectin in rehydration process can protect the structure of O.japonica,reduce textural damage and improve the quality of O.japonica.With the increase of pectin content,the physicochemical properties increased such as rehydration ratio,water holding capacity,hardness,elasticity,chewiness and the nutritional properties as well as reducing sugar,soluble protein,total phenol and Vc.The results showed that variable temperature rehydration could improve the quality of rehydration O.japonica and had a good application prospect in practice.