Effects Of Different Drying Combinated Pretreatment Methods On The Quality And Antioxidant Capacity Of Arctium Lappal. Slices

Fresh burdock(Arctium Lappa.L)roots are easy to become fibrosis and hollow during late growth and storage,which has reduced the shelf life of Arctium Lappa.L roots significantly.Drying treatments could extend preservation period and increase the commercial value of the products.The effects of different drying and pretreatment methods on quality and antioxidant properties of Arctium Lappa.L slices were compared in this paper.The results could provide theory foundation and technical support for developing high nutritional value dried Arctium Lappa.L root slices.1.The effect of five different drying methods including hot air drying(AD),vacuum microwave drying(VMD),vacuum freeze drying(VFD),hot air combinated vacuum microwave drying(AD&VMD),vacuum freeze combinated vacuum microwave drying(VFD&VMD)on quality and antioxidant capacities of Arctium Lappa.L slices were studied.The results showed that the quality parameters including drying time,color,texture,microstructure,nutrient contents and antioxidant capacities of Arctium lappaL products dried by VFD&VMD had no significant difference with products dried by VFD but higher than that of the other drying methods.Meanwhile,the analysis results of polyphenol components of Arctium Lappa.L slices showed that temperature was an important factor,which affected the contents of chlorogenic acid,1,3-Di-O-caffeoylquinic acid and 3,5-Di-O-caffeoylquinic acid.VFD&VMD had a good protective effect for 5-O-caffeoylquinic acid and chlorogenic acid preservation,which leaded to high antioxidant abilities of the products.2.The effect of four different pretreatment methods including ultrasonic treatment(U),ultrasonic assisted vacuum treatment(U&V),blanching treatment(B)and ultrasonic assisted blanching treatment(U&B)on quality and antioxidant properties of Arctium Lappa.L slices were studied.The results showed that ultrasonic treatment of Arctium Lappa.L slices had the least time,the lowest values of hardness,fragility and shrikage,the best color and the highest contents of polyphenols,flavonoids and polysaccharides.Meanwhile,the analysisresults about polyphenol components showed that Arctium Lappa.L slices pretreated by U&V had the highest contents of 5-O-caffeoylquinic acid,1,3-Di-O-caffeoylquinic acid and 3,5-Di-O-caffeoylquinic acid,indicating ultrasound assisted vacuum had a good protective effect for the polyphenol compounds preservation.In addition,the Arctium Lappa.L slices had the highest ability of clearing DPPH free radical,ABTS free radical and reducing power of ferric ion.