Ffect Of Different Drying Methods On The Quality And Flavor Of Chinese Yam Chips

Yam is a kind of vegetables of medicine and food homology that has the effect of reducing blood pressure and strengthening the spleen and stomach.However,fresh yam is not easy to store for a long time.On the one hand,the development of non-fried yam chips not only prolongs the shelf life of yam,but also provides a new healthy snack food;on the other hand,there are few studies about yam's aroma.In order to deepen the understanding of different varieties of yam,it requires in-depth study of the aroma characteristics of fresh and dried yams.In this experiment,11 varieties of yams from China's five main yam producing areas were used as the research objects.Four single drying methods including vacuum freeze-drying,explosion puffing drying,vacuum drying,hot air drying,and HMVD+LMVD(The united drying of High power Vacuum Microwave Dring and Low power Vacuum Microwave Dring),LMVD+EPD(The united drying of Low power Vacuum Microwave Dring and Explosion Puffing Dring)were used to process yam chips.The quality indexes which including rehydration rate,color,volume ratio,hardness,brittleness,nutrient composition,microstructure,and sensory characteristics were measured.The volatiles of fresh yam and dried yam chips were determined by HS-SPME-GC-MS respectively.Based on coefficient of variation,grey correlation analysis and principal component analysis(PCA),hierarchical cluster analysis(HCA)and orthogonal partial least squares(OPLS-DA),these results were analyzed comprehensively.The results are as follows:1.Through the effects of the above-mentioned four single drying methods on the quality of Baiyu(Henan)yam chips,it was found that vacuum freeze-drying has a better rehydration rate,a smaller change in color,the best surface.The explosion puffing dried and freeze-dried yam chips maintained relatively intact microstructure.Vacuum drying and hot air drying have a greater damage to the microstructure and can affect the taste of the yam chips.Vacuum freeze-drying and explosion puffing drying have less damage to nutrients.According to comprehensive considerations,it was concluded that the drying method will affect the quality of yam chips in varying degrees,and explosion puffing dry is more appropriate to process non-fried yam chips.2.A total of 84 volatile components were identified from 11 fresh yam varieties.The aroma contained a large amount of alcohols and ethers,such as 1-octen-3-ol,which was a unique aroma component of yam;The multivariate analysis methods based on principal component analysis(PCA),hierarchical cluster analysis(HCA),orthogonal projections to latent structures discriminant analysis(OPLS-DA)were used to comprehensively analyze the results.The results of PCA showed that ZY was different from other varieties,and 11 varieties were divided into group A,group B1 and group B2 by HCA.OPLS-DA identified 3,3,6,6-tetramethyl-1,2,4,5-tetroxane and DL-2,3-butanediol as characteristic aroma components of ZY.3.The effect of combined drying of HMVD+LMVD and LMVD+EPD on the quality of yam chips found that the overall effect of HMVD+LMVD on these 11 kinds of yam chips was better than the latter.LMVD+EPD was superior to the retention of nutrients.However,vacuum microwave equipment at the present stage can easily cause uneven heating and low product yield when the sample has a low moisture content.Only the improved equipment can be used for large-scale production.The LMVD+EPD product was slightly worse than the former,but the scores of these two dried MM and XZ products were not much different,and this method has high retention of nutrients.So LMVD+EPD was suitable for the processing of MM and XZ yam chips.PCA and HCA indicated that dried MM and LT yam chips are of similar quality.The study of two kinds of drying methods provided important data for the processing of yam chips.The research of different varieties of yam chips provided help for variety screening.4.A total of 108 aroma components were detected in LMVD+EPD and HMVD+LMVD yam chips,including 57 hydrocarbons,11 aldehydes,12 alcohols,2phenols,12 esters and 14 others.PCA and HCA divided these 22 varieties into 5categories: 1)WJ-B;2)ST-B,XZ-B,CJ-A,LT-B,CJ-B;3)MN-A;4)BY-A,BC-A,ZI-A,XZ-A,LT-A,ZY-A,ZY-B;5)BY-B,BC-B,ZI-B,WJ-A,MM-A,MM-B,MN-B,ST-A.OPLS-DA indicated that dodecane,2,5,9-trimethyl-decane and hexanal were the characteristic aromas of HMVD+LMVD yam chips;2,7,10-trimethyl-dodecane,undecanal and estragole were the characteristic aroma of HMVD+EPD yam chips.