The Effect Of Drying Methods On The Flavor Compounds Of Durian

Durian is a tropical fruit with a unique flavor and has a broad consumer market.In particular,durian products are sought after by many consumers.During the drying process,the flavor of durian undergoes complex and dynamic changes,and its law remains to be studied.In this research,Golden durian were used as the experimental material,to study the composition and change law of various main volatile and non-volatile flavor substances in durian pulp during three drying processes,including integrated freeze-drying(IFD),traditional freeze-drying(CFD)and hot air drying(AD),and to analyze the nutritional quality of dry durian soluble protein,vitamin C and crude fat,and related quality indicators such as color,shrinkage ratio,texture characteristics,and microstructure.To provide a theoretical basis for the optimization of durian drying process conditions and the improvement of quality,and provide guidance for the production of durian dried products.The results as follow:The conditions of Solid phase Micro-Extraction(SPME)extraction were optimized to determined the time was 30 min and the temperature was 60 ?.HS-SPME-GC-MS detected56 kinds of volatile flavor substances in fresh and three kinds of durian during drying process,including esters,alcohols,aldehydes,sulfur-containing and alkanes.There have different effects on the volatile flavor compounds of durianin three drying methods.With the progress of IFD and CFD,the content of esters,alcohols,and aldehydes gradually decreased.The content of sulfur-containing substances increased in the early stage of drying(FD4h),and gradually decreased in the middle and late stages of drying(FD8h and FD12h),and significantly Lower than fresh samples(P < 0.05).and the types and content of alkanes gradually increase during the freeze-drying process.With the progress of AD,the content of esters,alcohols,and alkanes gradually decreased,and the types and content of aldehydes and sulfur-containing substances increased,and newly formed ethyl methyl disulfide,ethyl vinyl sulfide,etc.The content of esters,alcohols,and alkanes of the three dry products from high to low is IFD>CFD>AD,and the content of aldehydes and sulfur-containing materials from high to low is AD>CFD>IFD.Through electronic nose analysis,it can be seen that the flavors of different samples are significantly different.Principal Component Analysis(PCA)can distinguish well,and can distinguish fresh from IFD,CFD,and AD dry products.The change trend of flavor in the aroma radar spectrum is similar to the change rule of volatile flavor compounds detected by GC-MS.The free amino acids and soluble sugars of fresh and three dry durian samples weredetermined by HPLC.In the pre-freezing stage of FD(vacuum freezing for 0.5h and atmospheric freezing for 4h),the total content of free amino acids was significantly lower than that of fresh samples(P <0.05).With the progress of drying(FD and AD),the total amount of free amino acids increased first and then decreased.The free amino acids of IFD12 h samples were significantly higher than that of fresh samples(P<0.05),and there was no significant difference between CFD12 h samples and fresh samples(P > 0.05),AD9 h samples were significantly lower than fresh samples(P<0.05).The fresh and sweet amino acids of the three dried durian samples were significantly different.The fresh and sweet amino acids of IFD and CFD were significantly higher than the fresh and AD samples(P<0.05),and the fresh and sweet amino acids of AD samples were all lower than fresh.The total amount of soluble sugar gradually decreased,and the sample content from high to low was fresh>IFD>CFD>AD,and the main soluble sugar was sucrose.Through principal component analysis and cluster analysis,it is believed that the variation of free amino acids and soluble sugar flavor substances of durian in the process of IFD,CFD and AD is mainly caused by the difference in drying technology.Judging from the comprehensive score ranking,the free amino acid and solubility of the sample after IFD drying are the best.The main nutrients,sensory indicators and microstructure of durian dried products obtained by three drying methods were measured and analyzed.IFD and CFD sample are significantly better than AD in the retention of nutrients such as soluble sugar(P < 0.05),vitamin C and crude fat,and IFD is more conducive to the retention of Vc than CFD.The AD sample is brown,the color is dim,and the color is not as bright as the two FD products.The microstructure of the AD sample is severely damaged,the surface of the dry product is obviously shrunk,the texture is too hard,and the brittleness is significantly lower than that of the FD dry product.From the sensory evaluation,it can be concluded that the FD dried product does not have the strong pungent smell of fresh durian and AD dried product,and the taste is crisp,and the sweetness is not significantly different from that of the fresh one.