Ivestigating The Effect Of Four Glucosidase On Volatile Compounds And Aroma Of Instant Green Tea Infusion

Instant teas are the most important tea products.However,during the processes of leaching,concentrating and drying,the loss of volatile compounds lead to negative changes on aroma profiles,making instant teas having the aroma inferior to the non-instant teas,thus affecting its application in food.Enzyme technology is an important way to improve the flavor of instant tea,and it is of great significance to explore enzymatic resources for improving the flavor of instant tea.In this study,the treatment β-glucosidase,α-L-rhamnosidase,β-xylosidase andα-L-arabinosidase were investigated in the effects on volatile compounds and aroma profiles of instant green tea infusion,via gas chromatography-mass spectrometry(GC-MS)combined with headspace solid phase microextraction(HS-SPME),sensory evaluation,odor activity value(OAV)analysis and omission experiment.The results are as follows:(1)GC-MS was used to analyze the samples of the instant green tea infusion(IGT)and the counterparts treated by β-glucosidase,α-L-rhamnosidase,β-xylosidase and α-L-arabinosidase(GIGT,LIGT,XIGT,AIGT)and they combination(GLIGT,GXIGT,GAIGT),respectively.Total 37 volatile compounds were detected,including 3 kinds of furans,6 kinds of aldehydes,4 kinds of alcohols,3 kinds of esters,3 kinds of ketones,14 kinds of terpenes and 4 kinds of other kinds.(2)Sensory evaluation and GC-MS analysis showed that IGT is mainly dominated with caramel and sweet notes.In comparison to IGT,LIGT had decreased caramel note and increased concentration of 2-ethylhexylsalicylic acid,decanal,nonanal etc.;GIGT is mainly dominated with grassy,floral and sweet notes,and increased in the concentration of volatile compounds such as cis-3-hexenol,geraniol,methyl salicylate,benzaldehyde etc;GLIGT showed increased content of grassy note and enhanced concentrations of cis-3-hexenol,methyl salicylate and 2-undecone.OAV analysis found that the main aroma contributing components of IGT were 3-methylbutanal,2-methylbutanal,2-ethylfuran,limonene and nonanal;the aroma-active compounds of LIGT was similar to IGT;main aroma contributing components in GIGT were cis-3-hexenol,geraniol,methyl salicylate,3-methylbutanal,2-methylbutanal,2-ethylfuran and decanal etc.;the OAV value of cis-3-hexenol was further increased in GLIGT.Omission experiment showed that cis-3-hexenol and geraniol were the major contributors to grassy and floral notes.(3)Sensory evaluation,GC-MS and OAV analysis of XIGT and GXIGT indicated that the aroma of GXIGT was grassy,floral and sweet notes.In comparison to IGT,XIGT and GIGT,the GXIGT had enhanced grassy and woody notes,increased concentrations of cis-3-hexenol,linalool,decanal,2-undecone and methyl salicylate,and promoted OAV value of cis-3-hexenol,linalool,2-ethylfuran,decanal and methyl salicylate.(4)Sensory evaluation,GC-MS and OAV analysis showed that the main aroma of GAIGT was grassy and sweet notes.Compared to IGT,AIGT and GIGT;GAIGT increased in grassy note and concentrations of cis-3-hexenol,2-undecane and methyl salicylate,as well as increased OAV values of cis-3-hexenol,2-ethylfuran and methyl salicylate.The above results indicate that the β-glucosidase and complex enzyme have significant effects on volatile compounds in the instant green tea infusion,resulting in effective improvement of the aroma,which provides a theoretical reference for developing enzymatic processes to improve the aroma of instant tea.