Study On The Flavor Chemical Components And Quality Of Yunnan Coffee Prepared By Different Primary Processing

In this study,coffee beans prepared through seven different primary processing methods were used as raw materials,which could provide a beneficial theoretical basis for the improvement in the process and quality of Arabica coffee bean primary processing methods.The specific research content and results are as follows:(1)In this study,the effect of different primary processing treatments on the volatile flavor components of Yunnan Arabica coffee beans is investigated.Coffee samples prepared through seven different primary processing methods:Traditional dry processing(CG),Dry processing Ⅰ(GA),Dry processing Ⅱ(GB),Traditional wet processing(CS),Honey processing Ⅰ(MA),Honey processing Ⅱ(MB)and Honey processing Ⅲ(MC),were comprehensively analyzed using head space solid phase microextraction gas chromatography-mass spectrometry(HS-SPME/GC-MS),head space gas chromatography-ion mobility spectrometry(HS-GC-IMS)and odor activity value(OAV)determination.The results showed that the content of furans and pyrazines was the highest in the GA treatment.Through a HS-GC-IMS analysis,coffee prepared through GB had the highest volatile strength and the richest aroma characteristics.The differences in volatile compounds among coffee beans prepared through different primary processing methods were better characterized based on a principal component analysis(PCA)and a partial least squares discriminant analysis(PLS-DA).Twelve and fifteen aroma substances were respectively selected as the potential markers based on the variable importance in the projection variable selection methods.(2)Primary processing is the key process used to produce the unique coffee,but the effect of the primary processing on coffee quality and chemical composition remains unclear.In this study,seven coffee beans samples were subjected to an electronic tongue and ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry(UPLC-ESI-MS/MS)to investigate the effect of primary processing methods on its metabolic profile and taste quality,elucidating a chemical basis for their taste quality.The chemical phenotypes of coffee were classified into CS,GAGB,CG and MA-MB-MC,whereas their taste phenotypes were classified into CS,CG-GA-GB and MA-MB-MC.Totally,221 compounds were identified as differential metabolites,with a higher content of amino acids and derivatives in GB,and a higher content of phenolic acids as well as lipids in MC.CG showed the strongest aftertaste-astringency and umami.MB presented the strongest astringency,whereas GB showed the strongest aftertaste-bitterness among all coffee samples prepared through the seven primary processing methods.Among them,D-Glucono-1,5-lactone and Lys-Pro-Cys contributed more to coffee astringency.The astringent aftertaste of coffee was negatively correlated with 1,3-O-Dip-Coumaroylglycerol and Stilbostemin B.This study provides a comprehensive insight into the chemical composition and sensory quality of coffee.(3)In this chapter,the effect of different primary processing treatments on the physicochemical properties,taste chemical composition content and antioxidant capacity of coffee samples is investigated.In addition,sensory attributes were determined via an electronic nose analysis and a sensory cup measurement,meanwhile a correlation analysis was performed on the chemical composition and sensory quality.The results of the study showed that the physicochemical indices of TA,TSS and pH of the roasted beans in the samples treated through each method differed significantly(p<0.05),except for TS,and pH was the highest in the CS-treated coffee.All the seven primary processing methods had effect on the content of taste characteristic components such as active ingredients,alkaloids,chlorogenic acid and organic acids in coffee beans.The taste component content of roasted beans varied significantly when using different processing methods,with the lowest and highest level of caffeine detected in MC-and GA-prepared beans,the highest trigonelline content in MA-prepared beans as well as the lowest and highest total content of eight chlorogenic acids and seven organic acids in CS-prepared beans respectively.The electronic nose data was analyzed using PCA,and the results showed that the samples were mainly divided into 3 clusters with similar flavor sensations among samples in close proximity.The results of the seven coffee cups were diffrent,with GAprepared beans showing the highest total score of 83.13±0.55.This study reveals the chemical composition and quality characteristics of coffee prepared through different primary processing methods,which is important for coffee flavor quality improvement and the screening as well as identification of high-quality products.