Study On The Chemical Components And Flavor Quality Of Hainan Coffees From Different Geographical Origins

Coffee,a tropical plant in the Rubiaceae family,is native to Ethiopia and is widely loved by consumers for its functionality and unique taste.Coffee is mainly distributed in tropical regions at 20 degrees north and south latitudes,and is widely cultivated in Central America,South America and Africa.In China,Yunnan and Hainan regions are the main producing areas of coffee.In recent decades,the demand for coffee has been increasing continuously,and global consumption has increased by 1%to 2%per year.According to the International Coffee Organization,the annual value of coffee is about 200 billion US dollars.It is expected that future consumption will continue to drive coffee demand.Hainan coffee is popular among consumers because of its unique aroma and taste characteristics.Coffee flavor is crucial to coffee quality,which is mainly composed of two components:volatile flavor components and flavor presentation components.Aiming at coffee flavor components,this paper conducted the following studies on six kinds of coffee from different producing areas in Hainan,which can provide scientific and reasonable technical support for the in-depth development and efficient utilization of Hainan coffee beans resources,as well as the cultivation of domestic coffee beans market.The main research contents and results areas follows:(1)Identification and analysis of six species of Hainan coffee beans based on volatile component fingerprintingThe analysis was performed using headspace solid phase microextraction-comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry(HS-SPME-GC×GC-TOFMS),complemented by headspace-gas chromatography ion-mobility spectrometry(HS-GC-IMS)were used to comprehensively extract and identify the volatile organic compounds(VOCs)of six coffee roasting beans from different origins in Hainan.The full two-dimensional results showed that a total of 599 VOCs were identified in the six coffees,with the most in XL beans(503)and the least in MS2 beans(377).And the VOCs content in the six coffees varied significantly,with thelowest and highest VOCs contents were 193.034μg/g and 415.747 μg/g respectively in FS and MS2 coffees.Ion mobility spectroscopy detected 71 substances,and provided the characteristics and intensity information of 34 volatile flavor compounds,including 8 alcohols,6 ketones,3 furans,5 esters,4 sulfur-containing compounds,4 aldehydes,2 pyrazines,1 pyridines and 1 organic acid.Finally,the flavor fingerprints of 6 Hainan coffees were successfully established by HS-GC-IMS.(2)Chemical characterization of six kinds of coffee beans in Hainan based on fingerprints of major taste componentsThe experiment studied the main taste components of six coffee beans from different origins in Hainan,and compared the differences in the composition and content of taste characteristics among roasted beans from different origins.The contents of chlorogenic acid,alkaloids(caffeine and trigonelline)and organic acids in six coffee beans were determined by ultra performance liquid chromatography(UPLC).The composition and content of monosaccharides in coffee samples were determined by high performance anion exchange chromatography-phy with pulsed amperometric detector(HPAEC-PAD),and the composition and content of amino acids in coffee samples were determined by fully automated amino acid analyzer.The results showed that there were significant differences in the contents of the six coffee taste components.The contents of caffeine and amino acids were the highest in QH bean,on the contrary,the contents of chlorogenic acid,trigonelline and monosaccharide in QH bean were the lowest.Combining with principal component analysis(PCA)and other stoichiometric analysis,the six coffees were successfully distinguished,among which XL,YSL and MS2 coffee had high similarities,indicating that the taste main chemical components could be used to identify coffees from different producing areas in Hainan.(3)Correlation of sensory quality and taste components of coffee beans from different origins in HainanThe experiments were conducted to determine the physical and chemical indexes such as TA,TS,TSS and pH of six kinds of coffee beans in Hainan,and combined sensory instrument analysis(electronic tongue and electronic nose)with human sensory evaluation to evaluate the sensory quality of 6 kinds of coffee.Finally,Pearson correlation analysis was conducted between sensory score,physical and chemical indexes and main taste components of coffee.The water-soluble components in coffee were identified by hydrogen nuclear magnetic resonance spectroscopy in order to reveal the chemical composition of coffee from different producing areas by fingerprint.The results showed that,in addition to TS,TA,TSS,pH and other physical and chemical indicators were significantly different(P<0.05);the results of the six coffee cups were different,and the XL beans scored the highest;the sensory scores of coffee were not directly related to most indicators.The data of electronic nose and electronic tongue combined with chemical multivariate statistical analysis showed that the six coffee varieties in Hainan were different in overall flavor and taste characteristics and could be distinguished well.(4)Study on the effect of different roasting speeds on the volatile components of Xinglong coffee beansThis study investigated the physicochemical properties and volatile components of coffee beans(C.robusta)from XL,Hainan province at three conditions(fast,medium,and slow roasting speed).Headspace solid phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)was used to identify the volatile components generated at three roasting speeds,and PCA combined with electronic nose was used to further distinguish the differences of overall flavor among different roasted bean samples.A total of 82,72,and 76 volatile components were identified in fast,medium and slow roasted coffee beans respectively.The contents of volatile components were different among the roasting samples,and the level of volatile components at medium roasted beans was the highest and reached a maximum of 1080.51μg/g.Electronic nose analysis showed significant differences in volatile components among coffee samples roasted by different methods.Results from PCA using the data of major volatile class as input variables showed that there were obvious differences among the three.And there were overlaps in section between medium and slow roasted coffee samples,which was a big difference from fast roasted samples.This research could provide some reference for the improvement of the roasting process and the optimization of quality in coffee production.