Identification Of Key Aromas Of Grapefruit Juice And Study Of Their Contributions To The Enhancement Of Sweetness Perception

In recent years,grapefruit has become more and more popular among people because of its high nutritional value and taste.This thesis takes "Red Blush" grapefruit as the research object.After qualitative and quantitative analysis on its aroma compounds,the characteristic aroma compounds are obtained,and studies the interaction between aroma compounds and sweetness perception brought by sweet compounds through sensory evaluation.This topic uses headspace solid-phase microextraction(HS-SPME)and solventassisted flavor evaporation(SAFE)to extract aroma components from grapefruit juice.The volatile compounds were analyzed by gas chromatography-mass spectrometry(GC-MS),gas chromatography/olfactory-associated taste(GC/O-AT),and gas chromatography-flame photometric detector(GC-FPD).A total of 59 volatile compounds were identified by GC-MS,5 volatile sulfides were detected by GC-FPD,and 32 aroma active compounds were detected by GC/O-AT,among which 10 aroma compounds were related to sweet taste,7 were related to sour taste,and 18 were related to bitter taste.The quantitative results showed that terpenes were the main aroma substances in grapefruit juice,and the highest content of terpenes were limonene,β-caryophyllene,δ-cadinene,etc.According to GC-O aroma intensity and aroma activity value(OAV)results show that 2-methyl ethyl butyrate,ethyl butyrate,(+)-limonene,linalool,anise aldehyde,citral,decanal,myrcene,(E)-3,7-dimethylocta-1,3,6-triene had higher aroma intensity.A total of 31 aroma compounds were found to have OAV greater than 1,among which the aroma compounds with higher OAV were 2-methyl butyrate,(+)-limonene,octyl aldehyde,anisaldehyde,and linalool.According to the results of omission experiment,2-methyl ethyl butyrate,myrcene,(+)-limonene,β-caryophyllene,decanal,octyl aldehyde,linalool,(E)-3,7-dimethylocta-1,3,6-triene as the main characteristics of aroma compounds in grapefruit juice.Finally,the sweetening effects of 10 sweet-related aroma compounds selected by GC/O-AT were evaluated through sensory experiments,and the mechanism of binding between aroma compounds and human sweet receptors was analyzed at the molecular level.According to sensory evaluation,eight aroma compounds can significantly enhance the perception of sweetness in 50 g/L sucrose solution,namely ethyl butyrate,ethyl 2-methyl butyrate,linalool,ethyl isobutyrate,terpinolene,ethyl caproate,limonene,and ethyl propionate.In addition,a molecular docking technique was used to dock human sweet taste receptor T1R2 protein with sucrose,and then eight aroma compounds were connected with the T1R2-sucrose complex respectively.The docking results showed that the eight aroma molecules were effectively docked with the receptors.It was found that interactions between amino acid residues and small molecular aroma substances were mainly hydrogen bonding and hydrophobic interactions.Interactions were found between amino acid residues Glu758,Phe761,Tyr756,Ser598 multiple times and small molecular aroma substances.These amino acid residues play an important role in binding to aroma compounds.The above research provides more theoretical support for citrus flavor regulation and sugar reduction and sweetening in the food industry.