The Key Aroma Compounds Of Vidal Icewine And Their Contribution To The Icewine Sensory Characteristic

Chinese Vidal icewine is very popular in the wine markets. The sensory characteristics of Vidal icewine and the key aroma compounds of it are still not clear. Exploring the key aroma compounds of Chinese icewine more comprehensive and accurate is helpful for quality evaluation and production of icewine; it can also provide a theoretical basis for the protection of the region. Exploring key aroma sensory characteristics in different groups of non-volatile matrix can provide some theoretical support for the interaction between non-volatile substances and aroma compounds in sweet wines.In this study, by choosing the appropriate aroma extraction technology, combined with gas chromatography-olfactometry(GC-O), gas chromatography-mass spectrometry(GC-MS) and other advanced detection instruments, Vidal icewine aroma compounds were determinded and quantified and the key aroma compounds were obtained. By aroma recombination and omission test, these aroma compounds contributing to Vidal icewine aroma profile were verified. The roles of non-volatile components played in icewine for aroma sensory perceptions were preliminary inquiried. The main conclusions were below:(1) Extraction methods selection for icewine aroma compoundsFour common used aroam pretreatment methods, stir bar sorptive extraction(SBSE), headspace solid-phase microextraction(SPME), solid-phase extraction(SPE) and liquid-liquid extraction(LLE) were chosen and evaluated for icewine aroma extracting. The results showed that SPME and SBSE had poor efficience on some important aroma compounds. Because of the icewine matrix interfering, LLE had less power than SPE for icewine extraction. As SPE samples was represented exactly the typical icewine aroma profile, and SPE had good extraction performance on important compounds of icewine, it will be selected to extract icewine aroma compounds.(2) Characterization of the aroma compounds in different label grade Vidal icewine by aroma extract dilution analysis(AEDA)The different grade icewine in the same vintage were extracted by SPE, A total of 63 odor-active aroma compounds were identified by means of AEDA coupled with GC-MS. The results showed that the major aroma compounds in different grade icewine were the same, although some kinds of aroma compounds had little different. These important aroma compounds mainly formed by esters, alcohols, terpenes, sulfide compounds and furanones, including ethyl isobutyrate, ethyl octanoate, isoamyl alcohol, 2,3-butanedione, 1-heptanol, cis-rose oxide, methional, geraniol, hotrienol, β-damascenone and furaneol. β-Damascenone had the highest factor of dilution(FD), while methional and furaneol had never been reported as important icewine aroma compounds.(3) Quantitation of important odor-active compounds in Vidal icewineSome effective quantitation methods were selected to determinded the concentration of 27 kinds of aroma compounds(FD ≥9). SPE quantitation method was established for guaiacol, methional, furaneol and homofuraneol. Derivatization with SPME was used to evaluate 2, 3-butanedione and1-octen-3-one. The concentrations of β-damascenone, cis-rose oxide and so on were determinded by SPME. By OAV analysis, 13 kinds of aroma compounds with OAV above 10 were obtained. β-Damascenone had the highest OAV of 5580. OAV of methional was 38, and OAV of furaneol was 35, these two compounds were first reported in icewine.(4) Aroma Recombination and Omission ExperimentsFor evaluation the aroma profile difference between the reconstruction icewine and the real icewine, six major descriptions were selected, they were honey, cameral, apricot, rose, topical fruit and raisin. The yellow grade Vidal icewine could be well recombined using 27 important odorants. The aroma profile of complete reconstitution icewine model was similar with real icewine. Omission tests indicated that β-damascenone, methional, furaneol were important and contributed a lot to Chinese Vidal icewine.(5) The impacts of non-volatile matrix on aroma compounds in icewineBy instrumental analysis and sensory evaluation, the impacts of non-volatile system on 4 kinds of important aroma compounds in icewine were explored. The thresholds of cis-rose oxide and β-damascone in icewine model system were measured. The results show that the fructose and(-)-epigallocatechin(EGC) can have a significant impact on headspace concentration of aroma compounds, but the difference of aroma perception intensity was not significant. Add 250 g·L-1 of fructose, the perception of ethyl isobutyrate and β- damascone was significantly affected; adding 100 mg·L-1 of EGC was only significant impacted β-damascone perception. The thresholds of the cis-rose oxide and β-damascone in icewine model system were 1.05 μg·L-1 and 0.09 μg·L-1 respectively.