Characterization of odor-active compounds in the head, heart, and tail fractions of freshly distilled spirit from Spine grape (Vitis davidii Foex) wine by gas chromatography-olfactometry and gas chromatography-mass spectrometry.

Differences in key odor-active volatile compounds among the head, heart, and tail fractions of freshly distilled spirits from Spine grape (Vitis davidii Foex) wine were identified for the first time by gas chromatography-olfactometry and gas chromatography-mass spectrometry. Results from aroma extract dilution analysis (AEDA) showed that there were 34, 45, and 37 odor-active compounds in the head, heart and tail fractions, respectively. Besides, 20, 22, and 17 quantified compounds, respectively, showed odor activity values (OAVs) > 1. The head fraction was characterized by fruity, fusel/solvent notes owing to higher concentrations of higher alcohols and esters, while the tail fraction had more intense smoky/animal, sweaty/fatty attributes due to higher concentrations of volatile phenols and fatty acids. Finally, the heart fraction was characterized by ethyl octanoate, ethyl hexanoate, ethyl 3-phenylpropanoate, ethyl cinnamate, isoamyl alcohol, guaiacol, 4-ethylguaiacol, 4-vinylguaiacol, 2,3-butanedione, and (E)-ß-damascenone. Furthermore, observation of the distillation progress indicated that different volatiles with various boiling points and solubilities followed diverse distillation patterns: concentrations of most esters, higher alcohols, terpenes and C13-norisoprenoids decreased, while concentrations of volatile phenols, fatty acids and some aromatic compounds increased during distillation. As a result, their final concentrations in the three distillate fractions varied significantly.

Post-storage changes of volatile compounds in air- and sun-dried raisins with different packaging materials using HS-SPME with GC/MS.

Free- and bound-form volatiles in sun-dried raisins (SDRs) and air-dried raisins (ADRs) of 'Thompson Seedless' were analyzed by gas chromatography-mass spectrometry (GC/MS) for 0, 3, 6, 9 and 12 months of storage. The compounds originating from glycosidically bound (GB) volatiles were significantly more abundant in bound-form than their free-form. A total of 89 and 88 free-form compounds were identified in ADRs and SDRs, respectively. Overall, higher concentration of unsaturated fatty-acid-oxidation (UFAO) and Maillard reaction (MR) compounds were observed in the SDRs. The plastic and woven bags have an insignificant effect on the volatiles in the raisins. The main characteristics of ADR aroma were floral and fruity, while fatty, roasted, and chemical aromas were prominent in SDRs. With the exception of chemical aroma, the aromatic series (fruity, floral, herbaceous and roasted) increased during the storage duration and become more compelling in 12 month. The packaging materials have similar effect on aromatic series, except fruity note, which was higher in woven bag. The main floral and fruity aroma contributors were decanal, ß-ionone, ethyl hexanoate, ß-damascenone, and 1-octen-3-ol. Herein we identified UFAO and MR compounds as the main contributors of raisin aromas.

Changes of free-form volatile compounds in pre-treated raisins with different packaging materials during storage.

The aroma profiles of volatile compounds (VOCs) were analyzed by GC/MS in pre-treated air-dried (PAD) and sun-dried (PSD) raisins during storage. Total 98, 94 and 81 VOCs were identified in Zixiang Seedless raisins (ZSRs), Centennial Seedless raisins (CSRs) and Thompson Seedless raisins (TSRs), respectively. During storage, the overall concentrations of VOCs of PSD raisins were higher in plastic bag (PB) compared to those in woven bag (WB). Regarding fruity and floral aromas, the effect of PAD and PB was significant throughout the storage periods (3, 6 and 9 months), however, fatty aroma was higher in PSD raisins due to the major contribution of 2,3-butanedione. The main fruity and floral aroma contributors were ß-damascenone, limonene, rose oxide, geraniol and ethyl hexanoate. This study showed that compounds came from unsaturated fatty acid oxidation, glycosidically-derived and grape-derived source were contributed to fruity, floral or herbaceous aromas, but Maillard reaction-derived VOCs imparted fatty and roasted aromas.

Study of free and glycosidically bound volatile compounds in air-dried raisins from three seedless grape varieties using HS-SPME with GC-MS.

Volatile compounds in air-dried raisins from Turpan, China were analysed, with 77 volatiles identified in Flame Seedless, Thompson Seedless, and Crimson Seedless raisins, 37 of which had never been reported as raisin volatiles. Odour activity values (OAVs) of these volatiles were calculated; 20 compounds had OAVs above 1. The aroma characters of the three varieties were quite similar except for some differences in the intensity of each aroma character. The main free-form volatiles were ethyl acetate, hexanoic acid, (E,E)-2,4-heptadienal and geraniol, with ß-damascenone, 3-ethyl-2,5-dimethylpyrazine, 1-octen-3-ol and hexanal making the highest contribution to the aroma. Fruity and floral were the main characteristics of the free-form aromas in raisins. The main bound-form volatiles were benzyl alcohol and acetoin, with ß-damascenone contributing most to the bound-form aromas, enhancing the floral, fruity and fatty aroma.

Rapid HPLC analysis of amino acids and biogenic amines in wines during fermentation and evaluation of matrix effect.

A rapid HPLC method has been developed for the simultaneous determination of 23 amino acids, 10 biogenic amines and the ammonium ion in wine. Samples were pre-column derivatised with diethyl ethoxymethylenemalonate and separated using reversed-phase HPLC within 30 min. The matrix effect was evaluated when measuring samples taken from different stages of fermentation. Most compounds showed no obvious matrix effect, whereas proline, ethanolamine and spermine had remarkably different responses to variable concentrations of sugar. High concentrations of sugar affected the pH of the derivatisation reaction system; proline, ethanolamine and spermine derivatives were sensitive to this effect. Matrix-matched calibration was used for the quantification of these compounds. Validation of the method showed that it was accurate, reproducible and efficient for the simultaneous determination of amino acids and biogenic amines in wines during fermentation. As a specific application of the method, red wine samples taken from different stages of fermentation were analysed.