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The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is one of the most important pests of fruits worldwide. In the present study, we investigated the ovipositional response of C. capitata females to 37 compounds of fruit volatiles from various chemical groups and the dose response to five of them. Red plastic hollow hemispheres (domes) were used as oviposition substrates in all tests. Twenty of the compounds tested increased female egg laying compared to control substrates that contain no chemicals. With 16 compounds, similar number of eggs was deposited in treated and in control oviposition substrates. One terpene ((±)-linalool) reduced egg laying indicating a deterrent ovipositional effect. Both the esters and aldehydes tested increased the ovipositional responses in C. capitata. Most of the monoterpene hydrocarbons increased oviposition, while oxygenated monoterpenes, sesquiterpenes hydrocarbons, and oxygenated sesquiterpenes had mostly neutral effect. Ethyl hexanoate and R-(+)-limonene increased oviposition in the majority of doses tested. Different doses of (−)-linalool elicited differential female ovipositional responses. In contrast, valencene and citral, regardless of dose did not affect female oviposition. Practical implications of these findings are discussed.

The key odorants of tartary buckwheat (TB) were researched by a sensory-directed flavor analysis approach for the first time. After the volatiles of TB were isolated by solvent-assisted flavor evaporation (SAFE), 49 aroma-active components with flavor dilution (FD) factors in the range of 1-2187 were identified using gas chromatography-olfactometry-mass spectrometry (GC-O-MS) combined with aroma extract dilution analysis (AEDA). Geranylacetone, phenethyl alcohol, and β-damascone showed the highest FD factors of 2187. All 49 odorants were further quantitated by the internal standard curve method, and their odor activity values (OAVs) were obtained. The overall aroma of TB was successfully simulated (similarity > 98.16%) by mixing 16 odorants (OAV ≥ 1) with their natural concentrations. The omission tests revealed that geosmin, α-isomethylionone, α-methylionone, β-ionone, linalool, β-damascone, geranylacetone, guaiacol, ethyl hexanoate, geraniol, vanillin, tetrahydrolinalool, and 2,5-dimethyl-4-hydroxy-3-(2H)-furanone were the key odorants of TB. Chiral analysis showed that tetrahydrolinalool and linalool existed as racemics in the commercial TB. The relative content of R-enantiomers of α-isomethylionone and α-methylionone was slightly higher than that of their S-enantiomers. The odor thresholds of R- and S-enantiomer of tetrahydrolinalool were first detected as 0.029 and 3.8 μg/L in air, respectively.

Ripe durian fruits produce unique volatiles of pungent odor comprising esters, alcohols, ketones, and sulfur-containing compounds. Recently, “Chanthaburi 1” hybrid bred from 2 famous commercial cultivars of “Chanee” and “Monthong” claimed to be less fragrant during ripening, but there was no report. The present study compared the volatile profiles from 3 Thai commercial cultivars of “Kanyao,” “Chanee,” and “Monthong” compared to “Chanthaburi 1”, and the relationships of the cultivars were organized using the volatile fingerprints. Out of 41 volatile compounds detected by SPME/GC-MS in ripe durian flesh, 33 compounds were esters, but only 14 esters were found in “Chanthaburi 1.” Ripe flesh of most durian cultivars contains ethyl-2-methyl butanoate and ethyl hexanoate as the active volatiles. “Chanthaburi 1” contained fewer components with low odor activity value (OAV) of the volatiles. “Chanee” ripe flesh exhibited the strongest durian smell among the four varieties, whereas “Monthong” exhibited a strong apple-like fruity odor and “Kanyao” was more green fruity. Diethyl disulfide and 3, 5 dimethyl-1, 2, 4-trithiolane contributing pungent smells of garlic or onion were found only in “Chanthaburi 1” and “Monthong.” In terms of detected volatiles, “Kanyao” and “Chanee” were highly close when “Monthong” was apart. PCA analysis revealed that “Chanthaburi 1” contained ester compounds ancestrally related to the parents, “Chanee” in the component I and “Monthong” in the component II. These data could be beneficial for managing the status of Thai durians in global markets.

Volatile constituents in jambolan [Syzgium cumini (L.) Skeels] wine were isolated by headspace–solid phase microextraction (HS–SPME) and analyzed by gas chromatography-flame ionization detector (GC–FID), gas chromatography-mass spectrometry (GC–MS), and gas chromatography–olfactometry (GC–O). The composition of the jambolan wine included 52 esters, 20 terpenes, 13 alcohols, 12 acids, 11 aldehydes, 4 ketones, 4 oxides, and 5 miscellaneous compounds. Aroma extract dilution analysis and odor activity units were used for the determination of odor-active compounds. A total of 19 odor-active compounds were found as odor-active volatiles, from which (E)-β-ionone, phenylacetaldehyde, ethyl acetate, ethyl hexanoate, and ethyl benzoate were the most important. The similar results of the GC–O and OAV approaches suggests that HS–SPME–GC–O could be used as a fast and simple tool to quality control of the jambolan wine aroma.

BACKGROUND Strong-flavor baijiu is a traditional distilled alcoholic beverage with a long history in China. The fermented grains play a pivotal role in the production of baijiu. The purpose of this study was to evaluate and compare the microbiota and flavor substances present in fermented zaopei (ZP) from pits of different ages. High-throughput sequencing, headspace solid-phase microextraction gas chromatography-mass spectrometry, principal component analysis, community composition analysis, and redundancy analysis were used to analyze and evaluate the impact of environmental factors on microbial communities and flavor substances. RESULTS Six genera of bacteria (e.g., Caproiciproducens, Syntrophaceticus, Sedimentibacter, Hydrogenispora, Pelotomaculum and Bacillus) and seven genera of fungi (Cladosporium, Debaryomyces, Dipodascus, Auxarthron, Cephalotrichum, unclassified Stachybotryaceae, unclassified Microascaceae and Cephalotrichum) notably affected the production of hexanoic acid (an important flavor compound). Moisture and alcohol content also had considerable effects on the production of the flavor compounds such as ethyl lactate, hexanoic acid, and ethyl hexanoate. The profiles of volatile compounds present in ZP were different between the aged and new pits; these profiles were mainly reflected in the concentration and types of alcohols, aldehydes, esters, and aromatic compounds. CONCLUSIONS This paper provides a comprehensive overview of the physicochemical parameters, flavor substances, and microbial population distribution of ZP. Characterization of various ZP samples help to elucidate the fermentation mechanisms and offer a theoretical reference to control and enhance the quality of Baijiu. © 2021 Society of Chemical Industry.

Petit Manseng (Vitis vinifera L.) has become a popular variety in China for the production of semisweet and sweet wines. However, few studies focused on investigating the molecular odor code of its key odorants. In this study, the key odor-active compounds of Chinese sweet Petit Manseng wine were identified by gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). Fifty-five odorous zones were sniffed and identified by application of aroma extraction dilution analysis on a distillate prepared by liquid-liquid extraction and solvent-assisted flavor evaporation. Among them, isoamyl alcohol, ethyl octanoate, isovaleric acid, (E)-β-damascenone, and phenylethanol particularly displayed with highest flavor dilution factors above 1024. The quantification of volatiles by headspace solid-phase microextraction coupled with GC-MS and GC coupled with triple quadrupole MS/MS and a calculation of odor activity values (OAVs) indicated 23 volatiles with OAVs above 1. Ethyl hexanoate showed the highest OAV with 208.8, followed by (E)-β-damascenone (189.0), 3-mercaptohexanol (60.3), isoamyl acetate (45.4), and furaneol (40.1). The aroma of the sweet wine was successfully reconstituted by combining 42 aroma compounds in a model wine solution. 3-Mercaptohexanol, (E)-β-damascenone, furaneol, γ-octalactone + γ-decalactone + γ-hexalactone, and ethyl cinnamate had important influence on the aroma of sweet Petit Manseng wine assessed by omission tests. Moreover, the discrimination of wines from three regions was successfully achieved by partial least squares discriminant analysis based on quantitative results of key odorants. 3-Mercaptohexanol was considered as the most responsible for the region discrimination and had highest concentrations in Petit Manseng wines from Jiaodong Peninsula. PRACTICAL APPLICATION: Understanding of the knowledge in key odorants of Petit Manseng wines could be useful to improve wine quality through viticultural and enological practices.

The purpose of this research was to evaluate the microbiological, chemical, and volatile compounds of mixed juices comprised of cashew apple and longan fermented with two yeast strains of Saccharomyces cerevisiae (C12 and EC1118). The two fermentations in the mixed juices were similar physicochemical parameters (the growth of yeast, pH, total acidity, total soluble solids, and total sugar). The most abundant of the volatile compounds in these wines were ethyl acetate, ethyl hexanoate, ethyl octanoate, ethyl decanoate, isoamyl acetate, ethanol, isobutanol, isoamyl alcohol, 2-phenylethanol, β-ocimene, and acetic acid. Seven volatile compounds in the wines had odor activity values (OAVs) higher than 1, and also were selected and quantified (ethyl octanoate, ethyl hexanoate, ethyl decanoate, isoamyl acetate, isoamyl alcohol, 2-phenylethanol, and linalool). Ethyl octanoate (fruity, floral, and pineapple) had the highest OAVs in both of the mixed juices fermented with the yeast strains C12 and EC1118. The S. cerevisiae strain EC1118 can significantly produce the highest total volatile contents (359.23 mg/L), and we also found a higher level of total ester (95.50 mg/L) in the wines. Additionally, the S. cerevisiae strain EC1118 can provide a higher content of fruity aroma in wines, as indicated by the calculation of OAVs. The sensory analysis of the wines was acceptable to all the panelists, who gave color, clarity, taste, flavor, and overall acceptance scores as “like slightly” to “like moderately.”

Three main varieties of kiwifruit exhibiting marked differences in flavor were selected for the study. Volatile profiles of three representative kiwifruit varieties were separated and identified by headspace-solid phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS). A total of 48 compounds were identified by GC-MS in three samples, including aldehydes (16), alcohols (11), esters (16), and other compounds (5). Meanwhile, methyl hexanoate, ethyl hexanoate, hexanol, (E)-2-hexenal, hexanal, ethyl butanoate, and ethyl acetate were identified at a higher level by GC-IMS in all three varieties. Descriptive sensory (DSA) analysis was also performed to distinguish subtle differences of the kiwifruit varieties. Further partial least square regression analysis (PLSR) revealed that the fruity attribute was positively associated with ethyl butanoate, methyl hexanoate, and hexyl benzoate, while the grass aroma might be mainly due to (E)-2-hexenal, 3-hexenal, hexanol, and (E)-2-hexen-1-ol. As for sweet note, some esters, such as methyl butanoate ethyl butanoate and methyl hexanoate, were the main contributors. In addition, the cucumber-like and pungent notes were positively associated with (E,Z)-2,6-nonadienal and 1-penten-3-one, respectively.

The West Indian fruit fly, Anastrepha obliqua (Macquart), infests a wide diversity of tropical fruit. Previous studies suggest that A. obliqua adults are attracted to volatile compounds common in different hosts. However, to date, most studies have used ripe fruit for the identification of attractive compounds. In this study, we investigated the attraction of sexually mature A. obliqua females and males to two cultivars and three ripening stages of guava. We also identified the attractive compounds to A. obliqua by combined gas chromatography-electroantennographic detector (GC-EAD) and gas chromatography-mass spectrometry (GC–MS) and evaluated the biological activity of the identified compounds in field-cage tests. We found that individuals of both sexes of A. obliqua showed no preference to the volatiles of either of the two cultivars of guava evaluated. In contrast, flies were more attracted to ripe and half-ripe fruit than to unripe ones. GC-EAD analyses of extracts of ripe “Creole” or “Thai” cultivars identified six compounds that elicited antennal responses by A. obliqua females and males. The compounds were identified by GC–MS as ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, cis-3-hexenyl acetate, ethyl benzoate, and ethyl octanoate. Half-ripe guava emit ethyl butyrate, cis-3-hexen-1-ol, ethyl hexanoate, and cis-3-hexenyl acetate, while only traces of cis-3-hexenyl-acetate were found in unripe guava. Field-cage tests with synthetic standards confirmed that the compounds identified are responsible for the attraction of A. obliqua flies to ripe guava.

The aim of this work was to study the composition of aroma volatile compounds (AVCs) of blood orange cv. Moro treated with γ-aminobutyric acid (GABA), methyl jasmonate (MeJA) or methyl salicylate (MeSA) by headspace gas chromatography-mass spectrometry (HS-GC-MS). GABA at 20 and 40 mM was vacuum infiltrated (at 30 kPa for 8 min), and MeJA or MeSA at 50 and 100 μM (vapour treatments) was applied separately at 20 °C for 18 h. AVCs were measured at harvest and at the end of the experiment (150 days at 3 °C + 2 days at 20 °C, shelf life) for all control and treated fruits. The most abundant compound was limonene, followed by β-myrcene and α-pinene. α-Thujene, camphene, β-pinene, n-decane, α-phellandrene, α-terpinene, p-cymene, (E)-β-ocimene, citronellyl acetate and γ-terpinene were affected by treatments after long-term cold storage. The highest and the lowest percentages of limonene were measured in control samples (94.31 ± 1) and fruits treated with 100 μM MeSA (86.68 ± 1), respectively. (E)-Caryophyllene and (E)-ethyl cinnamate were not detected in all samples after 150 days of cold storage. The multivariate statistical analysis revealed that β-myrcene, n-decane, linalool, limonene, trans-limonene oxide, ethyl hexanoate and sabinene were positively correlated with chilling injury. Overall, it can be concluded that these compounds can be used as biological markers related to CI based on the multivariate statistical analyses.

This study aims to examine the effect of the non-Saccharomyces yeast Saccharomycopsis fibuligera on the sensory quality and flavour characteristics of a sweet rice alcoholic beverage. The strain S. fibuligera was isolated from a traditional Chinese hand-made starter with the purpose to improving sweet rice wine fragrance. Here, sweet rice wines were produced by six combinations of three species of fermentation strains, including S. fibuligera, Rhizopus and Saccharomyces cerevisiae, for evaluation. The study results showed significant diversities within these rice wines based on indicators including the score of quantitative descriptive analysis and volatile variety and content as well as odour activity value (OAV). Quantitative results showed that 43 volatile compounds were identified by headspace-solid phase microextraction with gas chromatography-mass spectrometry among samples. Based on the principal component analysis and OAV calculation, the two samples (S-2 and S-3) fermented with S. fibuligera and Rhizopus possessed high scores and were distinguished from the others, and ethyl butanoate, ethyl hexanoate, β-phenylethyl alcohol and 1-octen-3-one with high OAVs were responsible for the key aroma of sweet rice wine fermented with S. fibuligera. Co-inoculating S. fibuligera, Rhizopus or/and S. cerevisiae generated more pleasant aroma compounds in a sweet rice alcoholic beverage than when inoculated individually. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13197-020-04833-4) contains supplementary material, which is available to authorized users.

The aroma-active compounds of three Xi baijiu samples (Xijiulan, Y1, Xijiuyinxiangguizhou, Y2 and Xijiuyinzhi, Y3) were analyzed by gas chromatography–olfactometry (GC–O), GC–flame photometric detection (FPD) and odor activity value (OAV). The results indicated that a total of 92 aroma compounds were determined, including 16 sulfur compounds. Furthermore, 2-methyl-3-furanthiol (OAV: 31–220), 3-mercapohexyl acetate (OAV: 1870), dimethyl trisulfide (OAV: 333–400), 3-mercaptohexanol (OAV: 34–36), β-damascenone (OAV: 1317–1342), 2-butylfuran (OAV: 629–672), ethyl 3-methylbutanoate (OAV: 655–899), ethyl hexanoate (OAV: 687–729), and ethyl octanoate (OAV: 1164–1362) exhibited much higher OAVs and aroma intensities (AIs) than other compounds. Finally, the perceptual interactions between five sulfur compounds and six esters were studied using Feller’s additive model in Y2. Among the 30 binary mixtures, 12 groups showed an additive effect, 4 groups exhibited a synergistic effect, and 14 groups exerted a masking effect. These data indicated that dimethyl disulfide and 2-methyl-3-furanthiol had masking and additive effects on the aroma of esters.

Background Icewine produced in China is becoming popular, but there is only limited knowledge available on the yeast population that occurs during fermentation and also on the selection of indigenous Saccharomyces cerevisiae strains for its production. In this work, we first investigated yeast species and the evolution of yeast population in spontaneous fermentations of icewine produced in the Qilian region of China and then analyzed the biodiversity and important enological properties of S. cerevisiae isolates. Results Seven species of five genera including S. cerevisiae, S. uvarum, Torulaspora delbrueckii, Hanseniaspora uvarum, Lachancea thermotolerans, Metschnikowia aff. fructicola and H. osmophila were identified by the colony morphology on Wallerstein Laboratory Nutrient medium and sequence analysis of the 26S rRNA gene D1/D2 domain. Saccharomyces cerevisiae, H. uvarum and L. thermotolerans were the dominant species, representing almost 87% of the total yeast isolates. Microvinification with seven preselected S. cerevisiae strains were performed on Vidal. All selected strains could complete fermentations, and the enochemical parameters were within the acceptable ranges of the wine industry. W5B3 produced higher amounts of ethyl hexanoate and ethyl octanoate than other strains. R3A10 was a low volatile acid producer and the corresponding icewine presented the highest values on some odorants including β-damascenone, 1-octen-3-ol, ethyl 2-methylbutyrate, and isoamyl alcohol. Vidal icewines fermented with R3A10, R3A16 and W5B3 were well accepted by the judges because of superior sensory quality. Conclusion Three indigenous strains (R3A10, R3A16 and W5B3) could be used as starters and could potentially improve the regional character of the icewine in Qilian. © 2020 Society of Chemical Industry.

Physical and chemical properties of 190 fruit samples from 26 matrices of a new population of Caryocar spp. were investigated. Whole fruit, named giant pequi, was composed of 67% shell (exocarp and external mesocarp) and 33% pyrene, and the edible pulp (internal mesocarp) comprised 46% pyrene and 15% total fruit mass. The pulp presented moderate contents of energy (269 kcal/100 g) and lipid (16/100 g), mainly monounsaturated fatty acids (56/100 g lipids); high carotenoid concentration (47 µg/g) and considerable phenolic content (101 mg GAE/100 g). Gallic and p-coumaric acids were the main phenolic compounds identified in the pulp, and the larger classes of volatile compounds were esters and monoterpenes, mostly ethyl hexanoate (44%) and β-cis-ocimene (21%). The giant pequi features higher pyrene and pulp yields, and its edible pulp has a lighter color and lower energy and lipid contents compared to those of common species of pequi, as well as is rich in carotenoids and is a source of polyphenols and volatile compounds. These attributes are highly promising for agro-industrial use, with great potential for nutritional and nutraceutical applications.

Changes in the oenological parameters, total phenols, total flavonoids, and individual phenols of persimmon during spontaneous and inoculated fermentation were investigated. The volatile compounds and sensory character of the persimmon wine were compared and evaluated simultaneously. Results show that at the end of fermentation, spontaneous persimmon wine (SPW) has higher contents of total flavonoids, total phenols yet lower concentrations of alcohol and volatile compounds than inoculated persimmon wine (IPW). Catechin, salicylic acid, quercetin, and vanillic acid were the main phenolic compounds in both types of persimmon wine. There are six volatile components in the IPW with an OAV greater than 1, which are isoamyl acetate, ethyl hexanoate, methyl octanoate, ethyl octanoate, phenethyl acetate, and 2, 4‐di‐tert‐butylphenol, and these compounds contribute to the IPW with brandy and fruity sensory properties, while only three volatile components in SPW have OAV greater than 1, which are isoamyl acetate, ethyl hexanoate, and ethyl octanoate. Spontaneous fermentation increased the proportion of esters and alcohols in the overall volatile compounds. During sensory evaluation, IPW was characterized by “brandy,” “bitterness,” and low “sweetness,” and SPW has a high score of “sweetness,” “balance,” desirable “color,” and “body.”, Changes in the oenological parameters, total phenols, total flavonoids, and individual phenolic compounds of persimmon wine during spontaneous and inoculated fermentation were investigated. The volatile compounds and sensory character of the persimmon wines were compared and evaluated simultaneously.

The aim of this study was to investigate the effects of Torulaspora delbrueckii and Saccharomyces cerevisiae, as pure fermenters and mixed fermenters (simultaneous and sequential culture), on the production of nonvolatiles and volatiles, and on the antioxidant activity in Golden Dried Longan juice and Golden Dried Longan wines. Alanine, arginine, glutamic acid, leucine, proline, and gamma-aminobutyric acid (GABA) were the most prominent amino acids that were found in these wines. The Golden Dried Longan Wine fermented with monocultures of S. cerevisiae and T. delbrueckii produced a total volatile aroma content of 393.21 mg/l and 383.20 mg/l, respectively. Simultaneous culture of the two organisms produced the highest total volatile aroma content, that affected most volatile compounds including isobutanol, ethyl acetate, ethyl decanoate, ethyl heptanoate, ethyl hexanoate, ethyl pentanoate, isoamyl acetate, and isobutyl acetate. Of the four treatments, the sequential culture possessed the highest total phenolic content (5.80 mg gallic acid equivalents (GAE)/ml). In addition, the total phenolic content significantly correlated with the antioxidant activity of the Golden Dried Juice and Golden Dried Longan Wine. These results suggest that co-cultures of the two organisms used in the production of the Golden Dried Longan Wine may improve the intensity and complexity of its aroma.

A lipase from Sporisorium reilianum SRZ2 (SRL) with 73% amino acid sequence identity to Candida antarctica lipase B (CALB) was cloned and overexpressed in Pichia pastoris. The recombinant SRL showed a preference for short-chain p-nitrophenyl esters. It achieved maximum activity at pH 8.0 and 65°C for p-nitrophenyl hexanoate (C6) with Km and kcat/Km values of 0.14 mmol·L−1 and 1712 min−1 · mmol · L−1 at 30°C, respectively. SRL displayed excellent thermostability and pH stability, retaining more than 79% of its initial activity after incubation at 60°C for 72 h and 75% at pH 3 to 11 for 72 h. It also maintained most of its activity in the presence of inhibitors and detergents except sodium dodecyl sulfate, and it tolerated organic solvents. SRL was covalently immobilized and successfully used for ethyl hexanoate synthesis in cyclohexane or in a solvent-free system with a high conversion yield (> 95%). Furthermore, high conversion yield was also achieved for the synthesis of various short-chain flavor esters when high substrate concentrations of 2 mol · L−1 were applied. This study indicated that a CALB-type lipase from S. reilianum SRZ2 showed great potential in organic ester synthesis.

Smen is a fermented Moroccan butter highly regarded for its unique flavor characteristics. For the first time, this study aimed to evaluate the suitability and complementary performance of purge-and-trap extraction (PTE) and solvent-assisted flavor evaporation (SAFE) extraction methods prior to gas chromatography–mass spectrometry–olfactometry (GC–MS–O) in order to characterize key compounds in Smen. According to the representativeness tests, both SAFE and PTE aromatic extracts gave satisfactory similarity and intensity scores and were representative aromatic extracts, being similar to the Smen reference odor. Thirty-four volatile compounds were identified in Smen including acids, alcohols, esters, and ketones. Aroma extract dilution analysis (AEDA) was applied to characterize potent odorants, and odor activity values (OAVs) were calculated to authenticate these compounds. Twenty-two and nineteen aroma-active compounds were revealed by SAFE and PTE methods, respectively, with flavor dilution (FD) factors ranging from 4 to 4096, and OAVs between 1 and 3359. Ethyl butanoate, ethyl lactate, ethyl hexanoate, butanoic acid, and hexanoic acid were the main potent odorants in Smen, producing fruity-rose, creamy-whey, overripe fruit, ripened cheese, and rancid buttery/soapy odors, respectively. Therefore, SAFE and PTE methods were not only representative, but also complementary for elucidating potent aroma compounds of Smen.

Sweetness is an important Baijiu quality marker, but there is limited research on it. In this study, the main contributors to Baijiu sweetness were identified by “sensomics” combined with “flavoromics”. A total of 43 volatile compounds (mostly esters) were found that appeared to contribute to Baijiu sweetness, through sensory-guided fractionation and compositional analysis. Correlation analysis between the volatile composition and perceived sweetness of 18 Baijiu samples with different sweet intensities identified 14 potential contributors. Additional testing verified that combining the 14 compounds reproduced Baijiu sweetness exactly, and omission testing identified ethyl hexanoate, hexyl hexanoate and ethyl 3-methylbutanoate as the major contributors to Baijiu sweetness. These findings not only broadened our understanding of Baijiu sweetness, but also highlighted the major contribution of volatile compounds to sweetness perception, knowledge which may facilitate future flavor modification of a wide variety of foods and beverages.

Rosa roxburghii tratt (RRT), widely distributed in the southwest of China, is favored by consumers for its good taste and healthy functions. In this study, thirty-seven compounds of Rosa roxburghii Tratt (RRT) were identified and quantified by gas chromatography–olfactometry (G–O) and gas chromatography–mass spectrometry (GC–MS) analysis. Furthermore, ethyl 2-methylpropanoate, ethyl butanoate, ethyl 2-methylbutyrate, and ethyl hexanoate were present with much higher odor activity values (OAVs) than other compounds. The key notes were confirmed by omission tests. Possible interaction among key notes was investigated through odor intensity determination and sensory analysis. It showed fruity and woody notes had synergistic effects. Full factorial design was used to evaluate the notes contribution to the whole odor. One important finding is the major effect of order interactions, fruity note (X1) and woody note (X4) especially, emphasizing the existence of complex interactions occurring between odor notes. The interaction X1X4 was further investigated. The woody note has a positive effect when the fruity note is also in the mixture but tends to show a negative effect otherwise.

Riesling wines are mostly enjoyed as young wines, usually consumed within the first few years after bottling. Throughout several years of aging, Riesling wines begin to develop more robust flavor profiles, often displaying less fruity and floral notes and more pronounced maple, honey, and caramel notes. A body of scientific literature has been conducted on the aroma chemistry of young Riesling wines; however, comparatively less scientific reports have been published on the aroma chemistry of aged Riesling wines, and a comprehensive aroma analysis of a 10-year-old Riesling wine has not been previously completed. In this study, a total of 36 odorants were identified in a 10-year-old aged Riesling wine using solvent-assisted flavor evaporation and aroma extract dilution analysis. A total of 26 odorants were quantitated by employing stable isotope dilution assays. Odorants with high odor activity values (OAV) included wine lactone (coconut, OAV 460), ethyl octanoate (fruity, OAV 240), ethyl hexanoate (fruity, OAV 97), s-damascenone (cooked apple, OAV 60), 5-ethyl-3-hydroxy-4-methyl-(5H)-furan-2-one (maple, OAV 33), (S)-ethyl 2-methylbutanoate (fruity, OAV 22), 3-(methylsulfanyl) propanal (cooked potato, OAV 20), ethyl 2-methylpropanoate (fruity, OAV 9.5), ethyl butanoate (fruity, 7.1 OAV), and 1,1,6-trimethyl-1,2-dihydronapthalene (petrol, OAV 6.4). An odor simulation model prepared from all the odorants with an OAV greater than 1 closely matched the sensory profile of the authentic wine. The results of this study provide insight about odorants present in a 10-year-old bottle aged Riesling wine, and this knowledge may be useful for future studies aimed at probing the influence of aging on the aroma chemistry of Riesling wines and other white wines.

Earthworms shape the biological and physicochemical qualities of the soil they choose to reside in, but our understanding of the specific chemicals that attract or repel a particular species of earthworm remains incomplete. Current research indicates that some species feed on and are attracted to fungi, such as Geotrichum candidum. In the present study, as part of our continuing effort to characterize mechanisms of earthworm chemosensation, we tested whether ethyl hexanoate and ethyl pentanoate, two compounds produced by G. candidum, are appetitive to the European nightcrawler (Dendrobaena veneta). In a soil T-maze, both of these compounds significantly repelled individual earthworms in a dosage-dependent manner, this result ran counter to our initial hypothesis. D. veneta also avoided ethyl hexanoate and ethyl pentanoate in an assay we specifically developed to test an earthworms aversion to chemical stimuli in soil. In both of these assays, ethyl hexanoate was aversive at lower concentrations than ethyl pentanoate. These findings further clarify our understanding of the chemical cues that trigger the decision of D. veneta to select a particular soil-environment, and emphasize that different earthworm species may react very differently to commonly encountered chemical stimuli.

The effect of different yeast strains on the quality of kiwi wine was investigated by polyphase determine approaches in the present research. The influence of co-culture and inoculation sequence on the quality was also explored simultaneously. Results suggested that the characteristics of the kiwi wine were affected by the metabolic characteristic of strains. The flavor content and their flavor profile of samples fermented by co-culturing of strain among species, genus, and families. When Saccharomyces bayanus (Y5 or Y6) co-cultured with Torulaspora delbrueckii Y7, the ratio of phenethyl alcohol increased, but that of octanoic acid and ethyl octanoate decreased significantly. The odor activity value (OAV) of ethyl octanoate and ethyl hexanoate was increased by co-culturing Saccharomyces with T. delbrueckii, and that of decanal and terpinen-4-ol was enhanced by co-culturing of different strains of Saccharomyces. It was an excepting process to obtain high quality of kiwi wine by co-culturing technology of yeasts, and was very effective to optimize the process by polyphase analysis approaches.

We obtained volatile aroma compounds from the juices extracted from three different Red Delicious apple (Malus domestica) varieties, which included esters, alcohols, and aldehydes. Among these compounds, ethyl 2-methylbutanoate, methyl 2-methylbutanoate, ethyl butanoate, ethyl hexanoate, hexanal, and butyl 2-methylbutanoate showed high odour active values in the juices. Four compounds (ethyl 2-methylbutanoate, ethyl octanoate, ethyl butanoate, and ethyl hexanoate) were selected to investigate possible interactions occurring in the apple juices. The results demonstrated that the additions of these four aroma volatile compounds could decrease the threshold and intensity of the sensory notes of the solutions compared to those without the addition of these compounds. Lastly, ethyl 2-methylbutanoate was added to the solutions to investigate interactions with σ–τ function. Here, σ represents the ratio of the aroma intensity of the mixed solution to the sum of aroma intensities of all compounds in the solution before blending. The τ represents the aroma of the mixture ratio between the mixture and the sum of aroma compounds before mixing. The results clearly indicated that additive or synergistic effects occurred among these volatiles at sub-threshold concentrations.

Thermal conductivity is a very important transport property of fluids. In this work, the liquid thermal conductivity of five aliphatic esters (ethyl acetate, ethyl propionate, ethyl butyrate, ethyl pentanoate and ethyl hexanoate) were measured by transient hot wire method at atmospheric pressure and with temperature range (249.13 to 348.46) K, (263.55 to 356.28) K, (268.57 to 363.52) K, (249.21 to 363.57) K, (254.29 to 383.37) K, respectively. It was estimated that the total relative standard uncertainty of the experimental results was smaller than 2 % (in the 95 % confidence level) and repeatability was better than ± 0.5 %. The liquid thermal conductivity results of the five esters were fitted as a polynomial function of temperature. The mean deviation and the maximum deviation of the fitted function from the experimental data of the five esters were 0.15 % and 0.36 % for ethyl acetate, 0.15 % and 0.42 % for ethyl propionate, 0.21 % and -0.41 % for ethyl butyrate, 0.21 % and -0.42 % for ethyl pentanoate, 0.32 % and -0.69 % for ethyl hexanoate, respectively.