Characterization of Key Aroma Compounds of Zhuyeqing by Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies
1
Laboratory of Brewing Microbiology and Applied Enzymology, State Key Laboratory of Food Science & Technology, Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Ave, Wuxi 214122, China
2
Laboratory of Analytical, Quality Inspection Center, Key Laboratory of Plant Extraction and Health of Chinese Lujiu (Shanxi), Shanxi Xinghuacun Fenjiu Distillery Co., Ltd., Fenyang 032205, China
*
Authors to whom correspondence should be addressed.
Foods 2025, 14(3), 344; https://doi.org/10.3390/foods14030344
Submission received: 10 December 2024
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Revised: 14 January 2025
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Accepted: 17 January 2025
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Published: 21 January 2025
(This article belongs to the Special Issue Fermented Alcoholic Beverages: Microorganisms, Quality, and Flavor Analysis)
Abstract
:Zhuyeqing is a flavored liquor with a unique flavor blended with Qingxiangxing Baijiu (Fenjiu) and botanical extracts. The aroma characteristics of Zhuyeqing were investigated using a sensomics approach. Ninety-three odorants, among them 64 odorants with flavor dilution (FD) ≥ 32, were confirmed in Zhuyeqing by gas chromatography-mass spectrometry/olfactometry (GC-MS/O) analysis. Quantitative analysis revealed that 22 odorants with odor activity values (OAVs) ≥ 1. Aroma recombination tests showed that 22 odorants with OAV ≥ 1 can recombine the aroma characteristics of Zhuyeqing; omission tests revealed that ethyl cinnamate, ethyl octanoate, ethyl acetate, β-damascenone, and eugenol with OAV ≥ 10 had significant effects on Zhuyeqing.
1. Introduction
Zhuyeqing is the most renowned Chinese functional and flavored distilled spirit with a distinctive flavor. This flavored liquor consists of botanical extracts with 12 Chinese herbs in the base liquor of Fenjiu [1]. Fenjiu is one of the most representative brands of Qingxiangxing Baijiu. The addition of these non-Fenjiu materials may introduce additional aromatic compounds to the Fenjiu matrix, significantly contributing to the flavor and mouthfeel of Zhuyeqing. Consequently, this unique production process imparts a distinctive aroma profile to Zhuyeqing (Figure 1), and the recipe is secret in China.
The aroma of alcoholic beverages is a critical factor influencing product quality and consumer preference [2,3]. Flavored alcoholic beverages are primarily categorized into two types: those based on fermented spirits (called flavored fermented spirits, FFS) and those based on distilled spirits (called flavored distilled spirits, FDS). Many aroma studies on flavored alcoholic beverages have mainly focused on flavored wine, a type of FFS. Vermouth, Bermet, Retsina, and Vesper are typically traditionally flavored wines [4]. Studies on the aroma of flavored wines have demonstrated that the aroma characteristics of flavored wines vary significantly depending on flavor additives [4]. Flavor additives can be categorized as herb-based [5,6,7], fruit-based (including grape-derived extracts like grape marc [8] and grape skin [9]), non-grape fruits [7,10,11,12], or other seldom-used materials such as rice [13]. Research has indicated that both the order of herb-based extract additions (pre- and post-fermentation) and the amount of extract additions can influence the particular aroma compounds and sensory properties of the resultant wine [5]. The floral and fruity aromas of wine can be masked by other scents introduced from herb-based extract additions, including medicinal, moldy/earthy, nutty, vegetal, solvent, and spice notes [6]. In contrast, the addition of fruit-based extracts significantly enhanced the overall fruity and floral aromas due to the increased concentrations of terpenes and esters [8,9,11,12], and the flavoring effect was also affected by the amount of extract added.
However, published studies on the aromatic characteristics of FDS are quite limited, focusing primarily on gins, Zhizhonghe Wujiapi, and Chinese JingJiu. Vichi, et al. [14] studied the volatile compositions of different distilled dry gins with geographical indications and the aroma profiles and key odorants in two gins with different botanicals from a German distillery. This research used headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Buck, et al. [15] employed the sensomics approach to investigate the aroma profiles and key odorants in two gins with different botanicals sourced from a distillery in Germany. Similarly, Ma, et al. [16] and Sun, et al. [17] studied the aromatic characteristics of Wujiapi and Chinese JingJiu, respectively.
The sensomics approach, also known as molecular sensory science, involves discovering and accurately quantifying odor-active compounds, followed by aroma reconstitution and omission experiments [18]. This method has proven effective in identifying the aroma compounds responsible for the unique aroma profiles of various foods, such as Baijiu [19], tea [20], cheese [21], and broth [22]. Zhuyeqing is the most historically significant representative of FDS. The production process and selected herbs contribute to the unique aroma and flavor of Zhuyeqing. However, limited research exists on the aromatic characteristics of Zhuyeqing.
Consequently, the sensomics approach was used to study the aroma characteristics of Zhuyeqing in this paper and the purpose was as follows: (1) clarify the aroma composition of Zhuyeqing using aroma extract dilution assays (AEDA) connected with gas chromatography-mass spectrometry/olfactometry (GC-MS/O); (2) quantify the odor-active compounds by several quantitative approaches and calculate odor activity values (OAVs); and (3) construct a recombination and omission model of aroma to validate the key odorants that contribute to the odor of Zhuyeqing.
2. Materials and Methods
2.1. The Samples
The samples were produced based on traditional processes (as shown in Figure 1) and were supplied by Xinghuacun Fenjiu Distillery Co., Ltd. (Fenyang, China). The 12 Chinese herbals were mixed according to the secret recipe (step 2), soaked in base Fen produced via solid-state brewing technology (step 1), and filtered to obtain a 65% botanical extract after 21 days (step 3). Subsequently, the plant extracts were added to aged Fen wine in specific proportions, followed by the processes of reducing alcohol, cooling, filtration, and blending. The final Zhuyeqing product was obtained after aging, bottling, and labeling.
The representative samples were confirmed by sensory evaluation using a sensory panel composed of 10 nationally certified Chinese liquor tasters from the Laboratory of Xinghuacun Fenjiu Distillery Co., Ltd. A typical Zhuyeqing and a base Fenjiu (500 mL in each bottle, all with alcohol content of 45% v/v) were selected to conduct the sensory and gas chromatography- olfactometry (GC-O) analyses. The samples (three bottles per sample) were stored at 25 °C in the dark before use.
2.2. Reagents and Chemicals
Dichloromethane (HPLC grade, ≥99.8%) and absolute ethanol (HPLC grade, ≥99.8%) were purchased from Dikma Technologies Inc. (Beijing, China). Dichloromethane was redistilled prior to use. Sodium chloride (NaCl) and anhydrous sodium sulfate (Na2SO4) were obtained from China National Pharmaceutical Group Co. (Shanghai, China). Ultrapure water was obtained using a Milli-Q purification system (Millipore, Bedford, MA, USA).
All analytical standards and internal standards (ISs) (as shown in Table S1) with at least 95% purity were obtained from Aladdin Biochemical Technology Co., Ltd. (Beijing, China), Sigma-Aldrich Co., Ltd. (Shanghai, China), Innochem Science & Technology Co., Ltd. (Beijing, China), Macklin Biochemical Technology Co., Ltd. (Shanghai, China), Toronto Research Chemicals Inc. (Toronto, ON, Canada), TMRM Quality Inspection Technology Co., Ltd. (Changzhou, China), and ZZBIO Co., Ltd. (Shanghai, China). A C7-C30 n-alkane mixture (Dikma Technologies Inc., Beijing, China) was used to determine the retention indices (RIs).
2.3. Sensory Analysis
A sensory assessment panel (10 members with 3 males and 7 females, 27–40 years old) from Xinghuacun Fenjiu Distillery Co., Ltd. (Fenyang, China) was employed to obtain the aroma profile. Le nez du vin (Jean Lenoir, France) with 54 standard odor descriptors and extracted solutions with 12 traditional Chinese herbs of Zhuyeqing were used to train the evaluation panel. The particular training sessions were performed according to previously published procedures [23] as follows:
At first, participants provided sensory descriptors autonomously. Later, the panelists engaged in a discussion to determine the full list of descriptors from which the most cited descriptors were selected. Ultimately, 11 descriptors of aroma were selected for evaluation. The assessors rated the perceived strength of each descriptor in the sample on a scale of 0 (very weak) to 6 (very strong). Table 1 lists the reference solutions containing the chemicals and extractions.
After training, the panelists judged the samples (base Fenjiu and Zhuyeqing) at 25 °C. The tested samples (~20 mL) were filled in glasses and labeled with three-digit codes.
2.4. Comparative Aroma Extract Dilution Analysis of Zhuyeqing and Base Fenjiu
2.4.1. Aroma Compound Extraction Methods
The liquid-liquid extraction (LLE) method was performed according to a published report [24], with minor modifications, to detect aroma compounds in Zhuyeqing and base Fenjiu. Each sample (50 mL) was diluted with 10% (v/v) ethanol and saturated with NaCl. Extraction was then carried out with 50 mL dichloromethane (CH2Cl2, 50 mL each time) for 5 min (repeated 3 times), and the collected organic phases were combined. Finally, anhydrous Na2SO4 was used to dry the organic phases overnight, and the sample was concentrated to 500 μL by nitrogen with a slow-flow stream and stored at −20 °C for use.
2.4.2. Gas Chromatography-Mass Spectrometry/Olfactometry (GC-MS/O) Analysis
In this study, a gas chromatograph (Agilent 7890A) connected to a mass-selective detector (Agilent 5977B) and an olfactometry system (ODP 2, Gerstel, Mülheim an der Ruhr, Germany) (GC-MS/O) were used. A DB-FFAP (60 m × 0.25 mm i.d., 0.25 μm, Agilent, Santa Clara, CA, USA) and a DB-5 (30 m × 0.25 mm i.d., 0.25 μm, Agilent, Santa Clara, CA, USA) columns were used for compounds separation and perform the GC-O analysis. In splitless mode, 1 μL of the sample was injected at 250 °C with a 5 min solvent delay. The oven temperature settings were as follows: start at 45 °C and hold for 2 min, with a 4 °C/min ratio to increase to 80 °C, keep for 1 min, then with a 5 °C/min ratio to increase to 150 °C, keep 2 min, finally, with a 10 °C/min ratio to increase to 230 °C, hold for 10 min at 230 °C (DB-FFAP) or start at 45 °C and keep for 2 min, with a 5 °C/min ratio to increase to 150 °C, keep for 3 min, then with a 10 °C/min ratio to increase to 320 °C, and keep for 10 min at 320 °C (DB-5). The carrier gas for the column was helium (purity > 99.999%) at a flow rate of 1.5 mL/min. The quadrupole ionization energy was set at 70 eV in electron ionization mode, the temperature of the ion source was 250 °C, and the range of mass scan was from m/z 40 to 350. The sniffer port temperature was set at 250 °C for the entire duration of the GC-O. GC-O analysis was performed as previously reported [2]. Three experienced students (two females and one male) formed a team from our laboratory at Jiangnan University to carry out GC-O analysis. First, the evaluators analyzed the extracts on the DB-FFAP and DB-5 columns and noted each compound’s retention time and odor descriptors. Then, they discussed the odor descriptors of the compounds, verified them with chemical standards, and memorized these odor characteristics. Finally, AEDA was used to identify the significance of the odorants.
2.4.3. Aroma Extract Dilution Analysis
Initially, AEDA was used to evaluate each aroma contribution detected by GC-MS/O and then to analyze the difference in aroma compounds between the Zhuyeqing and base Fenjiu samples.
The concentrated samples of Zhuyeqing and base Fenjiu were diluted in a 1:2 ratio with CH2Cl2 for AEDA. The flavor dilution (FD) value was defined as the highest dilution at which aroma compounds could be identified. Three experienced assessors (two females and one male) conducted the AEDA experiment. Each assessor repeated the analysis at least twice for each sample (including the original aroma extract and stepwise-diluted sample). The aroma components (Table 2) were identified by comparing the odor descriptors, mass spectrometry (MS), and retention indices (RIs) with those of real standards (Std). Referring to the modified Kovats method [25], the RIs of the odorants on the DB-FFAP and DB-5 columns were calculated from the retention times of the n-alkane (C7-C30) standards.
2.5. Quantitative Analysis of Aroma Compounds
Three instrumental analytical techniques with various extraction methods were used to establish targeted and accurate quantitative procedures based on the concentration ranges and the properties of the compounds. The standard curves of the horizontal coordinates were the concentration ratios of the target compound to the internal standard, and the vertical coordinate was the peak area ratio (Table 3). All calibration curves were within the linear range (R2 ≥ 0.99), and each sample was quantified in triplicate for accuracy.
2.5.1. Liquid-Liquid Microextraction Combined with Gas Chromatography-Mass Spectrometry (LLME-GC-MS)
Thirty-one compounds with strong polarity and high concentrations were quantified by LLME-GC-MS, as previously reported [23]. Each sample (8 mL) was diluted with 10% ethanol (v/v), saturated with NaCl, and 50 μL of mixed ISs was added. The mixed ISs containing 1-butanol-d10 (IS1, 500.00 mg/L), ethyl octanoate-d15 (IS2, 500.00 mg/L), (±)-linalool-d3 (IS3, 100.00 mg/L), l-menthol (IS4, 100.00 mg/L), 2-ethylbutyric acid (IS5, 300.00 mg/L), 2-methoxyphenol-d3 (IS6, 100.00 mg/L), benzyl alcohol-d7 (IS7, 100.00 mg/L) with final concentrations. Then, 5 mL of CH2Cl2 was added, vortexed at 800 rpm for 5 min (repeated 3 times), and concentrated to 1 mL as mentioned above in the LLE method. GC-MS was performed as previously described for DB-FFAP in Section 2.4.2.
2.5.2. Liquid-Liquid Extraction Combined with Gas Chromatography-Mass Spectrometry (LLE-GC-MS)
Thirty-one compounds were quantified using LLE-GC-MS. Each sample (50 mL) was diluted to 10% ethanol (v/v), saturated with NaCl, and mixed with 50 μL ISs identical to the LLME-GC-MS method. The extraction process using the LLE method is described in Section 2.4.1. The condition of GC-MS was performed as previously described on DB-FFAP in Section 2.4.2.
2.6. Determination of Odor Thresholds
In this study, the odor thresholds for most odorants were reported in published papers (in ethanol/water solution) to calculate the OAVs. Liu, et al. [26] confirmed that the measurements of odor thresholds determined by the ten-sample test (TST) and three-alternative forced-choice (3-AFC) method did not differ significantly or negligibly. Thus, using the TST method to determine the odor thresholds of the other odorants at 7 concentrations in 45% vol ethanol/water refers to a previously described method [27]. These compound’s odor thresholds were determined, including 2,6-dimethyl-2,4,6-octatriene, (2,2-diethoxyethyl) benzene, ethyl 3-hexenoate, 4-allylphenol, α-santalol, α-bisabolol, and β-bisabolol.
2.7. Aroma Recombination Tests and Omission Tests
Aroma recombination tests were carried out in a dilute alcohol solution (45% vol) and dearomatized Zhuyeqing (45% vol) and compared with the corresponding real Zhuyeqing. Aroma omission tests were conducted only in dearomatized Zhuyeqing and were compared with the aroma recombination model in dearomatized Zhuyeqing.
Table 3.
Information on the quantitative method, internal standard (IS), quantitative ions, and quantitative parameters of chemical standard curves, odor thresholds, concentrations, and OAVs of major aroma compounds (OAV ≥ 1) in Zhuyeqing and base Fenjiu samples.
Table 3.
Information on the quantitative method, internal standard (IS), quantitative ions, and quantitative parameters of chemical standard curves, odor thresholds, concentrations, and OAVs of major aroma compounds (OAV ≥ 1) in Zhuyeqing and base Fenjiu samples.
| Compounds | * Quantitative method | * IS | Quantitative ion (m/z) | Slope | Intercept | R2 | Odor Threshold (μg/L) | Concentrations (μg/L) | OAV | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Zhuyeqing | Base Fenjiu | Zhuyeqing | Base Fenjiu | ||||||||
| ethyl cinnamate | LLME | IS7 | 131 | 1.6352 | −0.0068 | 0.9940 | 0.70 [28] | 290.06 ± 16.88 | 0.00 ± 0.00 | 414.37 | <0.01 |
| β-damascenone | LLE | IS4 | 69 | 2.0132 | 0.0243 | 0.9935 | 0.10 [29] | 16.65 ± 1.35 | 28.53 ± 1.18 | 166.50 | 285.30 |
| ethyl octanoate | LLME | IS2 | 88 | 1.0479 | −0.0156 | 0.9997 | 12.90 [30] | 1113.92 ± 120.50 | 2398.83 ± 50.03 | 86.35 | 185.96 |
| ethyl hexanoate | LLE | IS2 | 88 | 0.3419 | 1.9693 | 0.9981 | 55.33 [29] | 3107.04 ± 234.61 | 7115.64 ± 174.68 | 56.15 | 128.60 |
| ethyl acetate | LLME | IS2 | 43 | 0.7268 | −0.0175 | 0.9989 | 32,600.00 [30] | 1,696,667.43 ± 230,056.14 | 2,048,863.56 ± 9325.78 | 52.05 | 62.85 |
| d-limonene | LLME | IS4 | 68 | 1.5852 | −0.2081 | 0.9993 | 34.00 [31] | 1302.01 ± 42.04 | 0.00 ± 0.00 | 38.29 | <0.01 |
| ethyl butanoate | LLME | IS2 | 71 | 0.6505 | −0.0021 | 0.9995 | 81.50 [29] | 2596.35 ± 268.14 | 3214.48 ± 75.96 | 31.86 | 39.44 |
| eugenol | LLME | IS6 | 164 | 0.9889 | 0.4755 | 0.9988 | 470.00 [31] | 13,617.04 ± 388.13 | 0.00 ± 0.00 | 28.97 | <0.01 |
| 3-methylbutyl acetate | LLE | IS2 | 43 | 2.8633 | 0.0002 | 0.9959 | 93.93 [29] | 1305.53 ± 58.25 | 578.79 ± 58.54 | 13.90 | 6.16 |
| β-myrcene | LLE | IS3 | 93 | 4.6837 | 0.0598 | 0.9932 | 4.90 [31] | 40.32 ± 3.15 | 4.53 ± 0.32 | 8.23 | 0.92 |
| ethyl pentanoate | LLE | IS2 | 85 | 0.8355 | −0.0044 | 0.9992 | 26.80 [30] | 144.23 ± 8.13 | 205.44 ± 7.14 | 5.38 | 7.67 |
| phenylacetaldehyde | LLME | IS7 | 91 | 1.3633 | −0.0008 | 0.9982 | 25.00 [32] | 114.59 ± 9.99 | 263.06 ± 4.88 | 4.58 | 10.52 |
| 2-methyl-1-propanol | LLME | IS1 | 43 | 0.4691 | −0.0082 | 0.9998 | 1045.47 [29] | 4666.62 ± 24.52 | 8787.20 ± 334.79 | 4.46 | 8.41 |
| 3-methylbutanoic acid | LLE | IS5 | 60 | 0.0669 | −0.0499 | 0.9995 | 28,300.00 [30] | 114,253.65 ± 5675.61 | 175,888.78 ± 1010.46 | 4.04 | 6.22 |
| bornyl acetate | LLME | IS4 | 95 | 1.0059 | −0.0020 | 0.9953 | 75.00 [31] | 210.51 ± 5.47 | 0.00 ± 0.00 | 2.81 | <0.01 |
| guaiacol | LLME | IS6 | 109 | 1.6209 | −0.0107 | 0.9993 | 9.50 [17] | 23.70 ± 0.39 | 61.39 ± 1.38 | 2.50 | 6.46 |
| 1-nonanol | LLE | IS1 | 56 | 7.6307 | −0.0557 | 0.9987 | 50.00 [33] | 125.23 ± 20.3 | 213.25 ± 26.12 | 2.50 | 4.27 |
| 3-methyl-1-butanol | LLME | IS1 | 55 | 0.5552 | 0.2263 | 0.9993 | 179,000.00 [30] | 396,642.77 ± 25,104.53 | 581,270.14 ± 22,380.84 | 2.22 | 3.25 |
| phenol | LLME | IS7 | 94 | 2.5256 | 0.0045 | 0.9979 | 30.00 [17] | 59.43 ± 4.05 | 34.23 ± 0.04 | 1.98 | 1.14 |
| ethyl 2-hydroxybutanoate | LLME | IS2 | 59 | 0.5596 | −0.0007 | 0.9976 | 800.00 [31] | 1441.25 ± 82.99 | 730.12 ± 18.59 | 1.80 | 0.91 |
| trans-isoeugenol | LLE | IS6 | 164 | −0.0210 | 0.1110 | 0.9930 | 22.54 [29] | 35.53 ± 1.62 | 0.00 ± 0.00 | 1.62 | <0.01 |
| ethyl 3-phenylpropanoate | LLME | IS7 | 104 | 0.1195 | 0.0001 | 0.9965 | 125.00 [30] | 192.95 ± 37.03 | 600.15 ± 2.11 | 1.54 | 4.80 |
| linalool | LLE | IS3 | 71 | 0.0294 | 0.4743 | 0.9918 | 30.00 [31] | 29.50 ± 0.27 | 0.00 ± 0.00 | 0.98 | <0.01 |
| (-)-myrtenol | LLE | IS4 | 79 | 19.5732 | −0.0910 | 0.9967 | 7.00 [31] | 6.34 ± 0.85 | 2.63 ± 0.06 | 0.91 | 0.38 |
| butanoic acid | LLME | IS5 | 60 | 1.2345 | −0.0081 | 0.9996 | 964.00 [30] | 613.63 ± 103.31 | 826.73 ± 23.23 | 0.64 | 0.86 |
| β-cyclocitral | LLE | IS4 | 137 | 0.0792 | 0.0001 | 0.9943 | 5.00 [31] | 2.65 ± 0.23 | 0.82 ± 0.12 | 0.53 | 0.16 |
| (+)-2-bornanone | LLME | IS4 | 95 | 1.2116 | 0.0010 | 0.9954 | 1470.00 [31] | 674.80 ± 29.53 | 0.00 ± 0.00 | 0.46 | <0.01 |
| acetic acid | LLME | IS5 | 43 | 0.7482 | −0.5177 | 0.9930 | 160,000.00 [30] | 71,164.03 ± 6150.23 | 70,146.27 ± 2227.35 | 0.44 | 0.44 |
| 4-ethylguaiacol | LLME | IS6 | 137 | 3.0432 | −0.0171 | 0.9993 | 123.00 [32] | 41.70 ± 0.91 | 96.50 ± 1.28 | 0.34 | 0.78 |
| nonanal | LLE | IS2 | 57 | 2.2321 | −0.0998 | 0.9954 | 122.45 [29] | 40.59 ± 3.46 | 37.64 ± 1.01 | 0.33 | 0.31 |
| 2-phenylethyl acetate | LLME | IS7 | 104 | 2.6561 | −0.0008 | 0.9986 | 200.00 [34] | 58.48 ± 7.37 | 197.95 ± 1.80 | 0.29 | 0.99 |
| 2-furanmethanol | LLME | IS7 | 98 | 0.6940 | −0.0072 | 0.9983 | 2000.00 [35] | 545.01 ± 59.82 | 35.42 ± 12.88 | 0.27 | 0.02 |
| hexanoic acid | LLME | IS5 | 60 | 1.4758 | −0.0786 | 0.9963 | 2520.00 [32] | 667.35 ± 58.42 | 804.02 ± 84.03 | 0.26 | 0.32 |
| vanillin | LLE | IS6 | 151 | 6.2539 | −0.0601 | 0.9984 | 438.52 [29] | 106.70 ± 0.03 | 3.14 ± 0.30 | 0.24 | 0.01 |
| 4-vinylguaiacol | LLE | IS6 | 150 | 0.9611 | −0.0080 | 0.9989 | 209.30 [29] | 47.27 ± 0.19 | 4.96 ± 0.27 | 0.23 | 0.02 |
| creosol | LLME | IS6 | 138 | 1.6221 | −0.0048 | 0.9988 | 315.00 [32] | 65.23 ± 0.74 | 90.44 ± 3.17 | 0.21 | 0.29 |
| α-santalol | LLE | IS4 | 69 | 0.1410 | −0.0006 | 0.9936 | 1193.25 a | 138.00 ± 0.12 | 0.00 ± 0.00 | 0.12 | <0.01 |
| benzaldehyde | LLME | IS7 | 106 | 0.9835 | 0.0003 | 0.9984 | 515.00 [36] | 56.25 ± 7.01 | 95.94 ± 4.57 | 0.11 | 0.19 |
| α-ionone | LLE | IS4 | 121 | 1.3452 | 0.0016 | 0.9942 | 13.70 [37] | 1.54 ± 0.15 | 0.00 ± 0.00 | 0.11 | <0.01 |
| geraniol | LLE | IS4 | 69 | 0.0942 | −0.0005 | 0.9931 | 80.00 [38] | 7.35 ± 0.46 | 4.32 ± 0.02 | 0.09 | 0.05 |
| nerolidol | LLE | IS3 | 69 | 1.0404 | −0.0109 | 0.9990 | 250.00 [31] | 21.03 ± 1.93 | 7.37 ± 0.79 | 0.08 | 0.03 |
| ethyl 2-phenylacetate | LLME | IS7 | 91 | 2.5002 | −0.0005 | 0.9983 | 407.00 [30] | 31.97 ± 2.02 | 70.07 ± 1.55 | 0.08 | 0.17 |
| (2,2-diethoxyethyl) benzene | LLME | IS7 | 103 | 1.1973 | −0.0003 | 0.9984 | 995.50.00 a | 67.37 ± 6.18 | 209.08 ± 3.72 | 0.07 | 0.21 |
| 2-phenylethanol | LLME | IS7 | 91 | 2.7553 | 0.4170 | 0.9933 | 40,000.00 [34] | 2368.18 ± 40.49 | 3687.14 ± 131.73 | 0.06 | 0.09 |
| α-bisabolol | LLE | IS4 | 109 | 0.2030 | −0.0026 | 0.9825 | 756.42.00 a | 44.50 ± 0.27 | 0.00 ± 0.00 | 0.06 | <0.01 |
| furfural | LLME | IS7 | 96 | 0.7745 | 0.0093 | 0.9967 | 39,000.00 [31] | 1838.44 ± 10.45 | 4220.33 ± 171.02 | 0.05 | 0.11 |
| p-cresol | LLE | IS6 | 107 | 2.2287 | −0.0035 | 0.9995 | 166.97 [29] | 8.31 ± 0.26 | 9.56 ± 0.42 | 0.05 | 0.06 |
| β-caryophyllene | LLE | IS4 | 93 | 0.0163 | 0.0055 | 0.9876 | 150.00 [31] | 6.20 ± 0.72 | 0.65 ± 0.15 | 0.03 | <0.01 |
| γ-terpinene | LLE | IS4 | 93 | 2.5737 | 0.0970 | 0.9939 | 1000.00 [31] | 33.90 ± 3.23 | 0.00 ± 0.00 | 0.03 | <0.01 |
| ethyl nonanoate | LLE | IS2 | 88 | 1.2116 | 0.0084 | 0.9982 | 3150.00 [30] | 70.87 ± 6.67 | 204.84 ± 6.76 | 0.02 | 0.07 |
| ethyl 3-hexenoate | LLE | IS7 | 69 | 2.4232 | −0.0094 | 0.9982 | 289.75 a | 8.43 ± 0.89 | 5.42 ± 0.47 | 0.03 | 0.02 |
| isoamyl lactate | LLME | IS2 | 45 | 0.4669 | 0.0188 | 0.9971 | 131,703.40 [33] | 1932.33 ± 133.66 | 3402.51 ± 251.35 | 0.01 | 0.03 |
| 2-nonanol | LLE | IS1 | 45 | 0.6103 | 0.0023 | 0.9998 | 75.00 [39] | 0.68 ± 0.12 | 2.87 ± 0.42 | 0.01 | 0.04 |
| 4-allylphenol | LLE | IS6 | 134 | 1.6081 | 0.0112 | 0.9987 | 2934.70 a | 22.51 ± 0.82 | 0.00 ± 0.00 | 0.01 | <0.01 |
| β-bisabolol | LLE | IS4 | 82 | 0.1757 | 0.0019 | 0.9939 | 1948.01 a | 19.50 ± 1.20 | 0.00 ± 0.00 | 0.01 | <0.01 |
| β-ionone | LLME | IS4 | 177 | 2.0709 | 0.0001 | 0.9993 | 963.00 [40] | 6.25 ± 0.47 | 0.00 ± 0.00 | 0.01 | <0.01 |
| terpinen-4-ol | LLE | IS4 | 71 | 0.0148 | 0.0452 | 0.9968 | 1540.00 [16] | 7.82 ± 0.24 | 0.45 ± 0.12 | <0.01 | <0.01 |
| benzyl alcohol | LLME | IS7 | 108 | 1.1002 | −0.0018 | 0.9950 | 40,900.00 [28] | 61.06 ± 6.62 | 76.97 ± 4.15 | <0.01 | <0.01 |
| 2,3,5,6-tetramethylpyrazine | LLME | IS7 | 136 | 2.3661 | 0.0023 | 0.9978 | 80,073.16 [29] | 13.30 ± 2.80 | 60.70 ± 4.30 | <0.01 | <0.01 |
| isoamyl isovalerate | LLE | IS7 | 70 | 0.0469 | −0.0031 | 0.9908 | 1000.00 [31] | 3.02 ± 0.21 | 1.59 ± 0.05 | <0.01 | <0.01 |
| caryophyllene oxide | LLE | IS4 | 79 | 0.4438 | 0.1134 | 0.9950 | 410.00 [31] | 0.62 ± 0.09 | 0.00 ± 0.00 | <0.01 | <0.01 |
| 2,6-dimethyl-2,4,6-octatriene | LLE | IS3 | 121 | 0.0616 | 0.0035 | 0.9921 | 2137.24 a | 2.05 ± 0.07 | 0.00 ± 0.00 | <0.01 | <0.01 |
* Quantitative method: “LLME” stands for liquid-liquid microextraction with gas chromatography-mass spectrometry; “LLE” stands for liquid-liquid extraction with gas chromatography-mass spectrometry. * IS: the internal standard used to quantitate the compounds: 1-butanol-d10 (IS1), ethyl octanoate-d15 (IS2), (±)-linalool-d3 (IS3), l-menthol (IS4), 2-ethylbutyric acid (IS5), 2-methoxyphenol-d3 (IS6), benzyl alcohol-d7 (IS7). a Odor thresholds were calculated in 45% ethanol/water detected in this study.
2.7.1. Aroma Recombination Tests by Descriptive Analysis
A dilute alcohol solution was prepared using ethanol and microfiltered water to obtain an ethanol level of 45% vol as a model solution. Following the methodology outlined in [41], dearomatized Zhuyeqing was prepared by evaporation using a Rotavapor (RV 10 digital V Rotary Evaporators, IKA, Marseille, Germany) with a bath temperature of 20 °C to two-thirds of its original volume. The evaporated liquid was then mixed with ethanol and microfiltered water to match the volume and alcohol concentration of the original Zhuyeqing. The dearomatized Zhuyeqing was further treated with 5 g/L LiChrolut EN resin (40–120 μm) and stirred for 12 h. The headspace-gas chromatography-mass spectrometry (HS-GC-MS) test confirmed that the resulting dearomatized Zhuyeqing did not contain any trace of the compounds included in this study. The sensory test confirmed that dearomatized Zhuyeqing had a very low-intensity neutral aroma that could barely be perceived.
The aroma compounds with OAVs ≥ 1 in Zhuyeqing were added to the model solution, dearomatized Zhuyeqing based on their actual concentrations (Table 3) to create a recombination model, and then compared with the original features of real Zhuyeqing. The simulated aroma model and real Zhuyeqing samples were evaluated by a panel of 10 assessors, as mentioned in the sensory analysis (Section 2.3). Assessors scored the perception strength of the seven aroma profiles of Zhuyeqing from 0 (very weak) to 6 (very strong).
2.7.2. Omission Tests by Discrimination Analysis
According to a previously published method [2], 22 omission (Table 4) tests were prepared to ascertain the significance of these compounds using a triangle test. Three samples (~20 mL) were simultaneously placed in glasses for evaluation, containing one omission model and two recombination models. The 10 judges were required to identify the sample with the most noticeable perceptual difference from the other two. Each test was repeated in triplicate, and the results were statistically analyzed.
2.8. Statistical Analysis
Statistical analyses were carried out using SPSS (Chicago, IL, USA) version 26.0, for Windows. The aroma profiling data were assessed by analysis of variance (ANOVA) with SPSS.
3. Results and Discussion
3.1. Sensory Analysis of Zhuyeqing and Base Fenjiu Samples
Aroma profiling analyses were performed to preliminarily assess the overall difference in aroma profiles between Zhuyeqing and base Fenjiu, and 11 odor features that agreed with the sensory group were used. The results shown in Figure 2a reveal significant differences between the Zhuyeqing and base Fenjiu samples. The general aroma profiles of Zhuyeqing were richer than those of the base Fenjiu. Statistical analysis showed that the medicinal, woody, smokey, sweet, grass, grain, fruit, and floral aroma features were significantly different (p < 0.01) between the two samples. Of these, medicinal, woody, and smokey aromas were unique aroma characteristics of Zhuyeqing compared to the base Fenjiu, and sweet intensities were higher in Zhuyeqing, but grain, grass, floral, and fruit intensities were higher in base Fenjiu. To further explain the factors causing the differences in aroma between Zhuyeqing and the base Fenjiu, GC-O was used to study the odor differences in these two samples.
3.2. Identification of Aroma-Active Compounds in Zhuyeqing and Base Fenjiu Samples
The aroma extracts of Zhuyeqing and base Fenjiu were compared by AEDA to obtain the FD value of each aroma compound that could be detected by GC-O (Figure S1). One hundred and two odorants were confirmed by comparing their RIs on DB-FFAP and DB-5 columns, odor characteristics, and/or mass spectra with reference compounds. These substances included 27 esters, 24 terpenes, 14 alcohols, 12 phenols, 8 aldehydes, six acids, two lactones, three furans, two ketones, one pyrazine, and three other compounds (Table 2).
In Zhuyeqing, 93 odorants were detected, and 64 odorants had FD ≥ 32. The highest FD factors (FD ≥ 1024) were obtained for eugenol (92, clove), 4-vinylguaiacol (94, smokey), and trans-isoeugenol (96, clove). In addition, ethyl octanoate (35, pear), β-damascenone (73, honey, floral, apple-like), ethyl cinnamate (89, cinnamon), α-santalol (98, woody), vanillin (101, vanillin), acetic acid (38, vinegar), furfural (40, almond), linalool (46, floral), 3-methylbutanoic acid (59, sour), geraniol (74, rose), and β-ionone (81, orris) had higher FD factors (FD ≥ 256) (Table 2). In the base Fenjiu, a total of 73 odorants were detected, and 27 odorants had FD ≥ 32. Among these compounds, ethyl butanoate (11, pineapple), ethyl hexanoate (22, fruity), and β-damascenone (73, honey, floral, apple-like) displayed the highest FD of 512, followed by 2-phenylethyl acetate (72, floral), and ethyl 3-phenylpropanoate (78, floral). These odorants may be the main ingredients responsible for the distinctive aroma characteristics of Zhuyeqing and base Fenjiu. Among all odorants with FD ≥ 32, 22 odorants were detected only in Zhuyeqing, and most of them were terpenes and phenols, such as eugenol (FD = 2048), trans-isoeugenol (FD = 1024), α-santalol (FD = 512), linalool (FD = 256), and β-ionone (FD = 256).
Aroma profiling analyses of Zhuyeqing and base Fenjiu showed that medicinal, smokey, woody, and sweet aromas were developed after adding the infusion extracts of 12 traditional Chinese herbs to the base Fenjiu, creating a more complex flavor. In addition to the previously published important compounds in FDS rich in herbal extracts [15,16,17,40], this part of the study newly detected some aroma compounds that may be due to extracts with different types of herbals. These included ethyl 3-hexenoate (27, fruity), 2,6-dimethyl-2,4,6-octatriene (30, herbal), β-cyclocitral (55, sweet), endo-borneol (66, woody), geranyl acetate (69, rose), geraniol (74, rose), ethyl cinnamate (89, cinnamon), β-bisabolol (90, citrus), 4-vinylguaiacol (94, smokey), and α-bisabolol (95, floral).
3.3. Quantification of Aroma Compounds and OAV Analysis
Except for ethyl dl-2-hydroxycaproate and ethyl 2-hydroxy-3-methylbutanoate, which could not find standards, a total of 62 aroma compounds (FD > 32) were quantified using various quantification methods. An equal amount of internal standards for calibration was added during the extraction of the aroma compounds, and the construction of standard curves to compensate for the loss of compounds in the course of extraction and to ensure the accuracy of the quantitative results. Quantitative results combined with odor activity values (OAV, the ratio between concentration and odor threshold) of each volatile component were used to explain the causes of the olfactory differences and to verify the contributions of these aroma compounds to the aromas of the Zhuyeqing and base Fenjiu samples (Table 3). Quantitative analysis showed that ethyl acetate had the highest concentrations in the Zhuyeqing and base Fenjiu samples (>1.60 and >2.00 g/L, respectively), followed by 3-methyl-1-butanol (397 and 581 mg/L, respectively), and 2-methyl-1-propanol (114 and 176 mg/L, respectively).
Among the 62 aroma compounds quantified, only 22 were further confirmed as important aromas in Zhuyeqing, with OAVs ≥ 1.00. This difference may be the result of two reasons: (1) FD was obtained from the air, and the odorant thresholds in the air were lower than those in the other matrixes; and (2) the thresholds listed in Table 3 were derived either from Baijiu, Whiskey, or ethanol solution systems, and no literature has reported these odorant thresholds in the Zhuyeqing matrix.
Ethyl cinnamate, β-damascenone, ethyl octanoate, ethyl acetate, and ethyl hexanoate had the highest OAVs of ≥50.00. d-limonene, ethyl butanoate, eugenol, and 3-methylbutyl acetate had OAVs > 10.00. The compound with the highest OAV of 414.37 was ethyl cinnamate, followed by β-damascenone (OAV = 166.50) and ethyl octanoate (OAV = 86.35); their OAVs were much higher than those of other compounds. Ethyl cinnamate (FD = 512), β-damascenone (FD = 512), and ethyl octanoate (FD = 512) also had higher FD values in GC-O analysis. Thus, ethyl cinnamate, β-damascenone, and ethyl octanoate should be regarded as important aroma compounds in Zhuyeqing. Ethyl cinnamate with cinnamon, sweet, and fruity notes was confirmed as a key aroma in Huangjiu [42]. β-damascenone, which contributes to the fruity character (apple, honey, citrus, rose, pear), was demonstrated to be a key food odorant in many natural foods [43], such as grapefruit juice [44], wine [45], flavored wine [4] and Baijiu [30]. Dunkel et al. [43] concluded that ethyl octanoate is a key odorant in all alcoholic beverages. This compound is also a key aroma in Zhuyeqing. In addition, eugenol, trans-isoeugenol, ethyl hexanoate, d-limonene, ethyl butanoate, and 3-methylbutyl acetate had higher FDs ≥ 128, and all of their OAVs ≥ 1.00. These compounds could also be important aroma compounds in Zhuyeqing and might give its possible characteristics, such as sweetness, fruit, and floral. Eugenol and trans-isoeugenol are mainly derived from clove, emitting smokey, clove, and spice aromas, which are also important odorants in Chinese JingJiu [17] and Wujiapi [16]. The use of 12 Chinese herbs also brings some flavors that are different from common liquor samples and resulted in some compounds with high FD and low OAV, such as geraniol (FD = 256, OAV < 1), β-caryophyllene (FD = 62, OAV < 1), caryophyllene oxide (FD = 32, OAV < 1), 2-furanmethanol (FD = 128, OAV < 1), and nerolidol (FD = 32, OAV < 1).
Similarly, sixteen important odorants in base Fenjiu had OAVs of ≥1.00, and β-damascenone, ethyl octanoate, ethyl hexanoate, ethyl acetate, and ethyl butanoate had the highest OAVs of ≥10.00. Phenylacetaldehyde, 3-methylbutanoic acid, 2-methyl-1-propanol, guaiacol, 3-methylbutyl acetate, ethyl 3-phenylpropanoate, 1-nonanol, 3-methyl-1-butanol, ethyl decanoate, and phenol had OAVs ≥ 1.00. β-damascenone (OAV = 287.46), ethyl octanoate (OAV = 185.96), and ethyl hexanoate (OAV = 128.6) were the most important key aroma compounds with higher FD values in GC-O analysis. All sixteen aroma compounds (OAV ≥ 1.00) in the base Fenjiu had higher OAVs than those in the Zhuyeqing (except 3-methylbutyl acetate). Therefore, these compounds in Zhuyeqing may be derived from the base Fenjiu.
Only seven aroma compounds, ethyl cinnamate, d-limonene, eugenol, 3-methylbutyl acetate, β-myrcene, bornyl acetate, and ethyl 2-hydroxybutanoate, had higher OAVs (>1) in Zhuyeqing than in the base Fenjiu.
3.4. Aroma Recombination
To validate the aroma contributions of odorants determined by AEDA and OAV analysis, compounds with OAV ≥ 1 to Zhuyeqing were recombined in dearomatized Zhuyeqing (45% vol ethanol) and model solution (45% vol ethanol) and compared with the corresponding real Zhuyeqing by trained panelists.
As shown in Figure 2b, compared to the original Zhuyeqing, there were only minor differences between the recombinant model and the original sample regarding the seven aroma descriptors (except medicinal). The aroma strength of the dearomatized Zhuyeqing reconstitution was more similar to that of the model solution reconstitution, suggesting that the flavor profile of the dearomatized Zhuyeqing reconstitution was simulated more successfully than that of the model solution reconstitution. Therefore, the overall aroma perception of Zhuyeqing can be affected by its matrix. In addition, the intensity of the medicinal flavor was still significantly different from that of the original Zhuyeqing. This may be due to the composition complexity of FDS, making overlapping chromatographic peaks that lead to missing key compounds. Thus, the medicinal aroma characteristic will be further investigated in the next study.
3.5. Omission Tests
To investigate the potential contributions of these odorants, 22 omitted models were created (Table 4). The differences between each of the omitted models and the full model were compared by a triangle test. The results revealed that M1 (esters), M2 (terpenes), and M3 (phenols) were the key groups in Zhuyeqing. All the assessors could detect the difference when missing these groups, indicating their highly significant influence on the overall aroma. However, only four of the ten evaluators could correctly distinguish the omission of M4 (all acids) and M5 (all alcohols). Perhaps the presence of abundant terpenes and phenols affects their perception and makes them insignificant in the overall profile.
When M1-1 (ethyl cinnamate), M1-2 (ethyl octanoate), and M1-3 (ethyl acetate) with fruity notes were omitted, very high significance was observed in the evaluation. M1-6 (3-methylbutyl acetate) showed a significant difference. M2-1 (β-damascenone), with honey, floral, and apple-like notes, was the most important terpene with a highly significant influence on the overall aroma. M2-4 (bornyl acetate), with woody, herbal, and cool notes, was an important odor that affected the overall aroma with highly significant differences. M3-1 (eugenol), with sweet, clove, and spice notes, was the most important phenol with a highly significant influence on the overall aroma and medicinal characterization. M3-2 (guaiacol) had a highly significant influence on the medicinal aroma. However, when the remaining compounds were omitted, no significant differences were observed. This means that these compounds were not the most important aroma contributors or they affected the overall profile of the odor interaction.
Zhuyeqing is a very complex system. Our current research has enriched the flavor theoretical system of Zhuyeqing, even the Chinese traditional flavored distilled liquor. The medicinal character of Zhuyeqing will be a direction for our future research on Zhuyeqing. In addition, the aroma characteristics of Zhuyeqing during aging remain mysterious and need to be investigated.
4. Conclusions
This study provides a preliminary understanding of the aroma compounds in Zhuyeqing and Fenjiu. Sixty-four odorants (FD > 32) were confirmed by GC-O. Using various quantification methods and calculating the OAVs, 22 odorants had OAVs > 1. These compounds were reconstituted in the model solution (45% vol ethanol) and dearomatized Zhuyeqing (45% vol ethanol), and the overall aroma characteristics of Zhuyeqing were better reconstituted in the dearomatized Zhuyeqing. Recombination and omission model sensory studies confirmed that the compounds of esters, terpenes, and phenol groups have an important influence on the overall aroma of Zhuyeqing. Among these, ethyl cinnamate, ethyl octanoate, ethyl acetate, β-damascenone, and eugenol were confirmed to be the key aroma components of Zhuyeqing.
In this paper, the matrix of Zhuyeqing had a very important effect on its aroma, and the medicinal character intensity of Zhuyeqing was still significantly different from that of the original Zhuyeqing.
Supplementary Materials
The following supporting information can be downloaded at https://www.mdpi.com/article/10.3390/foods14030344/s1, Figure S1: FD chromatograms obtained by AEDA of the extracts of Zhuyeqing and base Fenjiu samples, all odorants are displayed, and numbering corresponds to that in Table 1; Table S1: information of analytical standards.
Author Contributions
L.W.: conceptualization, methodology, validation, formal analysis, data curation, writing—original draft, writing—review and editing, visualization. Y.H.: resources, project administration. X.Z.: formal analysis, project administration. X.G.: data curation, resources. Y.X.: supervision, project administration, resources, funding acquisition. Q.W.: supervision, project administration, resources, investigation. K.T.: conceptualization, supervision, project administration, resources, investigation. All authors have read and agreed to the published version of the manuscript.
Funding
This research was supported by the National Key R&D Program of China (No. 2022YFD2101200), Postgraduate Research & Practice Innovation Program of Jiangsu Provence (KYCX23_2499), and Program of Science and Technology Plan of Lvliang Shanxi (2021SHFZ-1-02) and (2023SHFZ03).
Institutional Review Board Statement
The research was reviewed and licensed by the Jiangnan University IRB (JNU20220901IRB19, approval 1 September 2022), and informed permission was obtained from each subject before they participated in this study.
Informed Consent Statement
Informed consent was obtained from all subjects involved in the study.
Data Availability Statement
The original contributions presented in this study are included in the article/Supplementary Materials. Further inquiries can be directed to the corresponding author.
Acknowledgments
We gratefully thank the Laboratory of Brewing Microbiology and Applied Enzymology at Jiangnan University, who provided much help in this study, particularly in the GC-O and AEDA analyses. We also thank the sensory evaluation panel of the Master Studio of Fengxian Wang and Jiansheng Liu at Shanxi Xinghuacun Fenjiu Distillery Co., Ltd. for their help with the sensory evaluation.
Conflicts of Interest
Author Lihua Wang, Ying Han, Xing Zhang, and Xiaojuan Gao were employed by Shanxi Xinghuacun Fenjiu Distillery Co., Ltd. They participated in the project administration and resources in the study. The role of the company was to provide experimental samples. The involvement of the authors from the company had no effect on the objectivity and authenticity of the study. This study will not be used for future product development. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as potential conflicts of interest.
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Figure 1.
Process diagram for the production of Zhuyeqing.
Figure 2.
(a) Aroma profiles of Zhuyeqing and base Fenjiu samples; (b) Aroma profile analyses of Zhuyeqing and the complete aroma reconstitution model in model solution (45% vol ethanol) and dearomatized Zhuyeqing (45% vol ethanol). “*”, “**”, and “***” indicate significance at p < 0.05, 0.01, and 0.001, respectively.
Figure 2.
(a) Aroma profiles of Zhuyeqing and base Fenjiu samples; (b) Aroma profile analyses of Zhuyeqing and the complete aroma reconstitution model in model solution (45% vol ethanol) and dearomatized Zhuyeqing (45% vol ethanol). “*”, “**”, and “***” indicate significance at p < 0.05, 0.01, and 0.001, respectively.
Table 1.
Definitions and references of aroma attributes.
| No. | Aroma | Definition | Reference (in 45% v/v Ethanol/Water) |
|---|---|---|---|
| 1 | medicinal | aroma of herbs | ethyl 2-hydroxybutanoate (50 mg/L) |
| 2 | sweet | aroma similar to honey and sweet fruits | β-damascenone (100 μg/L) |
| 3 | alcoholic | aromas presented by alcohols | 45% v/v ethanol/water |
| 4 | woody | like wood | extraction of Muxiang |
| 5 | floral | similar to the aroma of florals | extraction of Juhua |
| 6 | fruity | aroma like ripe fruits | ethyl acetate (2 g/L) and ethyl hexanoate (10 mg/L) |
| 7 | smokey | similar to smoke | sotolon (1 mg/L) |
| 8 | grain | aroma obtained by fermenting and distilling sorghum, rice, and wheat. | cooked sorghum |
| 9 | acid | aroma presented by volatile acidic components | acetic acid (1 g/L) |
| 10 | grass | grass-like aroma | hexanal (2 mg/L) |
| 11 | bitter almond | aroma presented by bitter almond | furfural (50 mg/L) |
Table 2.
The FD factors of the aroma compounds in Zhuyeqing and base Fenjiu.
| No a | CAS | Compounds b | RI c | RT | Odor Descriptor d | Identification | FD Factor e | ||
|---|---|---|---|---|---|---|---|---|---|
| FFAP | DB-5 | DB-5 | Zhuyeqing | Base Fenjiu | |||||
| 1 | 75-07-0 | acetaldehyde | 700 | 415 | 1.008 | pungent, ethereal | MS, RI, Odor, Std | 4 | 8 |
| 2 | 123-38-6 | propanal | 810 | 515 | 1.050 | pungent, ethereal | MS, RI, Odor, Std | 4 | 8 |
| 3 | 123-72-8 | butanal | 870 | 545 | 1.065 | fresh, aldehydic | MS, RI, Odor, Std | 16 | 8 |
| 4 | 141-78-6 | ethyl acetate | 870 | 612 | 1.453 | pineapple, fruity | MS, RI, Odor, Std | 64 | 32 |
| 5 | 105-57-7 | 1,1-diethoxyethane | 898 | 730 | 2.117 | fruity | MS, RI, Odor, Std | 2 | 64 |
| 6 | 105-37-3 | ethyl propanoate | 965 | 737 | 2.241 | fruity | MS, RI, Odor, Std | 1 | 32 |
| 7 | 431-03-8 | 2,3-butanedione | 989 | nd | nd | buttery | MS, RI, Odor, Std | n.d | 1 |
| 8 | 97-62-1 | ethyl 2-methylpropanoate | 998 | 760 | 2.725 | floral, fruity | MS, RI, Odor, Std | 8 | 16 |
| 9 | 78-92-2 | 2-butanol | 1005 | 615 | 1.523 | fruity | MS, RI, Odor, Std | n.d | 32 |
| 10 | 71-23-8 | propanol | 1015 | 575 | 1.125 | alcoholic, plant | MS, RI, Odor, Std | n.d | 16 |
| 11 | 105-54-4 | ethyl butanoate | 1035 | 791 | 3.362 | pineapple, fruity | MS, RI, Odor, Std | 128 | 512 |
| 12 | 108-64-5 | ethyl 3-methylbutanoate | 1075 | 855 | 4.681 | sweet, fruity | MS, RI, Odor, Std | n.d | 16 |
| 13 | 78-83-1 | 2-methyl-1-propanol | 1086 | 705 | 1.746 | mellow, nail polish | MS, RI, Odor, Std | 32 | 16 |
| 14 | 66-25-1 | hexanal | 1100 | 785 | 3.263 | green | MS, RI, Odor, Std | n.d | 8 |
| 15 | 71-36-3 | butanol | 1110 | 670 | 1.654 | alcoholic | MS, RI, Odor, Std | n.d | 1 |
| 16 | 123-92-2 | 3-methylbutyl acetate | 1122 | 867 | 4.956 | banana | MS, RI, Odor, Std | 128 | 64 |
| 17 | 539-82-2 | ethyl pentanoate | 1134 | 894 | 5.508 | fruity, strawberry | MS, RI, Odor, Std | 128 | 32 |
| 18 | 123-35-3 | β-myrcene | 1161 | 987 | 7.930 | grassy, woody | MS, RI, Odor, Std | 128 | n.d |
| 19 | 137-32-6 | 2-methyl-1-butanol | 1190 | 743 | 2.363 | alcoholic | MS, RI, Odor, Std | 8 | 16 |
| 20 | 123-51-3 | 3-methyl-1-butanol | 1198 | 748 | 2.465 | banana, ether | MS, RI, Odor, Std | 64 | 16 |
| 21 | 5989-27-5 | d-limonene | 1203 | 1024 | 8.946 | orange, lemon | MS, RI, Odor, Std | 128 | n.d |
| 22 | 123-66-0 | ethyl hexanoate | 1234 | 995 | 8.197 | sweet, fruity, pineapple | MS, RI, Odor, Std | 128 | 512 |
| 23 | 71-41-0 | pentanol | 1240 | 766 | 2.851 | fruity, alcoholic | MS, RI, Odor, Std | n.d | 2 |
| 24 | 99-85-4 | γ-terpinene | 1244 | 1059 | 9.952 | gasoline, turpentine | MS, RI, Odor, Std | 128 | n.d |
| 25 | 659-70-1 | isoamyl isovalerate | 1294 | nd | nd | sweet, fruity, green, apple | MS, RI, Odor, Std | 32 | 2 |
| 26 | 7789-92-6 | 1,1,3-triethoxypropane | 1298 | 1075 | 10.401 | fruity | MS, RI, Odor, Std | 8 | 4 |
| 27 | 2396-83-0 | ethyl 3-hexenoate | 1303 | nd | nd | fruity, pineapple, green, candy | MS, RI, Odor, Std | 64 | 1 |
| 28 | 513-86-0 | acetoin | 1349 | 731 | 2.149 | creamy, buttery | MS, RI, Odor, Std | 16 | 2 |
| 29 | 111-27-3 | hexanol | 1366 | 859 | 4.763 | ethereal, fusel | MS, RI, Odor, Std | 2 | 4 |
| 30 | 673-84-7 | 2,6-dimethyl-2,4,6-octatriene | 1372 | nd | nd | spices, nutty, skin, peppery, herbal | MS, RI, Odor, Std | 32 | n.d |
| 31 | 97-64-3 | ethyl lactate | 1382 | 815 | 3.862 | fatty, pineapple | MS, RI, Odor, Std | 8 | 4 |
| 32 | 124-19-6 | nonanal | 1393 | 1101 | 11.133 | citrus-like, soapy | MS, RI, Odor, Std | 128 | 32 |
| 33 | 3391-86-4 | 1-octene-3-ol | 1410 | 980 | 7.745 | soapy, mushroom | MS, RI, Odor, Std | n.d | 1 |
| 34 | 52089-54-0 | ethyl 2-hydroxybutanoate | 1427 | 900 | 5.621 | floral, fruity | MS, RI, Odor, Std | 128 | 64 |
| 35 | 106-32-1 | ethyl octanoate | 1434 | 1194 | 13.756 | pear, lychee | MS, RI, Odor, Std | 512 | 256 |
| 36 | 2441-06-7 | ethyl 2-hydroxy-3-methylbutanoate | 1441 | 959 | 7.197 | pineapple-like | MS, RI, Odor, Std | 64 | 32 |
| 37 | 616-09-1 | propyl lactate | 1451 | nd | nd | winey, yogurt, milky | MS, RI, Odor, Std | 1 | 4 |
| 38 | 64-19-7 | acetic acid | 1459 | 696 | 1.703 | vinegar | MS, RI, Odor, Std | 256 | 64 |
| 39 | 585-24-0 | isobutyl lactate | 1471 | 978 | 7.693 | buttery, fruity, caramellic | MS, RI, Odor, Std | 8 | 8 |
| 40 | 98-01-1 | furfural | 1473 | 822 | 3.998 | almond | MS, RI, Odor, Std | 256 | 8 |
| 41 | 1124-11-4 | 2,3,5,6-tetramethylpyrazine | 1492 | 1085 | 10.676 | roasted, nutty | MS, RI, Odor, Std | 32 | n.d |
| 42 | 628-99-9 | 2-nonanol | 1514 | nd | nd | cucumber | MS, RI, Odor, Std | 32 | 64 |
| 43 | 464-49-3 | (+)-2-bornanone | 1519 | 1138 | 12.202 | camphoraceous | MS, RI, Odor, Std | 32 | n.d |
| 44 | 100-52-7 | benzaldehyde | 1532 | 951 | 6.967 | almond | MS, RI, Odor, Std | 32 | 8 |
| 45 | 123-29-5 | ethyl nonanoate | 1534 | 1294 | 16.394 | fruity, grassy, grape | MS, RI, Odor, Std | 64 | 32 |
| 46 | 78-70-6 | linalool | 1542 | 1099 | 11.078 | floral, woody | MS, RI, Odor, Std | 256 | n.d |
| 47 | 6946-90-3 | ethyl dl-2-hydroxycaproate | 1545 | 1055 | 9.848 | floral, herbal | MS, RI, Odor, Std | 128 | 32 |
| 48 | 79-09-4 | propionic acid | 1548 | 700 | 1.719 | fruity, creamy | MS, RI, Odor, Std | 16 | 8 |
| 49 | 76-49-3 | bornyl acetate | 1569 | 1282 | 16.043 | woody, herbal | MS, RI, Odor, Std | 32 | n.d |
| 50 | 19329-89-6 | isoamyl lactate | 1571 | 1064 | 10.091 | fruity, creamy, nutty | MS, RI, Odor, Std | 128 | 64 |
| 51 | 513-85-9 | 2, 3-butanediol | 1579 | 796 | 3.463 | fruity, creamy | MS, RI, Odor, Std | n.d | 1 |
| 52 | 620-02-0 | 5-methylfurfural | 1585 | 972 | 7.532 | sweet, caramel | MS, RI, Odor, Std | 16 | 2 |
| 53 | 87-44-5 | β-caryophyllene | 1598 | 1418 | 19.608 | woody, spices, citrus | MS, RI, Odor, Std | 64 | n.d |
| 54 | 562-74-3 | terpinen-4-ol | 1600 | 1173 | 13.181 | woody, earthy, peppery | MS, RI, Odor, Std | 128 | n.d |
| 55 | 432-25-7 | β-cyclocitral | 1624 | nd | nd | herbal, clean, sweet, damascone | MS, RI, Odor, Std | 32 | n.d |
| 56 | 107-92-6 | butanoic acid | 1631 | 894 | 5.491 | cheesy, creamy | MS, RI, Odor, Std | 128 | 32 |
| 57 | 110-38-3 | ethyl decanoate | 1638 | 1392 | 19.036 | grape | MS, RI, Odor, Std | 8 | 16 |
| 58 | 122-78-1 | phenylacetaldehyde | 1651 | 1040 | 9.402 | honey-like, floral, rose | MS, RI, Odor, Std | 128 | 16 |
| 59 | 503-74-2 | 3-methylbutanoic acid | 1652 | 875 | 5.097 | sour, cheese, sweaty, fruity | MS, RI, Odor, Std | 256 | 2 |
| 60 | 96-48-0 | butyrolactone | 1653 | nd | nd | milk, creamy | MS, RI, Odor, Std | 8 | 8 |
| 61 | 143-08-8 | 1-nonanol | 1656 | 1172 | 13.154 | citrus, rose, fatty | MS, RI, Odor, Std | 32 | 64 |
| 62 | 98-00-0 | 2-furanmethanol | 1668 | 860 | 4.784 | bitter | MS, RI, Odor, Std | 128 | 32 |
| 63 | 93-89-0 | ethyl benzoate | 1673 | 1225 | 14.609 | fruity, sweet, herbal | MS, RI, Odor, Std | 8 | 16 |
| 64 | 123-25-1 | ethyl succinate | 1678 | 1171 | 13.107 | fruity | MS, RI, Odor, Std | 2 | 4 |
| 65 | 10482-56-1 | (-)-α-terpineol | 1696 | 1189 | 13.622 | grapefruit | MS, RI, Odor, Std | 8 | n.d. |
| 66 | 507-70-0 | endo-borneol | 1701 | 1160 | 12.818 | woody, camphor, balsamic | MS, RI, Odor, Std | 16 | n.d. |
| 67 | 6314-97-2 | (2,2-diethoxyethyl) benzene | 1709 | 1321 | 17.093 | fresh, green, almond, sweet | MS, RI, Odor, Std | 32 | 8 |
| 68 | 109-52-4 | n-pentanoic acid | 1736 | 979 | 7.706 | cheesy, dairy-like | MS, RI, Odor, Std | 8 | 4 |
| 69 | 105-87-3 | geranyl acetate | 1753 | nd | nd | rose | MS, RI, Odor, Std | 16 | n.d |
| 70 | 19894-97-4 | (-)-myrtenol | 1788 | nd | nd | woody, sweet, mint, medicinal | MS, RI, Odor, Std | 64 | n.d |
| 71 | 101-97-3 | ethyl 2-phenylacetate | 1790 | 1240 | 14.949 | fruity, floral, cocoa | MS, RI, Odor, Std | 128 | 64 |
| 72 | 103-45-7 | 2-phenylethyl acetate | 1817 | 1252 | 15.343 | fruity, floral | MS, RI, Odor, Std | 128 | 128 |
| 73 | 23726-93-4 | β-damascenone | 1820 | 1382 | 18.609 | honey, floral, apple-like | MS, RI, Odor, Std | 512 | 512 |
| 74 | 106-24-1 | geraniol | 1842 | nd | nd | rose, geranium | MS, RI, Odor, Std | 256 | n.d |
| 75 | 142-62-1 | hexanoic acid | 1844 | 981 | 7.762 | rotten cheesy | MS, RI, Odor, Std | 32 | 32 |
| 76 | 127-41-3 | α-ionone | 1855 | 1424 | 19.748 | orris, fruity, sweet, floral, woody | MS, RI, Odor, Std | 64 | n.d |
| 77 | 90-05-1 | guaiacol | 1869 | 1086 | 10.732 | spices, smokey | MS, RI, Odor, Std | 128 | 16 |
| 78 | 2021-28-5 | ethyl 3-phenylpropanoate | 1881 | 1344 | 17.677 | dried, floral | MS, RI, Odor, Std | 64 | 128 |
| 79 | 100-51-6 | benzyl alcohol | 1884 | 1034 | 9.254 | floral, phenolic | MS, RI, Odor, Std | 32 | 16 |
| 80 | 60-12-8 | 2-phenylethanol | 1919 | 1106 | 11.275 | floral, rose, fresh-bread | MS, RI, Odor, Std | 128 | 16 |
| 81 | 79-77-6 | β-ionone | 1953 | nd | nd | orris, fruity, sweet, floral, woody | MS, RI, Odor, Std | 256 | n.d |
| 82 | 93-51-6 | creosol | 1978 | 1190 | 13.661 | smokey, spices, herbal | MS, RI, Odor, Std | 128 | 16 |
| 83 | 1139-30-6 | caryophyllene oxide | 1992 | 1927 | 30.961 | sweet, fresh, dry, woody | MS, RI, Odor, Std | 32 | n.d |
| 84 | 108-95-2 | phenol | 2021 | 990 | 8.008 | phenol, smokey | MS, RI, Odor, Std | 64 | 16 |
| 85 | 7212-44-4 | nerolidol | 2036 | nd | nd | floral, green, citrus, woody | MS, RI, Odor, Std | 32 | n.d |
| 86 | 2785-89-9 | 4-ethylguaiacol | 2037 | 1274 | 15.927 | smokey, spices, herbal, woody | MS, RI, Odor, Std | 128 | 2 |
| 87 | 2305-25-1 | ethyl 3-hydroxyhexanoate | 2046 | nd | nd | fresh | MS, RI, Odor | 8 | 4 |
| 88 | 106-44-5 | p-cresol | 2089 | 1076 | 10.446 | phenol, smokey-like | MS, RI, Odor, Std | 32 | 16 |
| 89 | 103-36-6 | ethyl cinnamate | 2140 | 1460 | 20.570 | cinnamon, sweet and fruity notes | MS, RI, Odor, Std | 512 | 32 |
| 90 | 15352-77-9 | β-bisabolol | 2152 | 1666 | 25.907 | citrus, floral, sweet, herbal | MS, RI, Odor, Std | 128 | n.d |
| 91 | 123-07-9 | 4-ethylphenol | 2170 | 1175 | 13.256 | spices, clove | MS, RI, Odor, Std | 16 | 8 |
| 92 | 97-53-0 | eugenol | 2179 | 1353 | 17.970 | smokey, clove, spices | MS, RI, Odor, Std | 2048 | n.d |
| 93 | 134-96-3 | syringaldehyde | 2196 | 1651 | 25.480 | sweet, clove | MS, RI, Odor, Std | 2 | n.d |
| 94 | 7786-61-0 | 4-vinylguaiacol | 2211 | 1308 | 16.838 | smokey | MS, RI, Odor, Std | 2048 | 32 |
| 95 | 515-69-5 | α-bisabolol | 2221 | 1683 | 26.425 | floral, peppery, balsamic, clean | MS, RI, Odor, Std | 128 | n.d |
| 96 | 5932-68-3 | trans-isoeugenol | 2271 | 1445 | 20.243 | sweet, clove, spices | MS, RI, Odor, Std | 1024 | n.d |
| 97 | 501-92-8 | 4-allylphenol | 2349 | nd | nd | anise-like, clove | MS, RI, Odor, Std | 64 | 32 |
| 98 | 115-71-9 | α-santalol | 2442 | 1674 | 26.131 | woody, sweety, nut | MS, RI, Odor, Std | 512 | n.d |
| 99 | 644-30-4 | α-curcumene | 2502 | 1480 | 21.108 | herbal | MS, RI, Odor | 8 | n.d |
| 100 | 67-47-0 | 5-hydroxymethylfurfural | 2526 | 1223 | 14.556 | smokey-like | MS, RI, Odor | 16 | n.d |
| 101 | 121-33-5 | vanillin | 2601 | 1391 | 18.940 | vanilla, sweet, creamy | MS, RI, Odor, Std | 512 | 8 |
| 102 | 81944-08-3 | (E)-ligustilide | 2622 | 1730 | 27.655 | sweet | MS, RI, Odor, Std | 16 | n.d |
a Odorants were numbered consecutively according to their retention indices on a capillary DB-FFAP column. b Odorants were identified by comparison of their odor quality, retention indices (RIs) on DB-FFAP and DB-5 capillary columns, as well as mass spectrometry (MS) data with the data of authentic standard compounds (Std). c Retention indices were determined using a homologous series of n-alkanes. d Odor quality was detected at a sniffing port. e FD factors were determined by AEDA on a capillary DB-FFAP column. n.d: not detected at the sniffing port.
Table 4.
Omission tests from complete aroma reconstitution in the dearomatized Zhuyeqing model.
| No. | Omitted Compounds | n/10 | Significance a |
|---|---|---|---|
| M1 | all esters | 10/10 | *** |
| M1-1 | ethyl cinnamate | 9/10 | *** |
| M1-2 | ethyl octanoate | 9/10 | *** |
| M1-3 | ethyl acetate | 9/10 | *** |
| M1-4 | ethyl hexanoate | 4/10 | ns |
| M1-5 | ethyl butanoate | 3/10 | ns |
| M1-6 | 3-methylbutyl acetate | 7/10 | * |
| M1-7 | ethyl pentanoate | 2/10 | ns |
| M1-8 | ethyl 2-hydroxybutanoate | 3/10 | ns |
| M1-9 | ethyl 3-phenylpropanoate | 2/10 | ns |
| M2 | all terpenes | 10/10 | *** |
| M2-1 | β-damascenone | 10/10 | *** |
| M2-2 | d-limonene | 5/10 | ns |
| M2-3 | β-myrcene | 3/10 | ns |
| M2-4 | bornyl acetate | 8/10 | ** |
| M3 | all phenols | 10/10 | *** |
| M3-1 | eugenol | 10/10 | *** |
| M3-2 | guaiacol | 8/10 | ** |
| M3-3 | phenol | 5/10 | ns |
| M4 | all acids | 4/10 | ns |
| M4-1 | 3-methylbutanoic acid | 5/10 | ns |
| M5 | all alcohols | 4/10 | ns |
a “*”, “**”, and “***” indicate significance at p < 0.05, 0.01, and 0.001, respectively, “ns” indicate no significance.
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MDPI and ACS Style
Wang, L.; Han, Y.; Zhang, X.; Gao, X.; Xu, Y.; Wu, Q.; Tang, K. Characterization of Key Aroma Compounds of Zhuyeqing by Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies. Foods 2025, 14, 344. https://doi.org/10.3390/foods14030344
AMA Style
Wang L, Han Y, Zhang X, Gao X, Xu Y, Wu Q, Tang K. Characterization of Key Aroma Compounds of Zhuyeqing by Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies. Foods. 2025; 14(3):344. https://doi.org/10.3390/foods14030344
Chicago/Turabian StyleWang, Lihua, Ying Han, Xing Zhang, Xiaojuan Gao, Yan Xu, Qun Wu, and Ke Tang. 2025. "Characterization of Key Aroma Compounds of Zhuyeqing by Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies" Foods 14, no. 3: 344. https://doi.org/10.3390/foods14030344
APA StyleWang, L., Han, Y., Zhang, X., Gao, X., Xu, Y., Wu, Q., & Tang, K. (2025). Characterization of Key Aroma Compounds of Zhuyeqing by Aroma Extract Dilution Analysis, Quantitative Measurements, Aroma Recombination, and Omission Studies. Foods, 14(3), 344. https://doi.org/10.3390/foods14030344
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