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Article

Major Sensory Attributes and Volatile Compounds of Korean Rice Liquor (yakju) Affecting Overall Acceptance by Young Consumers

by
JeongAe Heo
1,
Han Sub Kwak
2,
Miran Kim
2,
Jae-Ho Kim
3,
Hyung Hee Baek
4,
Hyukjin Shin
4,
Young-seung Lee
5,
Sanghyeok Lee
5 and
Sang Sook Kim
2,*
1
Technical Assistance Center, Korea Food Research Institute, Wanju-gun 55365, Korea
2
Research Group of Food Processing, Korea Food Research Institute, Wanju-gun 55365, Korea
3
Planning Division, Korea Food Research Institute, Wanju-gun 55365, Korea
4
Department of Food Engineering, Dankook University, Cheonan 31116, Korea
5
Department of Food Science and Nutrition, Dankook University, Cheonan 31116, Korea
*
Author to whom correspondence should be addressed.
Foods 2020, 9(6), 722; https://doi.org/10.3390/foods9060722
Submission received: 11 May 2020 / Revised: 28 May 2020 / Accepted: 29 May 2020 / Published: 2 June 2020
(This article belongs to the Special Issue Sensory and Volatile Flavor Analysis of Beverages)
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Abstract

:
The sensory characteristics and volatile compounds that affect consumers’ acceptance of rice liquors were investigated. A total of 80 consumers evaluated 12 yakju samples and descriptive analysis by 11 trained panelists was conducted. Solvent-assisted flavor evaporation-gas chromatography-mass spectrometry analysis also was conducted revealing 120 volatile compounds in the yakju samples. Sensory attributes (n = 31) except appearance attributes were used for principal component analysis (PCA). As results, fruit odor (apple, hawthorn, omija, and pineapple odor) and flower odor (chrysanthemum, pine, and peppermint odor) were placed on the positive side of PC1 whereas persimmon vinegar odor, bitter taste, alcohol flavor, stinging and coating mouthfeel were located on the negative side of PC1. The yakju samples were mainly characterized by their alcohol content and supplementary ingredients. Sensory descriptors (n = 31; except appearance attributes and p > 0.05) and volatile compounds (n = 30; p > 0.5 correlation coefficient with overall acceptance) were chosen for multiple factor analysis (MFA). The MFA correlation map showed that ethyl propanoate, ethyl-2-hydroxy-2-methylbutanoate, methyl 2-furoate, γ-butyrolactone, 4-ethoxycarbonyl-γ-butyrolactone, hawthorn odor, apple flavor, grape flavor, and sweet taste were positively correlated with young consumers’ overall acceptance. Additionally, negative correlation with overall acceptance was found in 1,3-butanediol, 2,3-butanediol, and 1,1-diethoxy-3-methylbutane.

Graphical Abstract

1. Introduction

Yakju is a representative traditional Korean rice wine along with makgeolli. Yakju is made with rice as a starch source, water, and nuruk. Nuruk is a starter made from grains and it plays an important role in the flavor of yakju during fermentation because it contains various microorganisms, including fungi and wild types of yeast [1,2]. Thus, during fermentation, sugars, various organic acids, and numerous volatile compounds are produced, affecting the flavors of the yakju [3]. The sensory properties of yakju are affected by various factors, and they are influenced not only by the yeast strain [2] but also by the fermentation process and the starch ingredients [4], and by the degree of milling of the rice used for the nuruk [5]. In addition, supplementary ingredients, such as mulberry [6], Codonopsis lanceolate [7], Ganoderma lucidum [8], and buckwheat sprouts [9] are used to improve the flavor and biological activities of yakju.
Regarding the studies on yakju, Lee et al. [10] characterized five commercial rice wines containing supplementary ingredients through descriptive and physicochemical analyses. Additionally, Lee [11] reported the extrinsic factors, such as brand and familiarity, that affect the acceptance of yakju. However, limited information is available on the specific volatile compounds and sensory attributes associated with consumer acceptance of yakju.
Studies focusing on the characterization of liquors using instrumental analysis were recently conducted. For example, Kang et al. [12] discriminated traditional Korean liquor (makgeolli and yakju) and Japanese (sake samples) using solid-phase microextraction gas chromatography-mass spectrometry (SPME-GC/MS). Kang et al. [13] also discriminated Korean rice wine (makgeolli) samples using electronic tongues (e-tongues) and LC-MS/MS. However, the bitterness of the makgeolli samples caused by amino acids was not well predicted by the e-tongue in the study of Kang et al. [13]. Xiao et al. [14] reported on the aroma profiles of three types of liquor (strong/light/sauce odor type) using GC-MS. They characterized the samples based on sensory attributes and volatile compounds through partial least squares (PLS) regression. Xiao et al. [15] also conducted a sensory evaluation as well as an instrumental analysis of liquors, and they investigated the correlation between sensory attributes and volatile compounds in cherry wines. They reported that volatile compounds such as 1-propanol, 2-ethyl-1-hexanol, geraniol, ethyl hexanoate, ethyl octanoate, and butanoic acid were positively correlated with sweet aroma (>0.9) in cherry wine samples.
A limited number of studies have focused on volatile compounds, sensory attributes, and consumers’ acceptance of yakju products containing various supplementary ingredients, which might produce complex and diverse flavors. Furthermore, Kim et al. [16] reported that young consumers in Korea tended to prefer soju (diluted liquor) and beer over the traditional liquor because of price, flavor, and hangover. To overcome the low acceptance of traditional liquor among young consumers, the key sensory attributes and volatile compounds that affect the acceptance of yakju containing supplementary ingredients must be identified. Therefore, this study was conducted to identify the key sensory attributes and volatile compounds that affect the acceptance of yakju containing supplementary ingredients by investigating the relationship of sensory attributes and volatile compounds with young consumers’ acceptance of yakju.

2. Materials and Methods

2.1. Yakju Samples

The 12 yakju samples used in this study were selected based on their availability in online stores and based on the specialty of the liquor-producing regions in Korea. Information on the ingredients of the products obtained from the label of each product, is shown in Table 1. The samples were refrigerated at 4 °C until they were used.

2.2. Descriptive Analysis

Descriptive analysis and consumer test were approved by the institutional review board of Dankook University (DKU 2018-10-002). Eleven panelists (females, aged 37–49 years) were selected from 30 preliminary panelists based on their ability to discriminate and describe tastes and flavors in a screening test. These panelists participated in 15 training sessions (2 h per session, twice a week). During the panel training, 48 sensory descriptors (appearance = 3, odor = 17, taste/flavor = 13, mouthfeel = 6, and aftertaste/after-mouthfeel = 9), definitions, reference materials, and intensity of reference materials for the 12 yakju products were developed (Table 2). The samples were evaluated in an individual sensory booth equipped with a computerized data collection system (Korea Food Research Institute, Wanju-gun, Korea) using a 15 cm line scale (0: none to 15: very strong). The panelists evaluated six samples for each session, and they were given 15 min to test one sample. After testing three samples, they were required to rest for 15 min to prevent sensory fatigue. The yakju samples (40 g) were monadically presented in a glass cup (55 mL, diameter of top of cup = 5 cm) coded with a three-digit randomized number and were presented in a randomized order to prevent bias. Each sample was covered with a watch glass (7 cm in diameter) to minimize changes in odor during the evaluation. Filtered water and crackers were provided as palate cleansers. A spit cup was also provided for panelists to use when they did not want to swallow the samples. Evaluation sessions were conducted in three replications.

2.3. Consumer Test

All of the consumers who participated in this study were users of yakju, and they were recruited based on them having no allergies to alcohol or yakju and based on their willingness to participate in the study. A total of 80 consumers (in their 20 s; male = 38, female = 42) participated in the evaluations. The samples were served following the Williams Latin Square design. The participants evaluated the overall acceptance using a 9-point hedonic scale. Six samples were provided for one evaluation session. Each sample (30 mL) was served in a paper cup (70 mL), and filtered water was provided as a palate cleanser. The consumers were asked not to consume any food for at least 1 h before the evaluation.

2.4. Identification of Volatile Compounds by GC-MS

Prior to the GC-MS analysis, the volatile compounds of the samples were extracted using the liquid-liquid continuous extraction (LLCE)/solvent-assisted flavor evaporation (SAFE) method. Each sample (1150 mL) and 3-heptanol (328 μg; internal standard) were placed in LLCE apparatus and extracted for 8 h at room temperature using 300 mL of redistilled dichloromethane as an extraction solvent. The LLCE extracts were frozen for 12 h at −20 °C to remove water and then concentrated to 120 mL using a gentle N2 gas stream. SAFE was applied to remove non-volatile compounds and impurities, such as pigments. The extract (120 mL) was distilled for 30 min at 40 °C under 8.0 × 10−3 Pa, and the SAFE extract was frozen for 12 h at −20 °C and then dried over anhydrous sodium sulfate (3 g). This extract was concentrated to 500 μL using a gentle N2 gas stream and then analyzed by GC-MS.
Analyses were performed using an Agilent 7890B GC/Agilent 5977A mass selective detector (Agilent, Santa Clara, CA, USA) with a DB-wax column (60 m length × 0.25 mm i.d. × 0.25 µm film thickness; J&W Scientific, Folsom, CA, USA). Helium was used as a carrier gas with a flow rate of 1.0 mL/min. The oven temperature was initially set at 40 °C for 5 min and then increased at a rate of 5 °C/min to 200 °C, which was held for 20 min. The samples (1 µL) were injected into GC-MS apparatus at split mode (50:1). The injector and detector temperatures were 200 °C and 250 °C, respectively. The ionization voltage was 70 eV, and the mass range was 33–350 m/z. Analyses were conducted in triplicate.
Volatile compounds were identified based on their retention indices (RI), Wiley Registry of Mass Spectral Data (9th ed.) and by using a NIST08 database (Agilent). The concentration of the volatile compounds was semi-quantified using Formula (1), wherein the correlation coefficient of the peak area ratio and the amount ratio was assumed to be 1.
Concentration   ( ppb ) = Peak   area   ratio × µ g   of   3 - heptanol   L   of   samples

2.5. Statistical Analysis

The descriptive analysis results and the consumers’ acceptance data were analyzed by analysis of variance (ANOVA) to determine the differences among the samples. Student–Newman–Keuls (SNK) multiple comparison was used when a significant difference was found among the samples (p < 0.05). Principal component analysis (PCA) was conducted to summarize the results of the sensory characteristics of the yakju samples. Pearson’s correlation analysis was performed to investigate the relationship between consumers’ acceptance and volatile compounds. Moreover, multiple factor analysis (MFA) was performed to investigate the relationship among sensory attributes, volatile compounds, and consumers’ overall acceptance of the 12 yakju samples. All statistical analyses were conducted using XLSTAT (Ver. 2017.1, Addinsoft, Paris, France).

3. Results and Discussion

3.1. Descriptive Analysis of Yakju Samples

The results of the ANOVA showed significant differences in 33 attributes of the 48 attributes (Table 3). Among the samples, Y10 and Y8 showed the highest scores for redness and yellowness, respectively. The redness of Y10 might be due to the red color of the raw materials, such as the Schizandra chinensis fruit (omija), Cornus officinalis, and the Lycium chinense fruit. Similarly, some of the samples were characterized by attributes induced by their raw materials. For example, Y5, which contained chrysanthemum, had a strong chrysanthemum, peppermint, and pine odor. Y1 was highest in ginseng and hawthorn odor and Y7 had the highest score for bitterness and bitter aftertaste. This result might be due to saponin, which has a bitter taste [17]. Other ingredients such as fructose, also seemed to affect sweet taste in the Y2 and Y10 samples. In terms of alcohol flavor, samples with high alcohol contents such as Y7 (16.0%) and Y8 (18.0%) tended to be the highest in alcohol flavor, whereas Y10 (12.0%) and Y12 (11.0%), which contained relatively low alcohol content, were the lowest in alcohol flavor. Especially, Y8, which had the highest alcohol content, was the highest in body, coating and residue mouthfeel.
Y4 showed the highest scores for persimmon vinegar odor, sourness, stinging mouthfeel, and stinging aftertaste. This result is possibly due to the formation of acetic acid during fermentation, considering that acetic acid is associated with vinegar scent and a pungent odor [18].
The PCA result for the 31 sensory descriptive attributes of the 12 yakju samples is shown in Figure 1. Appearance-related descriptors (degree of clearness/redness/yellowness) were excluded to focus on the odor and flavor of the yakju samples, and attributes that had significant difference among the samples (n = 31) were used for the PCA. A total of 67.6% of variance could be explained by PC1 (40.4%) and PC2 (27.3%). Characteristics related to sweetness, flower, and fruit ingredients were located on the positive side of PC1, whereas bitter taste, burning mouthfeel, and alcohol odor and flavor were located on the negative side of PC1. Specifically, samples such as Y1, Y2, Y3, Y5, Y10, and Y12, which contained fruit or floral ingredients, were located on the positive side of PC1; these samples had hawthorn odor, sweet taste, sour taste, apple flavor, grape flavor, or tangerine peel odor/flavor.
On the contrary, samples containing Supplementary Materials other than fruit or floral ingredients, such as sweet pumpkin (Y4), balloon flower root (Y6 and Y7), or soy bean (Y8), were located in quadrant 2. These samples were mainly characterized by yeast odor, roasted grain odor, alcohol flavor, and body and stinging attributes. Characteristics related to mouthfeel and taste were located on the positive side of PC2, whereas most of the attributes related to odor were located on the negative side of PC2. Particularly, salty taste, sour taste/aftertaste, and body mouthfeel were located on the positive side of PC2, whereas pine odor, peppermint odor, and chrysanthemum odor were located on the negative side of PC2. Samples with high alcohol levels were located on the positive side of PC2, whereas those with relatively low alcohol content, such as Y5 and Y12, were located on the negative side of PC2. Among the samples, Y9 was the only sample located in quadrant 3, and it had a low score for sour, sweet, umami, and fruit-related notes compared with other samples.
Overall, the present results indicated that the yakju samples were characterized mainly by their supplementary raw materials and alcohol content, which affect the overall odor and flavor of the samples.

3.2. Consumers’ Acceptance

The mean overall acceptance scores by 80 young consumers are shown in Table 4. Significant differences among the 12 samples were found in the overall acceptance scores. Overall acceptance was highest for Y3 (6.71), followed by Y10 (6.41), and Y2 (6.34) and was lowest for Y8 (3.25). Generally, overall acceptance was higher for samples with fruit-related supplementary ingredients (Y2, Y3, and Y10) than that for samples with root-related bitter ingredients (Y7 and Y8). Apparently, consumers preferred those samples with fruit-related characteristics over the bitter and yeasty samples. Similarly, Lee and Lee [19] studied the sensory attributes and acceptance of 10 yakju samples with supplementary ingredients, and they reported that the acceptance of various clusters of consumers were positively associated with fruit flavor, sweet aroma, and medicinal herb aroma but astringent mouthfeel, bitter taste, and yeast flavor were negatively associated with consumers’ acceptance. Moreover, Kwak et al. [20] reported that the key liking factors of rice wine by American panelists were sweet, sour, and apricot flavors, whereas the key disliking factors were yeasty and nutty characteristics. They reported positive correlations between overall acceptance and fruit-related characteristics (apple, peach, and pear), confirming the key liking factors for the yakju samples [20].

3.3. Volatile Compounds Identified Using GC/MS

A total of 120 volatile compounds (acids = 14, alcohols = 26, aldehydes = 2, esters = 32, furans = 2, ketones = 11, lactones = 7, phenols = 8, terpenoids = 6, and miscellaneous = 12) were identified (Table 5). Thirty-five volatile compounds were found in all of the samples.
Generally, acetic acid is responsible for the pungent odor in vinegar [18]. Huh et al. [21] reported that high acetic acid content could decrease the taste of a liquor, although the threshold for acetic acids is approximately 280,000 µg/L in a 10% ethanol system [22]. Among the 12 samples, Y4 had the highest acetic acid content (14,700 µg/L) followed by Y8 (5038 µg/L), while Y12 had the lowest acetic acid content (624 µg/L). Y7 was the only sample contained formic acid (11.3 µg/L) and 2-butenoic acid (12.4 µg/L). Fan and Qian [23] suggested that free fatty acids such as hexanoic acid and octanoic acid were produced by bacteria during the fermentation process. Y9 had the lowest content of 2-methyl propanoic acid (105 µg/L), butanoic acid (20.1 µg/L), 3-methyl butanoic acid (104 µg/L), and hexanoic acid (56.7 µg/L), which seemed to be associated with the degree of fermentation.
Alcohols, the largest group of volatile compounds in alcoholic beverages such as red wine [24,25], are produced during yeast metabolism, and alcohol content varies depending on the yeast starters [26]. Fusel alcohols, such as n-propyl alcohol, iso-butyl alcohol, and iso-amyl alcohol, are produced during the fermentation of amino acid in yeast [12,27]. Among them, isoamyl alcohol has the highest amount of the volatile compounds as reported by Kim et al. [28]. Isoamyl alcohol is known to boost aroma and flavor when it exists in low amounts [27]. Additionally, 2-methyl-1-propanol, which is one of the aliphatic alcohols related to alcohol odor [1], was high in Y1 (10,085 µg/L), Y2 (12,313 µg/L), and Y5 (10,222 µg/L).
Esters are produced during alcoholic fermentation by yeast; they have a fruit-like aroma and thus they positively influence the aroma quality of liquors [29,30,31]. The large number of volatile ester compounds (n = 32) could be explained by the various supplementary ingredients used to produce the samples. Isoamyl acetate is related to sweet and fruity aromas, and Mamede et al. [29] reported that low concentration of isoamyl acetate results in low consumers’ acceptance of sparkling wine samples. Isoamyl acetate content was highest in Y10 and lowest in Y8. Considering that overall acceptance of Y10 (6.41) was much higher than that of Y4 (3.25) as in Table 4, the results of this study confirmed that isoamyl acetate might be one of the key compounds affecting consumer acceptance. Among the samples, Y4 contained high amounts of ethyl lactate (45,468 μg/L), isoamyl lactate (446 μg/L), diethyl succinate (8015 μg/L), and ethyl hydrogen succinate (6056 μg/L). Apostolopoulou et al. [32] showed that the ethyl lactate content of samples of bottled Greek distillates (tsipouro) differs from that of homemade samples, suggesting that production methods might influence the amount of ethyl lactate. Argyri et al. [33] also analyzed the volatile compounds of meat samples under different temperatures. As the temperature increased (from 0 °C to 15 °C), the amount of ethyl lactate also increased. These results suggested that the ethyl lactate content of Y4 was affected by the manufacturing environment, such as production methods and temperature.
Ethyl octanoate contents in all of the samples was less than the threshold, which was reported to be 170 μg/L [34]. Y7 had the highest level of 2-phenylethyl acetate (759 μg/L), followed by Y6 (600 μg/L). This might be due to the specific yeast used in Y6 and Y7, considering that this compound is known to be formed during fermentation by yeast [34]. The intensity of 2-phenylethyl acetate in Y7 and Y6 was much higher than threshold (180 μg/L), which was reported in [34].
A high amount of terpenes is associated with a flower-like odor [35]. Given that eucalyptol, α-terpineol, and 4-terpinenol are found in Chrysanthemum morifolium R. [36], the five terpenes (eucalyptol, 4-terpineol, α-terpineol, borneol, and p-cymen-8-ol) found in Y5 might have originated from Chrysanthemum morifolium R., which was that sample’s major supplementary ingredient.

3.4. Relationship among Sensory Attributes, Volatile Compounds and Consumers’ Acceptance of Yakju Samples by MFA

For the MFA, 30 volatile compounds (acids = 3; alcohol = 8; aldehyde = 1; ester = 8; ketone = 2; lactone = 3; phenol = 1; miscellaneous = 4) were selected from the 120 volatile compounds based on a correlation coefficient of >0.5 with consumers’ overall acceptance. A correlation map of descriptive attributes, volatile compounds, and consumer acceptance is in Figure 2a and loading of 12 yakju samples in the first two dimensions by MFA is shown in Figure 2b. A total of 59.3% of variance was explained by F1 (47.7%) and F2 (11.7%). Similar to the results in Figure 1, fruit-related sensory attributes were placed on the negative side of F1, while bitterness, mouthfeel, and alcohol flavor were placed on the positive side of F1 (Figure 2a).
Of the volatile compounds, all esters (n = 8) were in quadrant 2 and 3, along with fruit-related sensory attributes such as omija odor, hawthorn odor, tangerine peel odor/flavor, apple flavor and grape flavor. These sensory attributes and volatile ester compounds were closely related with consumers’ overall acceptance. Not only two esters (ethyl propanoate, r = 0.80; ethyl-2-hydroxy-2-methylbutanoate, r = 0.92), but also two lactones (γ-butyrolactone, r = 0.85; 4-ethoxycarbonyl-γ-butyrolactone r = 0.78), two miscellaneous volatile compounds (2-methyl-1,3-dioxane, r = 0.72; 5-hydroxy-2-methyl-1,3-dioxane, r = 0.72), and one phenols (4-vinylphenol, r = 0.64) were highly correlated with consumers’ overall acceptance (Figure 2a). The volatile esters such as ethyl propanoate and ethyl 2-methyl propanoate in Y1, Y2, Y3, Y5, Y10, and Y12 are known to be found in strawberry juice [37] and durian [38], and methyl 2-furoate is known to be found in dried omija fruit samples [39]. The results of this study implied that the odor characteristics of yakju samples might be affected by the volatiles from the fruit or medicinal herbs used in the yakju samples. In addition to these volatile esters, ethyl butanoate, known to have a fruity aroma, with an odor threshold of 20 μg/L [40], was positively associated with the overall acceptance scores of most samples (Y1, Y2, Y3, Y5, Y6, Y7, Y,10, Y11, and Y12). However, those of Y4, Y8, and Y9, which were negatively associated with ethyl butanoate, contained under the threshold of ethyl butanoate (Y4 = not detected; Y8 = 16.2 μg/L; Y9 = 7.0 μg/L).
One of the abundant and important volatile lactones found in wine is γ-butyrolactone [25], which has a fruity aroma [31]. Not only γ-butyrolactone but also 4-ethoxycarbonyl-γ-butyrolactone was positively related with consumers’ acceptance. Considering that the content of volatile lactones varies depending on aging time and type of yeast strain in sherry wine [41], the type of yeast strain in the nuruk used for the yakju samples might have influenced the production of those volatile compounds. In addition, Lee et al. [40] reported that nuruk generally contains various kinds of microorganisms compared with to ipguk (koji), which only contains Aspergilus oryzae, leading to the production of more volatile compounds in nuruk than in ipguk. Lee et al. [42] reported an absence of 2,3-butanediol in ipguk samples, and a relatively low amount of 2,3-butanediol in Y2 (198.9 μg/L) and Y3 (205.5 μg/L) in this study implies that Y2 and Y3 samples might be made of ipguk.
Volatile alcohol compounds have a pungent mouthfeel and a pungent and “herbaceous” odor [43]. Described as having a grassy, medicinal, fusel, and spirituous odor, 1-butanol has an odor threshold of 150,000 µg/L [22,43,44]. Although 1-butanol correlated with consumers’ acceptance, the odor of 1-butanol may be imperceptible considering that the 1-butanol contents in the samples ranged from 44.8 μg/L to 1,159.9 μg/L, which was considerably lower than the threshold value.
Volatile phenolic compounds are also formed primarily through alcoholic fermentation [45] and are known to be important in the overall aroma of wine [46] and flavors of dark beer [47]. Generally, volatile phenolic compounds such as 4-vinylphenol have a “nutty” odor similar to “almond shell” [45], spicy, and medicinal-like aromas [48]. Butkhup et al. [46] also reported that these compounds had “heavy pharmaceutical” odor. The existence of 4-vinylphenol was only found in Y1 (111 μg/L), Y2 (73.1 μg/L), Y3 (85.4 μg/L), and Y12 (36.8 μg/L). Although this compound had a positive relationship with young consumers’ acceptance (r = 0.64), the effect of 4-vinylphenol on young consumers’ overall acceptance for yakju might be negligible considering its threshold (610 μg/L) [46].
Some volatile alcohols (3-butanediol, 2,3-butanediol, 1-octanol, and propylene glycol), acetic acid, γ-hexalactone, and 1,1-diethoxy-3-methylbutane were associated with persimmon vinegar odor, roasted grain odor, yeast odor, kudzu flavor, and coating mouthfeel. Y4 and Y8, which had lower consumer acceptance than other samples, were associated with volatile alcohols such as 1,3-butanediol, 2,3-butanediol, and propylene glycol. This result implied that lower consumer acceptance of these samples might be caused by those volatile alcohol compounds and bitter taste, bitter aftertaste, alcohol flavor, and kudzu flavor. Butanediols were produced from carbohydrates during the alcoholic fermentation primarily by S. cerevisiae, a major yeast in yakju [49,50,51]. In particular, 2,3-butanediol is the dominant volatile compound in wine, and it has a bitter taste [50]. The highest contents of these compounds in Y4 and Y8 might be due to yeast, such as S. cerevisiae, which is involved in the fermentation of rice or supplementary starch ingredients, such as sweet pumpkin and soybean. This result suggested pungent and sour odors like persimmon vinegar odor, related to volatile acetic acid, and some volatile alcohols such as 1,3-butanediol, 2,3-butanediol, and propylene glycol, might negatively affect young consumers’ acceptance.
Furthermore, one of the volatile acetals, 1,1-diethoxy-3-methylbutane, was also associated with Y4 (49.4 μg/L) and Y8 (142 μg/L), which had lower consumers’ acceptance than other samples. This compound was found in liquor samples such as Chinese liquor [23] and Italian grape marc spirit [52]. Volatile acetals are known to be produced by aldehydes in the presence of excessive content of ethanol [23,53]. This suggested that 1,1-diethoxy-3-methylbutane might be produced by relatively high contents of ethanol or aldehyde-related compounds, as in Y4 and Y8. Significant differences in fruit-related attributes were found among the samples, even though the intensities of fruit-related attributes were weak. Thus, overall, the correlation map by MFA showed that fruit-related sensory attributes and volatile compounds were closely related with consumer acceptance. The fruit-related sensory attributes and volatile esters were placed in quadrant 2 and 3, while roasted grain odor, yeast odor, root-related flavor (kudzu flavor), and all mouthfeel attributes were placed in quadrant 1 and 4. The result of this study confirmed the results by Jung et al. [1], who reported that rice wine samples were distinguished by their volatile alcohol and volatile ester. Furthermore, descriptors such as yeast odor and cereal flavor were located opposite to the fruit and sweet aroma in the PCA map.
In addition to volatile compounds that might originate from supplementary ingredients, major ingredients such as different sources of starch might affect the flavors and therefore consumers’ acceptance. While most of the samples were produced mainly from rice, Y1, Y2, Y3, and Y5 used corn starch in addition to rice. Kim et al. [4] conducted a sensory evaluation of traditional liquor samples made from various starch sources. They showed that the acceptance of liquors made with corn starch and brown rice was higher than that of liquors made with glutinous rice or non-glutinous rice or potato starch. Liquors made with corn starch or brown rice tended to contain a relatively lower amount of acetic acid and a higher amount of fructose than the liquors made with non-glutinous rice, suggesting that the type of starch could affect the sensory and chemical properties of liquors. Apart from starch source, rice protein in yakju samples increases the pH of yakju samples, causing the formation of off-flavor [54]. Moreover, León-Rodríguez et al. [55] suggested that the presence of minor compounds (e.g., some volatile ethyl esters, terpenes, acids, and furans) at low concentrations could cause a synergic effect with other volatile compounds, leading to the production different odor characteristics. Therefore, further investigation on interactions among volatile compounds is needed to understand the odor characteristics and volatile compounds that affect consumers’ overall acceptance.

4. Conclusions

Twelve yakju samples were characterized, based on sensory descriptors by PCA. The result of the PCA showed that yakju samples were characterized mainly by their supplementary raw materials, which affect their overall odor and flavor. As shown by the result of the MFA correlation map, the yakju samples tended to be classified by sensory attributes and volatile compounds. The results of this study showed that acceptance of yakju samples was largely influenced not only by their alcohol content but also by their supplementary ingredients, especially those related to fruit-related aroma. On the contrary, volatile acetic acid, and some volatile alcohols (1,3-butanediol, 2,3-butanediol, and propylene glycol), and 1,1-diethoxy-3-methylbutane were related with persimmon vinegar odor, roasted grain odor, and yeast odor, and negatively correlated with young consumers’ acceptance of yakju. This is a first report on how the major sensory attributes and volatile compounds of Korean rice liquor (yakju) affect overall acceptance by young consumers, even though the number of consumers who participated in this study (n = 80) was not sufficient. Overall, the results of this study suggested that acceptance of yakju products could be improved by controlling some volatile esters that resulted from supplementary ingredients, or specific volatile alcohols and acids produced during fermentation. Considering that the aroma and flavor of yakju could vary depending on the starch source, supplementary ingredients, yeast strains, and fermentation process, further investigation is needed on the specific yeast strains and fermentation conditions that affect the formation of volatile compounds and consumers’ acceptance of yakju. Along with this, further research on interactions among volatile compounds is also needed to understand the odor characteristics that affect consumers’ overall acceptance.

Author Contributions

Conceptualization, S.S.K. and J.-H.K.; methodology, J.H. and H.S.K.; validation, M.K.; formal analysis, J.H., H.S. and S.L.; investigation, H.H.B. and Y.-s.L.; data curation, J.H.; writing—original draft preparation, J.H.; writing—review and editing, S.S.K.; visualization, J.H. and M.K.; supervision, S.S.K., H.H.B. and Y.-s.L.; project administration, H.S.K.; funding acquisition, S.S.K. All authors have read and agreed to the published version of the manuscript.

Funding

This research was supported by the Main Research Program (Grant number: E0187000-02) of the Korea Food Research Institute (KFRI) funded by the Ministry of the Science and ICT, Korea.

Conflicts of Interest

The authors declare no conflict of interest.

References

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Foods 09 00722 g001 550
Figure 1. PCA plot of the 31 sensory descriptors of the 12 yakju samples. O, T, F, M, AT, and AM stand for odor, taste, flavor, mouthfeel, aftertaste, and after-mouthfeel, respectively.
Figure 1. PCA plot of the 31 sensory descriptors of the 12 yakju samples. O, T, F, M, AT, and AM stand for odor, taste, flavor, mouthfeel, aftertaste, and after-mouthfeel, respectively.
Foods 09 00722 g001
Foods 09 00722 g002a 550Foods 09 00722 g002b 550
Figure 2. Correlation map of (a) descriptive attributes (magenta: O, odor; T, taste; F, flavor; M, mouthfeel; AT, aftertaste; AM, after-mouthfeel), volatile compounds (green) and consumers’ acceptance (red) and (b) yakju samples in the first two dimension of MFA.
Figure 2. Correlation map of (a) descriptive attributes (magenta: O, odor; T, taste; F, flavor; M, mouthfeel; AT, aftertaste; AM, after-mouthfeel), volatile compounds (green) and consumers’ acceptance (red) and (b) yakju samples in the first two dimension of MFA.
Foods 09 00722 g002aFoods 09 00722 g002b
Table
Table 1. Information for the yakju samples 1.
Table 1. Information for the yakju samples 1.
SampleIngredientsPlace of ManufactureEthanol Content (%)
Y1Water, rice, starch, high-fructose corn syrup, ginseng, Schizandra chinensis fruit (omija), Poria cocos, Lycium chinense fruit, Cornus officinalis, Dioscoreae Rhizoma, Crataegi fructus, Hydrangea macrophylla, ginger, licorice, Astragalus propinquus, Acanthopanax sessiliflorus, yeast, wheat koji, citric acidGangwon-do, Korea13.0
Y2Corn starch, rice, high-fructose corn syrup, sugar, Crataegi fructus, lactic acid, koji, Cornus officinalis, yeast, waterGyeonggi-do, Korea13.0
Y3Water, corn starch, rice, high-fructose corn syrup, sugar, koji, lactic acid, orange peel, yeast, dandelionGyeonggi-do, Korea13.0
Y4Water, rice, sweet pumpkin, nurukGangwon-do, Korea17.0
Y5Water, starch, glutinous rice, high-fructose corn syrup, wild chrysanthemum, acacia honey, nuruk, yeast, purified-yeast, citric acidGyeonggi-do, Korea12.5
Y6Water, popped rice, rice, glutinous rice, glucose, isomaltooligosaccharide, nuruk, balloon flower (root) concentrate, steviosideGyeongsang-do, Korea13.0
Y7Water, rice, glutinous rice, popped rice, glucose, isomaltooligosaccharide, nuruk, balloon flower (root) concentrate, steviosideGyeongsang-do, Korea16.0
Y8Glutinous rice, rice, nuruk, water, wild chrysanthemum, soybean, ginger, red pepperChuncheong-do, Korea18.0
Y9Water, glutinous/nonglutinous rice, nuruk, yeast, (Dendropanax morbifera Lev./licorice/Prunus mume), Lentinus edodes Mycelia, mold starter, refined liquor, aspartameJeolla-do, Korea13.0
Y10Water, rice, Schizandra chinensis fruit (omija), Cornus officinalis, Lycium chinense fruit, nuruk, crude amylolytic enzyme, fructose, sugar, steviol glycoside, glucose, citric acid, malic acidJeolla-do, Korea12.0
Y11Water, rice, ipguk (koji), Setaria italica Beauv., nuruk, yeast, refined yeast, licorice, Sasa borealis, Artemisia apiacea Hance, high-fructose corn syrupJeju, Korea15.0
Y12Rice, nuruk, dried orange peel, yeast, crude amylolytic enzyme, purified yeast, high-fructose corn syrup, citric acid, steviol glycosideJeju, Korea11.0
1 Information on ingredients of products was obtained from the label of each product.
Table
Table 2. Descriptors, definitions, and reference materials of 12 yakju samples.
Table 2. Descriptors, definitions, and reference materials of 12 yakju samples.
AttributesDefinitionReference Materials Reference Intensity
Appearance
ClearnessDegree of turbidityWater15.0
RednessDegree of rednessPantone color book (Pantone, NJ, USA)487 C = 7.5;
485 C = 15.0
YellownessDegree of yellowness Pantone color book (Pantone, NJ, USA)129 C = 7.5;
131 C = 15.0
Odor
AlcoholOdor associated with alcoholSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)8.44
ChrysanthemumAroma associated with chrysanthemum Chrysanthemum teabag (PurunSan Agricultural Co., Seoul, Korea)14.5
GinsengAroma associated with ginseng Ginseng powder (PurunSan Agricultural Co., Seoul, Korea)14.5
GrapeAroma associated with grapeGrape14.5
Hawthorn (Crataegi fructus)Aroma associated with hawthorn fruit (Crataegi fructus)Dried hawthorn fruit (PurunSan Agricultural Co., Seoul, Korea)14.5
Maesil (Prunus mume fruit)Maesil aromaMaesil 14.5
MakgeolliSour and sweet aroma associated with Nuruk, ipguk (koji), and fermentation.Rice Makgeolli (Kooksoondang Brewery Co., Ltd., Gangwon-do, Korea)10.9
Omija (Schizandra chinensis fruit)Aroma associated with omija omija 14.5
PeppermintAroma associated with peppermintPeppermint (Lipton peppermint herb tea, Unilever, London, England)14.5
Persimmon vinegarSweet and acidic aroma associated with persimmon vinegarPersimmon vinegar (Chungjungone Co., Seoul, Korea)13.3
PineAroma associated with pine Pine Bud Drink (Lotte Co., Ltd., Seoul, Korea)13.6
Roasted grainSavory aroma associated with roasted grainCornsilk Tea Drink (Kwangdong Pharmaceutical Co., Ltd., Seoul, Korea11.7
SourSour aroma associated with vinegar, fruitVinegar solution (Brewed vinegar, Ottogi, Gyeonggi-do, Korea)Vinegar vs. water (1:1) = 7.60; (2:1) = 11.4
SweetSweet aroma associated with honey, syrup Rice syrup (Chungjungone Co., Seoul, Korea)10.0
Tangerine peelAroma associated with tangerine peel Tangerine peel powder (PurunSan Agricultural Co., Seoul, Korea)14.5
YeastSalty and moldy aroma associated with meju, soy sauce, and soybean paste Yeast (Jeonwon Foods Co., Gyeonggi-do, Korea)12.2
Taste/Flavor
BitternessFundamental taste of bitterness1.0% (w/w) guarana solution
(Guarana extract powder, Cremar, Seoul, Korea)		5.3
SaltinessFundamental taste of saltiness0.1% (w/w) NaCl solution
(Morton iodized salt, Morton Salt, Inc., Chicago, IL, USA)		2.5
SournessFundamental taste of sourness0.1% (w/w) citric acid solution
(EdentownF&B, Incheon, Korea)		5.5
SweetnessFundamental taste of sweetness1.0% (w/w) sucrose solution
(CJ Cheiljedang Co., Seoul, Korea)		2.40
UmamiFundamental taste of umami0.5% MSG solution
(Miwon, Daesang Co., Seoul, Korea)		13.0
AlcoholFlavor associated with alcohol Soju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)7.50
AppleFlavor associated with appleApple14.5
Balloon flower rootFlavor associated with balloon flower rootBalloon flower root14.5
GrapeFlavor associated with grapeGrape14.5
Maesil (Prunus mume fruit)Flavor associated with maesil Maesil 14.5
Roasted grainSavory flavor associated with roasted grainCornsilk Tea Drink (Kwangdong Pharmaceutical Co., Ltd., Seoul, Korea)13.1
Tangerine peelFlavor associated with tangerine peelTangerine peel powder (PurunSan Agricultural Co., Seoul, Korea)14.5
Mouthfeel
AstringentDry and a feeling of shrank skin in the mouth0.3% (w/w) alum solution
(Alum, McCormick & Co., Inc., Baltimore, MD, USA)		2.6
BodyMouthfeel associated richness and heavinessSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)4.5
BurningMouthfeel associated with mouth-burning feeling caused by alcoholSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)8.7
CoatingMouthfeel associated with wrapping the mouth with a soft and slippery feelingSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)4.6
PungentMouthfeel associated with stimulation of the nasal cavity and mouthPersimmon vinegar
(Chungjungone Co., Seoul, Korea)		14.5
StingingMouthfeel associated with stinging, tingling sensationRadish sprouts13.5
Aftertaste/mouthfeel
BitternessTaste of bitterness after swallowing1.0% (w/w) Guarana solution
(Guarana extract powder, Cremar, Seoul, Korea)		5.26
SournessTaste of sourness after swallowing0.1% (w/w) citric acid solution
(EdentownF&B, Incheon, Korea)		5.47
SweetnessTaste of sweetness after swallowing1.0% (w/w) sucrose solution
(CJ Cheiljedang Co., Seoul, Korea)		2.40
UmamiTaste of umami after swallowing0.5% MSG solution
(Miwon, Daesang Co., Seoul, Korea)		13.0
AstringentMouthfeel of drying, shrinking after swallowing 0.3% (w/w) alum solution
(Alum, McCormick & Co., Inc., Baltimore, MD, USA)		2.6
BurningMouthfeel of alcohol after swallowingSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)8.7
CoatingMouthfeel of wrapping the mouth with a soft and slippery feeling after swallowingSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)4.6
ResidueMouthfeel of residue after swallowingMilk (SeoulMilk, Seoul, Korea)9.60
StingingMouthfeel of stinging, tingling sensation after swallowingSoju (Chamisul Fresh, Hitejinro Co., Ltd., Seoul, Korea)13.5
Table
Table 3. Mean intensity scores of the sensory attributes for 12 yakju samples 1–3.
Table 3. Mean intensity scores of the sensory attributes for 12 yakju samples 1–3.
SamplesY1Y2Y3Y4Y5Y6Y7Y8Y9Y10Y11Y12
Attributes
Appearance
Clearness14.4 ± 0.9514.4 ± 0.9414.6 ± 0.5714.2 ± 1.3914.3 ± 2.5914.2 ± 1.2914.2 ± 1.3713.8 ± 1.8114.3 ± 2.6014.0 ± 1.8714.6 ± 0.6414.4 ± 0.92
Redness ***1.25 c ± 1.392.07 b ± 2.250.00 d ± 0.020.03 d ± 0.080.43 d ± 2.450.04 d ± 0.110.03 d ± 0.090.08 d ± 0.220.02 d ± 0.0911.5 a ± 2.720.01 d ± 0.030.00 d ± 0.01
Yellowness ***4.20 c ± 3.502.98 d ± 3.412.02 d ± 1.676.95 b ± 2.901.40 d ± 0.717.58 b ± 2.469.18 a ± 2.3010.1 a ± 1.991.37 d ± 0.881.71 d ± 4.001.98 d ± 1.414.67 c ± 2.06
Odor
Apple **0.21 ab ± 0.560.43 ab ± 1.060.46 ab ± 0.740.22 ab ± 0.450.12 b ± 0.340.12 b ± 0.380.03 b ± 0.090.19 ab ± 0.650.29 ab ± 0.530.32 ab ± 0.910.71 a ± 1.240.19 ± 0.51
Alcohol 3.65 ± 2.033.53 ± 1.833.75 ± 2.063.71 ± 1.873.50 ± 1.953.83 ± 1.913.81 ± 1.673.56 ± 2.143.78 ± 1.993.48 ± 1.943.56 ± 2.193.20 ± 1.84
Chrysanthemum ***0.09 b ± 0.410.03 b ± 0.110.02 b ± 0.090.05 b ± 0.182.09 a ± 2.980.19 b ± 0.460.15 b ± 0.340.16 b ± 0.510.02 b ± 0.120.60 b ± 2.660.26 b ± 1.190.64 b ± 1.45
Ginseng ***1.97 a ± 2.410.06 b ± 0.220.46 b ± 1.780.21 b ± 0.830.09 b ± 0.370.06 b ± 0.180.39 b ± 1.470.53 b ± 1.670.40 b ± 1.120.11 b ± 0.570.34 b ± 1.220.03 b ± 0.08
Hawthorn ***1.38 a ± 2.110.80 abc ± 1.570.29 bc ± 1.210.24 bc ± 0.560.48 bc ± 1.150.22 bc ± 0.450.19 bc ± 0.360.10 bc ± 0.220.01 c ± 0.030.86 ab ± 0.870.02 c ± 0.060.67 bc ± 1.32
Maesil (Prunus mume fruit)0.74 ± 1.271.22 ± 2.120.63 ± 0.810.82 ± 1.140.31 ± 0.550.77 ± 0.850.66 ± 1.060.88 ± 1.210.51 ± 0.880.75 ± 1.390.64 ± 0.800.59 ± 0.95
Makgeolli2.22 ± 1.812.21 ± 1.732.70 ± 1.962.26 ± 1.411.89 ± 2.022.57 ± 1.632.45 ± 2.171.96 ± 1.332.49 ± 1.751.32 ± 1.432.69 ± 1.971.63 ± 1.35
Omija (Schizandra chinensis fruit) ***0.98 b ± 1.490.50 b ± 0.870.01 b ± 0.020.27 b ± 0.940.17 b ± 0.380.17 b ± 0.500.13 b ± 0.320.16 b ± 0.480.00 b ± 0.025.75 a ± 3.630.01 b ± 0.020.28 b ± 0.64
Peppermint ***0.13 b ± 0.500.07 b ± 0.410.05 b ± 0.170.26 b ± 1.041.11 a ± 1.860.07 b ± 0.380.00 b ± 0.020.07 b ± 0.410.00 b ± 0.010.17 b ± 0.640.00 b ± 0.020.47 b ± 1.02
Persimmon Vinegar ***0.34 bcd ± 0.810.36 bcd ± 0.640.11 d ± 0.241.09 a ± 1.650.06 d ± 0.170.98 ab ± 1.250.74 abcd ± 1.110.86 abc ± 1.330.24 cd ± 0.440.64 abcd ± 1.340.31 bcd ± 0.640.21 cd ± 0.37
Pine ***0.10 b ± 0.280.01 b ± 0.020.06 b ± 0.230.14 b ± 0.812.05 a ± 2.490.00 b ± 0.010.01 b ± 0.020.05 b ± 0.270.00 b ± 0.020.10 b ± 0.470.01 b ± 0.020.71 b ± 1.51
Pineapple **0.02 b ± 0.060.14 b ± 0.350.30 b ± 1.310.20 b ± 0.890.15 b ± 0.500.27 b ± 0.810.01 b ± 0.030.02 b ± 0.090.11 b ± 0.220.14 b ± 0.581.02 a ± 2.630.07 b ± 0.34
Roasted grain ***0.72 ab ± 1.370.49 b ± 0.820.93 ab ± 1.211.32 ab ± 2.140.30 b ± 0.591.53 a ± 2.201.15 ab ± 1.601.60 a ± 2.010.43 b ± 0.610.78 ab ± 1.150.41 b ± 0.550.43 b ± 0.58
Sour 2.94 ± 2.873.11 ± 2.762.70 ± 2.413.67 ± 3.002.69 ± 2.593.00 ± 2.702.64 ± 2.573.60 ± 3.352.36 ± 2.534.15 ± 3.093.04 ± 2.703.01 ± 3.02
Sweet 2.93 ± 1.842.65 ± 1.882.42 ± 1.472.99 ± 1.582.40 ± 1.983.05 ± 1.832.58 ± 1.683.28 ± 1.542.58 ± 1.513.68 ± 2.303.06 ± 2.032.94 ± 1.52
Tangerine peel ***0.25 b ± 0.670.08 b ± 0.250.22 b ± 0.960.37 b ± 0.820.19 b ± 0.380.11 b ± 0.220.40 b ± 0.860.20 b ± 0.430.07 b ± 0.230.33 b ± 0.940.09 b ± 0.361.13 a ± 1.32
Yeast ***0.89 b ± 1.381.86 b ± 2.100.91 b ± 1.003.26 a ± 2.050.65 b ± 0.883.60 a ± 2.703.73 a ± 2.553.46 a ± 2.271.00 b ± 1.220.86 b ± 1.251.68 b ± 1.981.25 b ± 1.18
Taste/Flavor
Bitterness **2.59 abc ± 1.961.77 c ± 1.542.19 abc ± 1.572.96 abc ± 2.182.65 abc ± 1.672.78 abc ± 1.483.55 a ± 1.963.24 ab ± 2.103.05 abc ± 1.812.40 abc ± 1.482.60 abc ± 1.872.12 bc ± 1.45
Saltiness ***0.85 bc ± 0.900.85 bc ± 0.930.85 bc ± 1.001.52 ab ± 1.190.53 c ± 0.721.35 ab ± 1.171.37 ab ± 1.191.89 a ± 1.420.48 c ± 0.621.23 abc ± 1.070.90 bc ± 0.931.04 bc ± 0.93
Sourness ***3.26 bcd ± 1.933.81 abc ± 2.252.86 bcd ± 1.874.74 a ± 2.072.39 d ± 1.662.97 bcd ± 1.672.97 bcd ± 1.842.62 cd ± 2.232.33 d ± 2.084.23 ab ± 1.604.07 ab ± 1.802.88 bcd ± 1.46
Sweetness ***2.80 abc ± 1.573.22 a ± 1.753.03 ab ± 1.562.67 abc ± 1.942.60 abc ± 1.471.85 cd ± 1.161.93 bcd ± 1.383.06 ab ± 1.581.36 d ± 0.893.37 a ± 1.732.59 abc ± 1.862.83 abc ± 1.40
Umami ***0.83 b ± 1.080.77 b ± 1.040.81 b ± 0.941.27 ab ± 1.710.71 b ± 1.191.21 ab ± 1.941.03 b ± 1.692.14 a ± 2.200.50 b ± 1.101.04 b ± 1.430.70 b ± 0.931.48 ab ± 1.58
Alcohol ***3.78 ab ± 1.823.56 ab ± 1.763.55 ab ± 1.774.49 ab ± 2.213.89 ab ± 1.784.56 ab ± 1.554.86 a ± 2.014.79 a ± 1.774.76 a ± 1.843.25 b ± 1.404.13 ab ± 1.903.27 b ± 1.69
Apple **0.64 ab ± 1.420.89 a ± 1.290.81 ab ± 1.500.38 ab ± 1.060.40 ab ± 0.880.13 ab ± 0.280.03 b ± 0.090.03 b ± 0.070.13 ab ± 0.370.59 ab ± 1.210.66 ab ± 1.330.54 ab ± 1.24
Balloon flower root 1.10 ± 1.670.23 ± 0.540.58 ± 1.940.60 ± 1.560.84 ± 1.380.70 ± 1.190.69 ± 1.210.74 ± 1.691.12 ± 2.130.33 ± 0.640.61 ± 1.480.33 ± 0.60
Grape ***0.73 ab ± 1.400.87 a ± 1.440.61 ab ± 1.500.33 ab ± 0.950.31 ab ± 0.880.09 b ± 0.310.01 b ± 0.030.02 b ± 0.090.05 b ± 0.140.89 a ± 1.390.79 ab ± 1.530.26 ab ± 0.80
Kudzu *0.23 ab ± 0.440.03 b ± 0.070.37 ab ± 1.400.51 ab ± 1.170.40 ab ± 0.810.54 ab ± 1.270.88 a ± 1.920.68 ab ± 1.500.30 ab ± 0.670.08 ab ± 0.260.15 ab ± 0.630.19 ab ± 0.39
Maesil (Prunus mume fruit)0.99 ± 2.181.05 ± 1.720.78 ± 1.540.91 ± 1.570.60 ± 1.070.29 ± 0.550.17 ± 0.360.45 ± 0.620.23 ± 0.471.11 ± 1.630.64 ± 1.100.78 ± 1.45
Roasted grain 1.23 ± 1.770.83 ± 1.351.36 ± 1.651.57 ± 1.970.67 ± 0.831.84 ± 2.510.97 ± 1.201.97 ± 2.260.79 ± 1.311.26 ± 1.540.86 ± 1.041.09 ± 1.17
Tangerine peel **0.40 b ± 0.880.18 b ± 0.420.27 b ± 0.900.55 b ± 0.880.51 b ± 0.730.42 b ± 1.000.53 b ± 1.280.20 b ± 0.390.33 b ± 0.960.61 b ± 1.030.47 b ± 1.201.22 a ± 1.44
Mouthfeel
Astringent 1.01 ± 0.821.16 ± 0.801.12 ± 0.891.26 ± 1.170.82 ± 0.741.05 ± 0.911.13 ± 0.810.93 ± 0.830.99 ± 1.091.24 ± 0.671.15 ± 0.850.83 ± 0.63
Body ***3.04 abc ± 2.122.82 bc ± 2.212.14 c ± 1.693.82 ab ± 2.362.23 c ± 1.793.08 abc ± 1.953.15 abc ± 1.924.43 a ± 2.481.98 c ± 1.433.32 abc ± 1.972.56 bc ± 2.103.11 abc ± 1.91
Burning3.56 ± 2.653.25 ± 2.743.62 ± 2.744.67 ± 3.013.54 ± 2.584.00 ± 2.534.80 ± 2.804.84 ± 2.954.77 ± 2.602.91 ± 2.304.21 ± 2.763.14 ± 2.47
Coating **1.84 b ± 1.421.72 b ± 1.481.60 b ± 1.332.64 ab ± 1.711.66 b ± 1.142.00 ab ± 1.312.14 ab ± 1.462.92 a ± 1.942.02 ab ± 1.351.67 b ± 1.241.83 b ± 1.331.77 b ± 1.44
Pungent 0.87 ± 1.070.75 ± 1.160.65 ± 0.981.67 ± 2.160.70 ± 0.821.08 ± 1.511.36 ± 2.341.15 ± 1.451.11 ± 1.441.21 ± 1.851.02 ± 1.340.84 ± 1.19
Stinging ***1.54 b ± 1.481.26 b ± 1.221.48 b ± 1.483.03 a ± 2.691.77 ab ± 1.692.31 ab ± 2.012.62 ab ± 2.002.70 ab ± 2.532.42 ab ± 2.191.43 b ± 1.421.87 ab ± 1.641.49 b ± 1.40
Aftertaste/mouthfeel
Bitterness **1.75 ab ± 1.701.25 b ± 1.371.65 ab ± 1.472.21 ab ± 2.061.86 ab ± 1.322.11 ab ± 1.192.72 a ± 1.802.29 ab ± 1.802.18 ab ± 1.761.53 ab ± 1.032.00 ab ± 1.611.43 b ± 1.23
Sourness ***2.16 bc ± 1.622.38 bc ± 1.721.77 bc ± 1.233.44 a ± 1.781.41 c ± 1.002.06 bc ± 1.462.19 bc ± 1.551.78 bc ± 1.651.38 c ± 1.452.72 ab ± 1.432.68 ab ± 1.541.91 bc ± 1.08
Sweetness ***1.78 abc ± 0.652.04 ab ± 0.841.93 ab ± 0.701.63 bcd ± 0.781.40 cd ± 0.561.23 de ± 0.631.18 de ± 0.672.16 a ± 0.800.84 e ± 0.601.94 ab ± 0.951.41 cd ± 0.671.84 abc ± 0.75
Umami **0.81 abc ± 0.990.59 abc ± 0.500.79 abc ± 1.111.05 abc ± 1.450.46 bc ± 0.810.83 abc ± 1.360.75 abc ± 1.151.36 a ± 0.910.23 c ± 0.310.97 abc ± 1.350.52 bc ± 0.871.09 ab ± 1.15
Astringent 0.79 ± 0.880.88 ± 0.730.81 ± 0.770.95 ± 0.950.84 ± 0.740.87 ± 0.691.07 ± 1.120.83 ± 0.760.76 ± 0.981.05 ± 0.701.01 ± 0.890.68 ± 0.50
Burning2.74 ± 2.352.18 ± 2.082.67 ± 2.053.39 ± 2.242.40 ± 2.173.15 ± 2.283.34 ± 2.033.67 ± 2.563.60 ± 2.421.91 ± 1.463.10 ± 2.172.31 ± 2.04
Coating1.22 ± 0.911.15 ± 1.011.26 ± 1.031.70 ± 1.271.29 ± 1.041.39 ± 0.901.52 ± 1.061.86 ± 1.231.55 ± 0.951.08 ± 0.891.35 ± 1.071.33 ± 1.02
Residue **0.92 ab ± 0.920.92 ab ± 0.840.81 ab ± 0.741.47 ab ± 1.260.83 ab ± 0.781.33 ab ± 1.551.09 ab ± 1.001.58 a ± 1.090.72 b ± 0.671.21 ab ± 1.210.80 ab ± 0.701.04 ab ± 0.96
Stinging ***1.30 abc ± 1.490.86 c ± 0.791.06 bc ± 1.002.32 a ± 2.441.32 abc ± 1.501.74 abc ± 1.882.07 abc ± 1.582.16 ab ± 1.961.97 abc ± 1.760.88 c ± 0.901.33 abc ± 1.541.19 abc ± 1.13
1 Mean values with different alphabet mean significantly different. 2 *, **, *** means significantly different at p < 0.05, p < 0.01, and p < 0.001 respectively. 3 15 cm line scale was used; 0 cm = none, 15 cm = very stron.
Table
Table 4. Mean scores for the consumers’ acceptance of the yakju samples 1,2.
Table 4. Mean scores for the consumers’ acceptance of the yakju samples 1,2.
SamplesOverall Acceptance Scores
Y15.12 d ± 2.10
Y26.34 ab ± 1.82
Y36.71 a ± 1.34
Y44.01 e ± 2.13
Y55.59 cd ± 1.80
Y64.02 e ± 1.71
Y73.43 f ± 1.57
Y83.25 f ± 2.25
Y94.06 e ± 1.72
Y106.41 ab ± 1.76
Y114.30 e ± 1.66
Y125.82 bc ± 1.63
1 Average scores of 80 consumers; 1 = dislike extremely, 9 = like extremely. 2 Mean values with different alphabet mean significantly different at p < 0.05.
Table
Table 5. Volatile compounds of the 12 yakju samples 1.
Table 5. Volatile compounds of the 12 yakju samples 1.
RI 2CompoundConcentration (μg/L)
Y1Y2Y3Y4Y5Y6Y7Y8Y9Y10Y11Y12
Acids
1434acetic acid1314 ± 319837 ± 176414 ± 60.814,700 ± 1524894 ± 1171230 ± 3301281 ± 4475038 ± 3011558 ± 3711436 ± 1852266 ± 407624 ± 69.8
1492formic acidNDNDNDNDNDND11.3 ± 6.7NDNDNDNDND
1524propanoic acid43.0 ± 7.0641.7 ± 10.032.6 ± 3.78751 ± 115843 ± 95.172.6 ± 7.0090.7 ± 17.065.3 ± 4.60200 ± 38.476.9 ± 7.36113 ± 12.678.5 ± 5.50
15542-methyl propanoic acid479 ± 85.3494 ± 80.5453 ± 50.0187 ± 59.4662 ± 82.6110 ± 21.0138 ± 24.9309 ± 20.6105 ± 13.6465 ± 48.4451 ± 70.3313 ± 18.8
1613butanoic acid148 ± 25.3172 ± 27.8137 ± 16.484.4 ± 27.9140 ± 19.9104 ± 23.3114 ± 18.9207 ± 14.320.1 ± 2.82146 ± 16.0178 ± 27.0162 ± 11.9
16563-methyl butanoic acid422 ± 61.5385 ± 73.7303 ± 27.1254 ± 67.2540 ± 59.8143 ± 52.2145 ± 16.9330 ± 28.2104 ± 8.31324 ± 49.7399 ± 21.2226 ± 45.2
1724pentanoic acidND16.2 ± 0.69ND22.3 ± 9.64ND43.2 ± 6.0556.6 ± 1.4044.2 ± 8.33ND73.1 ± 5.70ND29.1 ± 6.62
17592-butenoic acidNDNDNDNDNDND12.4 ± 1.79NDNDNDNDND
17712-methyl-2-butenoic acid33.2 ± 7.0426.1 ± 8.9133.2 ± 14.3ND35.2 ± 10.325.9 ± 6.1339.2 ± 11.4ND10.9 ± 0.8676.3 ± 32.151.0 ± 32.217.7 ± 5.12
1832hexanoic acid189 ± 28.7232 ± 35.3182 ± 18.5301 ± 151308 ± 37.4168 ± 7.83206 ± 21.6282 ± 22.256.7 ± 6.48194 ± 19.7232 ± 48.7304 ± 34.5
2034octanoic acid88.1 ± 9.82144 ± 24.4122 ± 4.65113 ± 78.789.6 ± 16.8142 ± 2.54155 ± 31.060.3 ± 21.3112 ± 17.9122 ± 15.4171 ± 27.8293 ± 16.7
2170lactic acid350 ± 1311777 ± 4211018 ± 1492277 ± 1032211 ± 135215 ± 62.781.8 ± 48.273.3 ± 91.7ND80.3 ± 16.6NDND
2256decanoic acid19.4 ± 9.5419.9 ± 4.4615.8 ± 2.7433.5 ± 16.514.7 ± 1.26NDNDNDNDNDND30.6 ± 6.40
2422benzoic acid36.6 ± 5.4324.2 ± 7.0426.2 ± 5.8246.7 ± 7.0038.3 ± 8.5316.2 ± 4.7939.5 ± 12.119.6 ± 3.9227.6 ± 8.3331.0 ± 5.6317.8 ± 1.5357.0 ± 9.00
Subtotal3122 ± 3624170 ± 4732737 ± 17418,770 ± 18553776 ± 2322269 ± 3422372 ± 4536429 ± 3192194 ± 3743024 ± 2043879 ± 4202135 ± 95.4
Alcohols
10251-propanol777 ± 142727 ± 125735 ± 68.1510 ± 106663 ± 37.7814 ± 161985 ± 101500 ± 42.7487 ± 86.9963 ± 1101969 ± 155954 ± 95.0
10852-methyl-1-propanol10,085 ± 152612,313 ± 16129109 ± 5174251 ± 101810,221 ± 9196989 ± 10357703 ± 6319469 ± 7064303 ± 5587171 ± 8157366 ± 7548548 ± 886
11341-butanol247 ± 28.8300 ± 52.4735 ± 43.444.8 ± 9.4132 ± 11.4456 ± 75.5460 ± 48.8119 ± 6.45288 ± 41.21160 ± 107289 ± 36.0511 ± 77.8
1210isoamyl alcohol41,034 ± 575144,956 ± 572539,224 ± 148015,567 ± 821445,159 ± 454031,676 ± 526936,373 ± 247534,114 ± 197418,342 ± 209232,551 ± 299835,548 ± 485030,988 ± 1902
12413-methyl-3-buten-1-ol43.3 ± 4.2930.0 ± 6.0428.9 ± 2.8843.7 ± 20.175.3 ± 3.7849.6 ± 3.6267.2 ± 15.870.9 ± 2.7414.8 ± 2.4548.8 ± 2.2253.9 ± 10.5825.5 ± 2.20
12481-pentanolNDNDNDNDNDNDND16.7 ± 2.49ND17.5 ± 6.76NDND
13112-methyl-2-buten-1-ol17.0 ± 2.28NDND50.7 ± 15.1NDND14.2 ± 3.2110.6 ± 0.61ND10.5 ± 0.6924.5 ± 5.3125.6 ± 1.86
13223-methyl-1-pentanol12.0 ± 4.0418.2 ± 2.0116.6 ± 1.19ND16.5 ± 1.578.91 ± 0.2112.4 ± 0.788.01 ± 1.09ND14.2 ± 1.7112.6 ± 8.138.59 ± 0.41
13421-hexanol71.8 ± 11.1NDNDND171 ± 16.3111 ± 11.6169 ± 16.1164 ± 7.9817.2 ± 1.5234.0 ± 7.2336.6 ± 6.4820.6 ± 1.37
13703-ethoxy-1-propanol1684. ± 296507 ± 78.2868 ± 86.6248 ± 89.7294 ± 36.3619 ± 123822 ± 149571 ± 48.7200 ± 38.01677 ± 75.53874 ± 6781254 ± 83.8
13763-hexen-1-ol8.91 ± 2.549.43 ± 1.44NDND9.57 ± 0.95NDNDNDNDNDNDND
14441-heptanol17.4 ± 2.4411.9 ± 1.3310.0 ± 0.73ND37.1 ± 4.3917.9 ± 1.6824.3 ± 6.9926.5 ± 0.8015.7 ± 6.1016.4 ± 5.2822.8 ± 2.8016.2 ± 0.66
14772-ethyl-1-hexanolNDNDNDND70.5 ± 2.8910.4 ± 0.8215.4 ± 4.6041.8 ± 1.3415.3 ± 2.7518.9 ± 3.70NDND
15321,3-butanediol2895 ± 6641260 ± 2571124 ± 1813457 ± 33981382 ± 2472155 ± 5502586 ± 7663387 ± 792803 ± 3541653 ± 1383193 ± 12861483 ± 103
15352,6-dimethyl-4-heptanolND104 ± 11.4141 ± 1.3ND60.7 ± 25.8NDNDNDNDNDNDND
15461-octanolNDNDND30.4 ± 9.3512.5 ± 1.7111.6 ± 1.2717.6 ± 1.6116.4 ± 1.55ND19.7 ± 8.9026.3 ± 5.4613.9 ± 0.83
15652,3-butanediol684 ± 169199 ± 37.0205 ± 35.81070 ± 561256 ± 46.0425 ± 121506 ± 176989 ± 302144 ± 66.6319 ± 36.1685 ± 355251 ± 17.4
1581propylene glycol138 ± 31.1143 ± 29.5120 ± 19.7180 ± 109117 ± 21.5154 ± 40.2168 ± 59.2315 ± 10958.8 ± 23.0115 ± 15.4177 ± 97.472.9 ± 4.45
16044-methyl-3-hexanol193 ± 41.848.0 ± 8.9522.4 ± 3.0427.6 ± 8.6379.7 ± 37.0121 ± 47.0125 ± 47.647.0 ± 3.9276.5 ± 7.8179.6 ± 5.8287.8 ± 23.165.4 ± 4.64
16492-furanmethanol81.8 ± 34.438.9 ± 8.4222.5 ± 7.85231 ± 132199 ± 34.0152 ± 36.1324 ± 197347 ± 30.223.7 ± 2.421048 ± 307248 ± 157144 ± 25.0
16872,3-hexanediolNDNDNDND10.3 ± 1.677.12 ± 3.1911.1 ± 4.594.89 ± 0.95NDNDNDND
1711methionol2450 ± 3951894 ± 1911930 ± 141651 ± 196511 ± 65.0431 ± 59.0603 ± 60.61263 ± 73.7631 ± 49.81441 ± 2181818 ± 2231915 ± 251
1872phenylmethanol54.6 ± 16.353.4 ± 19.614.7 ± 2.0042.1 ± 22.748.5 ± 9.7856.1 ± 6.1199.9 ± 7.4325.2 ± 5.3770.8 ± 6.6526.9 ± 2.8028.3 ± 16.938.7 ± 8.93
19192-phenylethanol28,572 ± 433924,887 ± 354020,061 ± 41420,658 ± 289516,549 ± 173420,417 ± 41022,932 ± 242817,507 ± 175816,920 ± 131920,396 ± 214623,663 ± 169224,511 ± 973
2310glycerolNDNDNDND25.7 ± 7.6475.9 ± 16.141.7 ± 17.941.1 ± 29.4NDNDNDND
23252-(4-methoxy phenyl)ethanolNDNDNDND29.1 ± 1.1711.8 ± 0.96NDNDNDNDNDND
Subtotal89,064 ± 741487,499 ± 693174,368 ± 164247,062 ± 942676,131 ± 495364,769 ± 542074,058 ± 362269,054 ± 286942,411 ± 256368,782 ± 380179,122 ± 541370,847 ± 2334
Aldehydes
1456furfural107 ± 3.1588.0 ± 9.4169.4 ± 3.3669.1 ± 4.7684.9 ± 8.55318 ± 20.2468 ± 104145 ± 46.816.7 ± 0.90447 ± 31.484.8 ± 32.5189 ± 22.8
24915-(hydroxymethyl)-2-furaldehydeND28.0 ± 7.3239.2 ± 1.78ND127 ± 18.439.0 ± 7.85NDNDND84.2 ± 16.8NDND
Subtotal107 ± 3.15116 ± 11.9109 ± 3.8069.1 ± 4.76212 ± 20.3357 ± 21.7468 ± 104145 ± 46.816.7 ± 0.90531 ± 35.684.8 ± 32.5189 ± 22.8
Esters
946ethyl propanoate33.6 ± 3.1238.7 ± 6.1717.7 ± 1.22ND28.1 ± 10.417.6 ± 10.5NDNDND32.2 ± 6.42ND43.3 ± 1.78
953ethyl 2-methyl propanoateND40.2 ± 4.1928.3 ± 2.25ND40.2 ± 9.844.6 ± 0.85NDNDND23.4 ± 8.535.32 ± 1.7118.1 ± 0.90
970propyl acetateND20.0 ± 2.31NDND13.4 ± 3.4926.1 ± 2.95NDND13.8 ± 8.6538.4 ± 12.2ND31.7 ± 1.98
9982-methylpropyl acetate95.7 ± 17.359.4 ± 5.6428.6 ± 1.90ND60.7 ± 12.955.0 ± 2.1955.1 ± 4.80ND15.6 ± 8.30110 ± 58.771.2 ± 33.071.9 ± 5.95
1022ethyl butanoate53.6 ± 9.5957.2 ± 5.7937.9 ± 2.78ND40.6 ± 5.9838.9 ± 2.1332.2 ± 4.7016.2 ± 4.236.98 ± 1.3136.8 ± 8.6236.9 ± 3.7561.6 ± 5.02
1039ethyl 2-methyl butanoate19.7 ± 3.92NDNDNDNDNDNDNDNDNDNDND
1112isoamyl acetate540 ± 115359 ± 36.1298 ± 6.71373 ± 415365 ± 49.8486 ± 21.3467 ± 13430.4 ± 10.5100 ± 35.4807 ± 335625 ± 142562 ± 45.3
1125ethyl pentanoateNDNDNDNDND5.51 ± 0.196.95 ± 0.60NDNDNDNDND
1227ethyl hexanoate80.1 ± 10.457.0 ± 5.7450.8 ± 3.9472.3 ± 62.387.0 ± 10.751.2 ± 0.9657.1 ± 18.791.3 ± 7.6211.5 ± 2.1772.2 ± 21.868.0 ± 13.982.8 ± 5.19
1258ethyl pyruvate49.8 ± 6.5638.4 ± 3.3431.1 ± 3.29ND19.8 ± 2.2021.3 ± 2.2537.7 ± 6.2612.0 ± 2.0882.6 ± 6.55161 ± 21.043.8 ± 3.5278.2 ± 7.34
1309methyl lactateND132 ± 33.946.5 ± 6.77NDNDNDND12.6 ± 0.93NDNDNDND
1338ethyl lactate5843 ± 86416,778 ± 194911,329 ± 63145,468 ± 11,1023536 ± 3942311 ± 2202563 ± 1823585 ± 170747 ± 62.02330 ± 78.8936 ± 1511337 ± 76.3
1404ethyl 2-hydroxy butanoate9.52 ± 1.7810.2 ± 0.916.77 ± 0.5911.9 ± 1.606.95 ± 1.348.49 ± 1.1510.8 ± 2.01NDNDND14.5 ± 2.136.98 ± 0.34
1419ethyl-2-hydroxy-2-methylbutanoate30.6 ± 5.8828.7 ± 2.4627.8 ± 7.79ND31.6 ± 4.2016.2 ± 1.1119.8 ± 4.20ND7.15 ± 0.9645.5 ± 13.4ND19.2 ± 0.72
1424ethyl octanoate26.3 ± 3.9519.3 ± 1.8618.1 ± 1.69ND151 ± 17.212.2 ± 0.6723.5 ± 3.10ND34.0 ± 5.6628.7 ± 9.52ND58.2 ± 2.09
1429ethyl 2-(1-ethoxyethoxy)propanoateND16.0 ± 6.405.49 ± 1.71NDNDNDNDNDNDNDNDND
1451isobutyl lactate91.7 ± 10.8165 ± 5.7371.2 ± 7.76128 ± 48.1NDNDND146 ± 80.013.3 ± 6.6799.3 ± 5.4128.8 ± 9.60ND
1511ethyl 3-hydroxybutanoate178 ± 38.6229 ± 29.480.8 ± 6.74159 ± 46.6180 ± 20.7257 ± 32.8289 ± 54.31035 ± 21.518.5 ± 2.62196 ± 23.8205 ± 31.3243 ± 12.2
1562isoamyl lactate138. ± 21.7261. ± 25.7144. ± 20.9446. ± 20355.6 ± 9.0630.6 ± 2.6137.4 ± 10.4668.8 ± 5.5311.6 ± 2.60120 ± 94.149.0 ± 18.1031.6 ± 0.57
1626ethyl methyl succinate35.7 ± 5.31NDND21.8 ± 9.27ND9.14 ± 2.8614.7 ± 1.98NDNDND47.8 ± 8.7238.8 ± 3.19
1665diethyl succinate5462 ± 1207456 ± 50.1491 ± 42.58015 ± 1590344 ± 53.8255 ± 10.1371 ± 22.41183 ± 85.2199 ± 42.2411 ± 127317 ± 5.98483 ± 23.9
1669ethyl 3-hydroxyhexanoateND109 ± 16.849.2 ± 9.78ND73.5 ± 11.926.3 ± 11.046.1 ± 18.620.7 ± 7.0224.3 ± 3.6253.5 ± 3.5631.3 ± 7.6923.7 ± 6.00
1782ethyl phenylacetate28.0 ± 14.059.6 ± 36.939.4 ± 25.361.2 ± 16.327.8 ± 18.317.2 ± 5.7013.7 ± 7.86NDNDNDNDND
1799ethyl 4-hydroxybutanoate4225 ± 6353229 ± 8602905 ± 1191454 ± 2493713 ± 4264079 ± 6554698 ± 5223958 ± 3762091 ± 8143455 ± 3071916 ± 2143002 ± 463
18152-phenylethyl acetate378 ± 67.6ND180 ± 35.7125 ± 71.1118 ± 36.5600 ± 25.9759 ± 41.726.9 ± 6.11188 ± 67.5538 ± 139.3557 ± 109257 ± 29.7
1899ethyl 3-methylbutyl succinate47.2 ± 12.31287 ± 1891171 ± 53.1101 ± 47.9128 ± 14.710.9 ± 2.6619.8 ± 3.1613.7 ± 3.0426.3 ± 3.2439.6 ± 38.347.2 ± 12.31287 ± 189
1997methyl 2-furoate64.3 ± 13.951.8 ± 6.9841.9 ± 2.67ND70.7 ± 10.713.6 ± 1.0516.6 ± 2.2919.6 ± 9.42ND186 ± 32.064.3 ± 13.951.8 ± 6.98
2031diethyl malate120 ± 33.3133 ± 41.2161 ± 12.2NDNDNDNDND100 ± 15.436.8 ± 7.37120 ± 33.3133 ± 41.2
2098diethyl 2-hydroxypentanedioate43.3 ± 12.0117 ± 17.085.5 ± 12.9ND43.5 ± 6.6422.6 ± 1.9022.7 ± 6.90ND11.8 ± 2.4932.0 ± 19.743.3 ± 12.0117 ± 17.0
2278ethyl 2-hydroxy-3-phenyl propanoate313 ± 21.6112 ± 13.8157 ± 4.37416 ± 58.1119 ± 10.4144 ± 12.3152 ± 54.143.1 ± 16.3298 ± 71.6139 ± 28.082.3 ± 20.2273 ± 43.4
2367ethyl hydrogen succinate5490 ± 7722504 ± 4833442 ± 2456056 ± 6224328 ± 2842009 ± 1711956 ± 8261268 ± 544712 ± 260720 ± 115250 ± 64.2887 ± 147
2454ethyl citrateNDNDNDNDNDNDNDNDND34.1 ± 10.0NDND
Subtotal23,396 ± 179626,367 ± 219520,944 ± 69362,908 ± 11,24613,580 ± 65210,527 ± 71411,669 ± 100711,530 ± 6944713 ± 8659744 ± 5285333 ± 3297707 ± 498
Furans
14532-(diethoxymethyl)furan73.4 ± 22.7ND 341.3 ± 7.99ND135 ± 21.3235 ± 107130 ± 77.7NDNDND203 ± 136370 ± 13.9
14982-acetylfuran38.1 ± 9.2814.0 ± 0.6912.5 ± 1.05ND16.0 ± 2.107.47 ± 0.9710.0 ± 2.11ND30.0 ± 8.2435.5 ± 17.836.1 ± 37.017.7 ± 1.01
Subtotal112 ± 24.614.0 ± 0.6953.8 ± 8.06ND151 ± 21.4242 ± 107140 ± 77.7ND30.0 ± 8.2435.5 ± 17.8239 ± 141388 ± 14.0
Ketones
9712,3-butanedione70.8 ± 11.8ND14.2 ± 3.6827.3 ± 19.5ND26.7 ± 3.69ND33.6 ± 21.041.3 ± 25.324.7 ± 12.627.8 ± 10.827.6 ± 3.39
11163-penten-2-one19.4 ± 2.7736.6 ± 6.2329.6 ± 0.84ND8.30 ± 2.3829.7 ± 5.0116.8 ± 3.28NDND16.8 ± 1.169.82 ± 0.7021.2 ± 3.56
12803-hydroxy-2-butanone (acetoin)868 ± 103233 ± 24.258.4 ± 6.73135 ± 75.3114 ± 13.433.2 ± 5.0076.7 ± 13.3153 ± 12.8728 ± 101129 ± 8.78246 ± 38.999.2 ± 13.1
12941-hydroxy-2-propanone (acetol)93.2 ± 14.848.1 ± 18.935.0 ± 13.9ND64.9 ± 8.799.13 ± 3.738.36 ± 1.6918.8 ± 7.88190 ± 29.666.4 ± 33.070.3 ± 23.818.4 ± 9.63
13433,3,6-trimethyl-1,5-heptadien-4-oneNDNDNDNDNDNDNDNDNDND141 ± 31.9ND
17213-methyl-2(5 H)-furanoneNDNDNDND56.7 ± 7.34NDNDND9.57 ± 0.57ND7.82 ± 0.679.61 ± 1.38
1736piperitoneNDNDNDND25.3 ± 7.28NDNDNDNDNDNDND
1825tetrahydro-4-methyl-2H-pyran-2-oneNDNDND16.4 ± 1.45ND27.7 ± 2.11ND41.9 ± 7.64ND24.5 ± 6.5057.5 ± 2.5962.0 ± 7.78
1969maltolNDNDND41.3 ± 24.0NDNDNDNDNDNDNDND
20425-acetyldihydro-2(3H)-furanoneNDNDNDND16.0 ± 2.28NDNDNDNDNDNDND
24735-hydroxymethyl dihydrofuran-2-one41.0 ± 13.019.8 ± 8.3045.2 ± 9.52NDNDND29.6 ± 6.46NDNDNDNDND
Subtotal1093 ± 105338 ± 32.4182 ± 18.6220 ± 81.4285 ± 19.4126 ± 9.07131 ± 15.2247 ± 26.9969 ± 109262 ± 37.0560 ± 56.7238 ± 18.7
Lactones
1637γ-butyrolactone2386 ± 5302782 ± 2322813 ± 208544 ± 1562874 ± 415ND2161 ± 121596 ± 58.7580 ± 2003130 ± 270300 ± 34.3993 ± 21.4
1707γ-hexalactoneNDNDND12.4 ± 3.3911.5 ± 1.3113.5 ± 1.2212.4 ± 0.9913.0 ± 1.08NDND17.5 ± 1.9914.4 ± 1.95
1725γ-ethoxybutyrolactone22.3 ± 6.66ND24.0 ± 2.9811.0 ± 1.4576.4 ± 9.84NDND21.7 ± 4.2210.5 ± 3.74ND36.7 ± 6.16ND
2026pantolactone55.3 ± 9.0274.1 ± 12.3ND51.5 ± 7.13248 ± 37.5113 ± 10.8193 ± 71.657.3 ± 18.1NDND85.0 ± 34.1203 ± 15.0
2032γ-nonalactoneNDNDND83.9 ± 17.0112 ± 15.337.1 ± 0.9952.6 ± 14.550.4 ± 16.3ND5151 ± 109414.7 ± 3.7118.5 ± 1.56
22304-ethoxycarbonyl-γ-butyrolactone128 ± 35.390.0 ± 8.35101 ± 7.7734.6 ± 3.65112 ± 11.160.6 ± 3.2166.8 ± 20.422.4 ± 8.2626.2 ± 7.4057.7 ± 11.5ND43.4 ± 6.49
23774-(1-hydroxyethyl)-γ-butyrolactone65.9 ± 14.933.8 ± 12.939.1 ± 4.03159 ± 23.2127 ± 16.667.7 ± 15.369.7 ± 31.765.9 ± 28.119.6 ± 8.22NDND21.0 ± 3.99
Subtotal2657 ± 5322980 ± 2332977 ± 209896 ± 1593562 ± 417291 ± 19.12555 ± 146827 ± 70.2637 ± 2018339 ± 1127454 ± 48.91294 ± 27.3
Phenols
1857guaiacolND14.6 ± 3.81NDNDNDNDND11.9 ± 6.6423.5 ± 13.417.2 ± 6.01NDND
1983phenolNDND11.2 ± 1.4458.9 ± 8.5421.6 ± 7.8510.5 ± 0.1113.3 ± 0.6115.4 ± 2.798.51 ± 0.9511.2 ± 2.9017.0 ± 3.0627.4 ± 4.41
20164-ethylguaiacolNDNDND559 ± 69.4NDNDNDNDNDNDNDND
20634-methylphenolNDNDND38.6 ± 7.06NDNDNDNDND12.9 ± 5.0NDND
21654-ethylphenolNDNDND88.6 ± 9.39NDNDNDNDNDNDNDND
21922-methoxy-4-vinylphenol120 ± 18.8326 ± 94.858.1 ± 16.950.8 ± 19.521.5 ± 7.5729.4 ± 4.3758.2 ± 19.4369 ± 82.7ND68.6 ± 18.452.7 ± 23.1202 ± 18.4
22032-methyl-5-(1-methylethyl) phenolNDNDNDNDND11.7 ± 1.70ND21.9 ± 9.40ND28.1 ± 11.5ND35.1 ± 6.53
23824-vinylphenol111 ± 42.073.1 ± 26.685.4 ± 8.02NDNDNDNDNDNDNDND36.8 ± 2.12
Subtotal231 ± 46.0414 ± 98.5155 ± 18.8796 ± 73.543.1 ± 10.951.6 ± 4.6971.5 ± 19.4418 ± 83.532.0 ± 13.5138 ± 23.369.7 ± 23.3301 ± 20.2
Terpenoids
1223eucalyptol26.1 ± 6.87NDNDND120 ± 5.21NDND25.2 ± 7.50ND24.6 ± 11.738.6 ± 2.63ND
16004-terpineolNDND7.46 ± 0.80ND52.5 ± 11.015.5 ± 8.1317.3 ± 9.28NDNDND24.2 ± 10.753.6 ± 10.1
1692α-terpineol9.08 ± 1.10ND8.86 ± 0.8219.2 ± 4.0412.9 ± 1.25NDNDNDND52.7 ± 10.3ND41.9 ± 5.41
1701borneol15.9 ± 2.01NDNDND133 ± 15.1NDNDNDND25.1 ± 4.34NDND
1842p-cymen-8-olNDNDNDND14.6 ± 1.93ND9.38 ± 2.64NDNDND18.7 ± 3.4127.6 ± 0.72
2073p-cymen-7-olNDNDNDND12.7 ± 2.0NDNDNDNDNDNDND
Subtotal51.1 ± 7.24ND16.3 ± 1.1519.2 ± 4.04346 ± 19.615.5 ± 8.1326.7 ± 9.6525.2 ± 7.50ND102 ± 16.281.4 ± 11.5123 ± 11.5
Miscellaneous
9691-(1-ethoxyethoxy) propane18.8 ± 10.747.5 ± 18.618.3 ± 6.18ND24.7 ± 8.2611.9 ± 1.9315.0 ± 0.90ND8.12 ± 1.2034.2 ± 19.256.4 ± 13.525.6 ± 4.82
9742,4,5-trimethyl-1,3-dioxolane10.7 ± 1.9010.9 ± 2.55NDND5.62 ± 1.22ND9.66 ± 4.54ND14.1 ± 5.2812.5 ± 8.1226.3 ± 19.4ND
9871-(1-ethoxyethoxy) butane111 ± 66.2387 ± 165117 ± 42.4ND199 ± 66.349.9 ± 10.744.3 ± 14.715.2 ± 9.02192 ± 118109 ± 26.080.0 ± 24.1106 ± 21.5
10532-methyl-1,3-dioxane15.7 ± 2.8325.7 ± 3.2015.7 ± 5.18NDNDNDNDND9.46 ± 4.9616.5 ± 4.62ND7.91 ± 2.47
10681,1-diethoxy-2-methylbutaneND37.3 ± 22.612.9 ± 3.2620.8 ± 17.817.0 ± 8.3183.1 ± 6.0821.2 ± 6.6421.8 ± 12.413.1 ± 6.88ND12.8 ± 7.5317.7 ± 1.91
10691,1-diethoxy-3-methylbutane21.5 ± 7.3139.8 ± 10.319.6 ± 3.1849.4 ± 28.428.7 ± 4.8620.2 ± 2.2851.4 ± 38.1142 ± 88.153.6 ± 20.521.8 ± 14.036.9 ± 16.654.0 ± 7.11
10981-(1-ethoxyethoxy) pentane262 ± 171817 ± 366338 ± 130ND540 ± 183164 ± 43.7169 ± 91.241.8 ± 25.1598 ± 367279 ± 64.7248 ± 103268 ± 51.6
12251,1-diethoxyhexane18.9 ± 3.3312.1 ± 2.1513.7 ± 1.83ND31.6 ± 3.99ND50.5 ± 23.6NDNDNDND10.4 ± 0.39
14945-hydroxy-2-methyl-1,3-dioxane66.3 ± 14.1195 ± 31.1115 ± 16.4ND126 ± 18.527.9 ± 6.9048.3 ± 17.98.43 ± 0.1021.9 ± 2.7686.8 ± 6.3224.3 ± 4.3225.1 ± 2.78
1629ethyl acetamide10.7 ± 1.9111.5 ± 1.7011.7 ± 6.86ND33.1 ± 13.77.30 ± 0.539.27 ± 0.3910.9 ± 3.59ND21.6 ± 11.2NDND
1862N-(3-methylbutyl) acetamide22.9 ± 13.524.1 ± 9.49NDND16.3 ± 8.1815.3 ± 5.5147.0 ± 42.238.9 ± 5.6912.8 ± 1.57ND54.4 ± 30.757.8 ± 8.15
19702-acetylpyrroleNDNDNDNDNDND10.0 ± 2.1711.4 ± 2.00ND11.3 ± 2.51NDND
Subtotal558 ± 1841607 ± 404661 ± 13870.2 ± 33.51022 ± 197380 ± 46.3475 ± 113290 ± 93.2923 ± 386593 ± 75.4540 ± 114573 ± 57.3
Total120,390 ± 7658123,505 ± 7301102,204 ± 1808130,811 ± 14,79299,108 ± 502379,030 ± 547991,968 ± 379488,966 ± 297251,925 ± 276791,550 ± 400690,364 ± 544383,795 ± 2390
1 Mean value of 3 replications ± SD. 2 RI (Retention indices) were determined on DB-wax using C6-C26 as external reference. ND stands for not detected.

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MDPI and ACS Style

Heo, J.; Kwak, H.S.; Kim, M.; Kim, J.-H.; Baek, H.H.; Shin, H.; Lee, Y.-s.; Lee, S.; Kim, S.S. Major Sensory Attributes and Volatile Compounds of Korean Rice Liquor (yakju) Affecting Overall Acceptance by Young Consumers. Foods 2020, 9, 722. https://doi.org/10.3390/foods9060722

AMA Style

Heo J, Kwak HS, Kim M, Kim J-H, Baek HH, Shin H, Lee Y-s, Lee S, Kim SS. Major Sensory Attributes and Volatile Compounds of Korean Rice Liquor (yakju) Affecting Overall Acceptance by Young Consumers. Foods. 2020; 9(6):722. https://doi.org/10.3390/foods9060722

Chicago/Turabian Style

Heo, JeongAe, Han Sub Kwak, Miran Kim, Jae-Ho Kim, Hyung Hee Baek, Hyukjin Shin, Young-seung Lee, Sanghyeok Lee, and Sang Sook Kim. 2020. "Major Sensory Attributes and Volatile Compounds of Korean Rice Liquor (yakju) Affecting Overall Acceptance by Young Consumers" Foods 9, no. 6: 722. https://doi.org/10.3390/foods9060722

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