The soju (Korean traditional distilled liquor) market is increasing worldwide. However, in contrast to well-explored distilled liquors, including baijiu (China) and shochu (Japan), soju is less investigated, with limited research on its aroma characteristics. To facilitate better understanding of the aroma characteristics of soju, this study aims to overview recent research on the flavor characteristics of soju and compare data with those of baijiu and shochu, well-established products in the market. Soju is generally made using rice and nuruk (a traditional Korean fermentation starter). Previous studies have reflected that the aroma characteristics vary with raw materials’ nutrition percentages, microbial taxa influenced in fermentation starters, and/or pressure reduction during distillation. The research on the aroma characteristics of baijiu, characterized by solid-state fermentation involving qu (a traditional Chinese fermentation starter), is focused on differences in regional characteristics of the flavor type. Research on the aroma characteristics of shochu has primarily demonstrated that the microbial community could contribute significantly to the development of specific aromatic compounds and/or attributes. Moreover, the association of the aroma characteristics of baijiu and shochu with their volatile compound development by the determination of selective ingredients has been examined. Understanding the current research progress can potentially facilitate the improvement in the aroma characteristics of soju.

This study aimed to investigate the fermentation performance and quality characteristics of distilled soju produced from various rice cultivars using Saccharomyces cerevisiae N9 yeast. The rice cultivars included high-yield varieties such as Samkwang (SK, control), Shindongjin (SDJ), Baromi2 (BRM2), Guemgang-1 (GG-1), Hanareum-4 (HAR-4), Chohong (CH), Saemimyeon (SMM), Mirchal (MRC), Irumi (IRM), and Migam (MG). The fermentation results showed that the high-amylose SMM exhibited significantly lower CO2 production and alcohol content (16.57%), indicating its unsuitability for distilled soju production. The pH, total acid, and amino acid content were similar among the rice cultivars. However, volatile acid content was comparatively higher in the SDJ and SMM cultivars. Organic acid composition revealed that succinic acid, citric acid, and lactic acid were the predominant components contributing to ester compound formation. Distilled soju made from the SDJ, IRM, and MG cultivars exhibited higher organic acid levels, enhancing ester production. Sensory evaluation indicated that distilled soju made from SDJ, with the highest ethyl acetate concentration, scored the highest in aroma and overall preference. This result is likely due to the positive contribution of ester aroma compounds to the sensory profile. In contrast, SMM was found to be unsuitable for distilled soju production. The SDJ cultivar showed superior fermentation efficiency, higher volatile aroma compound formation, and greater consumer preference, making it suitable for producing distilled soju.

The study was conducted to confirm the possibility of producing alcohol beverages from Dae-hong peaches. Upon examining the quality characteristics of distilled soju using Dae-hong peaches, the alcohol content was 1.12 to 1.16 times higher than that from the atmospheric distillation method. Soju with 20 % peach extract content had the highest alcohol content and the lowest volatile acid content, indicating a low possibility of causing irritating odors. Acetaldehyde was 1.3-1.94 times lower in vacuum-distilled soju, and methanol was not detected in all samples. The absorbance value of furfural, a burnt component generated during distillation is high in atmospheric distillation, which can cause irritating odors. Upon examining the volatile fragrance components, isoamylalcohol and 1-propanol were found to be the main components, both of which were the highest in the treatment group with 20 % peach extract content. The electronic nose analysis revealed that this group showed the most opposing flavor patterns to the control group, and when distilled under reduced pressure with 20 % addition of Dae-hong peaches can produce high-quality soju.

The objective of this study was to evaluate the quality characteristics of makgeolli under conditions of nutrient deficiency and high-temperature fermentation. Makgeolli was prepared using rice, water, enzyme (glucoamylase), and yeast (La Parisienne, WB06). These ingredients were mixed and fermented for 6 days at 25°C, followed by 3 days each at 25°C, 35°C, and 45°C. The WB06 treatment resulted in lower alcohol content, with higher temperatures during the last 3 days of the 9-day fermentation process, further suppressing alcohol production. Conversely, the content of reducing sugar was highest when WB06 was fermented at 25°C. Although the lactic acid content of the alcoholic beverage made with WB06 was high, the elevated sugar content resulted in a suitable sugar-acid ratio. Yeast remained viable even when fermented at a high temperature of 45°C. This study demonstrated the feasibility of producing low-alcohol beverages with viable yeast cultures with nutrient deficiency and high-temperature fermentation.

This study aimed to assess the quality characteristics of barley nuruk and makgeolli based on grinding size and inoculation rates, with a focus on identifying key aroma compounds contributing to nuruk off-flavors. Barley was hulled to 30%, using coarse (5 mm) and fine (1 mm) ratios, and inoculated with Aspergillus luchuensis 34-1 at 0.1% and 1% rates. Quality parameters such as moisture, pH, acidity, amino acidity, organic acids, and free amino acids were analyzed. At the same time, enzyme activities like saccharogenic power, α-glucosidase, glucoamylase, α-amylase, and carboxypeptidase were measured. Microbial contamination was assessed, and volatile aroma compounds were quantified using gas chromatography. Results indicated that finer milling (1 mm) and higher inoculation (1%) significantly increased enzyme activity and free amino acid content in nuruk, leading to a higher concentration of fruity volatile compounds in makgeolli. Thus, adjusting the grinding size and inoculation rates in nuruk production is key to enhancing makgeolli flavor quality.

Purpose: The nutritional characteristics, processing properties of six domestic waxy and non-waxy foxtail millet cultivars were evaluated. Methods: The particle size ratio, water absorption ratio, recovery ratio, proximate composition, vitamin, minerals, starch and amylose contents, pasting properties, and color value were analyzed. Results: The waxy foxtail millet (WFM) had a higher quantity of vitamins and minerals than the non-waxy foxtail millet (NFM). The total starch of WFM and NFM was 66.38 and 66.65%, respectively, and the amylose of WFM and NFM was 5.22 and 21.63%, respectively. WFM showed a higher fine particles (FP) ratio, moisture, and water absorption ratio than NFM. Moreover, WFM showed a high gelatinization time and trough viscosity, whereas NFM showed a high breakdown, final, setback viscosity, and gelatinization temperature. Positive correlations were observed among moisture, water absorption, Vitamins B1 and B2, niacin, iron, zinc, recovery ratio of steamed flour, starch, peak, and trough viscosity. Keongkwan No.2 showed a significantly higher recovery ratio of steamed flour, moisture content, moisture absorption ratio, peak, and trough viscosity than the other cultivars. In addition, Hwangmichal showed a higher ratio of FP and moisture absorption ratio after steaming than the others. Dahwangme had a high ratio of CP, niacin, total starch, and amylose content. In contrast, the raw flour of Samdame had a high quantity of total starch with a high final viscosity and setback viscosity. Moreover, Samdame had significantly high levels of vitamins B1 and B2, calcium, and sodium. Chohwangme showed a significantly higher quantity of lipid, ash and β-carotene, phosphorus, iron, and magnesium than the others. Conclusions: Each cultivar of foxtail millet has different nutritional and physical qualities during the steam and dry process. The product quality can be improved by selecting suitable foxtail millet cultivars according to the processing method to be used.