Correlation between key aroma and manufacturing processes of rice-flavor baijiu and awamori, Chinese and Japanese traditional liquors

Enhancing synthesis of ethyl lactate in rice baijiu fermentation by adding recovered granular cells

Ethyl lactate is the most abundant ester in semi-solid rice baijiu fermentation, affecting the flavor of baijiu to a great extent. The present study aimed to investigate the spatial distribution and formation contributor of ethyl lactate by removing the microorganisms and extracellular enzymes from the upper, middle, and lower fermentation broth during the later fermentation stage. The removal of suspended substances by centrifugation did not affect the ethyl lactate content in the top and middle fermentation broth containing free cells, enzymes, and starch particles. After day 5 of fermentation, only the lower fermentation broth containing granular cells attached to the starch could continue to accumulate lactic acid, thereby increasing the ethyl lactate content. The results showed that the chemical reactions were the main contributor to the increased ethyl lactate content at the anaphase of fermentation rather than enzymatic catalysis or microbial metabolism. Sequencing of granular cells revealed the main lactic acid producers at different fermentation stages. Lactobacillus helveticus showed the highest abundance of 94.45-95.40% on day 5, which decreased to 29.58-30.20% on day 15, while Lactobacillus acetotolerans showed the highest abundance of 47.93-49.72% at day 15. Additionally, the granular cells were recovered and used for supplementary inoculation in the next batch, which significantly increased the ethyl lactate content. This study provided a novel strategy for improving the ethyl lactate content in semi-solid baijiu fermentation.

Comparison of Aroma Compounds and Sensory Characteristics between Two Different Types of Rice-Based Baijiu

Rice-based Baijiu has gained popularity in the Chinese market. Qingya-flavored Baijiu, a variant of Xiaoqu-fermented Baijiu, employs rice as its primary raw material, with an improved production process compared to traditional rice-flavored Baijiu. We comprehensively characterized and compared the aroma profiles of these two rice-based Baijiu types using static sensory experiments (QDA, quantitative descriptive analysis) and dynamic sensory experiments (TDS, temporal dominance of sensations). Qingya-flavored Baijiu exhibited pronounced plant, oily, and roasted aromas, while traditional rice-flavored Baijiu displayed more prominent fruity, floral, and sour notes. Utilizing GC-O-MS (gas chromatography-olfactometry-mass spectrometry) and multi-method quantification, we qualitatively and quantitatively analyzed 61 key aroma compounds, identifying 22 compounds with significant aroma contributions based on odor activity values (OAVs). Statistical analyses, combining sensory and chemical results, were conducted to predict important aroma compounds responsible for the aroma differences between the two Baijiu types. Aroma Recombination and Omission experiments showed that seven compounds play key roles in the aroma of Qingya-flavored Baijiu, including (2E,4E)-Deca-2,4-dienal, linalool, apricolin, ethyl acetate, ethyl isobutyrate, ethyl caprylate, and ethyl isovalerate.

Insights into microbial communities and metabolic profiles in the traditional production of the two representative Hongqu rice wines fermented with Gutian Qu and Wuyi Qu based on single-molecule real-time sequencing

Hongqu rice wine, a famous traditional fermented alcoholic beverage, is brewed with traditional Hongqu (mainly including Gutian Qu and Wuyi Qu). This study aimed to compare the microbial communities and metabolic profiles in the traditional brewing of Hongqu rice wines fermented with Gutian Qu and Wuyi Qu. Compared with Hongqu rice wine fermented with Wuyi Qu (WY), Hongqu rice wine fermented with Gutian Qu (GT) exhibited higher levels of biogenic amines. The composition of volatile flavor components of Hongqu rice wine brewed by different fermentation starters (Gutian Qu and Wuyi Qu) was obviously different. Among them, ethyl acetate, isobutanol, 3-methylbutan-1-ol, ethyl decanoate, ethyl palmitate, ethyl oleate, nonanoic acid, 4-ethylguaiacol, 5-pentyldihydro-2(3H)-furanone, ethyl acetate, n-decanoic acid etc. were identified as the characteristic aroma-active compounds between GT and WY. Microbiome analysis based on high-throughput sequencing of full-length 16S rDNA/ITS-5.8S rDNA amplicons revealed that Lactococcus, Leuconostoc, Pseudomonas, Serratia, Enterobacter, Weissella, Saccharomyces, Monascus and Candida were the predominant microbial genera during the traditional production of GT, while Lactococcus, Lactobacillus, Leuconostoc, Enterobacter, Kozakia, Weissella, Klebsiella, Cronobacter, Saccharomyces, Millerozyma, Monascus, Talaromyces and Meyerozyma were the predominant microbial genera in the traditional fermentation of WY. Correlation analysis revealed that Lactobacillus showed significant positive correlations with most of the characteristic volatile flavor components and biogenic amines. Furthermore, bioinformatical analysis based on PICRUSt revealed that microbial enzymes related to biogenic amines synthesis were more abundant in GT than those in WY, and the enzymes responsible for the degradation of biogenic amines were less abundant in GT than those in WY. Collectively, this study provides important scientific data for enhancing the flavor quality of Hongqu rice wine, and lays a solid foundation for the healthy and sustainable development of Hongqu rice wine industry.

Comparative analysis of microbial communities and volatile flavor components in the brewing of Hongqu rice wines fermented with different starters

As one of the quintessential representatives of Chinese rice wine, Hongqu rice wine is brewed with glutinous rice as the main raw material and Hongqu (Gutian Qu or Wuyi Qu) as the fermentation starter. The present study aimed to investigate the impact of Hongqu on the volatile compositions and the microbial communities in the traditional production of Gutian Hongqu rice wine (GT) and Wuyi Hongqu rice wine (WY). Through the OPLS-DA analysis, 3-methylbutan-1-ol, isobutanol, ethyl lactate, ethyl acetate, octanoic acid, diethyl succinate, phenylethyl alcohol, hexanoic acid and n-decanoic acid were identified as the characteristic volatile flavor components between GT and WY. Microbiome analysis revealed significant enrichments of Lactobacillus, Pediococcus, Aspergillus and Hyphopichia in WY brewing, whereas Monascus, Saccharomyces, Pantoea, and Burkholderia-Caballeronia-Paraburkholderia were significantly enriched in GT brewing. Additionally, correlation analysis showed that Saccharomyces, Lactobacillus, Weissella and Pediococcus were significantly positively correlated wih most characteristic volatile components. Conversely, Picha, Monascus, Franconibacter and Kosakonia showed significant negative correlations with most of the characteristic volatile components. Furthermore, bioinformatical analysis indicated that the gene abundances for enzymes including glucan 1,4-alpha-glucosidase, carboxylesterase, alcohol dehydrogenase, dihydroxy-acid dehydratase and branched-chain-amino-acid transaminase were significantly higher in WY compared to GT. This finding explains the higher content of higher alcohols and characteristic esters in WY relative to GT. Collectively, this study provides a theoretical basis for improving the flavor profile of Hongqu rice wine and establishing a solid scientific foundation for the sustainable development of Hongqu rice wine industry.

Characterization of aroma profiles of kokuto-shochu prepared from three different cultivars of sugarcane

Kokuto-shochu is a traditional Japanese spirit prepared from kokuto, obtained by evaporating water from sugarcane (Saccharum officinarum L.) juice. To clarify the effects of sugarcane cultivars on the sensory quality of kokuto-shochu, we investigated the flavor characteristics and composition of volatiles in kokuto-shochu prepared from kokuto using three different sugarcane cultivars, NiF8, Ni15, and RK97-14. Furthermore, experiments were conducted by using the cultivars collected between 2018 and 2020 to observe annual variations in their properties. The amino acid content of the three kokuto varieties did not differ significantly, but the amino acid content of NiF8 was two to five times higher than that of RK97-14, which was the same for all samples collected in the selected years. The browning degrees of kokuto were also higher in NiF8, and they were positively correlated to the amino acid contents of kokuto. The kokuto-like aroma of shochu made from Ni15 was stronger than that of shochu made from RK97-14. The concentration of ethyl lactate in shochu made from Ni15 was higher, however, the concentration of guaiacol was the lowest in the three cultivars' products. Shochu made from NiF8 had the highest levels of Maillard reaction products (MRPs; pyrazines and furans), β-damascenone, and guaiacol amounts. In contrast, shochu made from RK97-14 tended to have a fruity flavor, and lower MRP levels than those made from NiF8. Thus, it was shown that sugarcane cultivars affect the sensory characteristics and volatiles in kokuto-shochu.

Distribution and Quantification of Lactic Acid Enantiomers in Baijiu

Enantiomers of lactic acid were investigated in Baijiu, including soy sauce aroma-type Baijiu (SSB), strong aroma-type Baijiu (STB), and light aroma-type Baijiu (LTB), via high-performance liquid chromatography with a chiral separation column. The natural concentration and enantiomeric distribution of lactic acid were studied, and their contribution to the flavor of Chinese Baijiu was evaluated based on recognition threshold. The results showed that there were significant differences in the content of lactic acid and the ratio of enantiomeric isomers among different aroma types and storage year. In SSB, the concentrations of D-lactic acid and L-lactic acid were higher, with the highest concentrations of 1985.58 ± 11.34 mg/L and 975.31 ± 14.03 mg/L, respectively. In STB, the highest concentrations of D-lactic acid and L-lactic acid were 1048.00 ± 11.46 mg/L and 939.83 ± 0.23 mg/L, respectively. In LTB, the highest concentrations of D-lactic acid and L-lactic acid were 760.90 ± 9.45 mg/L and 558.33 ± 3.06 mg/L, respectively. The average D/L enantiomeric ratios were 78:22 ± 16.16 and 80:20 ± 9.72 in the Commercial Baijiu products of SSB and STB, respectively. The average D/L enantiomeric ratio in LTB was 90:10 ± 6.08. D-lactic acid in JSHS vintage Baijiu showed a wave variation with aging, while L-lactic acid gradually increased during aging, and the average D/L enantiomeric ratio was 76:24 ± 4.26. The concentration of D-lactic acid in XJCT vintage Baijiu also showed a wave variation with aging, and the concentration of L-lactic acid tended to be stable during aging, with an average D/L enantiomeric ratio of 88:12 ± 2.80. The content of the two configurations of lactic acid in the LZLJ vintage Baijiu showed a decreasing trend during aging, with an average D/L enantiomeric ratio of 60:40 ± 11.99. The recognition threshold of D-lactic acid in 46% ethanol solution was 194.18 mg/L with sour taste; while the L-lactic acid was 98.19 mg/L with sour taste. The recognition threshold of L-lactic acid was about half that of D-lactic acid, indicating that L-lactic acid has a stronger sour taste. The taste activity values (TAVs) of D-lactic acid and L-lactic acid were greater than 1 in most of the Baijiu samples, and the TAV of D-lactic acid was greater than that of L-lactic acid. The study showed that the lactic acid enantiomers contributed to the taste perception of Baijiu in most of the samples, and D-lactic acid contributed more to the Baijiu taste than L-lactic acid.

Hydrogen bonds and hydrophobicity with mucin and α-amylase induced honey aroma in Feng-flavor Baijiu during 16 years aging

Honey aroma is one of the most significant factors of Feng-flavor Baijiu, which is also an essential element to attract consumers. However, the evaluation and chemical basis of honey aroma is unclear. Palmitoleic acid, lagochilin, phomotenone and ethyl behenate were confirmed to be the strongest contributors to honey aroma by time-intensity analysis and UHPLC-Q-Orbitrap-MS. Predictive modeling was developed for processing honey aroma intensity responses in order to obtain significant Feng-flavor Baijiu rankings. In this study, the effects of ex-vivo saliva on Feng-flavor Baijiu were investigated for the first time. Mucin and α-amylase, as major proteins in ex-vivo saliva, were applied to simulate molecular docking of ethyl benzoate. Mucin and α-amylase modified the aroma release, which depended on hydrogen bonds and hydrophobic interactions, respectively. It is blazing a trail in the field in sensory experience of Feng-flavor Baijiu as well as contributes to our understanding of Feng-flavor Baijiu drinking process.

Effect of High-Pressure Treatment on the Quality of a Hericium erinaceus: Millet Composite Beverage

Hericiumerinaceus-millet (HM) composite beverage was prepared by mixing Hericium erinaceus juice and millet juice and then subjected to high-pressure processing (HPP) of 300 MPa and 600 MPa at room temperature and thermal processing (TP) of 100°C for 3 min. The differences in pH, total soluble solids, amino acid nitrogen content, total colony numbers, sensory scores, and shelf life of HPP-treated and TP-treated samples stored at 4°C, 27°C, and 37°C for 80 days and the differences in volatile substances stored at 4°C and 27°C for 30 days were studied. The results showed that there was no significant difference in total soluble solids, amino acid nitrogen, and pH when comparing HPP- and TP-treated HM beverages. The order of HM beverages’ shelf life following different treatments was as follows: TP-treated >600 MPa HPP-treated >300 MPa HPP-treated. When stored at 4°C, the shelf life of the three treatments was 63, 52, and 39 days, respectively. Compared with TP-treated beverages, HPP-treated beverages better retained their ester flavor compounds, especially ethyl acetate. Moreover, the main volatile compounds in TP-treated beverages changed more during storage than those in HPP-treated beverages. Overall, HPP-treated beverages had advantages in terms of flavor over TP-treated beverages.