Multivariate classification of rice wines according to ageing time and brand based on amino acid profiles

The insights into sour flavor and organic acids in alcoholic beverages

Alcoholic beverages have developed unique flavors over millennia, with sourness playing a vital role in their sensory perception and quality. Organic acids, as crucial flavor compounds, significantly impact flavor. This paper reviews the sensory attribute of sour flavor and key organic acids in alcoholic beverages. Regarding sour flavor, research methods include both static and dynamic sensory approaches and summarize the interaction of sour flavor with aroma, taste, and mouthfeel. In addition, this review focuses on identifying key organic acids, including sample extraction, chromatography, olfactometry/taste, and mass spectrometry. The key organic acids in alcoholic beverages, such as wine, Baijiu, beer, and Huangjiu, and their primary regulatory methods are discussed. Finally, future avenues for the exploration of sour flavor and organic acids by coupling machine learning, database, sensory interactions and electroencephalography are suggested. This systematic review aims to enhance understanding and serve as a reference for further in-depth studies on alcoholic beverages.

Effect of a New Fermentation Strain Combination on the Fermentation Process and Quality of Highland Barley Yellow Wine

Yellow wine fermented from highland barley is an alcoholic beverage with high nutritional value. However, the industrialization of barley yellow wine has been constrained to a certain extent due to the lack of a systematic starter culture. Therefore, the present study aims to simulate barley yellow wine fermentation using a starter culture consisting of Rhizopus arrhizus, Saccharomyces cerevisiae, Pichia kudriavzevii, and Lacticaseibacillus rhamnosus. In this study, changes in enzyme activity, fermentation characteristics, volatile substance production, and amino acid content during the fermentation of highland barley yellow wine brewed with different starter cultures were evaluated. The results of this study show that regulating the proportion of mixed starter bacteria can effectively control the various stages of the fermentation process and improve the organoleptic characteristics and quality of yellow wine to varying degrees. Additionally, we found that the addition of probiotics could effectively improve the palatability of yellow wine. To the best of our knowledge, we have validated for the first time the use of the above multispecies starter culture, consisting of R. arrhizus, S. cerevisiae, P. kudriavzevii, and L. rhamnosus, in the production of highland barley yellow wine. The obtained findings provided reference data for optimizing highland barley yellow wine fermentation.

Flavor characteristics of Shanlan rice wines fermented for different time based on HS-SPME-GC-MS-O, HS-GC-IMS, and electronic sensory analyses

Flavor characteristics of Shanlan rice wines with different fermentation time were analyzed. Results suggested that 3-methyl-1-butanol, phenylethyl alcohol, ethyl acetate, and diethyl succinate were the characteristic volatiles of Shanlan rice wine by using headspace solid-phase microextraction-gas chromatography-mass spectrometry-olfactometry. The most varieties (38) of volatiles appeared at a 3-year-fermentation time, contributing a unique and harmonious aroma to the Shanlan rice wine fermented for 3 years, but only 19 types were observed at 45-days and 1-year fermentation times. A similar trend was intuitively visible in the headspace-gas chromatography-ion mobility spectrometry analysis. The Shanlan rice wine fermented for 3 years had a similar taste profile to that fermented for 45 days, but with distinguishing contents of free amino acids (1352.80 mg/L and 2261.50 mg/L, respectively) and organic acids (9.58 g/L and 49.88 g/L, respectively). The Shanlan rice wine fermented for 1 year had a strong taste with more intensity of most taste attributes.

Integrated characterization of filler tobacco leaves: HS-SPME-GC-MS, E-nose, and microbiome analysis across different origins

This study delves into the aroma characteristics and microbial composition of filler tobacco leaves (FTLs) sourced from six distinct cigar-growing regions within Yunnan, China, following standardized fermentation. An integrated approach using gas chromatography-mass spectrometry (GC-MS), electronic nose (E-nose), and microbiome analysis was employed for comprehensive profiling. Results derived from Linear Discriminant Analysis (LDA) using E-nose data confirmed the presence of notable variability in flavor substance profiles among the FTLs from six regions. Additionally, GC-MS was used to discern disparities in volatile organic compound (VOC) distribution across FTLs from these regions, identifying 92, 81, 79, 58, 69, and 92 VOCs within each respective sample set. Significantly, 24 VOCs emerged as pivotal determinants contributing to the heterogeneity of flavor profiles among FTLs from diverse origins, as indicated by Variable Importance for the Projection (VIP) analysis. Furthermore, distinctions in free amino acid content and chemical constituents were observed across FTLs. Of noteworthy significance, solanone, isophorone, durene, (-)-alpha-terpineol, and 2,3'-bipyridine exhibited the strongest correlations with microbiome data, with fungal microorganisms exerting a more pronounced influence on metabolites, as elucidated through two-way orthogonal partial least-squares (O2PLS) modeling. These findings provide a theoretical and technical basis for accurately evaluating the synchronization of FTLs in aromas and fermentation processes, and they will enhance the quality of fermented FTLs and foster the growth of the domestic cigar tobacco industry ultimately.

Amino Acid Profiles and Nutritional Evaluation of Fresh Sweet–Waxy Corn from Three Different Regions of China

This study conducted a comparative analysis of the amino acid compositions of Chinese Huangnuo 9 fresh sweet–waxy corn from three different provinces in China—Inner Mongolia, Jilin, and Heilongjiang Province. Moreover, we established a nutritive evaluation system based on amino acid profiles to evaluate, compare, and rank the fresh sweet–waxy corn planted in different regions. A total of 17 amino acids were quantified, and the amino acid composition of fresh sweet–waxy corn was analyzed and evaluated. The amino acid quality was determined by the amino acid pattern spectrum, chemical evaluations (including CS, AAS, EAAI, BV, U(a,u), NI, F, predict PER, and PDCAAS), flavor evaluation, amino acid matching degree evaluation, and the results of the factor analysis. The results showed that the protein content of fresh corn 1–1 from Inner Mongolia was the highest (40.26 ± 0.35 mg/g), but the factor analysis results, digestion, and absorption efficiency of fresh corn 1–2 were the best. The amino acid profile of fresh corn 1–1 was closest to each evaluation’s model spectrum. The results of the diversity evaluations in fresh corn 3–2 were the best, and fresh corn 3–3 had the most essential amino acid content. A total of 17 amino acids in fresh corn were divided into three principal component factor analyses: functional principal components (Leu, Pro, Glu, His, Ile, Ser, Met, Val, Tyr, Thr), regulatory principal components (Lys, Gly, Ala, Asp, Arg, Trp), and protection principal components (Phe). The scores of the three principal components and the comprehensive score in fresh corn 1–2 were all the highest, followed by 3–3 and 1–1. The amino acid nutritional values of fresh corn 1–2 were the highest in 12 samples.

Flavor compounds with high odor activity values (OAV > 1) dominate the aroma of aged Chinese rice wine (Huangjiu) by molecular association

Aging is an essential operation to perfect the flavor quality of Hungjiu. In this study, formation mechanism of flavor compounds responsible for the characteristic flavor of aged Huangjiu was investigated. The contents of umami and bitter free amino acids (FAA) increased with the storage period prolonged, while that of sweet FAA showed downward trend. Gas chromatograph-mass spectrometry and principal component analysis indicated that the volatile flavor compounds with OAV exceed 1, especially middle-chain fatty-acid-ethyl-esters and aromatic compounds, dominated the characteristic flavor of aged Huangjiu. Low field-NMR was firstly applied to characterize the molecular association between water and dissolved flavor compounds in aged Huangjiu. The results showed that basic amino acids contributed greatly to the flavor formation of aged Huangjiu via molecular association. In addition, the molecular association significantly promoted the accumulation of flavor compounds with OAV > 1, especially ethyl esters.

Comparison of physicochemical properties, amino acids, mineral elements, total phenolic compounds, and antioxidant capacity of Cuban fruit and rice wines

Physicochemical characterization, amino acids contents, minerals composition, total phenolic compounds, and antioxidant capacity of Cuban wines from different raw materials were studied. The wines studied were grape wines, tropical fruit wines, and rice wines. Twenty-one amino acids were identified and quantified, being Asp and Glu detected in all wines. The highest concentration of total amino acid content was found in wines elaborated from Cimarrona grape subjected to maceration with grape skins, while the raisined mixture grape wine presented the lowest values, probably caused by the amino acid degradation during the dehydration process by sun exposure. Minerals quantified were range amount limits of acceptable according to the OIV recommendation. Total phenolic compounds and antioxidant capacity showed the greatest values in wine from roasting rice. No statistical separation could be clearly observed by multivariate principal component analysis; however, 3 wine groups could be defined taking account the scores on the PC1.

Quantitative structure-activity relationships (QSAR) of aroma compounds in different aged Huangjiu

Huangjiu is a traditional wine in China with special taste and flavor. However, changes of aroma compounds during storage of Huangjiu remain unclear. In this study, aroma compounds in Jinse Nianhua Huangjiu of three different storage ages were qualitatively and quantitatively analyzed via headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Based on odor activity value (OAV), the most important aroma compounds were found to be esters, aldehydes, alcohols, acids, ketones, phenols, and lactones. Even though the types of the aroma compounds were similar in different-aged Huangjiu, the concentrations of some compounds varied. Some aroma compounds' thresholds and OAV in Huangjiu were obtained by AC'Scent Intl. Olfactometer. It showed the key aroma compounds in Huangjiu had a positive correlation with their OAV instead of concentration. Quantitative structure-activity relationship (QSAR) models were developed to predict the flavor thresholds for alcohols, acids, and esters in Huangjiu, with higher accuracy for alcohols (R² = 0.978) and acids (R² = 0.987). This study will provide valuable information to unveil the regulation of Huangjiu flavor from molecular basis. PRACTICAL APPLICATION: The built mathematical model enables to predict changes of aroma compounds in Huangjiu during storage, based on the relationship between the quantum structure parameters of those aroma compounds and the odor activity value of flavor chemicals. This research will contribute to simplifying the wine flavor analysis for wine industry and also help to identify the age of the Huangjiu for customers.

Discrimination of Chinese yellow wine from different origins based on flavor fingerprint

In this study, discrimination of Chinese yellow wines from Shaoxing, Shandong, and Hubei in China has been carried out according to volatile flavor components. A total of 122 yellow wine samples were characterized by gas chromatography–ion mobility spectrometry (GC–IMS). A simple color mixing method was visually used to select characteristic peaks based on the RGB color model. Then, the volatile organic compounds corresponding to the selected characteristic peaks were identified via library searching, and the height values of those peaks were arranged for further chemometric pretreatment. Principal component analysis was employed to reveal significant differences and potential patterns between samples. Finally, quadratic discriminant analysis was applied to develop a classification model and achieved a correct classified rate of 95.35% for the prediction set. The results prove that the aroma composition combined with chemometric tools can be used as a fingerprinting technique to protect the product of origin and enable the authenticity of Chinese yellow wine.

Characterization of volatile organic compounds as potential aging markers in Chinese rice wine using multivariable statistics

BACKGROUND

There is a close relationship between certain 'aging markers' in wine and the wine's age. This study aimed to characterize all extracted aging markers in Chinese rice wine and distinguish the ages of Chinese rice wine using principal component analysis (PCA) and cluster analysis (CA).

RESULTS

A total of 49 potential aging markers (P ≤ 0.05*) were extracted from 71 volatile organic compounds (VOCs) in Chinese rice wine across a range of seven different ages. Of all 49 extracted aging markers, all furans, 2/3 aldehydes and ketones maintained significantly increasing levels with age (P ≤ 0.01**), especially sotolon (0.981**) and acetophenone (0.951**). On the other hand, all sulfides decreased significantly (P ≤ 0.01**). Changes in vanillin, guaiacol, 4-vinylguaiacol (4-VG) and 4-ethylguaiacol (4-EG) also suggested a potential synthesis during the aging process. The results of PCA and CA demonstrated that Chinese rice wines with different ages could be clearly distinguished from each other, which was consistent with the evolution of the 49 aging markers during the aging process.

CONCLUSION

These 49 potential 'aging markers' successfully distinguished ages using PCA and CA. Our results therefore throw light on the characterization of VOCs during Chinese rice wine aging, and provide a quantitative basis for discriminating the ages of Chinese rice wine. © 2019 Society of Chemical Industry.

Isolation and characterization of lactic acid bacteria from fresh Chinese traditional rice wines using denaturing gradient gel electrophoresis

Lactic acid bacteria (LAB) are a prevalent bacterial group in rice wine maturation that contributes to flavor, texture, and nutritive value. To better understand LAB diversity in rice wines, 6 rice wine varieties from different regions in China were investigated using denaturing gradient gel electrophoresis (DGGE). Lactobacillus plantarum, L. namurensis, and Pediococcus acidilactici were identified using DGGE. Forty nine isolates were screened using a culture-dependent method. Prominent taxa were identified as Enterococcus sp., Lactobacillus delbrueckii, L. rhamnosus, L. plantarum, and Pediococcus acidilactici. Isolates were grouped and used for fermentation of rice wines. Greater numbers of species involved in fermentation lead to better sensory attributes of wine. DGGE analysis combined with a culture-dependent method can be a tool for investigation of the bacterial compositions of fermented rice wines.

Characterization of Chinese rice wine taste attributes using liquid chromatographic analysis, sensory evaluation, and an electronic tongue

To evaluate the taste characteristics of Chinese rice wine, wine samples sourced from different vintage years were analyzed using liquid chromatographic analysis, sensory evaluation, and an electronic tongue. Six organic acids and seventeen amino acids were measured using high performance liquid chromatography (HPLC). Five monosaccharides were measured using anion-exchange chromatography. The global taste attributes were analyzed using an electronic tongue (E-tongue). The correlations between the 28 taste-active compounds and the sensory attributes, and the correlations between the E-tongue response and the sensory attributes were established via partial least square discriminant analysis (PLSDA). E-tongue response data combined with linear discriminant analysis (LDA) were used to discriminate the Chinese rice wine samples sourced from different vintage years. Sensory evaluation indicated significant differences in the Chinese rice wine samples sourced from 2003, 2005, 2008, and 2010 vintage years in the sensory attributes of harmony and mellow. The PLSDA model for the taste-active compounds and the sensory attributes showed that proline, fucose, arabinose, lactic acid, glutamic acid, arginine, isoleucine, valine, threonine, and lysine had an influence on the taste characteristic of Chinese rice wine. The Chinese rice wine samples were all correctly classified using the E-tongue and LDA. The electronic tongue was an effective tool for rapid discrimination of Chinese rice wine.

Differentiating Milk and Non-milk Proteins by UPLC Amino Acid Fingerprints Combined with Chemometric Data Analysis Techniques

Amino acid fingerprinting combined with chemometric data analysis was used to differentiate milk and non-milk proteins in this study. Microwave-assisted hydrolysis and ultraperformance liquid chromatography (UPLC) were used to obtain the amino acid fingerprints. Both univariate and multivariate chemometrics methods were applied for differentiation. The confidence boundary of amino acid concentration, principal component analysis (PCA), and partial least-squares-discriminant analysis (PLS-DA) of the amino acid fingerprints demonstrated that there were significant differences between milk proteins and inexpensive non-milk protein powders from other biological sources including whey, peanut, corn, soy, fish, egg yolk, beef extract, collagen, and cattle bone. The results indicate that the amino acid compositions with the chemometric techniques could be applied for the detection of potential protein adulterants in milk.

Changes in the charged metabolite and sugar profiles of pasteurized and unpasteurized Japanese sake with storage

Japanese sake (rice wine) is commonly heat treated (pasteurized) to maintain its quality. In this study, temporal changes in the metabolite profiles of pasteurized and unpasteurized sake were investigated during storage. Metabolomic analyses were conducted for eight sets of pasteurized and unpasteurized sake obtained from single process batches stored at 8 or 20 °C for 0, 1, 2, or 4 months. Capillary electrophoresis time-of-flight mass spectrometry and liquid chromatography tandem mass spectrometry were used to obtain charged metabolite and sugar profiles, respectively. The total amino acid concentration decreased with storage, and the decrease was faster in pasteurized sake than in unpasteurized. The organic acid concentrations were relatively constant in both types of sake. Peptide and glucose concentrations increased and polysaccharide concentrations decreased in unpasteurized sake, while they were relatively constant in pasteurized sake. Rather than stabilizing the sake metabolite profile during storage, pasteurization results in characteristic changes compared to unpasteurized sake.