Characterization of the volatile compounds of huangjiu using comprehensive two‐dimensional gas chromatography coupled to time of flight mass spectrometry (GC × GC‐TOFMS)

Characterisation of aroma compounds, sensory characteristics, and bioactive components of a new type of huangjiu fermented with Chinese wild rice (Zizania latifolia)

Chinese wild rice (CWR) is a nutritious and healthy whole grain, worth developing. To develop and use its value, a new type of huangjiu was brewed with CWR, and the flavour characteristics, sensory quality, functional and bioactive components were evaluated. CWR (67 flavour substances) and glutinous rice (GR)-CWR huangjiu (62 flavour substances) had a better flavour than GR huangjiu (54 flavour substances), and the overall style of GR-CWR huangjiu was more skewed towards GR. The fruity, honey, caramel-like, herb and smoky aroma attributes of CWR huangjiu were higher than those of GR huangjiu (P < 0.05), while only the alcoholic was weaker (P < 0.05) due to the lower alcohol content. The huangjiu brewed using CWR had a better taste than that brewed using only GR. Furthermore, CWR huangjiu had the highest content of total dietary fiber (732.0 ± 15.2 mg/100 g), followed by GR-CWR (307.0 ± 8.5 mg/100 g), and GR (127.0 ± 2.3 mg/100 g). CWR huangjiu also had the highest total phenolic compounds (3.32 ± 0.05 mg/100 g/%vol) and total saponins (2.46 ± 0.03 mg/100 g/%vol) contents, followed by GR-CWR and GR. This study provides guidance for exploring further possibilities for CWR in the future.

Research on the brewing technology of Dangshen Huangjiu with low biogenic amines and high functional factors

BACKGROUND

Biogenic amines (BA) are hazardous components in Huangjiu (HJ). To ensure the quality of Dangshen Huangjiu (DSHJ), an orthogonal experiment L9 (33) was proposed to optimize the process by the main brewing factors (pre-fermentation temperature, pre- and post-fermentation time) that may affect BA and functional factors in DSHJ. DSHJ was produced with low BA content and high functional factors. Gas chromatography-ion mobility spectrometry combined with a multivariate statistical method (GC-IMS-MSM) was used to analyze the volatile components in the brewing process of DSHJ.

RESULTS

The optimum brewing process parameters of DSHJ were as follows: pre-fermentation temperature, 28 °C; pre-fermentation time, 9 days; post-fermentation time, 18 days. The average content of BA in DSHJ was 33.12 mg L-1, and the sensory score, total phenol content and DPPH free radical scavenging rate of DSHJ were significantly higher than those of HJ. A total of 14 esters, 7 acids, 7 alcohols, 1 ketone, 5 aldehydes and 1 pyrazine in DSHJ and HJ were identified by GC-IMS. There were no significant differences (P > 0.05) in DSHJ and HJ in the soaking rice and saccharification stage. 11 components, such as ethyl acetate, and 12 components, such as acetic acid, were the different components of HJ and DSHJ in pre-fermentation and post-fermentation stages, respectively. In the post-fermentation stage, the contents of 8 components in DSHJ such as ethyl acetate were higher than in HJ.

CONCLUSION

The preparation process parameters of DSHJ optimized by orthogonal experiments can ensure that DSHJ has the advantages of low BA content, high total phenol content and good antioxidant activity. Sensory score and GC-IMS-MSM analysis found that DSHJ prepared using the optimal process had the characteristics of good taste and rich aroma. © 2024 Society of Chemical Industry.

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.

Solid-phase microextraction coupled to comprehensive multidimensional gas chromatography for food analysis

Solid-phase microextraction and comprehensive multidimensional gas chromatography represent two milestone innovations that occurred in the field of separation science in the 1990s. They have a common root in their introduction and have found a perfect coupling in their evolution and applications. This review will focus on food analysis, where the paradigm has changed significantly over time, moving from a targeted analysis, focusing on a limited number of analytes at the time, to a more holistic approach for assessing quality in a larger sense. Indeed, not only some major markers or contaminants are considered, but a large variety of compounds and their possible interaction, giving rise to the field of foodomics. In order to obtain such detailed information and to answer more sophisticated questions related to food quality and authenticity, the use of SPME-GC × GC-MS has become essential for the comprehensive analysis of volatile and semi-volatile analytes. This article provides a critical review of the various applications of SPME-GC × GC in food analysis, emphasizing the crucial role this coupling plays in this field. Additionally, this review dwells on the importance of appropriate data treatment to fully harness the results obtained to draw accurate and meaningful conclusions.

Optimizing the identification of thiols in red wines using new oak-wood accelerated reductive treatment

This study proposes a new method for identifying thiols in red wines by mimicking specific chemical mechanisms that occur during bottle-aging. It involves the reaction of oak-wood extracts with hydrogen sulfide and the reduction of disulfides with DIBAL. After optimization of the reaction conditions, the aroma of fresh oak wood turned into intense "meaty" nuances reminiscent of the aging bouquet of red wines. Samples were analyzed by gas chromatography coupled with olfactometry (GC-O) and coupled with a pulsed flame photometric detector. This resulted in the identification of six odorant zones with meaty descriptors associated with sulfur compounds. One of the odorant zones was identified as 2-methoxybenzenethiol by using heart-cutting multidimensional GC coupled with olfactometry and time of flight mass spectrometer. Its identification in aged red wines was confirmed by GC coupled with tandem mass spectrometry analyses. Five other thiols associated with oak-wood precursors were also identified in red wines.

Microbiota Composition during Fermentation of Broomcorn Millet Huangjiu and Their Effects on Flavor Quality

Broomcorn millet Huangjiu brewing is usually divided into primary fermentation and post-fermentation. Microbial succession is the major factor influencing the development of the typical Huangjiu flavor. Here, we report the changes in flavor substances and microbial community during the primary fermentation of broomcorn millet Huangjiu. Results indicated that a total of 161 volatile flavor compounds were measured during primary fermentation, and estragole was detected for the first time in broomcorn millet Huangjiu. A total of 82 bacteria genera were identified. Pediococcus, Pantoea, and Weissella were the dominant genera. Saccharomyces and Rhizopus were dominant among the 30 fungal genera. Correlation analysis showed that 102 microorganisms were involved in major flavor substance production during primary fermentation, Lactobacillus, Photobacterium, Hyphodontia, Aquicella, Erysipelothrix, Idiomarina, Paraphaeosphaeria, and Sulfuritalea were most associated with flavoring substances. Four bacteria, Lactobacillus (R1), Photobacterium (R2), Idiomarina (R3), and Pediococcus (R4), were isolated and identified from wheat Qu, which were added to wine Qu to prepare four kinds of fortified Qu (QR1, QR2, QR3, QR4). QR1 and QR2 fermentation can enhance the quality of Huangjiu. This work reveals the correlation between microorganisms and volatile flavor compounds and is beneficial for regulating the micro-ecosystem and flavor of the broomcorn millet Huangjiu.

The Production of Intensified Qu and Its Microbial Communities and Aroma Variation during the Fermentation of Huangjiu (Chinese Rice Wine)

In recent years, intensified Qu (IQ) has been gradually applied to brewing in order to improve the aroma of Huangjiu (Chinese rice wine). In this study, Saccharomyces cerevisiae and Wickerhamomyces anomalus solutions were added to Fengmi Qu (FMQ) from Fangxian, China to produce IQ, and brewing trial was conducted. High-throughput sequencing (HTS) was used to analyze the microbial community in fermentation broth of IQ (IQFB). Headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and sensory evaluation were performed to analyze volatile aroma compounds (VACs) in sample without Qu and both fermentation broths. The results showed that Pediococcus, Cronobacter, Enterococcus, Weissella, and Acinetobacter and Saccharomycopsis, Wickerhamomyces, and Saccharomyces were dominant bacterial and fungal groups, respectively. A total of 115 VACs were detected, and the content of esters including ethyl acetate, isoamyl acetate, and so on was noticeably higher in IQFB. The finding of sensory evaluation reflected that adding pure yeast to Qu could enhance fruit and floral aromas. Correlation analysis yielded 858 correlations between significant microorganisms and different VACs. In addition, prediction of microbial community functions in IQFB revealed global and overview maps and carbohydrate metabolism to be the main one. This study is advantageous for further regulation of the fermentation process of Huangjiu by microbial means.

Unraveling the difference in flavor characteristics of Huangjiu fermented with different rice varieties using dynamic sensory evaluation and comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry

To investigate the specific differences in flavor characteristics of Huangjiu fermented with different rice varieties, dynamic sensory evaluation, comprehensive two-dimensional gas chromatography-quadrupole mass spectrometry (GC × GC-qMS) and multivariate statistical analysis were employed. Dynamic sensory evaluation methods including temporal dominance of sensations (TDS) and temporal check all that apply (TCATA) were applied to explore the differences and variations in sensory attributes. The sensory results showed that the intensity of astringency and post-bitterness in the Huangjiu fermented with glutinous rice was weaker while ester and alcoholic aroma were more prominent than the one fermented with japonica rice. The results of free amino acids and aroma compounds analysis indicated that the amino acids were mainly sweet and bitter amino acids, and some key aroma compounds were predominant in the Huangjiu fermented with glutinous rice, such as ethyl butyrate (OAV: 38-59), 3-methylthiopropionaldehyde (OAV: 47-96), ethyl caprylate (OAV: 30-38), while nonanal, phenyl acetaldehyde and vanillin contributed significantly to the Huangjiu fermented with japonica rice. The multivariate statistical analysis further confirmed that 17 compounds (VIP > 1 and p < 0.05) could be supposed to be the key compouns that cause significant flavor differences in Huangjiu samples fermented with different brewing rice. Moreover, partial least-squares analysis revealed that most compounds (ethyl butyrate, 3-penten-2-one, isoamyl acetate, and so on) correlated with ester and alcoholic aroma. The results could provide basic data and theoretical basis for the selection of raw materials in Huangjiu.

Effects of Protein Components on the Chemical Composition and Sensory Properties of Millet Huangjiu (Chinese Millet Wine)

Millet Huangjiu is a national alcoholic beverage in China. The quality of Chinese millet Huangjiu is significantly influenced by the protein components in the raw materials of millet. Therefore, in this study, the impact of different protein components on the quality of millet Huangjiu was investigated by adding exogenous proteins glutelin and albumin either individually or in combination. The study commenced with the determination of the oenological parameters of different millet Huangjiu samples, followed by the assessment of free amino acids and organic acids. In addition, the volatile profiles of millet Huangjiu were characterized by employing HS-SPME-GC/MS. Finally, a sensory evaluation was conducted to evaluate the overall aroma profiles of millet Huangjiu. The results showed that adding glutelin significantly increased the contents of total soluble solids, amino acid nitrogen, and ethanol in millet Huangjiu by 32.2%, 41.5%, and 17.7%, respectively. Furthermore, the fortification of the fermentation substrate with glutelin protein was found to significantly enhance the umami (aspartic and glutamic acids) and sweet-tasting (alanine and proline) amino acids in the final product. Gas chromatography-quadrupole mass spectrometry coupled with multivariate statistical analysis revealed distinct impacts of protein composition on the volatile organic compound (VOC) profiles of millet Huangjiu. Excessive glutelin led to an over-accumulation of alcohol aroma, while the addition of albumin protein proved to be a viable approach for enhancing the ester and fruity fragrances. Sensory analysis suggested that the proper amount of protein fortification using a Glu + Alb combination could enhance the sensory attributes of millet Huangjiu while maintaining its unique flavor characteristics. These findings suggest that reasonable adjustment of the glutelin and albumin contents in millet could effectively regulate the chemical composition and improve the sensory quality of millet Huangjiu.

Organosulfur in food samples: Recent updates on sampling, pretreatment and determination technologies

Organosulfur compounds (OSCs), mainly found in garlic, are the main biologically active substances for their pharmacological effects, including lowering of blood pressure and cholesterol, anti-cancer effect, liver protection, and anti-inflammatory. Efficient and sensitive pretreatment and determination methods of OSCs in different food matrices are of great significance. This review provides a comprehensive summary about the pretreatment and determination methods for OSCs in different food samples since 2010. Commonly used pretreatment methods, such as liquid-liquid extraction, microwave-assisted extraction, pressurized liquid extraction, liquid-liquid microextraction, solid phase extraction, dispersive solid phase extraction, solid-phase microextraction, and so on, have been summarized and overviewed in this paper. In particular, we discussed and compared various analysis methods including high performance liquid chromatography coupled with different detectors, gas chromatography-based methods, and few other methods. Finally, we tried to highlight the applicability, advantages and disadvantages of different pretreatment and analysis methods, and identified future prospects in this field.

“Key Factor” for Baijiu Quality: Research Progress on Acid Substances in Baijiu

Baijiu is the national liquor of China, which has lasted in China for more than 2000 years. Abundant raw materials, multi-strain co-fermentation, and complex processes make the secrets of baijiu flavor and taste still not fully explored. Acid substances not only have a great influence on the flavor and taste of baijiu, but also have certain functions. Therefore, this paper provides a systematic review for the reported acid substances, especially for their contribution to the flavor and functional quality of baijiu. Based on previous studies, this paper puts forward a conjecture, a suggestion, and a point of view, namely: the conjecture of “whether acid substances can be used as ‘key factor’ for baijiu quality “; the suggestion of “the focus of research on acid substances in baijiu should be transferred to evaluating their contribution to the taste of baijiu”; and the view of “acid substances are ‘regulators’ in the fermentation process of baijiu”. It is worth thinking about whether acid substances can be used as the key factors of baijiu to be studied and confirmed by practice in the future. It is hoped that the systematic review of acid substances in baijiu in this paper can contribute to further in-depth and systematic research on baijiu by researchers in the future.

The way of Qu-making significantly affected the volatile flavor compounds in Huangjiu (Chinese rice wine) during different brewing stages

The volatile flavor compounds of Huangjiu (Chinese rice wine) brewed from different raw materials were obviously different, but there were few studies on the volatile flavor compounds of Huangjiu brewed from different wheat Qu at different brewing stages. In this paper, headspace-solid phase microextraction combined with gas chromatography-mass spectrometry, combined with principal component analysis and sensory evaluation, was used to determine the volatile flavor compounds in Huangjiu brewed from wheat Qu made by hand and wheat Qu made by mechanical. The results showed that there were significant differences in the contents and types of volatile flavor substances in Huangjiu brewed from different wheat Qu at fermentation stages, and the prefermentation and postfermentation Huangjiu samples could be well distinguished from each other. Compared with the Huangjiu brewed from wheat Qu made by mechanical, the Huangjiu brewed from wheat Qu made by hand has stronger aroma and better taste.

Comprehensive two-dimensional gas chromatography mass spectrometry-based untargeted metabolomics to clarify the dynamic variations in the volatile composition of Huangjiu of different ages

Aging plays an important role in the formation of aroma characteristics of Huangjiu, a traditional Chinese alcoholic beverage. Comprehensive two-dimensional gas chromatography mass spectrometry (GC×GC-qMS)-based untargeted metabolomics combined with a multivariate analysis was used to investigate the dynamic variations in the aroma profile of Huangjiu during aging process and to establish the relationship between the changing volatile metabolite profiles and the age-dependent sensory attributes. A total of 144 volatile metabolites were identified by GC×GC-qMS and 63 were selected as critical metabolites based on variable importance in projection values and p-values. Based on the results of principal component analysis, orthogonal partial least-squares discriminant analysis, and hierarchical clustering analysis, the samples of six different ages were divided into three groups: 1Y and 3Y samples, 5Y and 8Y samples, and 10Y and 15Y samples. The partial least-squares analysis results further revealed the relationship between the aromas attributes and variations of these volatile compounds. The high esters, aldehydes, and lactones contents contributed to the high intensities of the sweet and ester aroma attributes of the aged Huangjiu, while the high alcohols and ethyl esters contents contributed to the alcoholic and fruity aroma attributes of the newly brewed Huangjiu. These results improve our understanding of the chemical nature of the aroma characteristics of aged Huangjiu. PRACTICAL APPLICATION: Huangjiu is often labeled with its age as a measure of quality, which influences consumers' choice. Dynamic variations in volatile compounds of Huangjiu during aging and its contribution to the aroma characteristics of Huangjiu were figured out, which will assist the industry to produce better quality aged Huangjiu for consumers.

Characterization of the aroma compounds of Millet Huangjiu at different fermentation stages

Millet Huangjiu (MHJ), a type of northern Huangjiu with a long history, has attracted considerable attention in China and East Asia for its unique flavor. To elucidate the changing course of aroma components during the fermentation process of MHJ, 15 MHJ samples prepared at different fermentation stages were assessed by gas chromatography-olfactometry (GC-O) and odor activity value (OAV) coupled with multivariate data analysis. A total of 66 volatile compounds were identified, among which 21 odorant active substances were regarded as the main aroma components (OAVs ≥ 1). The numbers and contents of esters in MHJs accumulated with the extension of fermentation time. Ethanol, ethyl acetate, phenylethyl alcohol and other 7 aromatic substances are the key flavoring agents in the final fermented MHJ. Orthogonal partial least squares-discriminant analysis (OPLS-DA) showed that 14 volatile compounds (formic acid, ethanol, etc.) are supposed to be the key substances that cause significant differences in MHJ flavor at different fermentation stages.

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.