Oenological characteristics, amino acids and volatile profiles of Hongqu rice wines during pottery storage: Effects of high hydrostatic pressure processing

Effect of High-Pressure Processing on Color, Texture and Volatile Profile During Sardine Refrigeration

Extending sardine shelf life while maintaining their quality is challenging even with non-thermal technologies like high-pressure processing (HPP). This study examines the effects of HPP at 400 and 600 MPa for holding times of 1, 2.5, 5, and 10 min on fresh sardines during 14 days of cold storage. Physicochemical attributes, including texture, color, and volatile organic profiles, were assessed. Increasing both pressure and holding times resulted in increased levels of hardness, chewiness, and L* during storage. HPP-treated samples maintained lower a* values compared to the control ones by the end of the experiment. The volatile profile of HPP samples was significantly affected compared to control samples, which developed exclusively volatile oxidation compounds (hexanal and 2,4-hexadienal) by the end of the storage. Volatile groups such as aldehyde and ketone were slightly impacted by both storage and HPP treatments (i.e., pressure and holding time). Ketone levels were consistently lower in all treated samples, ranging from 25.3% to 33.6% at 400 MPa and 600 MPa, respectively, compared to the control samples, which had a ketone level of 40.5% on day 14. These findings indicate the potential of HPP in prolonging shelf life and preserving quality in the sardine market.

Research advances in technologies and mechanisms to regulate vinegar flavor

New vinegar needs a long maturing time to improve its poor flavor before sale, which greatly increases its production cost. Therefore, it is urgent to explore regulation technologies to accelerate vinegar flavor maturation. Based on literature and our research, this review introduces the latest advances in flavor regulation technologies of vinegar including microbial fortification/multi starters fermentation, key production processes optimization and novel physical processing technologies. Microbial fortification or multi starters fermentation accelerates vinegar flavor maturation via enhancing total acids, esters and aroma precursors content in vinegar. Adjusting raw materials composition, fermentation temperature, and oxygen flow reasonably increase alcohols, organic acids, polyphenols and esters levels via generating more corresponding precursors in vinegar, thereby improving its flavor. Furthermore, novel processing technologies greatly promote conversion of alcohols into acids and esters in vinegar, shortening flavor maturation time for over six months. Meanwhile, the corresponding mechanisms are discussed and future research directions are addressed.

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.

Optimization of fermentation conditions and quality evaluation of Chaenomeles sinensis glutinous rice wine

The present study was conducted to optimize fermentation conditions for preparation of Chaenomeles sinensis Glutinous Rice Wine (CRW). The dynamic changes of main substances in the liquor during fermentation process, aroma components, biologically active substances and antioxidant capacity in the CRW after 6 months of aging were tested. The results showed that under optimized conditions, the yield and alcohol content of wine was 44.97 and 20.00%, respectively. After aging, 64 aroma components were detected in the wine, mainly alcohols and esters. The alcohol content of the CRW was 14.8%. Polyphenols and flavonoids reached 0.23 g/L and 0.037 g/L respectively. Furthermore, the CRW had an excellent free radical scavenging ability.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05934-0.

Integrated network pharmacology, metabolomics, and transcriptomics of Huanglian-Hongqu herb pair in non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

The Huanglian-Hongqu herb pair (HH) is a synergistic drug combination used to treat non-alcoholic fatty liver disease (NAFLD). However, the molecular mechanism underlying the therapeuticeffects of HH requires further elucidation.

AIM OF THE STUDY

The present study explored the potential mechanism of HH in treating NAFLD.

MATERIALS AND METHODS

UPLC-Q-TOF-MS was employed to identify the drug constituents in HH. A NAFLD rat model was induced by a high-fat diet (HFD) and treated with different doses of HH. The functional mechanism of HH in NAFLD rats was predicted using network pharmacology, metabolomics and transcriptomics. Immunohistochemistry, real-time PCR, and Western blot were performed to validate the key mechanisms.

RESULTS

Pharmacodynamic assessment demonstrated that HH exhibited improvements in lipid deposition and reduced hepatic oxidative stress in NAFLD rats. Hepatic wide-target metabolomics revealed that HH primarily modulated amino acids and their metabolites, fatty acids, organic acids and their derivatives, bile acids, and other liver metabolites. The enriched pathways included metabolic pathways, primary bile acid biosynthesis, and bile secretion. Network pharmacology analysis indicated that HH regulated the key pathways in NAFLD, notably PPAR, AMPK, NF-κB and other signaling pathways. Furthermore, hepatic transcriptomics, based on Illumina RNA-Seq sequencing analyses, suggested that HH improved NAFLD through metabolic pathways, the PPAR signaling pathway, primary bile acid biosynthesis, and fatty acid metabolism. Further mechanistic studies indicated that HH could regulate the genes and proteins associated with the PPAR signaling pathway.

CONCLUSION

Our findings demonstrated that the potential therapeutic benefits of HH in ameliorating NAFLD by targeting the PPAR signaling pathway, thereby facilitating a more extensive use of HH in NAFLD.

Effects of different lactic acid bacteria on the characteristic flavor profiles of Chinese rice wine

BACKGROUND

It has been well accepted that lactic acid bacteria (LAB) are the main bacterial genera present during the brewing of Chinese rice wine (CRW). LAB plays a decisive role in the flavor quality of CRW; however, its application in CRW has previously been overlooked. Therefore, effects of different LAB as co-fermenter on the flavor characteristics of CRW were investigated.

RESULTS

Co-fermentation of LAB increased the utilization rate of reducing sugar, concentration of lactic acid, amino acid nitrogen and total acidity, as well as the content of volatile flavor compounds. Different LAB doses had little effect on the flavor profiles of CRW, but the species of LAB greatly affected the flavor characteristic. The flavor of CRW co-fermented with Lactococcus lactis was characterized by long-chain fatty acid ethyl esters, while co-fermentation with Weissella confusa highlighted the ethyl esters of low molecular weight and short carbon chains in the resultant CRW. Alcohol compounds were dominant in the CRW co-fermented using Pediococcus pentosaceus.

CONCLUSION

The co-fermentation of LAB increased the number of volatile flavor compounds, especially esters. LAB exhibited great potential in the application of CRW industry to enrich the flavor characteristics and enhance the flavor diversity of the final product. © 2023 Society of Chemical Industry.

Comparing the differences of physicochemical properties and volatiles in semi-dry Hakka rice wine and traditional sweet rice wine via HPLC, GC-MS and E-tongue analysis

This study aimed to explore effects of indica rice addition, rice soaking time and rice soup addition on total sugar and alcohol content of semi-dry Hakka rice wine (HRW) and compare its difference in physicochemical properties and volatiles with traditional sweet rice wine (TSRW) via HPLC, GC-MS and E-tongue. The optimal fermentation conditions of semi-dry HRW were 50 % indica rice addition, 12 h rice soaking time and 85 % rice soup addition. The total sugar (16.13 mg/mL) of semi-dry HRW was significantly lower than that of TSRW (135.79 mg/mL), especially the trehalose, glucose, sucrose and maltose. Its alcohol content was significantly higher than that of TSRW. There were significant differences in volatile components between semi-dry HRW and TSRW, especially esters, alcohols and ketones, but no significant differences in organic acids and amino acids. Results obtained could provide reference data for improving the fermentation process and quality of semi-dry HRW.

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.

Hongqu Rice Wines Ameliorate High-Fat/High-Fructose Diet-Induced Metabolic Syndrome in Rats

AIM

This study evaluated the possible protective impact of different vintages of Hongqu rice wines on metabolic syndrome (MetS) in rats induced by high-fat/high-fructose diet (HFFD).

METHODS

Rats were randomly divided into six groups and treated with (a) basal diet (13.9 kJ/g); (b) HFFD (20.0% w/w lard and 18.0% fructose, 18.9 kJ/g) and (c-f) HFFD with 3-, 5-, 8- and 15-year-aged Hongqu rice wines (9.96 ml/kg body weight), respectively, at an oral route for 20 weeks.

RESULTS

Hongqu rice wines could alleviate HFFD-induced augment of body weight gain and fat accumulation, and the release of pro-inflammatory cytokines. Glycolipid metabolic abnormalities caused by HFFD were ameliorated after Hongqu rice wines consumption by lowering levels of fasting insulin, GSP, HOMA-IR, AUC of OGTT and ITT, and lipid deposition (reduced contents of TG, TC, FFA and LDL-C, and elevated HDL-C level) in the serum and liver, probably via regulating expressions of genes involving in IRS1/PI3K/AKT pathway, LDL-C uptake, fatty acid β-oxidation, and lipolysis, export and synthesis of TG. In addition, concentrations of MDA and blood pressure markers (ANG-II and ET-1) declined, and activities of antioxidant enzymes (SOD and CAT) were improved in conditions of Hongqu rice wines compared to those in the HFFD group. Eight-year-aged Hongqu rice wine produced a more effective effect on alleviating HFFD-caused MetS among different vintages of Hongqu rice wines.

CONCLUSION

To sum up, Hongqu rice wines exhibited ameliorative effects on HFFD-induced MetS in rats based on antiobesity, antihyperlipidemic, antihyperglycemic, antioxidant, anti-inflammatory and potential antihypertensive properties.

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.

Improving Soy Sauce Aroma Using High Hydrostatic Pressure and the Preliminary Mechanism

Using high hydrostatic pressure (HHP) to treat liquid foods can improve their aroma; however, no information about the effects of HHP on soy sauce aroma has yet been reported. The effects of HHP on the aroma of soy sauce fermented for 30 d were investigated using quantitative descriptive analysis (QDA), SPME-GC-olfactometry/MS, hierarchical cluster analysis (HCA) and principal component analysis (PCA). Results showed that the pressure used during HHP treatment had a greater influence on soy sauce aroma than the duration of HHP. Compared to the control, soy sauce that was treated with HHP at 400 MPa for 30 min (HHP400-30) obtained the highest sensory score (33% higher) by increasing its sour (7%), malty (9%), floral (27%) and caramel-like (47%) aromas, while decreasing its alcoholic (6%), fruity (6%) and smoky (12%) aromas; moreover, the aroma of HHP400-30 soy sauce was comparable with that of soy sauce fermented for 180 d. Further investigation demonstrated that HHP (400 MPa/30 min) enhanced the OAVs of compounds with sour (19%), malty (37%), floral (37%), caramel-like (49%) and other aromas (118%), and lowered the OAVs of compounds with alcoholic (5%), fruity (12%) and smoky (17%) aromas. These results were consistent with the results of the QDA. HHP treatment positively regulated the Maillard, oxidation and hydrolysis reactions in raw soy sauce, which resulted in the improvement and accelerated formation of raw soy sauce aroma. HHP was capable of simultaneously improving raw soy sauce aroma while accelerating its aroma formation, and this could treatment become a new alternative process involved in the production of high-quality soy sauce.

Potential Use of Emerging Technologies for Preservation of Rice Wine and Their Effects on Quality: Updated Review

Rice wine, a critical fermented alcoholic beverage, has a considerable role in different cultures. It contains compounds that may have functional and nutritional health benefits. Bacteria, yeasts, and fungi commonly found in rice wines during fermentation can induce microbial spoilage and deterioration of the quality during its distribution and aging processes. It is possible to control the microbial population of rice wines using different preservation techniques that can ultimately improve their commercial shelf life. This paper reviews the potential techniques that can be used to preserve the microbial safety of rice wines while maintaining their quality attributes and further highlights the advantages and disadvantages of each technique.

Microbial Communities and Flavor Compounds during the Fermentation of Traditional Hong Qu Glutinous Rice Wine

As a traditional Chinese rice wine, Hong Qu glutinous rice wine (HQW) is popular among consumers due to its unique flavor. However, its quality changes during fermentation, and the potential relationships between flavor and microbes have not been systematically researched. In this work, physicochemical properties (pH, total sugar, alcohol, amino acid nitrogen), flavor compounds (organic acids, free amino acids, and volatile compounds), and microbial communities were investigated. The results revealed that Pantoea, Lactiplantibacillus, Lactobacillus, Leuconostoc, and Weissella predominated the bacterial genera, and Monascus was the predominant fungal genus. Organic acids, free amino acids, and key volatile compounds (esters and alcohols) significantly increased during fermentation. The correlations analysis showed that Lactiplantibacillus was closely associated with flavor compounds formation. This study deepens our understanding of the roles of microorganisms in flavor formation on traditional HQW fermentation.

Effect of thermal treatment on aroma compound formation in yeast fermented pork hydrolysate supplemented with xylose and cysteine

BACKGROUND

The present study has revealed an innovative method of coupling enzyme hydrolysis, yeast fermentation and thermal treatment to transform pork trimmings into a seasoning product. The pork trimmings were first enzymatically hydrolysed and fermented into liquid pork hydrolysates, followed by adding xylose and cysteine, then heat treatment.

RESULTS

Approximately 28% of xylose and 7% of glucose were consumed, and amino acids increased by around 31% after thermal treatment. The heated yeast fermented pork hydrolysates possessed a characteristic 'savoury, roasted-meat and fruity sweet' aroma as a result of the formation of thermally induced sulfur-containing volatiles such as 2-furfurylthiol, as well as retention of yeast generated esters including isoamyl acetate and hexyl acetate.

CONCLUSION

The heat-treated fermented pork hydrolysates impart an attractive and innovative aroma because of yeast fermentation and heat treatment. The innovative heated fermented pork hydrolysates could be further processed into a nutritional and savoury pork broth and/or a meat sauce. © 2021 Society of Chemical Industry.

The sensory and flavor characteristics of Shaoxing Huangjiu (Chinese rice wine) were significantly influenced by micro-oxygen and electric field

In order to improve the high cost of equipment and difficult management caused by the natural aging of Chinese rice wine (Huangjiu), micro-oxygen (MO) and electric field (PEF) technology are used to accelerate the aging of Huangjiu. The results showed that micro-oxygen and electric field have a significant effect on the sensory characteristics and flavor characteristics of Huangjiu. Compared with the naturally aged Huangjiu, the flavor compounds of Huangjiu treated with micro-oxygen and electric field increase significantly. Based on principal component analysis, Huangjiu processed at 0.35 mg L/day or 0.5 mg L/day combined electric field exhibited similar flavor to the natural aged Huangjiu, which was highly associated with long-chain fatty acid ethyl esters (C13-C18). Moreover, partial least squares regression demonstrated that sensory attributes of cereal aroma and astringency were highlighted after aging time, while fruit aroma, continuation, and full body were dominant after micro-oxygen and electric field treatment. Micro-oxygen and electric field effectively enhanced the quality of Huangjiu, which could be applied in other alcoholic beverages.

Development of a Novel Restrictive Medium for Monascus Enrichment From Hongqu Based on the Synergistic Stress of Lactic Acid and Ethanol

Hongqu is a famous fermented food produced by Monascus and has been used as food coloring, wine starters and food additives for thousands of years in China. Excellent Monascus strain is an important prerequisite for producing high-quality Hongqu. However, the isolation of Monascus pure culture from Hongqu samples is time-consuming and laborious because it is easily interfered by other microorganisms (especially filamentous fungi). Therefore, the development of restrictive medium for Monascus enrichment from Hongqu is of great significance for the preparation and screening of excellent Monascus strains. Results of this study showed that Monascus has good tolerance to lactic acid and ethanol. Under the conditions of tolerance limits [7.5% lactic acid (v/v) and 12.0% ethanol (v/v)], Monascus could not grow but it still retained the vitality of spore germination, and the spore activity gradually decreased with the increasing concentrations of lactic acid and ethanol. More interestingly, the addition of lactic acid and ethanol significantly changed the microbial community structure in rice milk inoculated with Hongqu. After response surface optimization, Monascus could be successfully enriched without the interference of other microorganisms when 3.98% (v/v) lactic acid and 6.24% (v/v) ethanol were added to rice milk simultaneously. The optimal enrichment duration of Monascus by the restrictive medium based on the synergistic stress of lactic acid and ethanol is 8∼24 h. The synergistic stress of lactic acid and ethanol had no obvious effects on the accumulation of major metabolites in the progeny of Monascus, and was suitable for the enrichment of Monascus from different types of Hongqu. Finally, the possible mechanisms on the tolerance of Monascus to the synergistic stress of lactic acid and ethanol were preliminarily studied. Under the synergistic stress of lactic acid and ethanol, the cell membrane of Monascus defends against lactic acid and ethanol into cells to some extent, and the superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) activities of Monascus were higher than those of other fungi, which significantly reduced the degree of lipid peroxidation of cell membrane, while secreting more amylase to make reducing sugars to provide the cells with enough energy to resist environmental stress. This work has great application value for the construction of Monascus strain library and the better development of its germplasm resources.

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data.

Induced Changes in Aroma Compounds of Foods Treated with High Hydrostatic Pressure: A Review

Since conventional thermal processing can have detrimental consequences on aroma compounds, non-thermal technologies such as high hydrostatic pressure (HHP) have been explored. HHP may alter the weak chemical bonds of enzymes. These changes can modify the secondary, tertiary, and quaternary structures of key enzymes in the production of aroma compounds. This can result in either an increase or decrease in their content, along with reactions or physical processes associated with a reduction of molecular volume. This article provides a comprehensive review of HHP treatment's effects on the content of lipid-derived aroma compounds, aldehydes, alcohols, ketones, esters, lactones, terpenes, and phenols, on various food matrices of vegetable and animal origin. The content of aldehydes and ketones in food samples increased when subjected to HHP, while the content of alcohols and phenols decreased, probably due to oxidative processes. Both ester and lactone concentrations appeared to decline due to hydrolysis reactions. There is no clear tendency regarding terpenes concentration when subjected to HHP treatments. Because of the various effects of HHP on aroma compounds, an area of opportunity arises to carry out future studies that allow optimizing and controlling the effect.

Fungal community diversity and fermentation characteristics in regional varieties of traditional fermentation starters for Hong Qu glutinous rice wine

Hong Qu glutinous rice wine (HQ wine) is a traditional alcoholic beverage produced in China by fermenting cooked rice using a fermentation starter prepared with the fungus Monascus purpureus. This starter (Hong Qu, HQ) is made empirically by open spontaneous fermentation that is hard to control and standardize, resulting in inconsistent wine quality. This study investigates representative HQ samples from a large geographic region. It explores fungal microbiome compositions, identifies characteristic differences important for the production of various HQ wine styles, and reveals the key fungi responsible for HQ wine fermentation characteristics. The source of the HQ inoculum was found to be the main factor influencing fungal community composition and diversity, followed by processing technology and geographical distribution. Linear discriminant analysis effect size (LEfSe) uncovered 14 genera as potential biomarkers to distinguish regional varieties of HQ. Significant differences were also found in fermentation characteristics such as liquefying power (LP), saccharifying power (SP), fermenting power (FP), total acid content (TA) and liquor-producing power (LPP). The key fungi responsible for LP (5 genera), SP (3 genera), FP (1 genera), LPP (4 genera), and TA (4 genera) were determined using redundancy correlation analysis. Finally, Spearman's correlation analysis indicated that LPP shows a strong positive correlation with FP and LP, while TA displays a strong negative correlation with FP. The results of this study may be utilized to prepare consistently high quality, next-generation HQ by better controlling fungal community structures, and to design fermentation processes for HQ wines with desirable oenological characteristics.

Flavor Formation in Chinese Rice Wine (Huangjiu): Impacts of the Flavor-Active Microorganisms, Raw Materials, and Fermentation Technology

Huangjiu (Chinese rice wine) has been consumed for centuries in Asian countries and is known for its unique flavor and subtle taste. The flavor compounds of Huangjiu are derived from a wide range of sources, such as raw materials, microbial metabolic activities during fermentation, and chemical reactions that occur during aging. Of these sources, microorganisms have the greatest effect on the flavor quality of Huangjiu. To enrich the microbial diversity, Huangjiu is generally fermented under an open environment, as this increases the complexity of its microbial community and flavor compounds. Thus, understanding the formation of flavor compounds in Huangjiu will be beneficial for producing a superior flavored product. In this paper, a critical review of aspects that may affect the formation of Huangjiu flavor compounds is presented. The selection of appropriate raw materials and the improvement of fermentation technologies to promote the flavor quality of Huangjiu are discussed. In addition, the effects of microbial community composition, metabolic function of predominant microorganisms, and dynamics of microbial community on the flavor quality of Huangjiu are examined. This review thus provides a theoretical basis for manipulating the fermentation process by using selected microorganisms to improve the overall flavor quality of Huangjiu.

Effect of high hydrostatic pressure conditions on the composition, morphology, rheology, thermal behavior, color, and stability of black garlic melanoidins

The effects of different high hydrostatic pressure (HHP) conditions on the composition, morphology, rheology, thermal behavior, color, and stability of high molecular weigh melanoidins from black garlic were investigated. Because HHP promoted Maillard reaction, HHP treatments decreased the aldehyde content from 46.76% to 11.92% but increased ketones and heterocyclic contents 4.46% to 6.66% and 9.32% to 11.55%, respectively. HHP treatments induced production of five compounds that were not present in the control sample, including 5-methyl-2(3H)-furanone, 3-methyl-2-cyclopentenone, 2,3-dihydrofuran, 2-ethylfuran, and 2-vinylfuran. The surface of HHP-treated melanoidins was rough and wrinkled, and composed of large particles compared with the control. In addition, HHP reduced viscosity of melanoidins solution at a shear rate of 1-10 s^-1. Moreover, HHP improved the thermal stability and the stability under UV light of black garlic melanoidins. In general, HHP treatment enhanced the composition and structure of black garlic melanoidins and improved stability.

Effect of high hydrostatic pressure on aroma components, amino acids, and fatty acids of Hami melon (Cucumis melo L. var. reticulatus naud.) juice

The changes and relationships between the volatile compounds and fatty acids, and between volatile compounds and free amino acids were analyzed after they were handled by 400 and 500 MPa (45°C/10 min) high hydrostatic pressure (HHP). The volatile components of 31, 30, and 32 were detected in the untreated, 400, and 500 MPa samples, respectively. Unlike the ketones and acids, the three contents, including ester (59.59%-71.34%), alcohol (5.95%-7.56%), and aldehyde (0.36%-1.25%), were greatly changed. While HHP treatment exerted a few effects on the contents of 12 kinds of fatty acids. With the increase in pressure, the contents of palmitic acid, linolenic acid, and α-linolenic acid were remarkably reduced. The correlations between flavor compounds and amino acids, and between flavor compounds and fatty acids were studied by Pearson's correlation analysis and visualized with using the corrplot package in R software. The analysis showed that the amino acids were positively correlated with (E)-6-nonenal, (2E,6Z)-nona-2,6-dienal and (Z)-6-nonen-1-ol, while they were negatively correlated with nonanal, (Z)-3-hexen-1-ol and ethyl caproate. Besides, the fatty acids were positively correlated with the esters of 2,3-butanediol diacetate and 2-methyl propyl acetate, while they were negatively correlated with (E)-2-octenal and (Z)-6-nonen-1-ol.

Bridging the Knowledge Gap for the Impact of Non-Thermal Processing on Proteins and Amino Acids

Proteins represent one of the major food components that contribute to a wide range of biophysical functions and dictate the nutritional, sensorial, and shelf-life of food products. Different non-thermal processing technologies (e.g., irradiation, ultrasound, cold plasma, pulsed electric field, and high-pressure treatments) can affect the structure of proteins, and thus their solubility as well as their functional properties. The exposure of hydrophobic groups, unfolding followed by aggregation at high non-thermal treatment intensities, and the formation of new bonds have been reported to promote the modification of structural and functional properties of proteins. Several studies reported the reduction of allergenicity of some proteins after the application of non-thermal treatments. The composition and concentration of free amino acids could be changed after non-thermal processing, depending on the processing time and intensity. The present review discusses the effects of different non-thermal treatments on protein properties in detail, and highlights the opportunities and disadvantages of these technologies in relation to protein functionality.