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Eurotium cristatum , a unique probiotic in Fu brick tea, is widely used in food processing to enhance added values. Here, green kernel black beans (GKBBs) were solid-fermented with E. cristatum and dynamic changes in flavour, chemical composition and metabolites during fermentation were investigated. As results, E. cristatum fermentation altered aroma profiles and sensory attributes of GKBBs, especially reduced sourness. After fermentation, total polyphenolic and flavonoid contents in GKBBs were elevated, while polysaccharides, soluble proteins and short-chain fatty acids contents were decreased. E. cristatum fermentation also induced biotransformation of glycosidic isoflavones into sapogenic isoflavones. During fermentation, dynamic changes in levels of 17 amino acids were observed, in which 3 branched-chain amino acids were increased. Non-targeted metabolomics identified 51 differential compounds and 10 related metabolic pathways involved in E. cristatum fermentation of GKBBs. This study lays foundation for the development of green kernel black bean-based functional food products with E. cristatum fermentation. [Display omitted] • Variations on flavour and nutritional property were tracked during fermentation. • E. cristatum enhances branched chain amino acids in green kernel black beans. • Glycosidic isoflavones were biotransformed into sapogenic ones after fermentation. • Fermentation reduced the acidic sensory attribute of green kernel black bean. • Untargeted metabolomics identified 51 differential compounds after fermentation. [ABSTRACT FROM AUTHOR]

Fu-brick tea (FBT) is predominately fermented by Eurotium Cristatum , FBT polysaccharides (FTPs) and Eurotium Cristatum extracellular polysaccharides (ECPs) are the main active substances in FBT and Eurotium Cristatum , respectively. FTPs was shown to exhibit higher levels of uronic acids, proteins, and polyphenols as compared to ECPs (p < 0.05), contributing to the superior antioxidant activity observed in FTPs. Additionally, FTPs had better water solubility and thermal stability than ECPs. Interestingly, in vitro digestive simulation revealed that FTPs and ECPs resist digestion in the stomach and small intestine. Excitingly, utilizing in vitro fermentation with feces from healthy individuals and type 2 diabetes mellitus (T2DM) patients demonstrated that FTPs and ECPs promote the production of SCFAs. Still, FTPs resulted in greater SCFAs contents than ECPs (p < 0.05). Moreover, FTPs and ECPs fermentation by T2DM patients' fecal microbiota affected different metabolomic pathways. Our findings suggested that FTPs holds great promise for application in functional foods. [Display omitted] • FTPs had higher uronic acids, proteins, and polyphenols levels than ECPs. • FTPs had better stability and superior antioxidant activity than ECPs. • FTPs and ECPs resisted digestion in the stomach and small intestine. • FTPs and ECPs acted as probiotics by promoting the production of metabolites. • FTPs helds greater promise for application in functional foods than ECPs. [ABSTRACT FROM AUTHOR]

Highlights • Angelica dahurica was fermented by Eurotium cristatum. • Antioxidant assays were used for comparing the antioxidant activity. • The on-line antioxidant system was used for screening the antioxidants in fermentation product for the first time, 12 antioxidants were identified. • The secondary metabolites showed high antioxidant capacity. • Characteristic of the indole alkaloid metabolites in ESI-MS was discussed. Abstract Eurotium cristatum , a beneficial fungus isolated from Fuzhuan tea, was used to ferment Angelica dahurica for the first time. The antioxidant capacities of the extracts before and after fermentation were compared using ABTS, DPPH and FRAP assays. The results showed that the antioxidant capacities of the extracts acquired using organic solvents were greater after fermentation. Moreover, based on a comparison of the HPLC chromatograms, the chemical composition of Angelica dahurica changed substantially during fermentation. To further understand the changes in its antioxidant constituents, an on-line HPLC-PDA-Triple-TOF-MS/MS-ABTS system was employed. Twelve antioxidants belonging to three different classes were detected and identified, and their antioxidant capacities were preliminarily evaluated. The results indicated that the substances produced during the fermentation of Eurotium cristatum played important roles in enhancing the antioxidant capacity. [ABSTRACT FROM AUTHOR]

• E. cristatum used in pure-culture fermentation of primary dark tea. • Metabolites evolutions of dark tea during SSF were determined by UPLC–QQQ–MS/MS. • 574 differential metabolites were detected during SSF of dark tea by E. cristatum. • Phenolic acids and flavonoids are the two largest classes of differential metabolites. • E. cristatum is favorable to the accumulation of theabrownins during SSF of dark tea. Eurotium cristatum is the predominant fungus and key contributor to the characteristics of post-fermented Fu brick tea (FBT) during manufacturing. In this study, the influence of solid-state fermentation (SSF) with E. cristatum on the chemical profile dynamic changes of dark tea was investigated. Results indicated that total phenolics, flavonoids, theaflavins, thearubigins, and galloyl catechins consistently decreased, degalloyl catechins and gallic acid increased in the initial stage of fermentation and decreased after long-term fermentation, and theabrownins continually increased. UPLC–QQQ–MS/MS-based widely targeted metabolomic analysis revealed that the metabolites of dark tea processed by SSF with E. cristatum were drastically different from the raw material. A total of 574 differential metabolites covering 11 subclasses were detected in the whole SSF of dark tea, and the most drastic changes occurred in the middle stage. Phenolic acids and flavonoids were the two major classes of differential metabolites. A series of reactions such as degradation, glycosylation, deglycosylation, methylation, and oxidative polymerization occurred during SSF. Overall, SSF with E. cristatum greatly influenced the metabolites of dark tea, which provided valuable insights that E. cristatum is critical in forming the chemical constituents of FBT. [ABSTRACT FROM AUTHOR]

• E. cristatum fermentation improved the aroma and taste quality of autumn green tea. • Increased terpene alcohols imparted fermented autumn green tea with flowery aroma. • Astringency of autumn tea was reduced by metabolizing catechins into theabrownins. • Theabrownins were observed to be umami but not astringent for the first time. • Results provided insights into utilizing autumn tea and reducing tea astringency. Autumn green tea (AT) has poor taste quality for its strong astringency. This study aims to improve the taste quality as well as the aroma of AT by Eurotium cristatum (MF800948) fermentation and to produce a fermented autumn green tea (FT). Results showed that the aroma quality of AT was improved, and the content of terpene alcohols that impart characteristic flowery aroma to FT significantly increased. The umami intensity of FT was comparable to that of AT while the astringency tasted much weaker mainly due to the oxidation of the catechins. The results also confirmed that theabrownins exhibited strong umami taste, not astringent taste. Finally, a metabolic map was analyzed to show the effect of E. cristatum (MF800948) on the quality of AT, and to visualize the changes of differential compounds in AT and FT. The work provides insights into the quality improvement of autumn green tea. [ABSTRACT FROM AUTHOR]

[Display omitted] • Volatile compounds were tentatively identified in four kinds of instant tea. • Instant green tea and fermented dark teas were discriminated by multiple analysis. • Microbial fermentation by E. cristatum and/or A. niger increased alcohols. • Fermentation by different microbes creates the unique aromas of instant dark tea. The three instant dark teas were produced from instant green tea (IGT) by liquid-state fermentations using the microorganisms Eurotium cristatum (EFT), Aspergillus niger (AFT), and sequential inoculation of E. cristatum / A. niger (EAFT), respectively. The volatile compounds of four tea samples were extracted by headspace-solid phase microextraction (HS-SPME) and analyzed using gas chromatography-mass spectrometry (GC-MS) coupled with chemometrics. A total of 97 volatile compounds were tentatively identified to distinguish three fermented instant dark from IGT. Alcohols, acids, esters, ketones, aldehydes, and heterocyclics could be clearly distinguished by principal component analysis (PCA), venn diagram, heatmap analysis and hierarchical cluster analysis (HCA). Descriptive sensory analysis revealed that AFT had a moldy, woody and herbal aroma; EFT showed woody and herbal aroma; and EAFT smelled an herbal, sweet, minty and floral aroma. This study indicates that fermentation using different microorganisms is critical in forming unique aroma characteristics of instant dark teas. [ABSTRACT FROM AUTHOR]