Dynamics changes in metabolites and pancreatic lipase inhibitory ability of instant dark tea during liquid-state fermentation by Aspergillus niger.

Instant dark tea (IDT), prepared by liquid-state fermentation using Aspergillus niger, is known for its high theabrownins content and lipid-lowering effect. To explore the impact of fungal fermentation on IDT compositions and its pancreatic lipase inhibitory ability (PLIA), untargeted and targeted metabolomic analysis were applied to track the changes of metabolites over a 9-day fermentation period, and correlation analysis was then conducted between metabolites and PLIA of IDT. There were 54 differential metabolites exhibited significant changes from day 3 to day 5 of fermentation. The concentrations of theabrownins and caffeine increased during fermentation, while phenols and free amino acids decreased. The PLIA of IDT samples significantly increased from day 5 to day 9 of fermentation. Theabrownins not only positively correlated with the PLIA but also exhibited a high inhibition rate. These findings provide a theoretical basis to optimize the production of IDT as functional food ingredient.

Sensomics-Assisted Characterization of Fungal-Flowery Aroma Components in Fermented Tea Using Eurotium cristatum.

Fermented tea (FT) using a single Eurotium cristatum strain can produce a pleasant fungal-flowery aroma, which is similar to the composite aroma characteristic of minty, flowery, and woody aromas, but its molecular basis is not yet clear. In this study, solvent-assisted flavor evaporation and gas chromatography-mass spectrometry/olfactometry were applied to isolate and identify volatiles from the FT by E. cristatum. The application of an aroma extract dilution analysis screened out 43 aroma-active compounds. Quantification revealed that there were 11 odorants with high odor threshold concentrations. Recombination and omission tests revealed that nonanal, methyl salicylate, decanoic acid, 4-methoxybenzaldehyde, α-terpineol, phenylacetaldehyde, and coumarin were the major odorants in the FT. Addition tests further verified that methyl salicylate, 4-methoxybenzaldehyde, and coumarin were the key odorants for fungal-flowery aroma, each corresponding to minty, woody, and flowery aromas, respectively. 4-Methoxybenzaldehyde and coumarin were newly found odorants for fungal-flowery aroma in FT, and 4-methoxybenzaldehyde had not been reported as a tea volatile compound before. This finding may guide future industrial production optimization of FT with improved flavor.

Untargeted and targeted metabolomics reveal changes in the chemical constituents of instant dark tea during liquid-state fermentation by Eurotium cristatum.

Instant green tea powder was used as raw material to prepare an instant dark tea via liquid-state fermentation by Eurotium cristatum. To understand how the chemical constituents present in fermented green tea develop during fermentation, samples were collected on different days during fermentation for qualitative analyses by ultra-performance liquid chromatography-Q Exactive Orbitrap/Mass spectrometry. Untargeted metabolomics analyses revealed that the levels of original secondary metabolites in the instant green tea changed significantly from day 3 to day 5 during fermentation. Targeted metabolomics indicated that the levels of galloylated catechins (GCs) and free amino acids (FAAs) significantly decreased, but the nongalloylated catechins (NGCs), alkaloids, thearubigins and theabrownins increased dramatically after fermentation. The changes in the contents of catechins, gallic acid and free amino acids in the instant dark tea samples were positively related to the DPPH radical scavenging activities in vitro, and the phenolic acids and FAAs were positively related to the inhibitory effects towards α-glucosidase. These results showed that fermentation by Eurotium cristatum is critical to the formation of certain qualities of instant dark tea.

Influence of Eurotium cristatum and Aspergillus niger individual and collaborative inoculation on volatile profile in liquid-state fermentation of instant dark teas.

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.

Nanocomplexes derived from chitosan and whey protein isolate enhance the thermal stability and slow the release of anthocyanins in simulated digestion and prepared instant coffee.

Anthocyanins (ACNs) are naturally derived colorants and antioxidants added to manufactured foods. ACNs were encapsulated in nanocomplexes with chitosan hydrochloride (CHC), carboxymethyl chitosan (CMC) and whey protein isolate (WPI). The ACN-loaded CHC/CMC-WPI nanocomplexes (ACN-CHC/CMC-WPI) showed a preferred particle size (332.20 nm) and zeta potential (+23.65 mV) and a high encapsulation efficiency (60.70%). ACN-CHC/CMC-WPI nanocomplexes exhibited a smooth spherical shape by transmission electron microscopy. Fourier transform infrared (FT-IR) and Raman spectroscopy confirmed interactions between the ACNs and the encapsulation materials (CHC/CMC-WPI). The nanocomplexes or the nanocomplexes incorporated into coffee beverage better protected ACNs at high temperature compared to the unencapsulated ACNs. In simulated gastrointestinal fluids, the ACNs in the ACN-CHC/CMC-WPI were more stable and more slower released over time. The nanocomplexes maintained high DPPH and hydroxyl free radical scavenging activities. This study indicated that CHC/CMC-WPI nanocomplexes can improve the thermal stability and slow the release of ACNs added to food products.

Gallic acid as a copigment enhance anthocyanin stabilities and color characteristics in blueberry juice.

The aim of this study was to evaluate the influence of adding copigment gallic acid (GA) on the stability of anthocyanin and color in blueberry juice, and assays were carried out with different anthocyanin:GA molar ratios (1:0, 1:1, 1:3, 1:5) in accelerated experiments (40 °C for 10 days). Results showed that the addition of GA made blueberry juice to appear more crimson color tonality, color saturation and anthocyanins stability. The most obvious hyperchromic effect appeared in juice with 1:5 of anthocyanin:GA molar ratios, and in this ratio, total anthocyanin content (137.67 mg/L) and main anthocyanin peonidin-3-glucoside content (51.68 mg/L) of the blueberry juice were higher than juice without copigment (total anthocyanin of 116.96 mg/L and peonidin-3-glucoside of 34.2 mg/L). Furthermore, anthocyanins in blueberry juice copigmented with molar ratios 1:5 of anthocyanin:GA were more stable at 4 °C than that at 25 °C and 40 °C. Thus, the addition of gallic acid at appropriate levels might be a promising juice process technology to obtain juices with high color quality and anthocyanin stability.

Structural characterization and antioxidant activity of a new polysaccharide from Bletilla striata fibrous roots.

A new polysaccharide (pFSP) was first isolated from the originally discarded fibrous roots part of Chinese traditional herb, Bletilla striata. pFSP was composed of D-glucose, D-galactose and D-mannose in a molar ratio of 1: 2.03: 3.45 with molecular weight of 9.1 × 104 Da. It could effectively scavenge DPPH and superoxide radicals with inhibition rate of 64.47% and 72.27% at 5.0 mg/ml, higher than that of polysaccharide from Bletilla striata tuber. Structural investigations of the periodate oxidation studies and Smith-degradation as well as the FT-IR spectroscopy were performed, and combined with 1D and 2D NMR spectroscopy, the repeating unit of pFSP contained (1→4)-linked-α-D-Glcp, (1→4)-linked-ß-D-Manp and (1→3,6)-linked-ß-D-Manp units, together with the branches of (1→6)-linked-ß-D-Galp and terminated with (1→)-linked-ß-D-Manp residue.

Anti-obesity effects of instant fermented teas in vitro and in mice with high-fat-diet-induced obesity.

Obesity is a chronic metabolic disorder that is associated with higher risks of developing diabetes and cardiovascular disease. Chinese dark tea is a fermented beverage with many biological effects and could be considered for the management of obesity. This study is aimed to assess the possible anti-obesity properties of instant dark tea (IDT) and instant pu-erh tea (PET) in high fat diet (HFD)-fed mice. Male C57BL/6 mice were divided into 5 groups. They received low-fat diet (LFD), HFD, HFD supplemented with drinking IDT infusion (5 mg mL-1), PET infusion (5 mg mL-1) or water for 8 weeks. The results showed IDT exhibited better inhibitory effect than PET on body weight gain and visceral fat weights. IDT also improved the serum high-density lipoprotein cholesterol (HDL-C) level, but decreased the low-density lipoprotein cholesterol (LDL-C) and leptin levels more effectively than PET. Both IDT and PET lowered the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the plasma and significantly increased the ratio of albumin to globin (A/G) in the serum compared to the control group. IDT treatment reduced the malondialdehyde (MDA) level in the liver. Histomorphology evidenced that the liver tissue architecture was well preserved by IDT administration. Moreover, IDT regulated the expression of obesity-related genes more effectively than PET. Overall, the present findings have provided the proof of concept that dietary IDT could provide a safer and cost-effective option for people with HFD-induced obesity.

Nanocomplexes composed of chitosan derivatives and ß-Lactoglobulin as a carrier for anthocyanins: Preparation, stability and bioavailability in vitro.

To improve sustained-release property, stability and bioavailability of anthocyanins (ACNs) in vitro, we fabricated the nanocomplexes with chitosan hydrochloride (CHC), carboxymethyl chitosan (CMC) and ß-Lactoglobulin (ß-Lg). Response surface methodology (RSM) combined with desirability function was employed to optimize ACNs-loaded chitosan/ß-Lg (CHC/CMC expressed with chitosan) nanocomplexes with maximum anthocyanins retention rate, preferred particle size and high encapsulation efficiency. The result suggested that the optimized conditions were 5.16 mg/mL of ß-Lg, 1.45 mg/mL of CMC and 6.09 of pH CMC solution. Based on optimized conditions, anthocyanins retention rate, particle size and encapsulation efficiency of ACNs-loaded chitosan/ß-Lg nanocomplexes were 68.9%, 91.71 nm and 69.33%, respectively. ACNs-loaded chitosan/ß-Lg nanocomplexes was more stable in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 6.8) by showing less ACNs release (%) than that ACNs solution and ACNs-loaded CHC/CMC nanocomplexes. Further, stability and bioavailability of ACNs in simulated gastrointestinal (GI) tract were significantly improved by nanocomplexes encapsulation. Compared with ACNs-loaded CHC/CMC nanocomplexes, ACNs-loaded chitosan/ß-Lg nanocomplexes displayed better sustained ACNs release, stability and bioavailability.

Multiple responses optimization of instant dark tea production by submerged fermentation using response surface methodology.

In this study, submerged fermentation mode for preparing instant dark tea production was developed through utilizing industrial low grade green tea as raw material and Aspergillus niger as fermentation microbe starter. The fermentation parameters (inoculum size, liquid-solid ratio and rotation speed) were optimized by using Box-Behnken design and response surface methodology (RSM) with desirability function, the theabrownins content, redness and turbidity value as responses. The optimal conditions were set as follow: inoculum size of 5.3% (v/v), liquid-solid ratio of 27.78 mL/g, and rotation speed of 182 r/min. The optimized conditions model showed a good correlation between the predicted and experimental values. Further, the optimum product of instant dark was achieved in a 3-L laboratory fermenter, and the main parameters of product were theabrownins content of 140.92 g/kg and redness value of 40.78 and turbidity of 90.98 NTU. Sensory evaluation showed that the instant dark tea infusion approached mellow mouthfeel, an aroma of mint and a good overall acceptance.

High-theabrownins instant dark tea product by Aspergillus niger via submerged fermentation: α-glucosidase and pancreatic lipase inhibition and antioxidant activity.

BACKGROUND: Theabrownins (TB) are bioactive components that are usually extracted from Chinese dark tea, in which they are present at low concentrations. The present study aimed to produce an instant dark tea high in theabrownins via submerged fermentation by the fungus Aspergillus niger. Three fermentation parameters that affect theabrownins content (i.e. inoculum size, liquid-solid ratio and rotation speed) were optimized using response surface methodology. RESULT: Optimum fermentation conditions were modeled to be an inoculum of 5.40% (v/v), a liquid-solid ratio of 27.45 mL g-1 and a rotation speed of 184 rpm and were predicted to yield 292.99 g kg-1 TB. Under these experimentally conditions, the TB content of the instant dark tea was 291.93 g kg-1 . The antioxidant capacity and α-glucosidase and pancreatic lipase inhibitory activities of the high-TB instant black tea were higher than four other typical instant dark tea products. CONCLUSION: The results of the present study show that careful management of culture conditions can produce a dark tea high in theabrownins. Furthermore, high-theabrownins instant dark tea could serve as a source of bioactive products and be used in functional foods as an ingredient imparting antioxidant properties and the ability to inhibit pancreatic lipase and α-glucosidase. © 2017 Society of Chemical Industry.

Loading of anthocyanins on chitosan nanoparticles influences anthocyanin degradation in gastrointestinal fluids and stability in a beverage.

The optimal preparation parameters to create anthocyanin-loaded chitosan nanoparticles was predicted using response surface methodology (RSM). A Box-Behnken design was used to determine the preparation parameters that would achieve the preferred particle size and high encapsulation efficiency. The result suggested that the optimized conditions were 2.86mg/mL carboxymethyl chitosan (CMC), 0.98mg/mL chitosan hydrochloride (CHC) and 5.97mg anthocyanins. Using the predicted amounts, the experimentally prepared particles averaged 219.53nm with 63.15% encapsulation efficiency. The result was less than 5% different than the predicted result of 214.83nm particle size and 61.80% encapsulation efficiency. Compared with the free anthocyanin solution, the anthocyanin-loaded chitosan nanoparticles showed a slowed degradation in simulated gastrointestinal fluid. Compared with the free anthocyanin solutions in a model beverage system, the stability of the anthocyanins was increased in the anthocyanin-loaded chitosan nanoparticles.

Optimization of Ultrasound-Assisted Extraction of phenolic compounds and anthocyanins from blueberry (Vaccinium ashei) wine pomace.

Ultrasound-Assisted Extraction (UAE) of total anthocyanins (TA) and phenolics (TP) from Blueberry Wine Pomace (BWP) was optimized using Response Surface Methodology (RSM). A Box-Behnken design was used to predict that the optimized conditions were an extraction temperature of 61.03°C, a liquid-solid ratio of 21.70mL/g and a sonication time of 23.67min. Using the modeled optimized conditions, the predicted and experimental yields of TA and TP were within a 2% difference. The yields of TA and TP obtained through the optimized UAE method were higher than those using a Conventional Solvent Extraction (CSE) method. Seven anthocyanins, namely delphinidin-3-O-glucoside, delphindin-3-O-arabinoside, petunidin-3-O-glucoside, cyanidin-3-O-arabinoside, cyanidin-3-O-glucoside, malvidin-3-O-glucoside and malvidin-3-O-arabinoside, were found in the BWP extract from both the UAE and CSE methods.