A variety of spectroscopic techniques were used to study the inhibitory effect and mechanism of rutin and quercetin on starch-digesting enzymes and their combined effect. The results showed that the types of inhibition of rutin and quercetin on α-amylase were competitive, mainly driven by hydrophobic interactions and hydrogen bonds, and the half maximum inhibitory concentrations (IC₅₀) were 0.36 and 0.22 mg/mL, respectively. The inhibition of α-glucosidase by rutin and quercetin was of mixed type, driven by hydrogen bonds, and the IC₅₀ were 1.30 and 0.362 mg/mL, respectively. Moreover, both flavonoids could combine with α-amylase and α-glucosidase at only one/kind of action site to form a complex, thus inhibiting the activity of the enzymes, and their combinations in different proportions had a synergistic inhibitory effect on α-amylase and α-glucosidase. When the concentration ratio between rutin and quercetin was 7:1 and 3.6:18, the combination index for α-amylase and α-glucosidase was 0.20 and 0.22, respectively, showing the best synergistic inhibitory effect. This study provides a theoretical basis for further research on the interaction mechanism between flavonoids and starch-digesting enzymes, is meaningful for guiding the processing and utilization of edible and medicinal plants rich in flavonoids, and helps to promote the virtuous cycle of the tartary buckwheat industry.

In this study, the changes in the viable count of lactic acid bacteria and the contents of major organic acids in sourdough were explored during spontaneous and inoculated fermentations with the typical sourdough starter cultures Lactobacillus plantarum (Lp), Lactobacillus paralimentarius (Lpa) and Lactobacillus fermentum (Lf) separately and in combination: Lpa + Lp (1:1), Lp + Lf (1:1) and Lpa + Lf (1:1), and the effect of co-fermentation with yeast on bread quality was evaluated. The results demonstrated that Lf grew fastest in sourdough among the single cultures, while the highest number of bacterial colonies of 9.20 (lg(CFU/g)) was observed in sourdough fermented with Lpa + Lp + Lf for 10 h. From 16 h onward, the number of bacterial colonies remained stable. Furthermore, the rate of inoculated fermentation (for both single and mixed culture fermentation) was always faster than that of natural fermentation, and the sourdoughs fermented with Lf and Lpa + Lp + Lf reached the desired pH 4.0 after 16 h. Moreover, at this time, the maximum contents of lactic acid and acetic acid in sourdough were obtained (9.05 and 2.31 mg/g, respectively). Compared with ordinary dry yeast fermented bread (OFB), the specific volume of Lpa + Lp + Lf fermented sourdough bread increased by 19.43%, the hardness decreased by 38.21%, and the resilience rose by 29.17%. In the case of flavor quality, Lpa + Lp + Lf fermented sourdough bread contained the largest number (49) and amount (352.39 μg/kg) of flavor compounds including four unique esters, namely ethyl lactate, ethyl palmitate, phenethyl 2-methylpropionate and ethyl caproate. In addition, anti-aging properties of the bread were evaluated, revealing that after 7 days of storage, the quality did not remarkably deteriorate, the hardness increased by only 1.93 times, and the rate of water migration was slow during storage. In summary, Lpa + Lp + Lf fermented sourdough can significantly improve the taste of bread and extend its shelf life.

In this study, Lactobacillus plantarum (Lp), Lactobacillus fermentum (Lf) and Weissella confusa (Wc) were selected as exogenous strains for the fermentation of sourdough. The growth of lactic acid bacteria, the distribution of major metabolites such as organic acid and sugar, and the distribution of protein in sourdough were evaluated by high performance liquid chromatography (HPLC) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Finally, the sourdough was applied to the production of frozen dough bread. The results showed that in the sourdough, the bacteria entered the logarithmic growth phase at 4–12 h, and mixed cultures grew better than individual ones, showing synergism. Particularly, the colony count of Lf + Wc in sourdough was as high as 9.18 (lg(CFU/g)) after 12 h fermentation, and a large amount of fructose (11.82 mmol/kg) and extracellular polysaccharide (EPS) (3.132 g/kg) were generated. Compared with the other groups, Lf + Wc exhibited moderate acid production rate, lower protease activity and slower protein degradation rate. The baking quality of bread made from Lf + Wc fermented sourdough frozen and stored for 13 weeks decreased slightly, and the baking loss rate decreased only by 5.3%. In addition, GC-MS analysis showed that the number of volatile compounds in frozen dough bread fermented with Lf + Wc increased by eight after 13 weeks of frozen storage. In conclusion, Lf and Wc have a good synergistic effect when used together. Notably, metabolites such as exopolysaccharides generated during metabolism are of great significance for delaying and controlling the deterioration of frozen dough bread quality. This study provides a certain theoretical basis for the application of multigrain sourdough as a natural antifreeze agent in the large-scale preparation of frozen dough.

The gut is home to a large number of intestinal microbiota that play an important role in the metabolism and immune system of the host. A growing body of evidence suggests that a high-fat diet is closely associated with many metabolic disorders, including fatty liver and type 2 diabetes. According to reports, Tartary buckwheat extract has a positive effect on intestinal microbiota in animals. The effects of Tartary buckwheat on biochemical indexes and intestinal microflora in mice were studied. Tartary buckwheat protein (FGP), Tartary buckwheat resistant starch (FGS) and Tartary buckwheat flour (FGF) alleviated organ damage in mice and lowered the atherosclerotic index (AI) in plasma. Otherwise, principal coordinate analysis (PCoA) showed that intestinal bacterial structure of FGF were separated apparently from other groups. The Firmicutes/Bacteroidetes (F/B) value of the high-fat (HF)-FGF group was significantly lower than that of the HF-FGP and HF-FGS groups. FGF significantly increases the abundance of beneficial bacteria such as Bifidobacterium, while decreasing the abundance of lipopolysaccharide (LPS)-producing bacteria. Observation of blood lipid metabolism parameters and analysis of the intestinal microbiota suggested that FGF can be more effective than FGP and FGS to reduce the effects of a high-fat diet in mice, restoring the blood parameters to values similar of those in mice fed a low-fat diet. FGF may be used to prevent or treat blood lipid metabolism disorders and intestinal microbiota disorders in mice fed a high-fat diet.

Excessive reactive oxygen species (ROS) can cause oxidative damage and lead to various metabolic disease. Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn) is a new kind of protein-rich functional food, the protein in which has been proved to have good antioxidant capacity. In this study, in order to further explore the antioxidant mechanism of Tartary buckwheat protein, 4 peptides (CR-8, LR-8, GK-10 and SR-12) were isolated and identified from it. H₂O₂ was used to induce oxidative damage to Caco-2 cells to evaluate antioxidant capacity of these peptides. The results of superoxide dismutase (SOD), total antioxidant capacity (T-AOC) and mitochondrial membrane potential etc. showed that these peptides have superior antioxidant capacity. CR-8 has the best antioxidant capacity. In order to further clarify the antioxidant mechanism of CR-8, metabolomics was used to analyze related metabolites and metabolic pathways. The results showed that after CR-8 intervention, the content of metabolites such as L-acetyl carnitine has increased. This indicated that CR-8 can improve the antioxidant capacity of damaged cells by intervening in multiple metabolic pathways. This also revealed the anti-oxidant mechanism of tartary buckwheat protein. In conclusion, it provided a theoretical basis for further studying the activity of tartary buckwheat portein and utilizing buckwheat resources.

Components with strong adsorption capacity for cholates from buckwheat proteins were screened, separated and purified by several methods, and the effects of ultra-high-pressure (UHP) on the structure and function of buckwheat 13S globulin (BW13SG) were studied. Samples were treated by UHP at different pH (3.0 and 7.0) value(s) and at 100–500 MPa for 10–30 min. The results showed that the tertiary structure of BW13SG was partially denatured and aggregated. The decrease in the unordered structure indicated that UHP resulted in a looser secondary structure of BW13SG. UHP treatment also increased solubility, emulsion activity and stability, foaming capacity and stability. The samples treated at 500 MPa, pH 3.0 for 30 min had the most enhanced functionality. Moreover, under this condition, the sodium cholate and sodium deoxycholate adsorption capacities of BW13SG were both higher than 98% and the adsorption capacity of sodium taurocholate, which can be difficult to adsorb, was higher than 60%.