The functional components in tartary buckwheat leaf powder can give flour products higher nutritional value. To comprehensively realize the high-value utilization of tartary buckwheat and its by-products, electric stone mill powder (EMP), ultra-fine mill powder (UMP), steel mill powder (SMP), and grain mill powder (GMP) from tartary buckwheat leaves were used in the preparation of wheat dough, and this was used to explore their effects on dough properties and protein microstructure. With an increase in tartary buckwheat leaf powder, the hydration characteristics, protein weakening rate, and starch gelatinization characteristics of the dough changed, and the water holding capacity and swelling capacity decreased. The retrogradation value increased, which could prolong the shelf life of related products. The water solubility of the dough showed an upward trend and was the lowest at 10% UMP. The addition of UMP produced a more uniform dough stability time and the lowest degree of protein weakening, which made the dough more resistant to kneading. An increasing amount of tartary buckwheat leaf powder augmented the free sulfhydryl content of the dough and decreased the disulfide bond content. The disulfide bond content of the dough containing UMP was higher than that of the other doughs, and the stability of the dough was better. The peaks of the infrared spectrum of the dough changed after adding 10% UMP and 20% EMP. The content of α-helical structures was the highest at 10% UMP, and the content of ordered structures was enhanced. The polymerization of low molecular weight proteins to form macromolecular polymers led to a reduction in surface hydrophobic regions and the aggregation of hydrophobic groups. The SEM results also demonstrated that at 10% tartary buckwheat leaf powder, the addition of UMP was significantly different from that of the other three leaf powders, and at 20%, the addition of EMP substantially altered the structure of the dough proteins. Considering the effects of different milling methods and different added amounts of tartary buckwheat leaf powder on various characteristics of dough, 10% UMP is the most suitable amount to add to the dough.

To functionally enhance Tartary buckwheat and elucidate the underlying mechanisms of change, solid-state fermentation (SSF) was conducted using three edible-medicinal fungi—Auricularia auricula (A. auricula), Ganoderma lucidum (G. lucidum), and Hericium erinaceus (H. erinaceus). The in vitro antioxidant (DPPH/ABTS) and α-glucosidase inhibitory activities were quantitatively evaluated. Notably, SSF with H. erinaceus specifically elevated α-glucosidase inhibitory activity by 50% under the tested conditions. Non-targeted metabolomics further profiled metabolite alterations to identify key up-regulated bioactive compounds. Epicatechin gallate (ECG) was significantly up-regulated in all three samples, and the fold change in quercetin 3′-O-sulfate in GFTB was significantly higher than that in the other two samples. Metabolic pathway analysis identified the biosynthesis of secondary metabolites and the metabolism of terpenoids and polyketides as the most prominently affected pathways. This study demonstrates that SSF with edible-medicinal fungi is an effective bioprocessing strategy to boost the bioactivity and value of Tartary buckwheat.