Investigation on Quality Characteristics and Antidiabetic Properties of Mulberry Leaf Fu Brick Tea

Mulberry leaves (Morus alba L.) exhibit antidiabetic properties; however, their taste is unappetizing, leading to limited practical applications. Although Fu brick tea has a favorable flavor, its hypoglycemic effects are weak. Hence, we combined the two to create mulberry leaf Fu brick tea (SF) and investigated its sensory perception, safety, microorganism content, key metabolites, and impact on hyperglycemic mice using the same raw materials and techniques to prepare Fu brick tea (F) and mulberry leaf brick tea (S) individually. Our study showed that SF, which comprises blended mulberry leaf primary dark tea and primary dark tea (1 : 3 g/g), was sweeter and smoother, with a median lethal dose of 22.3 g/kg, indicating that it is safe for consumption. Compared to F, caffeine levels were reduced in SF and 1-deoxynojirimycin and aminobutyric acid levels were increased. Phenolic substances and flavonoids showed increased levels in SF compared with S. These changes contribute to the taste and functionality of SF. The primary microorganisms in SF were Bacillus, Lactobacillus, and Aspergillus, which contributed to the improved quality. SF demonstrated its antidiabetic effects by reducing the blood sugar levels of hyperglycemic mice, restoring the function of pancreatic cells, reducing lipid levels, and improving the antioxidant capacity of the liver. Overall, SF exhibited a better taste and antidiabetic properties than F and S, highlighting its potential as a functional beverage.