Preparation and Properties of Functional Mulberry Leaf Tea by Salt-Vinegar Steaming-Fermentation

Functional mulberry leaf tea was obtained by salting-vinegar steaming-fermentation treatment. Water hardness,acetic acid content and 1-DNJ content were determined by EDTA titration,catalytic spectrophotometry and HPLC respectively. As the brine concentration was 2 g/L,water hardness of functional mulberry leaf tea was decreased from 1039.29 mg/mL to 310.14 mg/mL.The acetic acid content was reduced from 202.8 mg/kg to 139.4 mg/kg when the concentration of water in vinegar was 60 mL/L. After salting and vinegar-steaming,the mulberry leaf tea was fermented by koji at 12 h,the acetic acid content was further decreased to 43.52 mg/kg. The sensory score of mulberry leaf tea obtained by this method was 88.90 points. Compared with other mulberry leaf tea,the functional mulberry leaf tea had the most pleasant flavor and the lowest oxalic content with an acceptable content of the 1-DNJ and water hardness.