Method for producing a reducing mixture obtained from microorganisms having an oxidation-reduction potential of 0 mV or less

A method for producing a reducing mixture obtained from microorganisms having an oxidation-reduction 0 mV or less, which comprises subjecting a yeast or yeast extract to a treatment of superheated steam in the presence of silicic acid or a silicate where superheated steam treatment is carried out in the absence of oxygen and with superheated steam at a pressure of 0.9 MPa to 1.9 MPa at 150 ° C to 210 ° C.