MICROFILTRATION OF SOY-SAUCE SEDIMENT WITH ROTATING-DISK MEMBRANE MODULE

Soy sauce sediment is formed in pasteurization of raw soy sauce. It is treated as industrial waste, though its main component is soy sauce, because of difficulty in perfect clarification of the suspension. In this paper, we decided a suitable range of pore size of microfiltration and a cut-off level of ultrafiltration to clarify soy sauce sediment and we developed a rotating disk membrane module (RD Module) and compared performance with conventional a multi-tubular membrane module (MT Module). The optimum range to obtain soy sauce of quality was less than a pore size of 0.2 mu m for microfiltration, while ultrafiltration was not suitable for soy sauce sediment. Ultrafiltration was restricted by rejection of colors and nucleic acids and related compounds in soy sauce sediment, rather than rejection of bacteria and ethanol. An RD Module could recover soy sauce of quality and was superior to an MT Module for concentration ratio, but the permeate fluxes of the RD Module decreased under conditions of high revolution as centrifugal forces were exerted on the permeate in the disk membrane. The power consumption of the RD Module was proportional to the cube of number of revolutions and to the fifth power of the radius, so it was found that one of methods for the scale up is to increase the number of disk membranes than increase the radius.