Abstract
The pressed cake obtained through press-filtration of soy sauce mash was examine in respect to the difficulty in the press-filtration during soy sauce manufacturing process. The water-washed cake was estimated to be composed of about 10% microbial cells; 30% proteins; 20% non-nitrogen materials originated from soybean (involve 7% acidic poly-saccharides) and 30% of those from wheat. Among the components of the washed cake, the contribution of non-cellulotic polysaccharides on filtration resistance of the cake was calculated to about 70%, especially that of the acidic polysaccharides being to more than 40%. Except the acidic polysaccharides originated from soybean, the non-cellulotic poly-saccharides in the cake were composed of arabinoxylan and starch (2:1). These two neutral polysaccharides were supposed to be derived from wheat.
The acidic polysaccharides of which main chains were constituted through α-1, 4-linkage of D-galacturonic acid, were divided into four fractions. One of them seemed to be similar to the acidic polysaccharide in soy sauce, because of its highly branched structure. However, other three contained about 90% of D-galacturonic acid, respectively. The fact that the latters were insoluble in 17.5% NaCl solution and also remarkably decomposed by endo-polygalacturonase, suggested their considerable participations in difficulty in press-filtration of the fermented mash.
On the other hand, soybean preliminarily heat-treated with 0.5% H2O2 or 1% ammo-nium oxalate was enzymatically hydrolyzed with the crude enzyme preparation from Aspergillus sojae X-816. In another experiment, treatment with a plant cell wall lytic enzyme was applied in stead of the chemical treatments mentioned above. In both cases, the slurries of enzymatic soybean hydrolysates could be much more easily press-filtered than the hydrolysate from untreated control. This result suggests the possibility that the preliminary treatment of soybean polysaccharides prior to the fermentation may reduce the difficulty in press-filtration of fermented soy sauce mash.
