Ji-Hyun Seo

Production of Fibrinolytic Enzyme and Peptides from Alkaline Fermentation of Soybean Curd Residue by Bacillus firmus NA-1

To produce functional food ingredient from the soybean curd residue (SCR), alkaline fermentation was performed with SCR from cold processed (D-SCR) or hot processed (P-SCR) tofu. The solid- state fermentation was performed by Bacillus firmus NA-1 at . The fermentation of heat-treated D- SCR resulted in higher production of peptides and fibrinolytic enzyme compared with D-SCR without heating. The P-SCR showed higher production of peptides, fibrinolytic enzyme, indicating alkaline pH after fermentation for 18 hr. When the moisture content of P-SCR was reduced to , the production of peptides and fibrinolytic enzyme were enhanced. The P-SCR fortified with MFS (micronized full-fat soy flour) showed higher fibrinolytic enzyme activity and consistency index by fermentation of Bacillus firmus NA-1 Furthermore, the P- SCR fortified with MFS indicated relatively higher peptide content, fibrinolytic enzyme activity and enhanced flavor. By increasing the addition of MFS, the peptide content of fermented P-SCR was increased significantly, but fibrinolytic enzyme was slightly decreased.

Physicochemical properties of soy protein isolate gels emulsified with various oils using a microbial transglutaminase

Soy protein isolate (SPI) gels emulsified with oils including soybean, olive, palm, and eicosapentaenoic acid (EPA) were prepared by a microbial transglutaminase (MTGase). The hardness of 10% SPI gel was greatly increased by adding higher amount of oils. The emulsion gels prepared with 10% SPI and 30% olive oil showed the highest hardness of 1,711 g. In the gelation with various oil content (5–30%), the higher concentration of oils indicated the drastic increase of elastic modulus G′ and viscous modulus G″ during initial gelation for 7 min. The G′ value of SPI emulsion gel showed the 150 (soybean oil 30%), 147 (olive oil 30%), 121 (palm oil 30%), and 61 Pa (EPA 25%), respectively. In the color value of SPI emulsion gel, addition of higher concentration of oils resulted in the increase of L value (brightness), indicating 99.14 (L value) at 30% palm oil. The micro-structure of SPI emulsion gel entrapped with various oils showed the homogeneous network with small porosity compared with that of SPI gel without oil. In particular, SPI emulsion gel with 10% palm oil showed the compact structure distributed evenly with small porosity. Conclusively, the functional and rheological properties of SPI emulsion gel produced by catalytic action of MTGase could be modulated by the type and content of oils fortified.