Enzymatic Modification of Oat Protein Concentrate with Trans- and Protein-Glutaminase for Increased Fibrous Structure Formation During High-Moisture Extrusion Processing

Oat protein concentrate (OPC) was treated with transglutaminase (TG) and a combination of transglutaminase and protein-glutaminase (TG + PG), with or without preheating (95 degrees C, 15 min). The characteristics of the modified OPC were examined and further studied in high-moisture extrusion processing (HMEP). SDS-PAGE analysis showed that both enzyme preparations induced cross-linking between the OPC proteins and that the preheating step enhanced it. TG + PG treatments increased protein solubility and decreased the average particle size of OPC. TG treatment also decreased the particle size but had an insignificant effect on protein solubility. TG + PG 5 U treatment with preheating showed the highest RVA viscosity of 1076 mPa s. When OPC samples were studied during extrusion processing, enzyme treatments were found to affect the extrudate properties. The same OPC sample that showed the highest viscosity value, i.e. preheated TG + PG 5 U, showed also the most optimal fibrous structure formation and the strongest structure according to tensile strength results.