Effects of heat curing and transglutaminase treatments on the physical, mechanical, and water barrier properties of yuba films

Abstract

Yuba is a soy protein-lipid film formed on the surface of heated soymilk. Heat curing (HC) and a combination of HC and transglutaminase (TGHC) treatment were evaluated to improve the water vapor permeability (WVP) and mechanical properties of the 3rd, 5th, and 7th yuba film sheets. The performance of the yuba film was compared to no-treaded yuba (Con) and gelatin films. The tensile strength of the film was 118%–135% higher after HC and 78%–117% higher after TGHC compared to the Con. After HC, the elongation of the 3rd and 5th yuba film sheets was decreased to half of the Con. However, the 7th film was increased after HC (90%) and TGHC (23%–131%) treatment compared to the Con (22%–59%) or gelatin (37%). Heat treatment increased the –S–S– content, and transglutaminase (TGase) treatment increased the amide linkages at 1,623 and 1,535 cm−1. HC and TGHC reduced the WVP to half that in the Con or gelatin. TGase and heat cured yuba, especially the 5th sheet, has the potential for use as an alternative to gelatin as a plant-based edible film. Practical applications Yuba, a protein-lipid film, has been widely used in East Asia to wrap and shape vegetables, such as spring rolls, or as ingredients in many forms, such as meat mimics. As a plant-based source, yuba has many benefits as a natural and biodegradable material. However, yuba has poor mechanical and water barrier properties as an edible film. Yuba treated by both transglutaminase and heat curing showed better water barrier properties, 70% of the tensile strength, and twofold higher elongation values than gelatin film. The better performance of modified yuba indicates its potential as an alternative to gelatin film as a plant-based edible film.