Effects of moisture content on mechanical properties, transparency, and thermal stability of yuba film

- Yuba is a soy protein-lipid network formed on a heated soymilk surface.
- Moisture content has a significant effect on yuba film properties.
- Yuba with 25% moisture, stored at 39% RH, appears to have the most potential.
- These results are useful for developing yuba as edible film.

Yuba is the skin formed at the surface during the heating of soymilk. The 3rd, 7th, and 11th films were evaluated for properties at different RH. At 39% RH, the 11th film had the lowest moisture, while the 3rd film had the highest moisture. However, at 75% RH, reverse moisture results were obtained. The tensile strengths of the 3rd and 11th films were highest at 15% moisture, whereas the tensile strength of the 7th film was highest at 25% moisture. Elongation of the 3rd (127%) and 11th (85%) films were highest at 25% moisture. The light transmittance of the films was low and opaque at 5% moisture. The films were transparent at 23%-28% moisture, but became opaque as the moisture increased. The films at 39% RH (ΔH, 113-203 J/g) had higher thermal stability than those at 87% RH (ΔH, 315-493 J/g). Moisture content markedly changed the yuba film properties.