Abstract: Soy protein isolate (SPI) was used as the raw material and orthogonal tests were conducted to explore the optimal formula of SPI edible film through evaluating carrageenan addition amount, glycerol addition amount, pH and material-liquid ratio. The results showed that the optimal formula of SPI edible film was achieved under the conditions with carrageenan addition amount of 8%, glycerol addition amount of 0.4 mL/g on the basis of SPI, material-liquid ratio of 1:15 (g/mL) and pH of 7.0. Under the optimal process conditions, the content of water-soluble SPI was 32.7%, water vapor permeability was 2.348 g ·mm/(m2 ·h ·kPa), tensile strength was 7.192 MPa, and breaking elongation rate was 128.1%. The electron microscopic results revealed the best film to have uniformed distribution of SPI in the film. The film had water-blocking capacity to some extents. Therefore, this method can improve the homogeneity to result in better dispersion of SPI in the film surface and enhancement of water-blocking capacity of the film.

Key words: soy protein isolate, edible film, optimal formula