3. Results and discussion
3.1. Functional properties
Optical properties of the films are also relevant since they have a direct influence in the appearance of the film (Monedero et al.,2009).
It is well known that soy protein provides a characteristic yellowish color to the films and this can be confirmed by the values of the b parameter displayed in Table 1.
This parameter increased with pH and sorbitol content. Moreover, DE showed that there was an increase of color (P < 0.05) between the films with 20 wt% sorbitol prepared at pH 7, taken as the reference film, and the rest of the films, especially with those prepared at pH 10.