Results and discussion
3.1. Effect of acid treatment on extractable protein content
Effect of acid treatment of NRL on the EP content is shown in Fig. 1. It can be seen that the EP of the NRL films decreases with decreasing pH (increasing acid content). The reduction of EP with increasing acid content is due to the denaturation of the proteins by the acid. At low pH (more acid), the proteins are denatured and become insoluble [10] and tend to form aggregates [11] and [12]. From Fig. 1, it can be observed that the untreated films have EP which is 86.0% more than the films treated with HCl at pH 2.0. Results also show that acid treatment is effective in reducing EP content by denaturing the protein molecules.