Study of the swelling capacity of a mild laxative formulation

In this work, the swelling index is determined for various vegetable fibers (wheat bran. orange fibre and lemon fibre), and several granulated formulations to which different binding agents are added. The formulation that presents the highest swelling index (14.5 ml/g) was found to be composed of orange fibre, lemon fibre and pectin in a 1:1:1 proportion (OF + LF + PH). A study of the evolution of the swelling with time is also carried out, finding that the greatest volume increase is produced between 5 and 10 min from the start of the test. The application of the sigma-minus type calculation to the swelling rate curves produces correlation coefficients higher than 0.9. It is found that the swelling rate constant for lemon fibre is much lower than that of orange fibre. The addition of pectin lowers the swelling rate constant while the gum guar and polyvinylpyrrolidone increase the said constant. In addition, a general exponential equation is deduced which can be applied to all of the cases studied.