Development of a bioactive synbiotic edible film based on cassava starch, inulin, and Lactobacillus casei

One of the most important trends in the development of edible films is the inclusion of both probiotics and prebiotics in the polymeric matrix, so they can play an active role in the health of consumers. In this paper, a synbiotic film made from cassava starch as polymeric matrix, inulin as prebiotic molecule, and L. casei as the probiotic bacteria was developed. Several assays have been conducted on the effect of inulin concentration on the rheological, mechanical, barrier, and optical properties of the films, as well as on the effect of including probiotic bacteria in the films. Results showed that inulin has a plasticizing effect on the polymeric matrix, thus increasing its elongation at break, while reducing its tensile strength. Furthermore, the high water solubility of inulin increases significantly the film's water vapor permeability, so a threshold of 0.5% inulin was chosen for probiotic bacteria inclusion. Viability of L. casei during the film storage at 10 and 25 °C was also studied. Results showed reduced viability due to storage stress. However, this was slower at lower temperatures. Viability in simulated gastric conditions was also studied, lower viability values on cassava starch films that when inulin was included. Given that cassava starch is known for its low resistance to acid hydrolysis that leaves L. casei unprotected in gastric media; however, inulin seems to have a protective effect on the probiotic bacteria, thus decreasing the viability loss.