Production of active cassava starch films; effect of adding a biosurfactant or synthetic surfactant

Abstract

For the first time, it was investigated the film effects of surface-active agents - mannosylerythritol lipids-B (MEL) and sodium-dodecyl-sulfate (SDS) - into biodegradable films. The films were produced by casting technique using cassava starch, glycerol as the plasticizer; surface-active agents (20 g/100 g of starch), and water. The mechanical, functional, crystalline and antibacterial properties of films were characterized. Starch-films containing MEL were more flexible, water vapour permeable, and hydrophilic rather than control or starch-films containing SDS. On the other hand, the SDS led to films with higher rigidity, resistant at the break, crystalline, water-soluble, less flexible and water vapour permeable than the control or starch-films containing MEL. MEL can be used as a surface-active agent in biodegradable films, since MEL enhanced the wettability, resulting in superhydrophilic films. Regarding antimicrobial properties, SDS and MEL are both (bio)surfactants which implies that they have similar antimicrobial mechanisms. However, starch-films containing MEL or SDS showed different antibacterial properties. Starch-films containing SDS presented well-defined inhibition halos against the Weissella viridescens and Staphylococcus aureus, whereas starch-films containing MEL did not present well-defined inhibition halos, since MEL do not have diffusion property into agar. Therefore, MEL and SDS interact differently with the starch matrix, and thus, producing cassava films with unique properties.