Influence of Plasticizers in Enzymatic Degradation and Water Resistance of Starch Foam Trays Obtained by Thermal Expansion

Biodegradability and water resistance of cassava starch trays with different plasticizers [glycerol, sorbitol and polyvinyl alcohol (PVA)] were investigated. The degradability was tested by exposure at two amylolytic enzymes of microbial origin, one of them commercial (Termamyl®) and the other obtained in laboratory by the submerged cultivation of the fungus Penicilium echinulatum. The extent of degradation was analyzed by the percentage of weight loss and the concentration of released reducing sugars. The results showed that the packaging was sensitive to the action of the enzymes, because it was observed an increase in the concentration of reducing sugars in the first hours of reaction and percentages of weight loss near 90%. Water resistance was measured by solubility, contact angle and moisture sorption isotherms, with adjustment of the experimental data to mathematical models of Guggen-heim, Anderson de Boer (GAB), Brunauer–Emmet–Teller (BET), Oswin and Jaafar. Trays containing PVA addition showed less solubility, with greater contact angle and lower equilibrium moisture (in aw 0.98). The mathematical models of GAB and Oswin reproduced the best fit to the experimental data of the isotherms. The starch trays showed biodegradability independent of the material used as plasticizer.