Films were fabricated using a mixture of polyvinyl alcohol (PVA)/cassava starch and incorporated citric acid in a concentration range between 5% and 40%. The films were annealed through thermal treatment in a temperature range between 30 °C and 90 °C with 0.3% glutaraldehyde incorporated as the crosslinking agent. This study presents the results of an experimental design analyzed using the response surface methodology. The multiple regression analysis allowed us to obtain the second-order models, which relate the annealing factors and citric acid concentration to Maximum Tensile Strength (MTS), Young’s Modulus (YM), and the Maximum Elongation at Break (MEB). The optimization and validation of the obtained model were carried out with error values below 10.08% for all the response variables, indicating that the response surface methodology and optimization were correct. Finally, as a complementary analysis, the differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) tests were carried out, which revealed a higher packaging of the heat-treated films and verified their crosslinking.

El objetivo de este estudio fue evaluar el efecto de las condiciones del proceso de obtención de biocompuestos elaborados por la técnica de termo-compresión usando harina de yuca de variedad MPER 183, fibra de fique y glicerol. Se ha analizado contenido de agente de expansión, presión de compresión y humedad relativa sobre la densidad, esfuerzo de flexión y adsorción de vapor de agua. Los resultados mostraron que todas las condiciones de procesamiento evaluadas afectaron significativamente las variables de respuesta, con un nivel de significancia del 95% (p0,05). El aumento del bicarbonato de sodio como agente de expansión y los valores altos de humedad relativa incrementaron la densidad, adsorción de vapor agua y disminuyeron el esfuerzo de flexión. La ausencia de presión durante la compresión aumentó el esfuerzo de flexión, y disminuyó la densidad y la adsorción de vapor de agua de los biocompuestos.

Extended shelf-life of many foods is a modern requirement that has been achieved by means of fossil-based plastic films despite their environmental issues. Recently, starch-based, fully biodegradable thermoplastics are gaining momentum as packaging material; however, if they are in contact with food, aspects such storage, water interaction and spoilage due to microorganisms must be considered. Essential oils are of great interest due to their antimicrobial action, so incorporating these compounds into natural polymers can promote a longer shelf life through active packaging. In this study, antibacterial activity, optical, mechanical and barrier properties of thermoplastic starch (TPS) films based on cassava starch ( Manihot esculenta Crantz) and rosemary essential oil (REO) were studied. Furthermore, the effect of cellulose nanocrystals (CNC) on TPS properties were surveyed. Film mechanical properties and those related to the interaction with water, showed that the highest resistance and barrier properties corresponded to the TPS/CNC 15% film, while adding oil to the films increased morphological heterogeneity, contributed to reduce tensile strength, and increased water solubility and water vapor permeability. Likewise, TPS films containing rosemary oil showed enhanced antibacterial activity mostly against E. coli and S. aureus bacteria and A. niger fungus. Therefore, adding essential oils as natural additives favors using these biocomposites as functional packaging, and as potential replacements for single-use plastics.

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