Development and characterization of pH-indicator films based on cassava starch and blueberry residue by thermocompression

Due to the concern about the inadequate disposal of synthetic and non-biodegradable plastic packaging, a great number of researches pointing at the substitution of these materials by natural and biodegradable sources have been growing in recent years. Another important category recognizes as intelligent packaging has also received more prominence. The study intended to achieve the matter aforementioned developing starch-based films by thermocompression without and with blueberry residue as pH change indicator. Moisture content, water solubility, water vapor permeability, oxygen permeability, morphology, color, and mechanical properties of the films were analyzed. Moreover, analysis of color change and compounds migration were conduct in the films with blueberry. The residue insertion led to the formation of less compact films with high oxygen permeability. Despite the irregular dispersion of the blueberry residue on the polymer matrix identified by optical microscopy, the films showed equal values of water vapor permeability, hydrophilicity, and mechanical properties when compared to the samples without the residue. In addition, they exhibited visually perceptible color changes in the pH range between 2 and 12, which was confirmed by colorimetric analysis since the Delta E-94* values between the samples were greater than 3. The compounds migration after film immersion in aqueous simulant solution (acetic acid) showed a higher intensity in comparison to the samples immersed in a fatty simulant solution (ethanol) due to the anthocyanins hydrophilicity. Therefore, the film with blueberry has potential as intelligent packaging. Besides that, it present potential as active packaging due to the migration of phenolic compounds in aqueous solutions.