Thus, the amaranth flour film should meet some requirements, regarding mechanical strength, flexibility, and permeability to water vapor and gases, in order to ensure food preservation during storage. Therefore, the aim of this work was to examine the effect of the drying conditions find more on the mechanical, solubility, barrier properties, and drying time of amaranth flour films plasticized with glycerol or sorbitol and optimize the drying process by using a response surface methodology and multi-response analyses, targeting the production
of films with low solubility and good mechanical properties. The Amaranthus cruentus BRS Alegria seeds were grown in the state of Santa Catarina (Brazil) at 18.8–22 °C, soil pH of 5.5. The seeds were harvested in early October, transported to Campinas (Brazil), cleaned, and stored at 10 °C. The amaranth flour was obtained by using a modification to the alkaline wet milling method of Perez, Bahnassey, and Breene (1993), as proposed by Tapia-Blácido et al. (2005a). The composition of amaranth flour is: moisture content 8.3 ± 0.4 g/100 g, ashes 2.1 ± 0.0 g/100 g, lipids 7.9 ± 0.2 g/100 g,
protein 14.1 ± 0.3 g/100 g, and starch 75.7 ± 0.3 g/100 g (11.9 ± 0.3 g amylose/100 g flour) (db). All the reagents were analytical PI3K Inhibitor Library chemical structure grade. Sorbitol and NaOH were purchased from Synth (São Paulo, Brazil). All the solutions were prepared with deionized water. The films were produced by the casting method. Amaranth flour films were prepared by using the methodology proposed by Tapia-Blácido et al. (2005a). A suspension ifoxetine of flour in water (4 g/100 g) was homogenized in a mixer for 25 min, and the pH was regulated to 10.7 with 0.1 mol equi/L NaOH, to dissolve the protein. This suspension was then heated at 75 °C for 15 min, followed by addition of the plasticizer (29.6 g sorbitol/100 g flour or 20.02 g glycerol/100 g flour). For each film, 85 ± 3 g of the film-forming solution was poured onto acrylic plates (18 × 21 cm), in order to obtain a constant thickness
of 80 ± 5 μm. The films were dried under different drying conditions by using an oven with air circulation and controlled temperature (model MA 415UR, Marconi, Piracicaba, Brazil). The studied drying conditions were 30 °C, 40% RH; 30 °C, 70% RH; 50 °C, 40% RH; 50 °C, 70% RH; 25.9 °C, 55% RH; 54.1 °C, 55% RH; 40 °C, 33.8% RH; 40 °C, 76.2% RH; and 40 °C, 55% RH, defined according to the experimental design that was being used (Tables 1 and 2). The drying kinetics curves of the amaranth flour films were determined for all the studied conditions. Prior to characterization, all the films were preconditioned for at least 48 h in desiccators containing a saturated NaBr solution (25 ± 3 °C, 58 ± 2% RH). The thickness of the films was measured with a digital micrometer Fowler (average of 8 measurements).