Ma 420

Ground propolis (2 g) was extracted with ethanol (15 mL, 80%) by mixing the samples for 30 min under constant agitation (Incubation Shaker MA 420/MARCONI—Brazil) at 70°C and 710 rpm. The extract was recovered by centrifugation (Centrifuge SIGMA 2–16 KL) for 11 min at 8,800 rpm and 5°C. Then, an additional centrifugation step was performed with 10 mL of ethanol (80%). The supernatant was collected, homogenized, and kept at 50°C until completely dry. Afterwards, the extracts were stored in tubes, wrapped in aluminum foil at inert atmospheric conditions (N₂) to avoid degradation. All extracts were kept at 5°C until use [6 (link)].

Moisture was determined according to Gontard et al. [35 (link)], where film samples (2 cm × 2 cm) were oven dried (Fanem, 515, Sao Paulo, Brazil) at 105 °C for 24 h and the moisture content was determined considering the samples mass loss.
To determine solubility, samples (2 × 2 cm) were dried at 105 °C (24 h) and transferred to beakers with 50 mL of distilled water, submitted to shaking (100 rpm) in a Shaker incubator (Marconi, MA 420, Piracicaba, Brazil) for 24 h [35 (link)]. Subsequently, the samples were again oven dried (Fanem, 515, Sao Paulo, Brazil) at 105 °C for 24 h and the soluble material was determined according to Equation (2): $Solubility(\%)=\left(\frac{m_i-m_f}{m_i}\right)$
where: $m_i$ is the (g) sample initial dry mass and $m_f$ is the (g) sample final dry mass.
The contact angle was determined using a tensiometer (Attension Theta Lite, KSV Instruments, Filderstadt, Germany) according to Abdollahi et al. [36 (link)], which consisted of fixing the film sample (2 × 3 cm) to the base of the equipment and depositing a drop of ultrapure water (5 µL) onto the film surface. Images were recorded after 10 s and digital images were analyzed using the Attension Theta Lite software (Version 4.1.9.8).

Guaraná peels were dried in a convective oven (Marconi, MA035/1152) at 50 °C for 18 h and stored at −20 °C until further analysis. For carotenoid extraction, the peels were mixed with ethanol in a ratio of 1:10 (peel/solvent, w/v). According to Pinho et al. [4 (link)] ethanol presented ideal performance when extracting carotenoids from guaraná peels compared to other solvent systems tested (such as hexane and ethyl acetate). Furthermore, the use of ethanol as solvent was based on the fact that it is recognized as safe and is obtained from renewable sources.
The mixture was shaken using an orbital shaker (Orbital Shaker Marconi, MA420, Piracicaba, SP) for 4 h at 50 °C and centrifuged at 7168× g for 10 min [4 (link)]. Sunflower oil was added to the supernatant with a final concentration of 3% and thoroughly mixed to minimize carotenoid degradation (observed during preliminary experiments). A final concentration of 3% of the oil was selected after considering the liquid–liquid equilibrium for the system composed of sunflower oil and ethanol [27 (link)]. Afterward, the material was concentrated using a rotary evaporator (TE-211 Tecnal, Piracicaba, Brazil) at 48 ± 2 °C to 20% of the initial volume. The concentrate was named “carotenoid-rich extract”.