Edible films made from banana starch and curcumin-loaded nanoemulsions -

Edible films made from banana starch and curcumin-loaded nanoemulsions

This paper presents the development of an active film made from banana starch incorporated with curcumin-loaded orange oil nanoemulsion. Results showed that inclusion of the curcumin-loaded nanoemulsions reduced water vapor permeability, given the hydrophobic nature of curcumin. Likewise, elongation at break was also increased due to the plasticizing effect of the nanoemulsion. Results showed that curcumin release is diffusion driven in both aqueous and non-aqueous food simulants, however it seems that while the complete nanoemulsion droplets are released in the aqueous simulant, in non-aqueous simulant only curcumin molecules are released.

Materials

Banana starch was isolated by using the standard procedure from green bananas (Musa paradisiaca L.), immediately after harvest.

Curcumin-loaded orange oil nanoemulsion formation

Curcumin-loaded nanoemulsions were prepared by using the emulsion-phase inversion (EPI) method. Experiments were carried out so that the final emulsion mass was 50 g including 5 g of oil phase (curcumin + orange oil). The amount of curcumin was fixed at 1.5% (w/w) as results of particles size studies showed a particle size < 100 nm. Curcumin formation was performed in a 100-mL beaker. The oily phase and Tween 80 were mixed by using a magnetic stirrer at 650 rpm during 30 min and heated to 40 ◦C. Then, the aqueous phase was titrated into the oily phase by using a burette at a flow rate of approximately 1 mL/min, while maintaining constant stirring at 650 rpm. Once the entire aqueous phase was added to the oily phase, the emulsion was left stirring during 60 min. The amounts of Tween 80 and water in the nanoemulsions were determined by the surfactant-to-oil-ratio (SOR) and adjusted to SOR = 2.5.

Active film formation

Bioactive films were formulated by 15 g of banana starch and 5 g of glycerol were added to 500 mL of water to have final concentrations of 3% and 1% w/v of banana starch and glycerol, respectively. This suspension was heated to 80 ◦C with constant stirring (650 rpm) for 1 h to accomplish complete gelatinization. Then, the suspension was cooled to 35 ◦C with constant stirring and, when needed, an appropriate amount of curcumin-loaded orange oil nanoemulsion was added. The suspension was further stirred at 650 rpm during 1 h. Finally, 25 g of the suspensions were cast onto Petri dishes (diameter 8.1 cm); dried in a hot air oven at 35 ◦C until constant weight. Films were removed from the Petri dishes and stored at controlled temperature (25 ◦C) and humidity (60%). To study the effect of nanoemulsion concentration, varying amounts were added to the filmogenic solution, so final concentrations were 0%; 0.05%; 0.1%; 0.15%, and 0.2% (w/w).

Active film characterization

Film thickness was obtained by using a Fowler electronic micrometer (0–25.4 mm) with 1.27 μm precision. Water vapor permeability (WVP) of the bioactive films was determined according to the ASTM E96-05 method. Bioactive films were placed in permeation cells and maintained at controlled conditions (65% RH and 25 ◦C) during 8 h. The permeation cells were weighed every hour. The films’ WVP (g/m*s*Pa) was calculated by using the thickness of each film studied. Film water solubility (WS) was measured. Mechanical properties (tensile strength; TS; MPa and elongation at break; E; %) of bioactive films were determined by TA-XT Plus Stable Microsytems Texturometer with a tension grip system. Color of the bioactive films was measured in HunterLab ColorQuest XE spectrocolorimeter with D65 illuminant and 10◦ observer angle. CIE L* a* b* were determinant. Finally, film opacity (FO) was measured, as the relation between the film’s absorbance at λ = 600 nm and its thickness (mm). Measurements were performed in UV–VIS spectrophotometer. Film opacity was calculated by using Equation (1). FO = A600/X (1) Where A600 is absorbance at 600 nm and X is film thickness (mm).

Curcumin release into food simulant media

Curcumin release from the bioactive films to different food simulants was studied. Two types of food simulants were used; simulant A (ethanol 10% w/v); and simulant D1 (ethanol 50% w/v), representing highly aqueous foods, low pH foods and highly fermented foods, respectively. Rectangular samples of the films (6 cm2) were immersed in a glass tube with 20 mL of the food simulant and kept at 25 ◦C during seven days. Simulant samples were removed at different times and diluted in water for simulants A and ethanol for simulant D1. Curcumin release was quantified by using a UV–VIS spectrophotometer (Hewlett Packard, HP-8453) with calibration curves in each food simulant. Curcumin release was expressed as %R, as indicated in Equation (2). %R = Mt M0 x100 (2) Where Mt corresponds to the concentration of curcumin in the food simulant at any given time and M0 to the initial concentration of the bioactive molecule in the films. Release kinetics were studied according to two different models, the first used was the Ritger and Peppas model as represented in Equation (3). Mt M∞ = kptn (3) Where kp is the Ritger-Peppas release rate constant and n is the release exponent. The second kinetic model used was the Peppas-Sahlin model as expressed in Equation (4): Mt M∞ = k1tm +k2t2m (4) Where, k1 and k2 refer to the diffusion and erosion constants, respectively, and m is the diffusion exponent.

Curcumin release into simulated gastrointestinal conditions

Curcumin release from the bioactive films into different simulated gastrointestinal conditions was studied in simulated gastric fluid (SGF), simulated intestinal fluid (SIF), and simulated colonic fluid (SCF). Pieces measuring 4 cm² of the bioactive film were put in 20 mL of SGF and incubated at 37 ◦C in a shaking water bath at 200 rpm. After determined amounts of times, samples were quickly cooled to 4 ◦C to inactivate enzymatic activity and centrifuged at 6,000 rpm at 4 ◦C during 5 min. The supernatant was removed and the amount of curcumin released was determined. Studies in simulated gastric conditions were carried out for up to 2 h. Then, remaining pieces of the bioactive film were re-suspended in 20 mL of SIF and incubated at 37 ◦C in a shaking water bath at 200 rpm. After determined amounts of time, samples were acidified to pH 2 and centrifuged at 6,000 rpm at 4 ◦C during 5 min. The supernatant was removed and the amount of curcumin released was determined. The SIF release studies were carried out for up to 2 h. Finally, the remaining pieces of the bioactive film were re-suspended in SCF and curcumin release was studied as explained before. The amount of curcumin released was determined by using UV–VIS spectroscopy and unused simulated fluids were used as blanks.

Conclusion

This paper reports the formation and characterization of composite films from banana starch and curcumin-loaded orange oil nanoemulsions. Several properties of the composite films can be enhanced by adding curcumin-loaded nanoemulsions, such as reducing their WVP and increasing elongation at break. It was observed that the curcumin released from the composite films in different food simulants is carried out in two different mechanisms. In the lipophilic simulant, curcumin release showed a pseudo-Fickian type of release, driven by the affinity of curcumin with the release media. In the aqueous simulant, its release was carried out through a non-Fickian mechanism in which it seems that the complete nanoemulsion droplet moves from the film to the simulant media. Finally, films showed that they can hinder release in gastric media, due to the banana starch resistance to acid hydrolysis, while increasig release in intestinal media.

Reference:

Sanchez, L.T., Pinzon, M.I. and Villa, C.C., 2022. Development of active edible films made from banana starch and curcumin-loaded nanoemulsions. Food Chemistry, 371, p.131121.