Development of edible composite films from different hydrocolloids and gelatin

Edible films and coatings have been driving numerous advances in the food and pharmaceutical industries due to their versatile functions and tunability. They extend shelf life, carry active compounds, and modulate stability owing to their barrier, protective and responsive properties under controlled conditions. Proteins and polysaccharides are the major components of edible films, and their interactions are critical to the film's functionality and adaptability. This study explores the use of different anionic hydrocolloids (sodium alginate (SA) and gum tragacanth (GT) at 1% w/v) and gelatin at (9% w/v) to form edible composite films. The film-forming biopolymer solutions (1% SA, 1% GT, and 9% GL) were separately prepared and then mixed at a 1:1 ratio. The rheological properties and zeta potential of film-forming solutions were investigated. Later, the film-forming solutions were cast into Petri dishes (10 and 20 mL) and dried in a fume hood for two days. The film thickness values were recorded via handheld caliper. The transparency of the films was determined based on their absorbance values at 600 nm. In addition, their swelling properties in distilled water (10, 20 and 60 min) were investigated. The film thickness ranged between 0.2 and 0.70 mm. All samples exhibited gel-like behavior with varying modulus values. As expected, the increased volume of film-forming solution resulted in thicker films and higher swelling capacity in distilled water. The water uptake of the composite films exhibited dependency on the hydrocolloid used (p < 0.05). Films based on SA and GT showed different degrees of transparency (p < 0.05), which can be attributed to the degree and extent of intermolecular interactions of the film-forming components. The use of SA and GT in gelatin-based composite films is favorable owing to their excellent film-forming properties and desired characteristics, whichpresent numerous opportunities in different applications.