Effects of Stearic Acid and Zein Incorporation on Refined Kappa Carrageenan-Based Composite Edible Film Properties

Incorporating hydrophobic materials into a polysaccharide-based film to form a composite edible film has been considered an effective way to strengthen the film properties, especially the water vapor resistance. Fatty acids, such as stearic acid, with long-chain and straight structures, exhibit strong hydrophobic performance to prevent water vapor diffusion through the film surface. Meanwhile, zein has been revealed as an encouraging material due to its compactness, less allergic, and gas barrier properties. The investigation of kappa-carrageenan/zein/stearic acid-based green composite edible film has been limited. Thus, this study aims to examine the effect of increasing stearic acid and zein concentrations on improving the moisture barrier and mechanical properties of kappa carrageenan-based composite edible film. Different concentrations of stearic acid (5, 10, and 15% w/w carrageenan) and zein (2.5, 5, and 7.5% w/w carrageenan) were applied to the composite edible film prepared using the solution casting method. The fabricated films have a thickness of 0.092–0.122 mm. The results indicated that increasing the concentration of stearic acid enhances the water vapor barrier and tensile strength of the edible film (p < 0.05). However, the increased zein concentration slightly weakened the water vapor barrier properties. Then, the elongation of the manufactured films was quite improved by the increment of stearic acid proportion, but neither by the increment of zein proportion nor the combination of these two substances. However, the incorporation of stearic acid and zein into refined-kappa carrageenan-based film remarkably improved the tensile strength, elongation, and water vapor barrier properties by 12–18%, 23–27%, and 43–44%, respectively, in comparison to the neat film. Based on the analysis result, the manufactured film which consists of 10% stearic acid and 2.5% zein is considered as the best film formula. This study, therefore, revealed the potentiality of stearic acid enforcement in food packaging applications.