Effect of candelilla wax on functional properties of biopolymer emulsion films – A comparative study

The overall research objective was to compare the effects of increasing concentrations of candelilla wax (CnW) on the physicochemical and morphological properties of edible films based on different biopolymers: carboxymethyl cellulose (CMC), oxidized potato starch (OPS), soy protein isolate (SPI), and gelatin (GEL). The findings are discussed in terms of the stability of emulsion formulations. CnW was incorporated into film-forming solutions at 0, 0.5, 1.0, 1.5, and 2.0%; sorbitol and Tween 40 were used as the plasticizer and surfactant, respectively. It was found that, with the exception of GEL films, wax incorporation significantly decreased the WVP of the films (from 11.1 to 41.7% compared to the controls). Regardless of the wax concentration used, OPS films had the lowest WVP compared to other films. GEL-based films, in turn, were characterized by the highest mechanical resistance and elongation. The incorporation of CnW decreased both all the analyzed tensile parameters and the puncture strength of the films. Generally, as CnW concentration increased, the transparency and redness of the films decreased, while UV blocking ability and yellowness increased. The 0.5% CnW addition was the most effective in improving water barrier properties, and simultaneously had the lowest impact on the other physical properties of films. For OPS, SPI, and GEL films, sorbitol recrystallization was observed over time. Wax accelerated the sorbitol crystal growth process. CMC films, in contrast to those obtained using other polymers, were completely water soluble and did not exhibit sorbitol crystallization. The emulsion films differed from the wax-free in their surface characteristics.