Impact of gum arabic and sodium alginate and their interactions with whey protein aggregates on bio-based films characteristics.

Two polysaccharides (PS), gum arabic (GA) and sodium alginate (SA), and whey protein concentrate (WPC) were used to design bio-based films at two ratios (RPS:WPC, 1:2 and 1:3). The effects of PS, RPS:WPC and WPC thermal treatment (unheated vs. aggregate) were determined on films characteristics. Film-forming dispersions were tested using different complementary techniques: UV-Vis spectroscopy, electrophoretic mobility, bulk rheology and confocal microscopy. PS exhibited weak associations with proteins. However, this behavior was more significative in SA/WPC systems. Rheological and optical characteristics of filmogenic suspensions were influenced by PS, RPS:WPC and WPC heat treatment. Apparent viscosity values for SA/WPC systems were 80-250 times higher than the ones obtained for GA/WPC systems. Furthermore, thickness, moisture absorption, contact angle and mechanical properties were also affected by the film design factors. GA/WPC-aggregates films showed lesser moisture absorption; however, they have higher surface polarity than those made with SA/WPC-aggregates. Moreover, SA/WPC-aggregates systems provided stronger films in comparison with the GA/WPC-aggregates ones. In addition, mechanical properties were also affected by RPS:WPC and WPC treatment. It was observed that denatured WPC and 1:3 RPS:WPC produced weaker mechanical features. Results provide useful information for the design of bio-based mixed films with tailor-made properties.