Development and characterization of novel composite glycerol-plasticized films based on sodium caseinate and lipid fraction of tomato pomace by-product.

Tomato processing industries generate many byproducts that are mainly unexploited or underutilized. In order to convert tomato byproducts into added-value products, composite films made of sodium caseinate (NaCas), glycerol (25 wt%), and lipidic fraction of tomato pomace (LFTP) at different contents (0-40 wt%) were produced and characterized in terms of thermal stability, antioxidant activities, mechanical, hydrodynamic and optical properties. Our results showed that increasing LFTP concentration beyond 20 wt% increased the flexibility of NaCas films within the range of 17-25%. Moreover, LFTP incorporation at the highest content improved thermal stability of NaCas films and reduced their water absorption by >72%. Furthermore, increasing LFTP content led to a significant decrease in the light transmission of NaCas/LFTP composite films. Such improvement in functional and physical properties can be attributed not only to the establishment of specific interactions between NaCas and LFTP but also to their good miscibility in the blend along with the homogeneous dispersion of the incorporated LFTP in the polymeric matrix, as confirmed by FTIR and SEM analysis. On the other hand, the antioxidant capacity of NaCas/LFTP composite films was enhanced by increasing LFTP content most likely due to LFTP's high total phenolics content.