Comparison of protective supports and antioxidative capacity of two bio-based films with revalorised fruit pomaces extracted from blueberry and red grape skin

This work aimed to develop novel food packaging materials following eco-friendly concept. Chitosan (CS) and carboxymethyl cellulose (CMC) based films were developed with blueberry (B) and red grape skin pomace extracts (P) rich in antioxidants at different concentrations (1, 2 and 4% w/v). Physico-chemical (thickness, oxygen and water vapour permeability, solubility and moisture content) and antioxidant film properties and activities were determined. Adjustments in film formulations and quantity of plasticizer were done in order to obtain smooth films that are easy to manipulate and without cracks and mechanical failures. The extract of blueberry had higher levels of total phenolics, however films had lower antioxidant activity compared to red grape skin extracts, and the CMC resulted in more active films in the three concentrations of bioactives incorporation tested. On the other hand, with the extract of grape skin that had lower content of total phenolics, the films presented greater antioxidant activity, and the CS matrix, in general, showed more active efficacy. Both matrices showed antioxidant activities directly proportional to total phenolic contents incorporated into the films, being more effective those of CS containing 4% red grape skin pomace extract. The addition of red grape skin extracts increased oxygen permeability for 3 orders of magnitude in CMC films while it didn't influence OTR in CS films expect for 4% extract. Similarly, addition of blueberry extract significantly increased OTR only in 4% CMC films and one order of magnitude in CS films. The addition of extracts slightly changed WVP of control films.