Edible films based on black chia (Salvia hispanica l.) seed mucilage containing Rhus microphylla fruit phenolic extract

Functional films based on black chia (Salvia hispanica L.) seed mucilage (BCm) containing Rhus microphylla (Rm) fruit phenolic extract were built and characterized. A hydro-alcohol extract (HAE) of Rm was incorporated as the bioactive agent due to its noteworthy phenolic profile, and good antioxidant and antifungal activities. The effects of the BCm concentration (0.2% and 0.4%, w/v), HAE incorporation, and their interaction with glycerol (1.0%, w/v) and calcium chloride (0.05%, w/v) on the films physicochemical properties were evaluated. The filmogenic solutions successfully fitted to the HerschelBulkley model (R2 < 0.999), exhibiting a pseudoplastic and shear thinning character, typical of polymer solutions. Interestingly, their rheological properties were not (p > 0.05) changed by the HAE addition, but their surface tension was enhanced (p < 0.05), which could favor their coating ability. The polyanionic nature of the systems (zeta potential-Zp values from 26.9 to 33.3 mV) allowed them to interact with Ca2+ cations, thus forming stable and resistant films. All the films showed low water solubility (15.0% to 22.3%) and high permeability (3.7 to 4.0 × 1010 g m1 s1 Pa1), as well as high biodegradability (moisture content from 66.0% to 80.9%); although the moisture content was reduced (p < 0.05) with HAE addition. The combination of higher BCm ratio and HAE addition (BCm0.4+Rm) led to a more resistant, thick, opaque, and dark film compared with the others obtained. This study reveals the BCm-based films potential, highlighting those with HAE, representing a novel alternative to improve the quality of food products. Financial support from Universidad Autónoma Agraria Antonio Narro (UAAAN) is gratefully acknowledged by the authors. Zlatina Genisheva thanks to Foundation for Science and Technology (FCT) for the financial support (ref. SFRH/BPD/108868/2015) and to the project COMPETE 2020 (POCI-01-0145-FEDER-029145). This study was supported by FCT under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors would also like to thank to Pablo Virgen of Biocampo S.A. de C.V. and MSc Fidel Peña-Ramos from UAAAN, for their assistance during this study.