Effect of incorporating extracts from natural pigments in alginate/starch films

Abstract

Currently, growing interest exists in the development of packaging materials of natural origin for food applications. This study, conducted the extraction of pigments from natural sources (anthocyanin and betanin) from the exocarp of the black eggplant (Solanum melongena) and the mesocarp of beet (Beta vulgaris), which were incorporated in a film-forming solution based on sodium alginate and starch, as an indicator of films with natural pigment extract (FNE). In consequence, the objective of this work was to assess the effect caused by incorporating extracts of natural origin on the mechanical, optical, and structural properties of sodium alginate/yucca starch films. The films were elaborated with different concentrations of each pigment extracted (2% and 5%) and compared with a control film (CF). The films were exposed to a series of synthetic amines and the changes were observed in the UV-vis absorption spectra. In addition, the effect was evaluated when adding extracts from natural pigments into a polymer matrix, evaluating the mechanical, structural, and optical properties. The results showed that incorporation of natural extracts (NE) influenced on the mechanical properties, but did not influence on film thickness and water vapor permeability (WVP). X-ray diffraction (XRD) indicated increased film crystallinity when incorporating the natural extracts. The microstructure Fourier transform infrared analyses of the films showed that the extracts were compatible with the polymer matrix. Films with eggplant extract (FEE) had higher antioxidant activity against the 1,1–Diphenyl–2–picryl–hydrazyl (DPPH) radical and were more sensitive to the exposure of gaseous amines in comparison with films with beet extract (FBE). Hence, the results obtained show that the films developed with natural compounds are a visual method that could report and monitor the state of the foods.