Evaluation of structural integrity and functionality of commercial pectin based edible films incorporated with corn flour, beetroot, orange peel, muesli and rice flour

Abstract

The present study aims to develop functional composite edible films using varied film formulations containing pectin (P), corn flour (CF), beetroot powder (BP), orange peel powder + sodium alginate (OPS), muesli root powder (MRP) and rice flour (RF) along with their structural, mechanical and functional characterization. Strong intermolecular attachment evolved between starch and pectin molecules due to hydrogen bonding of their hydrophilic groups, confirmed through scanning electron micrographs and FTIR spectra. Also, P-CF ratio (1:1) might retained some crystalline regions of starch which has significantly enhanced structural integrity and functionality of films in terms of tensile strength (TS), water solubility (WS), water vapour permeability (WVP) and thermal stability. In accordance with Herschel-Bulkley model, the predicted consistency index and flow behaviour values were affected by film formulation and the model was of good fit with R2 = 0.81 (PC3), R2 = 0.74 (PCB3) and R2 = 0.99 (for rest formulations). Although, higher proportions of hydrophilic polymers (P, OPS & BP) due to higher molecular mobility resulted in less rigid, highly soluble, moisture permeable and thermally unstable films. Furthermore, RF films possessed cracks over the surface and insoluble fractions due to insufficient starch gelatinization which decreased their TS and barrier properties. The ATR-FTIR spectra confirmed the presence of functional groups corresponding to starch and pectin in range of 500–4000 cm−1. The variation among different films underlies only in peak intensities due to some molecular changes. Overall, the films made of P-CF ratio (1:1) were more functional and structurally stable as compared to rest of the films, thus, they would make a better alternative for synthetic packaging.