Comparison between anthocyanins from roselle and mulberry as pH indicators in development of intelligent films

Smart films incorporated with anthocyanins as color indicators to monitor the food spoilage has attracted great attention. However, the effectiveness comparison among anthocyanin sources remains limited. Hence in this study, chitosan-based films incorporated with varying concentrations of anthocyanins sourced from either roselle or mulberry were developed. Detailed structural, morphological, physical, mechanical, and functional characteristics of these films were evaluated and compared. In general, the composite films, incorporating anthocyanins from roselle or mulberry, exhibited a deeper red–purple hue and a rougher cross-sectional appearance than the one without anthocyanins. Furthermore, while all composite films shared some representative absorption bands of FTIR spectra, there were slight variations in their area and height due to the interaction between anthocyanins and film components. Incorporating anthocyanins into chitosan-based films did not significantly affect film thickness, ranging from 74.90 to 88.35 µm. However, it notably reduced light transmittance and water vapor permeability (from 9.46 to 4.69–7.88 × 10–11 gm−1 s−1 Pa−1) while enhancing tensile strength (from 4.68 to 5.66–11.78 MPa), elongation (from 12.4 to 19.63–23.60