Black chokeberry (Aronia melanocarpa) pomace extract immobilized in chitosan for colorimetric pH indicator film application

During this study, different amounts of black chokeberry (Aronia Melanocarpa) pomace extract were mixed with chitosan to prepare colorimetric pH indicator films. The monomeric anthocyanin and total phenol content of ultrasonically extracted chokeberry pomace solution were determined by pH differential method and FolinCiocaltau assay. ATR-FTIR spectroscopy, CIELab method, solubility, swelling ability, dye migration and tensile strength measurements were used to characterize the films. The pomace extract contained enough active components to highly reduce the solubility and swelling of chitosan. The indicator films maintained their integrity even at acidic pH which was attributed to the interactions between the polymer chains and the phenolic components of the extract. With higher extract content, a higher resistance to water was observed, which also resulted in reduced dye migration. The immobilized dye in chitosan films responded well to the pH change and showed a high color difference from pH 1 to pH 10.