Agar/cassava starch-based pH sensing film with purple yam (Dioscorea spp.) anthocyanin extract as indicator

ABSTRACT: An agar/cassava starch-based pH sensing film with purple yam (Dioscorea spp.) anthocyanin as indicator was prepared in this study. The final film was composed of 15% and 85% (w/w) agar and cassava starch concentration based on total polymers, respectively. Glycerol was used as plasticizer. Anthocyanins were extracted from purple yam powder using acidified ethanol as extraction solvent. The extracts were analysed using UV-visible spectrophotometry. The absorption spectra revealed that purple yam anthocyanins exhibited color variations (red to yellowish-brown) in response to different pH values ranging from 1.0 to 10.0. Fourier transform infrared spectroscopy results showed that film components were compatible due to the chemical interactions observed. The color change of films upon immersion in different pH buffers ranging from 1.0 to 10.0 were quantified using a chroma meter. Color analysis results, in CIELab parameters, showed that the films exhibited great color variations. Further, the pH sensing films in basic medium (pH 8) were used in detecting milk spoilage. The observed color variations ranged from purple to brownish pink. A representative film immersed in spoiled milk (Nestle) underwent color analysis where a great color difference was noted in comparison with the standard basic film (pH 8). Similarly, purple yam extract was used in detecting milk spoilage, wherein color variations from purple to pink. Based on the results in this study, it can be implied that the developed films could be a potential material in detecting milk spoilage.

Filipiniana