A new colorimetric pH indicator film was developed using agar, potato starch, and natural dyes extracted
from purple sweet potato, Ipomoea batatas. Both agar and potato starch are solid matrices used to immobilize
natural dyes, anthocyanins. The ultraviolet-visible (UV-vis) spectrum of anthocyanin extract solutions
and agar/potato starch films with anthocyanins showed color variations to different pH values (pH
2.0–10.0). Fourier transform infrared (FT-IR) and UV-vis region spectra showed compatibility between
agar, starch, and anthocyanin extracts. Color variations of pH indicator films were measured by a colorimeter
after immersion in different pH buffers. An application test was conducted for potential use
as a meat spoilage sensor. The pH indicator films showed pH changes and spoilage point of pork samples,
changing from red to green. Therefore, the developed pH indicator films could be used as a diagnostic tool
for the detection of food spoilage.