<![CDATA[Intelligent packaging can provide real-time information on food deterioration, but sustainable indicators for monitoring edible oil oxidation remain limited. This study developed a paper-based colorimetric indicator from areca nut tannin and evaluated its ability to monitor palm oil quality. Tannin was extracted with ethanol at 60°C for 5 h, immobilized on Whatman No. 42 paper at 1%, 3%, and 5%, and characterized by Fourier transform infrared spectroscopy. The 1% indicator was applied inside palm oil packages stored for 0, 1, 5, and 10 days. Indicator color was quantified through Red-Green-Blue image analysis and compared with acid and peroxide values. The indicator retained phenolic hydroxyl, aromatic, and ether-related functional groups after immobilization. Increasing tannin concentration produced darker initial colors, while the 1% formulation provided the clearest visual response. During storage, the Red-Green-Blue coefficient declined from 349.1 to 291.9, whereas acid value increased from 1.187 to 4.769 mg KOH/g and peroxide value from 8.88 to 20.65 meq O₂/kg. Red-Green-Blue values correlated strongly and inversely with acid value and peroxide value, with correlation coefficients of −0.922 and −0.920, respectively. These findings demonstrate that areca nut tannin can support low-cost, renewable, and non-destructive intelligent packaging for quantitative palm oil oxidation monitoring]]>
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