Smart Colorimetric Indicator for Dynamic Freshness Tracking of <i>Agaricus bisporus</i> in Intelligent Packaging Applications

ABSTRACT This study presents an innovative approach to intelligent packaging through the development of a cellulose‐based colorimetric freshness indicator label by immobilizing bromothymol blue (BTB) and methyl red (MR) chromophores onto cellulose filter paper, leveraging their pH‐sensitive properties for real‐time monitoring of white button mushroom quality. The BTB/MR solution exhibited a distinct colour transition from pink‐orange (acidic pH) to yellow‐green (alkaline pH) within the pH range of 2–10, confirming its high sensitivity to pH variations. Field emission scanning electron microscopy revealed the porous microstructure of the cellulose matrix, verifying successful physical adsorption of dyes without chemical alteration. Fourier transform infrared spectroscopy identified hydrogen bonding as the principal mechanism for dye immobilization, while x‐ray diffraction analysis showed a marginal reduction in crystallinity. Importantly, mechanical testing confirmed that the tensile strength of the cellulose matrix remained unaffected by the dye incorporation. The indicator was applied to fresh mushrooms stored in biodegradable trays at 4 ± 1°C. Performance evaluation included colorimetric response, physicochemical analysis, volatile organic compound profiling and principal component analysis (PCA). The indicator effectively classified freshness into the following three stages: fresh (Days 1–4), still fresh (Days 6–8) and spoiled (Day 10), with visually perceptible colour changes aligning with mushroom quality parameters. Total plate count ( r = 0.989, p &lt; 0.01) showed the strongest correlation with the indicator's response. PCA validated distinct clustering corresponding to freshness stages. This cellulose‐based freshness indicator offers a sustainable, nondestructive and real‐time solution for postharvest quality monitoring, demonstrating its applicability in intelligent packaging systems.