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<p>Monitoring food freshness is crucial for safety, driving demand for effective real-time detection. Recently, pH-responsive colorimetric sensors based on metal-organic frameworks (MOFs) are of great interest, though their performance needs improvement. Herein, a composite (UiO-66@MR) was prepared using UiO-66 as a porous carrier and methyl red (MR) as a colorimetric probe, showing excellent pH response across a broad range (pH 2.0–11.0). This composite was fixed onto paper to construct a UiO-66@MR paper-based sensor (UMPS). Using the&#xa0;spoilage markers ammonia (NH<sub>3</sub>), dimethylamine (DMA), and trimethylamine (TMA) as representative volatile organic compounds (VOCs), UMPS demonstrated high sensitivity, a wide detection range, and good selectivity due to UiO-66’s high surface area and MR’s color-changing properties. The UMPS showed linear responses toward NH<sub>3</sub>, DMA, and TMA over the ranges of 1–1000, 1–100, and 5–1000&#xa0;ppb, with detection limits of 0.724, 0.443, and 0.971&#xa0;ppb, respectively. In tests on shrimp and beef, UMPS showed clear color changes, and the color difference (Δ<i>E</i>) strongly correlated with total volatile basic nitrogen (TVB-N) content over time (<i>R</i><sup>2</sup> = 0.9699 and 0.9646). The sensor also exhibited excellent reproducibility, reusability, and stability. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) confirmed its effectiveness for real-time freshness assessment. Thus, UMPS offers a high-performance, convenient visual platform for monitoring food freshness.</p> Graphical abstract <p></p>

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A UiO-66@MR paper-based colorimetric sensor for sensitive detection of food spoilage volatile organic compounds and visual freshness monitoring

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Yijie Kong,
  • Xinyu Feng,
  • Weicheng Sun,
  • Yanming Bi,
  • Chengze Song,
  • Sha Liu

摘要

Monitoring food freshness is crucial for safety, driving demand for effective real-time detection. Recently, pH-responsive colorimetric sensors based on metal-organic frameworks (MOFs) are of great interest, though their performance needs improvement. Herein, a composite (UiO-66@MR) was prepared using UiO-66 as a porous carrier and methyl red (MR) as a colorimetric probe, showing excellent pH response across a broad range (pH 2.0–11.0). This composite was fixed onto paper to construct a UiO-66@MR paper-based sensor (UMPS). Using the spoilage markers ammonia (NH3), dimethylamine (DMA), and trimethylamine (TMA) as representative volatile organic compounds (VOCs), UMPS demonstrated high sensitivity, a wide detection range, and good selectivity due to UiO-66’s high surface area and MR’s color-changing properties. The UMPS showed linear responses toward NH3, DMA, and TMA over the ranges of 1–1000, 1–100, and 5–1000 ppb, with detection limits of 0.724, 0.443, and 0.971 ppb, respectively. In tests on shrimp and beef, UMPS showed clear color changes, and the color difference (ΔE) strongly correlated with total volatile basic nitrogen (TVB-N) content over time (R2 = 0.9699 and 0.9646). The sensor also exhibited excellent reproducibility, reusability, and stability. Hierarchical cluster analysis (HCA) and principal component analysis (PCA) confirmed its effectiveness for real-time freshness assessment. Thus, UMPS offers a high-performance, convenient visual platform for monitoring food freshness.

Graphical abstract