Enzymatic time–temperature indicators (TTIs) usually suffer from instability and inefficiency in practical use as food quality indicator during storage. The aim of this study was to address the aforementioned problem by immobilizing laccase on electrospun chitosan fibers to increase the stability and minimize the usage of laccase. The addition of NaN3, as and enzyme inhibitor, was intended to extend this laccase TTI coloration rate and activation energy (Ea) range, so as to expand the application range of TTIs for evaluating changes in the quality of foods during storage. A two-component time–temperature indicator was prepared by immobilizing laccase on electrospun chitosan fibers as a TTI film, and by using guaiacol solution as a coloration substrate. The color difference of the innovative laccase TTI was discovered to be <3, and visually indistinguishable when OD500 reached 3.2; the response reaction time was regarded as the TTI’s coloration endpoint. Enzyme immobilization and the addition of NaN3 increased coloration Km and reduced coloration Vmax. The coloration Vmax decreased to 64% when 0.1 mM NaN3 was added to the TTI, which exhibited noncompetitive inhibition and a slower coloration rate. Coloration hysteresis appeared in the TTI with NaN3, particularly at low temperatures. For TTI coloration, the Ea increased to 29.92–66.39 kJ/mol when 15–25 μg/cm2 of laccase was immobilized, and the endpoint increased to 11.0–199.5 h when 0–0.10 mM NaN3 was added. These modifications expanded the applicability of laccase TTIs in intelligent food packaging.

SummaryLaccase was immobilised on electrospun chitosan fibres to prepare a laccase time–temperature indicator (LTTI) to predict the quality deterioration of fresh‐cut papaya. Using sodium azide (NaN3) as an enzyme inhibitor could retard the laccase‐catalysed coloration and to expand activation energy (Ea) range, in which the LTTI was calibrated to correlate with fresh‐cut papaya deterioration. The fresh‐cut papaya reaching total plate count (TPC) of 105 CFU g−1 demonstrated unacceptable quality and the time it took was close to the coloration endpoint of formulated LTTI at different storage temperatures. The Ea of the LTTI, formulated with 20 μg cm−2 of laccase and 0.1 mm NaN3, was 55.69 kJ mol−1, which only differed by approximately 15 kJ mol−1 from the Ea of the TPC of fresh‐cut papaya. In the 5, 15, 25, and 35 °C isothermal response tests, the prediction errors were 1.15%, 2.78%, 2.78%, and 0.83%, respectively. In temperature fluctuation response experiments, the coloration endpoint of the LTTI was correlated with the quality deterioration of fresh‐cut papaya. These results revealed that the formulated LTTI had high reliability in evaluating the shelf life of fresh‐cut papaya.

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