Thermal history indicator hydrogel based on starch with multiple signal channels for visualized monitoring thermal accumulation of perishable products.

Perishable products are easily deteriorated due to thermal accumulation during storage and transport. A low-cost, environmental-friendly and visualized indicating device is of great importance for real-time monitoring the quality state of such products, but remains a significant challenge. Herein, a novel thermal history indicator (THI) based on readily available starch was developed. The resulting THI displayed sensitively response to the environmental time-temperature over a broad temperature range (15-55 ℃). The activation energies (E _a) according to the signals of absorbance, fluorescence emission and G' values are 95.97 kJ/mol 105.3 kJ/mol, and 114.53 kJ/mol, respectively. The continuous appearance changes from colorless to dark brown allowed user-friendly readout. In addition, the quantitative information could also be obtained by the signal changes of absorbance, fluorescence emission, and RGB values. The resulting THI also displayed the immediate response to temperature fluctuations during transportation and storage. The signal values from multiple channels were well correlated with the concentration of aerobic mesophilic bacteria (AMB) in milk under same storage conditions. The proposed THI show the potential application for real-time assessing the quality loss of perishable products. The low-cost, environmental-friendly, commercially available starting material makes it suitable for scalable manufacturing and wide application.

Supplementary information: The online version contains supplementary material available at 10.1007/s13197-024-06130-w.