Abstract
This study examined the effectiveness of passive insulation using ice packs in preserving the quality stability of tofu during simulated last-mile delivery. In the first experiment, tofu was packaged with 0-2 ice packs and stored at 30 °C. Temperature profiles were monitored at the product core and within the packaging, and quality changes were assessed through color, texture, pH, turbidity, and microbial counts. Ice packs significantly suppressed temperature rise and microbial growth, delaying quality deterioration. Partial least squares analysis identified turbidity, pH, and total aerobic bacteria as key freshness indicators. In the second experiment, configuration of tofu units (6-18) and ice packs (0-6) were evaluated. Thermal performance was quantified using the temperature inhomogeneity coefficient and heat exposure index. Configurations with over four ice packs maintained internal temperatures below 10 °C for over 23 h. These findings emphasize the importance of optimizing passive insulation strategies for high-moisture foods. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10068-025-02067-8.