Abstract:This study utilized RGB image analysis，low-field nuclear magnetic resonance （LF-NMR），and real-time thermocouple temperature monitoring to analyze the dynamic changes in color，moisture，and temperature during the frying of French fries，aiming to elucidate the internal heat and mass transfer processes under different frying temperatures and durations，as well as their effects on product quality. The results showed that at frying temperatures ranging from 110 ℃ to 170 ℃ for 20 s to 180 s，the color of the fries became darkened from light yellow to reddish brown，suggesting intensified browning reactions. As the temperature increased，the moisture migration rate was accelerated. At 170 ℃ for 180 s，the free water content decreased，shifting toward bound and immobilized water and forming a typical ′dry crust-moist core′ structure. In contrast，at lower temperatures （110 ℃ and 130 ℃），the moisture migration was slower，resulting in higher internal moisture content but insufficient surface browning，with crispy crust formation limited to the edges. Dynamic temperature monitoring revealed that the surface regions rapidly approached oil temperature at high temperatures，significantly enhancing internal heat transfer. In contrast，low-temperature frying led to slower core heating and pronounced thermal gradients，exhibiting a typical multi-stage heating pattern.