In contrast to the immediate temperature increase on the peach surface, peach interior temperatures increased slowly at the beginning of heating and rose up gradually as the time increased (Fig. 7). This is mainly because the transfer of thermal energy absorbed at peach surface to the peach interior tissue was governed by heat conduction, which inherently has a much lower heat transfer rate compared to the radiation heat transfer on the peach surface. The closer the location to the peach surface, the higher the maximum temperature. As a result, the location closest to peach surface (i.e., the location of 2 mm under the skin) had the highest
temperature after 180 s heating as seen in Fig. 7. After 180 s IR heating, the interior temperatures at the locations 4, 8, and 16 mm under the skin still increased. The occurrence of such delayed temperature increase was attributed to the slow heat conduction of the thermal energy from peach surface to peach center. In practice, after the IR heating process, the continued increase of peach interior temperatures will need to be minimized, which will help
prevent potential quality and nutritional loss in the flesh.