Documentation of surface temperature is challenging for short food surface pasteurization treatments, particularly in steam environments. In this study a spectroscopic approach is investigated for estimating thermal load while heat transfer modeling is used to estimate the surface temperature of a model fish product when heated in steam or immersed in water. Reflectance spectroscopic measurements show that visible spectroscopy (400-550 nm) has potential for assessing the thermal load of surimi heated in water in the temperature range between 70 and 95 degrees C. For treatment times >10 s, robust models (r(2) >= 0.9) with acceptable prediction errors (<3 degrees C) were achieved. A similar development in the absorption was seen in steam treated surimi, for short (<10 s) processing times. Heat transfer modeling confirmed the thermal load indicated by the measurements, and demonstrated the large temperature gradients that occur with short time, high temperature treatments. (C) 2013 Elsevier Ltd. All rights reserved.