Within a biorefinery production process, concentrating the sugar-rich hydrolysate stream by evaporation prior to fermentation can enhance the fermentation productivity and reduce downstream product recovery costs. However, fouling of the evaporator surface by soluble and suspended solids within the process steams can become problematic. In this study we analyzed fouling characteristics of an acid pretreated pine wood enzymatic hydrolysate using an annular fouling probe in batch mode at 110, 120, 130, and 140 degrees C with 0, 10, and 20% total suspended solids based on dry weight/volume. Results showed that the rate of fouling and the induction period for onset of fouling depended strongly on temperature, with a maximum fouling resistance of similar to 0.5 m(2).K/kW experienced at 130 and 140 degrees C with no suspended solids present. Characterization of the fouling deposits was studied using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), SEM energy dispersive spectroscopy (SEM-EDS), and inductively coupled plasma (ICP) analysis. CaSO4 was identified as the predominant foulant in the deposits at temperatures >120 degrees C with 10% total suspended solids. On the basis of the analyses and characterizations, an attempt was made to understand the fouling mechanisms, and fouling reduction techniques were suggested to improve the process efficiencies.