The thermal stability of purified lectin from the black turtle bean was studied at temperatures between 70 degrees C and 90 degrees C over treatment times from 0 to 30 min. The results of the hemagglutinating activity and the intrinsic fluorescence assays indicated that the thermal inactivation is associated with the unfolding of the protein. Based on the two-way analysis of variance, the heating temperature and treatment time significantly affected the stability of the lectin during thermal treatments. Analysis of kinetic data suggested that the thermal stability of the lectin followed first-order reaction kinetics. The activation energy for the lectin was 78.80 kJ/mol. This higher activation energy suggested hydrophobic stability and thermal sensitivity of the lectin during thermal processing. Additionally, a high temperature and short treatment time might eliminate the anti-nutritional functions of the lectin. The linear relationship observed could be used as a quality indicator for the thermal processing of the black turtle bean. (C) 2014 Elsevier Ltd. All rights reserved.