Thermal analysis of flaxseed (Linum usitatissimum) proteins by differential scanning calorimetry

The thermal properties of flaxseed (whole or dehulled), dehulled and delipidated meal, as well as proteins extracted and isolated from the meal, were investigated by differential scanning calorimetry (DSC). A high denaturation temperature (Td) of 114.7 °C was observed for the major fraction of flaxseed protein isolated by anion-exchange chromatography, representing the 11–12 S storage globulin. Marked decreases in Td and enthalpy were observed at pH 3 compared with pH of 5 or higher, while the presence of high salt (1.0 M NaCl) resulted in higher thermal stability, enthalpy and greater cooperativity of the transition. Thermal analysis of the major fraction in the presence of chaotropic salts or protein structure perturbants (sodium dodecyl sulfate, urea, dithiothreitol, N-ethylmaleimide, ethylene glycol) suggested the contributions of hydrophobic and ionic interactions, hydrogen bonding as well as disulfide linkages or disulfide–sulfhydryl (SS–SH) interactions, to the thermal stability of flaxseed protein.