Influence of NaCl concentration and high pressure treatment on thermal denaturation of soybean proteins

In the present work the effect of high pressure (HP) treatment in the presence of NaCl on the thermal behavior of soybean proteins was analyzed by differential scanning calorimetry. The thermograms obtained have shown that NaCl addition increased the thermal stability - increase in temperatures of denaturation (Td) - of both glycinin and beta-conglycinin. HP treatments increased thermal stability of glycinin, but decreased that of beta-conglycinin. High NaCl concentrations decreased (in glycinin) or inverted (in beta-conglycinin) the effects of HP on thermal stability. Cooperativity of denaturation of glycinin was enhanced by NaCl and HP. Cooperativity of denaturation of beta-conglycinin was enhanced by HP and also by NaCl at 0.2 mol/L but decreased with the combination of treatments. Salt addition increased the enthalpy. Delta H, of denaturation of glycinin and beta-conglycinin, being this effect stronger on glycinin. HP treatment provoked the denaturation of both protein fractions. The presence of NaCl protected glycinin against HP-denaturation at any assayed salt concentration and pressure level, while beta-conglycinin was only protected at 200 and 400 MPa, but was more denaturated at 600 MPa in the presence of 0.6 mol/L of NaCl. Industrial relevance: The knowledge provided by this work may be useful in the handling of high pressure-treated food with high NaCl content (e.g. meat emulsions, smallgoods) where soybean proteins are used as additives, in order to choose high pressure values to achieve their denaturation or predict the effects of ulterior thermal treatments. Thus, this knowledge may be useful to increase the use of high pressure in food industry. (C) 2011 Elsevier Ltd. All rights reserved.