THE EFFECT OF HEAT-TREATMENT AND ACID-TREATMENT ON THE STRUCTURE OF RAPESEED ALBUMIN (NAPIN)

The effect of heat and/or acid treatment on rapeseed albumin (napin) s tructure was monitored, using the hydrophobic fluorescence probe anili nonapthalene-8-sulfonate (ANS), at 20-90 degrees C and pH 1-10. Heat-t reatment of napin at T> 40 degrees C (20 min) led to an increase in th e protein surface hydrophobicity. The mid-point temperature for the ir reversible heat-modification of napin at pH 7 (Tm) was 60-67 degrees C depending on NaCl concentration. The Tm value for napin was independe nt of pH over the range pH 4-8. At pH less than or equal to 4.0, napin undergoes an acid-induced structural modification leading to a greate r change in the apparent surface hydrophobicity compared to the effect of heating alone. These results are discussed in terms of the effect of solvent pH and temperature on the heat-resistance and heat-stabilit y of napin. Copyright (C) 1996 Elsevier Science Ltd.