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Effect of pH and ionic strength on the heat stability of rapeseed 12S globulin (Cruciferin) by the ANS fluorescence method
- Folawiyo, Y.L., Owusu Apenten, R.K.
- Journal of the science of food and agriculture 1996 v.70 no.2 pp. 241-246
- rapeseed oil, heat stability, pH, ionic strength, heat treatment, acid treatment, hydrophobicity, fluorescence, globulins, temperature, inactivation
- The heat stability of rapeseed 12S globulin (cruciferin) was examined using 8-anilinonaphthalene-1-sulphonic acid (ANS) as a fluorescence probe. Heating cruciferin (0.06-0.3 mg ml-1 in 10 mM glycyl-glycyl piperizine buffer, pH 7.0, with 0.1-1.0 M NaCl) for 20 min increased its hydrophobicity as monitored by ANS fluorescence measurements. The mid-point temperature for the heat effect (Tm) increased linearly with increasing solvent pH (Tm (degree C) = 4.16 pH + 41 (micro = 0.1)) or sodium chloride concentration (Tm (degree C) = 14.7 [NaCl] + 71 (pH = 7.0)). The range of Tm values for cruciferin was 45-96 degrees C. At 20 degrees C cruciferin was unstable at pH < 3.0 but relatively stable under alkaline conditions (pH 8-10). Though possessing an oligomeric structure, cruciferin appears to heat denature in accordance with the two-stage deactivation model for simple globular proteins.