Abstract
The thermal behavior ofΒ-lactoglobulin (Β-lg) disperesed in distilled water (pH=3.2) is studied dy differential scanning calorimetry (DSC) in the temperature range 20‡C–120‡C and within a concentration region of 3.5% to 24%.
Recently [1] we have determined by DSC the kinetic parameters for the heat-denaturation ofΒ-lg. The effect of the protein concentration and of the thermal treatment on transition temperature (T trs), half-widths of the peak (δT 1/2), of apparent enthalpy changes (δapp H) and of Van't Hoff enthalpies (δVH H) have been examined for the concentrations of 8.8% and 24%.
In this study we have undertaken complementary experiments for the concentrations 3.5% and 10.8%. The half-widths of the peaks, which depend on the cooperativity of the denaturation process [2], decrease with increasing concentration. The ratio δapp H/δVH H tends to 1, with low values of the protein concentration and with high scanning rates. This implies the hypothesis of a reversible step for the denaturation process ofΒ-lg.
Zusammenfassung
Das thermische Verhalten vonΒ-Lactoglobulin (Β-lg), das in destilliertem Wasser beipH=3.2 dispergiert ist, wurde für Konzentrationen zwischen 3.5 und 24% im Temperaturbereich von 20–120‡C mittels DSC untersucht. In der vorliegenden Arbeit werden thermodynamische Daten des Denaturierungsprozesses ermittelt, wobei sowohl die Methode nach Kissinger als auch diejenige nach Borchardt-Daniels angewendet wurden. Insbesondere wird der Einfluss der Basislinie als auch unterschiedlicher Arten der thermischen Behandlung auf die Resultate behandelt.
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References
P. Relkin and B. Launay, Food Hydrocolloids, 4 (1990) 19.
P. L. Privalov, Adv. in Protein Chem., 33 (1979) 167.
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H. E. Kissinger, Anal Chem., 29 (1957) 145.
M. J. Borchardt and F. Daniel, J. Am. Chem. Soc., 79 (1957) 41.
W. P. Brennan, B. Miller and J. C. Whitwell, Proc. 2nd Symp. Analytical Calorimetry, 441 (R. S. Porter, editor), N.Y: Plenum Press, 1970.
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Relkin, P., Launay, B. On the partial reversibility of the Β-lactoglobulin heat denaturation. Journal of Thermal Analysis 37, 1887–1895 (1991). https://doi.org/10.1007/BF01912219
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DOI: https://doi.org/10.1007/BF01912219