Use of Differential Scanning Calorimetry and Infrared Spectroscopy in the Study of Thermal and Structural Stability of α-Lactalbumin
Joyce I. Boye, Inteaz Alli, Ashraf A. Ismail
Journal of Agricultural and Food Chemistry
Abstract
Structural changes of α-lactalbumin (α-lac) in response to pH, ionic strength, sugars, and heat treatment were investigated by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. From DSC, two reversible transitions at 39.6 °C (A) and 64.8 °C (B) were observed when α-lac was heated. At pH 3, transition A was partially reversible (14%) while transition B was completely reversible. At pH 9, both transitions were completely irreversible. Heating α-lac at pH 3 resulted in aggregation with no observed gelation; at pH 9 a translucent gel was formed. FTIR showed that at pH 3, denaturation of α-lac resulted in the appearance of two bands at 1616 and 1685 cm-1 attributed to intermolecular aggregation. These bands were absent at alkaline pH. The major effects of heat treatment of α-lac were loss in the bands attributed to α-helix, 310-helix, and β-sheet and increase in the bands attributed to turns. Keywords: α-Lactalbumin; infrared spectroscopy; differential scanning calorimetry; denaturation; secondary structure
Extracted Claims
8 claims extracted from this paper into the knowledge graph
α-lactalbumin (α-lac) exhibits partially reversible transition A (14%) and completely reversible transition B at pH 3
“At pH 3, transition A was partially reversible (14%) while transition B was completely reversible.”
α-lactalbumin (α-lac) exhibits completely irreversible transitions A and B at pH 9
“At pH 9, both transitions were completely irreversible.”
α-lactalbumin (α-lac) results in aggregation with no observed gelation at pH 3
“Heating α-lac at pH 3 resulted in aggregation with no observed gelation; at pH 9 a translucent gel was formed.”