Functional, Thermal and Structural Properties of Conophor (Tetracarpidium conophorum) Albumin
Keywords:
Protein solubility, foaming properties, DSC, near-UV-CD spectra, far-UV-CD spectraAbstract
The functional, thermal and structural properties of conophor albumins under various medium conditions were investigated with a view to elucidating its behaviour under these conditions for improved utilization as functional food ingredients. Conophor albumins were isolated by dialysis of the supernatant obtained after 1.0 M NaCl extraction of the defatted flour and samples were lyophilized. Protein solubility, emulsifying activity index (EAI) and emulsion stability index (ESI), foaming capacity (FC) and foaming stability (FS) under the influence of pH and NaCl were investigated. Thermal stability and structural properties as measured by Differential Scanning Calorimetry (DSC) and Circular Dichroism (CD) respectively were also investigated under various environmental conditions. Minimum protein solubility in water (44.36%), 0.5 M (41%) NaCl and 1.0 M (38.91%) NaCl occurred at pH 6. At pH 2-6, EAI decreased with increasing pH from 34.89 ± 5.68 to 9.00 ± 1.09 (m2g-1) and thereafter, increased with increasing pH. FC and FS ranged between 7.00 - 20.00% and 40.00 - 60.71%, respectively with the maximum value obtained at pH 10 for FC and pH 6 for FS. Decreases in enthalpy (ΔH) and denaturation temperature (Td) were observed under the influence of highly acidic and alkaline pHs. The progressive increase in Td (70.95 – 77.20 °C) with increase in salt concentration (0.00M – 0.10 M) suggests a more compact conformation for conophor albumin with higher thermal stability. Far-UV-CD spectra showed that the secondary structure was stable to changes in pH (3-9), ionic strength and temperature. The tertiary structure was found to be more sensitive to change in temperature as indicated by near-UV-CD spectra.
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