HEAT-INDUCED CHANGES IN THE SECONDARY STRUCTURE OF HEN EGG S-OVALBUMIN

Solutions of hen egg S-ovalbumin at pD or pH 3.0, 7.0, and 9.0 were heated at temperatures between 30 and 90-degrees-C to study changes in secondary structure by Fourier transform infrared spectroscopy (FTIR), storage moduli by dynamic rheological testing, and denaturation temperatures by differential scanning calorimetry. Second-derivative infrared spectra of native S-ovalbumin at pD 7.0 and 9.0 revealed protein absorption bands for beta-sheet (1626 cm-1), 3(10)-helix (1638 cm-1), alpha-helix (1656 cm-1), and tums (1682 and 1670 cm-1). The beta-sheet absorption band decreased to a shoulder for ovalbumin at pD 3.0. Bands at 1626,1638, and 1656 cm-1 decreased as heating temperature was increased, whereas bands at 1614 and 1682.5 cm-1, representing hydrogen-bonded beta-strands, increased in intensity. Changes in secondary structure were closely correlated to denaturation temperatures and increases in storage moduli of S-ovalbumin solutions. Results help elucidate texture formation in egg products by establishing a relationship between changes in protein secondary structure and viscoelasticity with heat.