Rheological, structural and thermal characteristics of protein isolates obtained from album (Chenopodium album) and quinoa (Chenopodium quinoa) seeds

Abstract

This study was carried out to examine the structural, rheological and thermal characteristics of protein isolates extracted from album and quinoa seeds. The results showed that surface hydrophobicity, free and total sulfhydryl groups were found significantly (p≤0.05) higher in quinoa protein isolates. Rheological parameters showed that both G' (storage modulus) and G'' (loss modulus) were higher in quinoa protein isolates than album protein isolates. Enthalpy of denaturation (∆H) was found significantly (p≤0.05) higher in quinoa protein isolates, however, denaturation temperature (Td) was found higher in album protein isolates. Thermal gravimetric analysis showed that album protein isolates were degraded much faster than quinoa protein isolates with increasing temperature. Both quinoa and album protein isolates had two diffraction peaks at 2θ=10° and 2θ=20° respectively, but the peaks were more intense in album protein isolates. Circular dichroism showed α-helical structure and a more dominant negative peak in album protein isolates. FTIR showed characteristic peaks at 1200, 1500, 1700 and 3100-3300 cm−1 for both album and quinoa seed proteins respectively. SDS-PAGE results confirmed the presence of globulins in quinoa and album protein isolates.

Keywords

• Protein isolate
• Dynamic rheology
• Thermal properties
• Secondary structure
• XRD, FTIR