Effect of high-pressure treatment on the rheological properties of Alyssum homolocarpum seed gum/grass pea protein isolate dispersions and comparison with heat-induced gels

Abstract

The effects of high-pressure (HP) treatment at 400 MPa for 15 min on rheological properties of dispersions and gels of grass pea protein isolate (10% GPPI) containing different concentrations of Alyssum homolocarpum seed gum (0.2, 0.4 and 0.6% AHSG) were investigated. With the addition of AHSG, the amount of α-helix, β-sheet, and random coils in pre-treated GPPI decreased, whereas after HP treatment, α-helix and β-turn content increased. For AHSG-GPPI mixtures, it was found that HP treatment increased the intensity of X-ray diffraction peaks at 2θ = 11 and 26°, which had previously been found to decrease and become flatter with increasing gum concentration. The thermal degradation temperature (Td) and enthalpy (ΔH) increased after the addition of AHSG and following HP treatment. All mixed solutions had shear thinning behavior before and after HP treatment. When AHSG was added to GPPI, η0 and η∞ increased for both HP-treated and untreated samples, while after the treatment, the magnitude of η0 and η∞ slightly decreased. G′ values were higher than G″ values for all AHSG-GPPI dispersions, indicating a gel-like behavior for these mixtures. With increasing gum concentrations, G′ and G″ values of dispersions increased; however, these moduli decreased after exposure to HP treatment, though they were not statistically significant. The addition of AHSG significantly decreased the gelation temperature, increased the G′ value, and made the system more elastic during conventional heating and cooling ramps. When the HP treated samples were heated, the G′ value increasing trend was almost identical to that of the untreated samples, but during the cooling stage, the value of G′ for the HP treated samples were significantly higher.