Effect of gums on the rheological characteristics and microstructure of acid-induced SPI-gum mixed gels

Synthesis of Carboxymethyl Flaxseed Gum and Study of Nonlinear Rheological Properties of Its Solutions

Flaxseed gum (FG) was carboxymethylated by reacting it with monochloroacetic acid (MCA). The effects of concentrations of NaOH and MCA, reaction temperature and reaction time, on the degree of substitution (DS) were investigated. Reaction between the FG and MCA at NaOH and MCA concentrations of 0.06 g/mL and 0.08 g/mL, respectively, at 70 °C for 60 min produced carboxymethyl flaxseed gum (CMFG) with a DS of 0.969. Carboxymethylation of FG increased its solubility and light transmittance in water. The nonlinear rheological properties of CMFG solutions were studied using large amplitude oscillatory shear (LAOS) tests, Fourier transform (FT) rheology and Chebyshev stress decomposition methods. The different nonlinear rheological behaviors observed were related to the microstructures of the CMFG solutions as a function of concentration and DS.

Effect of Trypsin on Antioxidant Activity and Gel-Rheology of Flaxseed Protein

Enzymatic hydrolysis of flaxseed protein (FP) was carried out using trypsin in order to obtain flaxseed protein hydrolysates possessing better antioxidative property and modified rheological properties. The antioxidative properties of hydrolysates were much higher than the unhydrolyzed flaxseed protein. The hydrolysis also significantly reduced the hydrodynamic diameter of the magnitude of zeta potential of the dispersions. The gelling point of the hydrolysates occurred earlier than the unhydrolyzed sample while the duration of hydrolysis (30–120 min) did not affect gelling point of the hydrolysates. Considerable decrease in the gel strength and the frequency dependence of gel strength were observed in gels produced using hydrolyzed flaxseed protein. The above findings indicate that hydrolysates possessing high degree of antioxidative properties. The gels produces from these hydrolysates will have fast gelling property and will produce gels with reasonable strength. Thus, flaxseed protein hydrolysates obtained from trypsin hydrolysis can be used in applications that require proteins with higher antioxidative properties but softer texture.

Rheology of Emulsion-Filled Gels Applied to the Development of Food Materials

Emulsion-filled gels are classified as soft solid materials and are complex colloids formed by matrices of polymeric gels into which emulsion droplets are incorporated. Several structural aspects of these gels have been studied in the past few years, including their applications in food, which is the focus of this review. Knowledge of the rheological behavior of emulsion-filled gels is extremely important because it can measure interferences promoted by droplets or particle inclusion on the textural properties of the gelled systems. Dynamic oscillatory tests, more specifically, small amplitude oscillatory shear, creep-recovery tests, and large deformation experiments, are discussed in this review as techniques present in the literature to characterize rheological behavior of emulsion-filled gels. Moreover, the correlation of mechanical properties with sensory aspects of emulsion-filled gels appearing in recent studies is discussed, demonstrating the applicability of these parameters in understanding mastication processes.