Effect of LBG on the gel properties of acid-induced SPI gels

Abstract

The effect of the addition of locust bean gum (LBG) on the rheological properties, microstructure and fractal dimension of glycono-δ-lactone induced soy protein isolate (SPI) gels were studied (LBG concentration = 0.01%–0.04%, SPI concentration = 6%). Both the small and large amplitude oscillatory shear measurements were carried out to characterize the rheological properties of SPI and SPI-LBG gels. The G′ of SPI-LBG gels was highly frequency dependent within the frequency range of 6.28 rad/s to 62.8 rad/s. Fourier transform rheology was used to analyze the higher harmonic signals from nonlinear stress waveform. SPI-LBG gels showed typical Type I network behavior similar to that of SPI gel at strain amplitude >2% in LAOS tests. Creep/recovery tests showed that the addition of LBG increased both the elastic and viscous moduli of SPI-LBG gels. The image of the microstructure captured by confocal laser scanning microscopic (CLSM) was used to determine the fractal dimension. The protein network structure of SPI-LBG gels showed greatly bigger pore volume, better scale behavior than SPI gels, and the chaos and complexity of the protein aggregates in SPI-LBG gels were much less than that in SPI gel. LBG was found to play an important role in a SPI-LBG gel system.