High-Pressure Homogenization Pretreatment before Enzymolysis of Soy Protein Isolate: the Effect of Pressure Level on Aggregation and Structural Conformations of the Protein

Abstract

The high-pressure homogenization (HPH) treatment of soybean protein isolate (SPI) before enzymatic hydrolysis using bromelain was investigated. Homogenization pressure and cycle effects were evaluated on the enzymatic degree of hydrolysis and the antioxidant activity of the hydrolysates generated. The antioxidant activity of SPI hydrolysates was analyzed by 1,1-dipheny-2-picrylhydrazyl (DPPH). The sizes and structures of the SPI-soluble aggregate after HPH treatment were analyzed using dynamic and static laser light scattering. The changes in the secondary structure, as measured by Fourier transform infrared spectroscopy (FTIR) and the macromorphology of SPI, were measured by scanning electron microscope (SEM). These results suggested that the HPH treatment (66.65%) could increase the antioxidant activities of the SPI hydrolysates compared with the control (54.18%). SPI hydrolysates treated at 20 MPa for four cycles obtained higher DPPH radical-scavenging activity than other samples. The control was predicted to be a hard sphere, and SPI treatment at 10 MPa was speculated to be Gaussian coil, polydisperse, and then the high-pressure treated SPI became a hollow sphere. Changes in the secondary structures showed protein aggregate formation and rearrangements. The image of SPI varied from a globular to a clump structure, as observed by the SEM. In conclusion, combining HPH treatment and enzymolysis could be an effective way to improve the antioxidant activity of the SPI.

Effects of High-Intensity Ultrasound Pretreatment on Structure, Properties, and Enzymolysis of Soy Protein Isolate

“…The angular dependence of hydrodynamic radius (R h ) obtained from dynamic light scattering (DLS). Light scattering is a rapid and efficient method for the determination of the protein aggregation behavior [40]. The light scattering data of SPI samples were shown in Table 1.…”

“…The parameter ρ is the ratio of R g to R h , and is an important parameter for characterizing macromolecules structure. In general, the ρ value increases with decreasing branching density, but a decrease in polydispersity counteracts the effect of branching [40]. The ρ value of the untreated protein was 0.78, which is predicted for a hard (homogeneous) sphere.…”

“…The samples prepared for DLS and SLS were filtered through 0.45 μm Millipore filters into a precision cylindrical cell (quartz, diameter: 25 mm). Light scattering measurements were measured in the angular range of 30–120° for static measurements and 30–90° for dynamic measurements [40]. The refractive index increment was determined to be 0.185 mL/g for SPI in aqueous solution.…”

Preparation and characterization of a novel environmentally friendly coal dust suppressant

“…It can be seen in the figure that the wave number of 3379.33 cm −1 primarily corresponds to the spectral peaks of OH, ‐NH and sulfonamide bond; the wave number of 2800 cm −1 corresponds to CH 2 absorption peak; the wave number of 1653.69 cm −1 corresponds to the CO stretching peak of amide I band; the wave number of 1529.78 cm −1 corresponds to the superposed peak associated with NH bending vibration and CN stretching vibration of amid II band, as well as the absorption peak of sulfonamide bond; the wave number of 1393.1 cm −1 corresponds to the characteristic peaks of sulfonamide bond and COO. The two peaks with wave numbers being1653.69 cm −1 and 1529.78 cm −1 , respectively, correspond to the characteristic spectral peaks of benzene ring and its bending vibration in CH plane …”

Bioactive Peptides from Walnut Residue Protein

“…Not only that, but also the biological activity of the hydrolysate was improved, which can significantly improve the growth and cell activity of yeast, promote the accumulation of glycogen and trehalose, and improve the taste of beer [28]. As far as we know, high-pressure homogenization, microwave and other pretreatment assisted enzymatic hydrolysis technologies have been successfully applied to the preparation of plant-derived active peptides such as soybean [29], peanut [30], but rarely used in the preparation of active peptides from walnut meal protein pretreatment.…”