The effect on the surface activity and the structure of SPI caused by cleavage of disulfide bonds and by subsequent glucose modification

Abstract

The main purpose of this study was to investigate the effects on the molecular structure and the properties of soybean proteins isolate (SPI) after two modifications: (1) peracetic acid oxidative cleavage of its disulfide bonds and (2) the subsequent addition of covalently bonded glucose to the SPI containing the cleaved disulfide bonds. An appropriate amount of peracetic acid will be capable of enhancing the surface properties of SPI significantly; however, excessive oxidation can obtain undesirable results. When the concentration of peracetic acid was 0.4%, following by 35.5% of the disulfide bond cleavage, compared with those of natural SPI, the foaming capacity (FC), foaming stability (FS), emulsifying capacity (EC), and emulsifying stability (ES) of oxidized-SPI were increased by 82.0%, 65.8%, 58.5%, and 41.5%, respectively. The surface activity of oxidized-SPI could be promoted by glucose modification, and the FC, FS, EC, and ES of oxidized-SPI have further risen to 146.8%, 96.0%, 131.4%, and 40.3%, respectively, after the further glucose modification. Particle size measurements showed bimodality for the SPI that was modified with glucose with a portion of smaller sizes seen. Fluorescence spectroscopy and circular dichroism measurements demonstrate that extensibility increases; flexibility is enhanced; and glycosylation occurs more readily due to the oxidation of SPI. When grafted with glucose, these oxidized soybean protein products produce more ideal foaming and display better emulsification properties.

Stability mechanism of Monascus pigment–soy protein isolate–maltodextrin complex

“…β‐sheet was a regular hydrogen bond formed between carbonyl oxygen and the same or adjacent peptide chain and hydrogen through a peptide bond, the increase of β‐sheet content improved the rigidity and compactness of the protein structure 33 . These CD spectroscopy results proved the conformational change of SPI upon MD and MP interaction, the decrease of α‐helix and the increase of β‐sheet enhanced the flexibility of protein, and made the complex structure more stable 34 . Zhao et al .…”

“…33 These CD spectroscopy results proved the conformational change of SPI upon MD and MP interaction, the decrease of ⊍-helix and the increase of ⊎-sheet enhanced the flexibility of protein, and made the complex structure more stable. 34 Zhao et al reported similar results that a decrease in ⊍-helix and an increase in ⊎-sheet content were observed for SPI with betalain. 16 MP, SPI and MD interacted to produce complexes, in which the structure of MP-SPI-MD had more hydrogen bonds, thereby improving the stability of MP and better resistance to photodegradation.…”

Impact of emulsifiers for the nanoencapsulation with maltodextrin of cannabis oil by spray drying on the physicochemical properties and bioaccessibility of cannabinoids

“…The molecular weights of β-conglycinin and glycinin are ∼150-200 and 300-380 kDa, respectively, 43 compared to ∼18 kDa for β-lactoglobulin and ∼14 kDa for α-lactalbumin. SPI also has more disulfide bonds (β-conglycinin and glycinin have 2 and 20 disulfide bonds, respectively 44 ) than WPI (β-lactoglobulin and α-lactalbumin have 2 and 4 disulfide bonds, respectively 16 ), conferring a stiffer structure. A more rigid structure that was obtained with the SPI may have caused more wrinkles at the surface of the powder particles, as seen in SEM images.…”