Related Experiment Video
Updated: Jul 6, 2026
14:22
Free Radicals in Chemical Biology: from Chemical Behavior to Biomarker Development
Published on: April 15, 2013
Carbon-centered radicals in isolated soy proteins
W L Boatright1, M S Jahan, B M Walters
1Department of Animal and Food Sciences, University of Kentucky, 412 W.P. Garrigus Building, Lexington, KY 40546-0215, USA. wlboat1@uky.edu
Journal of Food Science
|April 5, 2008
Summary
Isolated soy proteins (ISP) contain significantly higher levels of carbon-centered free radicals compared to other proteins like casein and albumin. Hydration and drying processes can further increase these trapped radicals in soy protein products.
Area of Science:
- Food Science
- Biochemistry
- Spectroscopy
Background:
- Isolated soy protein (ISP) is a widely used protein ingredient.
- Understanding the chemical properties of ISP, such as free radical content, is crucial for its application.
- Electron paramagnetic resonance (EPR) spectroscopy is a technique used to detect and quantify free radicals.
Purpose of the Study:
- To quantify the free radical content in commercial isolated soy proteins (ISP).
- To compare the free radical levels in ISP with other protein sources.
- To investigate the effect of hydration and drying on free radical levels in ISP.
Main Methods:
- Solid-state electron paramagnetic resonance (EPR) spectroscopy was used to analyze commercial ISP samples.
- Free radical levels were measured in ISP and compared to sodium caseinate, egg albumin, and casein.
- The impact of hydrating ISP with sodium erythorbate or L-cysteine, followed by freezing and drying, on free radical content was assessed.
- EPR spectra of defatted soybean flakes were analyzed to identify radical signals and manganese presence.
Main Results:
- Commercial ISP exhibited significant levels of carbon-centered free radicals (g=2.005), ranging from 2.96 x 10^14 to 6.42 x 10^14 spins/g.
- ISP contained substantially higher free radical levels (14-100 times more) than sodium caseinate, egg albumin, and casein.
- Soy protein powdered drink mixes showed even higher free radical concentrations, up to 4.10 x 10^15 spins/g.
- Hydrating ISP with sodium erythorbate or L-cysteine followed by drying increased trapped free radicals by 17- to 19-fold.
- Defatted soybean flakes showed overlapping signals of carbon-centered radicals and manganese-II, with manganese significantly reduced in processed ISP.
Conclusions:
- Isolated soy proteins possess a notable concentration of carbon-centered free radicals.
- Processing methods, including hydration and drying, can significantly enhance the free radical content in soy protein products.
- The findings provide insights into the chemical stability and potential reactivity of ISP in food systems.
Related Concept Videos
01:10Radical Reactivity: Steric Effects
The presence of electron-donating, electron-withdrawing, or conjugating groups adjacent to a radical center, imparts electronic stabilization to the radicals. Examples of such electronically-stabilized radicals are triphenylmethyl, tetramethylpiperidine‐N‐oxide, and 2,2‐diphenyl‐1‐picrylhydrazyl. These radicals are remarkably stable and are known as persistent radicals. Some of the persistent radicals can even be isolated and purified.
Along with electronic factors, steric factors also account...
Along with electronic factors, steric factors also account...
01:07Radicals: Electronic Structure and Geometry
This lesson delves into the geometry of a radical, which is influenced by the electronic structure of the molecule. The principle is similar to that of a lone pair, where the unpaired electron influences the geometry at the radical center.
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
Accordingly, the structure of a trivalent radical lies between the geometries of carbocations and carbanions. An sp2-hybridized carbocation is trigonal planar, while an sp3-hybridized carbanion is trigonal pyramidal. Here, the difference in geometry is...
01:02Radical Reactivity: Electrophilic Radicals
Radicals adjacent to electron‐withdrawing groups are called electrophilic radicals. These radicals readily react with nucleophilic alkenes. For example, the malonate radical, in which the radical center is flanked by two electron‐withdrawing groups, reacts readily with butyl vinyl ether, which consists of an electron‐donating oxygen substituent. The reaction between electrophilic malonate radical and nucleophilic vinyl ether is favored because the radical has a low‐energy SOMO, which interacts...
01:11Radical Reactivity: Overview
Radicals, the highly reactive species, gain stability by undergoing three different reactions. The first reaction involves a radical-radical coupling, in which a radical combines with another radical, forming a spin‐paired molecule. The second reaction is between a radical and a spin‐paired molecule, generating a new radical and a new spin‐paired molecule. The third reaction is radical decomposition in a unimolecular reaction, forming a new radical and a spin‐paired molecule. These three...
01:16Radical Reactivity: Nucleophilic Radicals
Radicals adjacent to electron-donating groups are called nucleophilic radicals. These radicals readily react with electrophilic alkenes. The SOMO–LUMO interactions are the driving force for the reaction, where the high-energy SOMO of the electron-rich, nucleophilic radicals interacts with the low-energy LUMO of the electron-deficient, electrophilic alkenes. Such SOMO–LUMO interactions are the basis of reactive radical traps, affecting the selectivity in radical reactions. For instance, consider...
01:33Radical Halogenation: Stereochemistry
Stereochemistry is the study of the different spatial arrangements of atoms in a given molecule. The stereochemistry of radical halogenations can be understood from three different situations:
Halogenation to form a new chiral center:
Halogenation to form a new chiral center: