Effect of Peroxyl‐Radicals‐Induced Oxidative Modification in the Physicochemical and Emulsifying Properties of Walnut Protein

Abstract

In this paper, the effects of peroxyl radical oxidation on the physicochemical and functional properties of walnut protein were investigated. Walnut protein isolate (WPI) containing 2,2 0 -azobis(2-amidinopropane) dihydrochloride (AAPH) was oxidatively stressed under aerobic conditions in peroxyl radical-generating media. Incubation of walnut protein with increasing concentration of AAPH resulted in gradual carbonyl generation and free sulfhydryl group degradation. The results of surface hydrophobicity implied that oxidation leads to protein aggregation thus decreasing protein solubility in an AAPH concentration-dependent manner (P < 0.05). Emulsifying properties exhibited a significant increase (P < 0.05) at AAPH concentrations up to 0.2 mM and higher AAPH concentrations reduced the emulsifying capacity of WPI. These results indicate that appropriate oxidation is helpful to improve the emulsifying properties of protein, and with an increase of oxidation degree, emulsifying functional will damage.

Effect of Oxidative Modification by Peroxyl Radical on the Characterization and Identification of Oxidative Aggregates and In Vitro Digestion Products of Walnut (Juglans regia L.) Protein Isolates

“…The amount of peroxyl radicals produced by AAPH is proportional to the concentration of AAPH [ 31 ]. As shown in Table 1 , the carbonyl content increased significantly with increasing AAPH concentration ( p < 0.05), and a similar trend was reported by Mao et al [ 5 ]. In this study, the initial carbonyl content of the walnut sample was 2.36 nmol/mg, and the carbonyl content increased 0.35-fold and 1.17-fold at AAPH concentrations of 1 mmol/L and 25 mmol/L, respectively, compared to the control.…”

“…Since defatted walnut meal contains 50–60% protein [ 4 ], it is an important source of walnut protein. In the pretreatment process of walnut oil, with the destruction of the walnut cell structure, the polyunsaturated fatty acids in walnut are prone to lipid peroxidation under the catalysis of lipoxygenase (LOX), resulting in lipid free radicals and active lipid oxidation products [ 5 , 6 ], which indirectly lead to protein oxidation. Moreover, walnut protein can affect the quality of the composite product as a raw material or ingredient due to its early oxidation.…”

Polyphenol removal with ultrasound‐assisted ethanol extraction from defatted walnut powder: optimization of conditions and effect on functional properties of protein isolates

“…The method of Mao et al 13 was used and slightly modified. Briefly, 1000 g of shelled walnut kernels (with inner seed coat) were crushed and extracted by maceration with hexane at a stockto-liquid ratio of 1:5 (w/v) for 1 h using Hetian thin-skinned walnuts as raw material.…”

“…The method of Mao et al 13 was used with slight modifications. WPI was prepared by alkali solubilization and acid precipitation method.…”

Effects of Peroxyl Radicals on the Structural Characteristics and Fatty Acid Composition of High-Density Lipoprotein from Duck Egg Yolk

“…Protein oxidation has been demonstrated to have significant impacts on the quality of protein-rich foods [ 18 , 19 ]. During the processing and storage of egg products, egg yolk is easily oxidized to produce some hydroperoxides and radicals, which thereby induce the oxidation of proteins and affect their structural characteristics and physicochemical properties, resulting in the deterioration of egg products [ 20 ].…”