Effect of maleylation on physicochemical and functional properties of rapeseed protein isolate

Abstract

Influence of maleylation on the physicochemical and functional properties of rapeseed protein isolate was studied. Acylation increased whiteness value and dissociation of proteins, but reduced free sulfhydryl and disulfide content (p < 0.05). Intrinsic fluorescence emission and FTIR spectra revealed distinct perturbations in maleylated proteins' tertiary and secondary conformations. Increase in surface hydrophobicity, foaming capacity, emulsion stability, protein surface load at oil-water interface and decrease in surface tension at air-water interface, occurred till moderate level of modification. While maleylation impaired foam stability, protein solubility and emulsion capacity were markedly ameliorated (p < 0.05), which are concomitant with decreased droplet size distribution (d 32 ). In-vitro digestibility and cytotoxicity tests suggested no severe ill-effects of modified proteins, especially up to low degrees of maleylation. The study shows good potential for maleylated rapeseed proteins as functional food ingredient.

Effects of Succinylation on the Physicochemical Properties and Structural Characteristics of Edible Rapeseed Protein Isolate Films

“…B, SRPI films exhibited lower values of ΔE, which means SRPI films are more similar to the white standard plate. These results are in agreement with the findings of Purkayastha et al (), when the films were brought into application, light color can make a good commercial effect.…”

“…Compared to the RPI film, the 5% SRPI film had an increased content of β‐sheet from 39.9% to 49.2%, whereas those of α‐helix, β‐turn, and the random coil decreased from 24.8%, 21.1%, and 14.2% to 21.3%, 18.8%, and 10.8%, respectively. These results are partly similar to the results determined by Purkayastha et al (), but are opposite to the results obtained by Zhao et al (). It might be stated that intermolecular hydrogen‐bonding interactions between β‐sheets may act as the major junction zones and thus stabilize the film network, as the content of the β‐sheet is about a half of the secondary structure of protein.…”

“…The results are similar to the findings (Wan et al, ; Zhao et al, ) that the high level of succinylation might weaken compact tertiary conformation. And according to the previous reports (Purkayastha et al, ; Tayyab and Qasim, ), the results proved that the structure of protein would become unstable under high electrostatic repulsion and steric hindrance of the bulky negatively charged acyl groups. Therefore, the thermal endurance of the SRPI films varies with their succinylation degree, and a low level degree of succinylation could improve thermal resistance of the RPI films.…”

“…Research (Dong et al, ; Jang et al, ) has shown that RPI has some excellent functional properties, especially water retention, film‐forming, and gelling. Actually, the rapeseed meal (residual from rapeseed oil extraction), which contains about 40% proteins (Purkayastha et al, ) and usually used as a fertilizer or feed, caused a great waste of protein resources. Recently, a study (Jang et al, ) determined that RPI is an edible film component in food packaging.…”

“…However, methods that modify proteins, adding various plasticizers and emulsifiers or via blending, can affect their physicochemical properties. Succinic anhydride, the most frequently used chemical agent for protein derivatization, can influence many properties of proteins such as the amounts of net negative charge, molecular structure, steric hindrance (Purkayastha et al, ; Zhao et al, ), and so on, all of which could enhance protein solubility, surface hydrophobicity, and thermal stability (Cuadri et al, ; Wang et al, ).…”