Defatted Wheat Germ Protein Research Articles

Complex coacervate of wheat germ protein/high methoxy pectin in encapsulation of d-limonene

d-limonene is a volatile compound widely used in food flavorings, but it is chemically unstable in the presence of air, light, moisture, and high temperatures. Coacervation is a well-established technique which involves the formation of biopolymer nanocomplexes between negatively charged polysaccharides and positively charged proteins to protect bioactive components. The study shows the effect of pH, protein/polysaccharide ratio and total biopolymer concentration on complex coacervation of defatted wheat germ protein (DWGP) and apple pectin (high methoxyl pectin (HMP)) in the food industry as a carrier and delivery system for d-limonene. DWGP was used for the first time to form coacervate with apple pectin. Turbidity, ζ-potential and particle size of the complex coacervate and their individual biopolymers were examined for preliminary assays of complex coacervation. The optimum condition for DWGP/pectin complex coacervation was found to be at a ratio of 4:1 with a total biopolymer concentration of 1% and a pH of 4.0. The rheological properties of DWGP, pectin, and their coacervate were measured at various pH levels and ratios. The resulting coacervates, used to microencapsulate d-limonene, underwent spray-dried and were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. These findings have the potential to contribute to the development of DWGP/pectin complex coacervates as effective delivery systems for volatile aromas or bioactive compounds.Graphical

Improving the extraction efficiency and functional properties of wheat germ protein by ultrasound-assisted

This study optimised the conditions for ultrasound-assisted extraction (UAE) of defatted wheat germ protein (WGP) and evaluated its effect on the functional properties. Single-factor and orthogonal experiment designs were combined to optimise the UAE extraction condition. The extraction of WGP reached the highest level, at 88.66%, with a solid : liquid ratio of 1 : 25 g·mL–1, pH value of 9.0, ultrasonic time of 10 min, and ultrasonic power at 400 W. Under these conditions, albumin, globulin, prolamin, and glutenin accounted for 32.26, 28.52, 5.42, and 22.40% of total protein, respectively. In addition, this study compared the functional properties of WGP extracted by UAE with the results based on a commercially available soy protein (SP) isolate (SPI). The UAE of WGP had better oil absorption, foaming, and emulsifying properties. Therefore, UAE is a promising technique for food protein extraction because it can change the protein efficiencies and properties of the extract.

Structural change and functional improvement of wheat germ protein promoted by extrusion

This study aim to evaluate the effects of extrusion treatment (130–150︒C, 40–48 Hz) on the physicochemical and functional properties of defatted wheat germ protein (DWGP). The results indicated that extrusion could cross-link proteins and starch in defatted wheat germ to produce protein-polysaccharide conjugates and effectively reduce free sulfhydryl groups and surface hydrophobicity of DWGP. The SDS-PAGE showed that DWGP molecular weight decreased after extrusion, but there was no significant difference between different extrusion conditions. The folding and spatial structural changes of DWGP conjugates molecules after extrusion were observed by fluorescence spectroscopy and FTIR. Transformation of α-helix to β-sheet caused high solubility and emulsification. The solubility, emulsification, and in vitro digestibility of DWGP conjugates were increased by 65.90%, 50.52% and 528%, respectively, after the extrusion of 140︒C and 44 Hz. As the extrusion temperature increased, the related functionality decreased. Also, many small and dense lumps in treated DWGP conjugates were observed by SEM. Therefore, extrusion possesses excellent potential as a processing technology to improve the functionality of DWGP.

Effects of multi-frequency ultrasound pretreatment under low power density on the enzymolysis and the structure characterization of defatted wheat germ protein

The effects of ultrasonic frequency mode, power density, pretreatment time and other parameters under low power density on the degree of hydrolysis (DH) of defatted wheat germ protein (DWGP) and angiotensin-I-converting enzyme (ACE) inhibitory activity of DWGP hydrolysate were studied in this research. Ultraviolet–visible (UV–Vis) spectra, free sulfhydryl (SH), disulfide bond (SS), surface hydrophobicity and hydrophobic protein content of ultrasound-pretreated protein and hydrophobic amino acid (HAA) content of alcalase-hydrolysate of DWGP were measured under optimized ultrasonic condition. The ultrasonic frequency mode with dual-fixed frequency combination of 28/40kHz showed higher ACE inhibitory activity of DWGP hydrolysate compared with that of other ultrasound frequency modes and all the ultrasonic frequency combinations involving in 28kHz showed higher ACE inhibitory activity. Under the dual-fixed frequency ultrasound mode of 28/40kHz, ultrasonic power density of 60W/L, pretreatment time of 70min, temperature of 60°C and substrate concentration of 60g/L, the ACE inhibitory activity of DWGP hydrolysate was the highest with its value of 74.75% (increased by 62.30% compared to control). However, all the ultrasonic pretreatment did not increase the DH of DWGP significantly (p>0.05). The changes in UV–Vis spectra, SH and SS groups, surface hydrophobicity and hydrophobic protein content indicated that the structure of DWGP unfolded after ultrasound pretreatment. The HAA content of hydrolysate from the pretreated DWGP increased significantly (p<0.05). The results proved that ultrasound pretreatment loosed the protein structure and exposed more HAA residues of protein to be attacked easily by alcalase. This resulted in the increase in the HAA content which related to the ACE inhibitory activity.

Enzymolysis reaction kinetics and thermodynamics of defatted wheat germ protein with ultrasonic pretreatment

This research explores the mechanism of ultrasonic pretreatment on enzymolysis of defatted wheat germ protein (DWGP). The enzymolysis reaction kinetics and thermodynamics were studied after ultrasonic pretreatments using a probe-type sonicator and an ultrasonic cleaning bath, and the results were compared with traditional enzymolysis. The results showed that both the traditional and ultrasonic pretreated enzymolysis fit well to first-order kinetics. Both the temperature and ultrasound had a positive effect on the enzymolysis of DWGP, with temperature playing a dominant role. Under the optimized conditions of DWGP concentration of 1% (w/v), Alcalase concentration of 2000U/g, time of 10min and temperature of 50°C, both the probe and cleaning bath ultrasonic pretreated enzymolysis showed high polypeptide concentrations (231.019 and 231.320μg/mL) and low energy requirements. In comparison with traditional enzymolysis, these methods significantly increased the reaction rate constant (k) by 166.7% and 144.4%, 92.9% and 85.7%, 28.0% and 28.0%, 16.1% and 12.9% at 20, 30, 40 and 50°C, and decreased the activation energy (Ea), enthalpy of activation (ΔH), Gibbs free energy of activation (ΔG) and entropy of activation (ΔS) by 68.6% and 62.4%, 74.1% and 67.5%, 34.3% and 31.2%, 1.4% and 1.3%. It can be concluded that ultrasonic pretreatment of DWGP can remarkably improve the enzymolysis efficiency and consequently leads to the production of higher polypeptide yield.

ACE-inhibitory peptides production from defatted wheat germ protein by continuous coupling of enzymatic hydrolysis and membrane separation: Modeling and experimental studies

To increase the yield and activity of angiotensin converting enzyme (ACE) inhibitory peptides from defatted wheat germ protein (DWGP), an efficient method of continuous coupling of enzymatic hydrolysis and membrane separation (CEH-MS) and its kinetics were systematically studied. The results showed the steady state theory fitted the continuous CEH-MS kinetics study well and the kinetic model was successfully established with Km of 8.163g/L and Vmax of 0.790g/Lmin. Both the degree of hydrolysis and the conversion rate of protein were significantly affected by substrate concentration. By the kinetic model prediction, the optimum substrate concentration was 10.65g/L. Considering the safe pressures of flushing and backflushing ultrafiltration, the maximum runtime of the continuous CEH-MS reactor was 300min. Under the optimum conditions of substrate concentration of 10.65g/L, Alcalase quantity of 0.51g, temperature of 50°C, pH of 9.0, permeation flux of 0.011L/min, effective volume of 0.4 L, and runtime of 300min, the continuous CEH-MS method showed high conversion rate of protein (65.21%), yield of peptides (34.10g/g), and IC50 of peptides (0.452g/L). The conversion rate of protein and yield of peptides were significantly increased by 63.4% and 7.1 times, and the IC50 of peptides was significantly reduced by 13.6% compared with the traditional EH and offline MS one. Therefore, the continuous CEH-MS reactor is beneficial to the efficient production of ACE-inhibitory peptides from DWGP.

Modeling the QSAR of ACE-Inhibitory Peptides with ANN and Its Applied Illustration

A quantitative structure-activity relationship (QSAR) model of angiotensin-converting enzyme- (ACE-) inhibitory peptides was built with an artificial neural network (ANN) approach based on structural or activity data of 58 dipeptides (including peptide activity, hydrophilic amino acids content, three-dimensional shape, size, and electrical parameters), the overall correlation coefficient of the predicted versus actual data points is R = 0.928, and the model was applied in ACE-inhibitory peptides preparation from defatted wheat germ protein (DWGP). According to the QSAR model, the C-terminal of the peptide was found to have principal importance on ACE-inhibitory activity, that is, if the C-terminal is hydrophobic amino acid, the peptide's ACE-inhibitory activity will be high, and proteins which contain abundant hydrophobic amino acids are suitable to produce ACE-inhibitory peptides. According to the model, DWGP is a good protein material to produce ACE-inhibitory peptides because it contains 42.84% of hydrophobic amino acids, and structural information analysis from the QSAR model showed that proteases of Alcalase and Neutrase were suitable candidates for ACE-inhibitory peptides preparation from DWGP. Considering higher DH and similar ACE-inhibitory activity of hydrolysate compared with Neutrase, Alcalase was finally selected through experimental study.

The use of ultrasound for enzymatic preparation of ACE-inhibitory peptides from wheat germ protein

Abstract The effects of ultrasonic treatment during proteolysis on kinetic characterisation of the hydrolysis of defatted wheat germ protein (DWGP), and on ACE-inhibitory activity of the hydrolysate, were investigated. The effects of ultrasonic pretreatment on the release of peptides with ACE-inhibitory were also studied. The results showed that the value of k A for DWGP hydrolysis under ultrasonic irradiation increased by about 22.2%, and K M decreased about 13.0%, compared with that obtained without ultrasound. Analysis of ACE-inhibitory activity indicated that ultrasound during enzyme treatments had less effect on the ACE-inhibitory activity, while ultrasonic pretreatment caused a 21.0–40.7% increase in ACE-inhibitory activity of DWGP hydrolysate. Analyses of hydrophobicity, microstructure, and amino acid composition revealed that ultrasonic pretreatment could accelerate the release of hydrophobic amino acids from DWGP during enzymatic hydrolysis. In conclusion, ultrasonic treatment during proteolysis could facilitate the enzymatic hydrolysis of DWGP, whereas ultrasonic pretreatment could promote the release of ACE-inhibitory peptides from DWGP during enzymatic hydrolysis.

Optimization of a novel backward extraction of defatted wheat germ protein from reverse micelles

Abstract In this work, a novel backward extraction procedure of defatted wheat germ protein (DWGP) from reverse micelles was explored. Isooctane was recovered by vaporization firstly. Then the remained residue was dissolved in a small amount of KCl solution. The recovery of DWGP was easily performed by the ternary liquid system (acetone: deionized water: isooctane = 15:5:1) precipitation, while most of sulphosuccinic acid bis (2-ethylhexyl) ester sodium salt (AOT) remained in the ternary liquid system. In the end, the precipitation of DWGP was washed with 65% ethanol solution to further remove any residual AOT. The effects of KCl concentration, the amount of KCl solution and pH on the backward extraction efficiency of DWGP were tested. On the basis of single-factor experiments, the optimum backward extraction was achieved by response surface methodology (RSM). When the operation ran under optimized conditions, the backward extraction efficiency of DWGP achieved 80% and the end protein product was completely free of AOT. Industrial relevance This experimental result confirmed that this novel backward extraction method had many advantages on the extraction of protein compared to the traditional backward extraction method (changing the conditions of pH and ionic strength in a fresh aqueous phase). This method increased the backward extraction efficiency of defatted wheat germ protein (DWGP) from 57% to 80%, saved the water resource and offered the possibility of precipitating nearly pure DWGP, completely free of surfactant. On the basis of these advantages, it appears that this novel backward extraction technique may have great potential for being scaled-up to a commercially extraction process of protein.

Protein extraction from defatted wheat germ by reverse micelles: Optimization of the forward extraction

In this work, the forward extraction of defatted wheat germ protein (DWGP) by reverse micelles was studied. The reverse micellar systems were formed by sulphosuccinic acid bis (2-ethylhexyl) ester sodium salt (AOT), isooctane and KCl solution. The effects of AOT concentration, pH, KCl concentration, extraction time, the amounts of defatted wheat germ flour (DWGF), W 0 (the molar ratio of water to surfactant, i.e. W 0 = [H 2O]/[AOT]) and temperature on the forward extraction efficiency of DWGP were tested. On the basis of single-factor experiments, the optimum extraction was achieved by response surface methodology (RSM). The experimental results lead to the conclusion that the highest forward extraction efficiency of DWGP was reached at the AOT concentration 0.06 g/mL, pH 8, KCl concentration 0.1 mol/L, time 30 min, the amounts of DWGF 0.500 g, W 0 25 and temperature 36 °C. Under these conditions, the forward extraction efficiency of DWGP achieved 37%.

ENZYMATIC HYDROLYSIS OF DEFATTED WHEAT GERM BY PROTEASES AND THE EFFECT ON THE FUNCTIONAL PROPERTIES OF RESULTING PROTEIN HYDROLYSATES

Endogenous enzymes of wheat germ were inactivated by heating for 15 min at 105C in an oven. The germ was defatted using supercritical carbon dioxide, smashed and solubilized by enzymatic hydrolysis. The enzyme hydrolysate was continuously stirred under conditions of optimum hydrolysis and centrifuged. Defatted wheat germ protein (DWGP) was obtained when the supernatant was spray-dried. The enzymes were used to enhance the solubilization of protein so as to increase the yield of DWGP. Alcalase and flavourzyme® solubilized 85 and 80% of the protein, respectively, while papain, neutrase and protamex solubilized 73, 66 and 61%, respectively. The functional properties of DWGP solubilized using alcalase were as follows: nitrogen solubility, 74% at pH 6; emulsifying activity, capacity and stability were 64, 62 and 57%, respectively. Water retention of DWGP solubilized using alcalase was 232% at pH 7 and temperature of 70C. DWGP is a potential source of functional protein for possible food applications.

Some nutritional and functional properties of defatted wheat germ protein.

Defatted wheat germ protein (DWGP) was isolated by alkaline extraction at pH 9.5 and subsequent isoelectric precipitation at pH 4.0, and its nutritional and functional properties were studied. The results showed that the amino acid content of defatted wheat germ was as high as 26.793 g/100 g, and the contents of eight essential amino acids were all relatively high. The isoelectric point of DWGP was 4.0. When pH >6.0, the DWGP had high solubility with a nitrogen solubility index of 70%. The emulsifying activity and emulsifying stability of DWGP were similar to those of bovine serum albumin and a little higher than those of casein. DWGP had good foaming capacity, but its foaming stability (FS) was not very good. However, the FS of DWGP can be improved through physical, chemical, or enzymatic methods. Moreover, DWGP had excellent water retention (WR); especially at pH 8.0 and a temperature of 70 degrees C, the WR of DWGP was the highest at 229.4%. DWGP offers is a potential source of functional protein isolate for possible food applications.