Wheat Gluten Hydrolysates Research Articles

FUNCTIONAL PROPERTIES OF ENZYMETICALLY MODIFIED WHEAT GLUTEN

This study was aimed to investigate the potentiality of gluten inclusion into functional foods. The effect of controlled enzymatic hydrolysis on the antioxidant properties of Pepsin, Trypsin, and Papain-assisted wheat gluten hydrolysates have been studied. Lyophilized and dried gluten from durum wheat, commercial durum gluten, and whey proteins were enzymatically hydrolyzed. Based on the antioxidant activity of the obtained hydrolysates, papain hydrolyzed gluten was selected for this study. Functional properties (water holding capacity, emulsifying capacity and stability, foam formation and stability, protein solubility, and oil binding capacity) were investigated for the selected samples. Results revealed that the enzymatic modification improved the functional properties of all selected proteins significantly (P<0.05), with the superiority of the lyophilized and dried wheat gluten in some functional properties especially in alkaline pH and pH 4.

Increased stability and intracellular antioxidant activity of chlorogenic acid depend on its molecular interaction with wheat gluten hydrolysate

Gastrointestinal stability and cell entry efficiency affect the biological accessibility of chlorogenic acid (CGA). Here, wheat gluten hydrolysate (WGH) was proven to improve the stability of CGA during simulated gastrointestinal digestion, promote the intestinal epithelial cell entry efficiency of CGA, and increase its intracellular antioxidant activity. The interaction between WGH and CGA was studied by fluorescence quenching and molecular dynamics simulations. The thermodynamic parameters and molecular dynamics simulation analysis showed that the interaction between WGH and CGA was dependent on hydrogen bonding and hydrophobic and electrostatic interactions. Analyses of the binding sites of WGH showed that Arg12, Arg49, Lys54, and Pro74-Gln89 had strong interactions with CGA molecules. This interaction between CGA and WGH was related to both electrostatic interactions and their respective concentrations. Taken together, the stability, intestinal epithelial cell entry, and antioxidant activity of CGA can be increased by its molecular interactions with WGH.

Identification of novel angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten hydrolysate by the protease of Pseudomonas aeruginosa

Abstract The feasibility of a protease of Pseudomonas aeruginosa (PaproA) to prepare angiotensin I-converting enzyme (ACE) inhibitory peptides from wheat gluten was evaluated according to physiochemical and antihypertensive performances. The wheat gluten hydrolyzed by Alcalase plus PaproA (WGH_APae) to produce small fragments (

Efficient fermentation of very high-gravity worts by brewer's yeast with wheat gluten hydrolysates and their ultrafiltration fractions supplementations

Very high-gravity (VHG) worts (24 °P) supplemented with wheat gluten hydrolysates (WGH) and their ultrafiltration fractions (Mw > 1 kDa and <1 kDa fractions) were used to evaluate their effects on physiological activity and ethanol fermentation of brewer's yeast. The results demonstrated that WGH and their ultrafiltration fractions supplementations could obviously improve the biomass and viability of yeast, and further enhance the sugar utilization and ethanol production under VHG fermentation. Supplementation with Mw < 1 kDa fraction exhibited the maximum biomass (6.90 g/L dry cell), sugar utilization (79.79%) and ethanol concentration (11.88%, v/v) during VHG fermentation. Meanwhile, the addition of Mw < 1 kDa fraction significantly decreased the plasma membrane permeability and intracellular reactive oxygen species (ROS) accumulation, and increased the mitochondrial membrane potential in cells during VHG fermentation. Moreover, Mw < 1 kDa fraction supplementation caused the highest accumulations of intracellular trehalose and glycerol, which were 12.10% and 31.22% higher than the control, respectively. These results illustrated that WGH (especially Mw < 1 kDa fraction) addition was an economic and efficient method to improve physiological activity and ethanol fermentation of brewer's yeast in VHG worts.

Chemical characteristics and antioxidant properties of wheat gluten hydrolysates produced by single and sequential enzymatic hydrolyses using commercial proteases and their application in beverage system

The objective of the study was to determine chemical characteristics and antioxidant properties of wheat gluten hydrolysates (WGH) and utilize the WGH as ingredients in a beverage system. Single (2, 6, 12, and 24 h) and sequential enzymatic hydrolyses (8, 10, and 12 h) were conducted using commercial proteases (Alcalase, Flavourzyme, Protamex, and Neutrase). Yields of all the produced WGH were over 50%. Degree of hydrolysis of the WGH produced by Flavourzyme was the highest, while that of the WGH by Neutrase was the lowest. Sequential enzymatic hydrolysis remarkably decreased the fraction with more than 10 kDa and increased the fraction with less than 500 Da. Contents and composition of free amino acids were affected by the enzyme types and hydrolysis conditions. DPPH radical scavenging activity of the WGH significantly increased with hydrolysis time. The WGH produced by Protamex showed lower turbidity, better thermal stability, and higher solubility, suggesting they may be suitable for beverage development.

Wheat gluten hydrolysates and their fractions improve multiple stress tolerance and ethanol fermentation performances of yeast during very high-gravity fermentation

Wheat gluten hydrolysates (WGH) and their fractions (0%, 20% and 40% ethanol fractions) obtained on XAD-16 were used to examine their effects on multiple stress tolerance and ethanol fermentation performances of yeast during very high-gravity (VHG) fermentation. Results showed that WGH and their fractions supplementations increased significantly osmotic/ethanol stress tolerance, growth and vitality of yeast cells. Supplementation with 40% ethanol fraction resulted in 46.54% and 35.01% of increase in cell membrane integrity, and 42.59% and 21.79% of reduction in intracellular ROS level under osmotic and ethanol stress conditions, respectively. Moreover, WGH and their fractions supplementations also increased physiological activity and ethanol yield of yeast cells under VHG fermentation, and 40% ethanol fraction supplementation caused the maximum biomass and ethanol production during VHG fermentation. These results suggested that WGH supplementation was an efficient and convenient method for improvement of yeast cells with enhanced multiple stress tolerance and ethanol fermentation performances.

Wheat gluten hydrolysate potently stimulates peptide-YY secretion and suppresses food intake in rats.

The study was aimed to compare the satiating effect of various protein hydrolysates in rats and examine the underlying mechanism associated with the satiety hormones. Food intake and portal satiety hormone levels were measured in rats. Enteroendocrine cell-lines were employed to study the direct effect of protein hydrolysates on gut hormone secretions. The results showed that oral preload of wheat gluten hydrolysate (WGH) suppressed food intake greater and longer than other hydrolysates. The portal peptide-YY levels in WGH-treated rats at 2 h and 3h were higher than those in control- and lactalbumin hydrolysate (LAH)-treated rats. In a distal enteroendocrine cell model, WGH more potently stimulated glucagon-like peptide-1 secretion than LAH, and the effect was largely enhanced by pepsin/pancreatin digestion of WGH. These results suggest WGH is potent in activating enteroendocrine cells to release satiety hormones leading to the prolonged suppression of food intake.

Effect of acid deamidation-alcalase hydrolysis induced modification on functional and bitter-masking properties of wheat gluten hydrolysates.

The low solubility of wheat gluten (WG) considerably limits its application. Owing to its high hydrolytic efficiency, alcalase was the protease selected for the enzymatic hydrolysis of WG. The functional properties of WG hydrolysate prepared by alcalase (AHWG) with a hydrolysis degree (DH) of 10% were better than those with DH 5% and DH 15%. The application of AHWG was hindered by its bitterness. To mask the bitterness of AHWG, WG was respectively deamidated with acetic acid, tartaric acid, and citric acid, followed by being hydrolyzed by alcalase to DH 10%. The citric acid deamidation-alcalase hydrolysis WG hydrolysate (CDAH) exhibited the best functional properties. Partial least squares regression analysis results indicated that CDAH exhibited an enhanced bitter-masking property attributable to a high content of umami taste amino acids (glutamic acid and aspartic acid). Thus, CDAH showed the greatest potential as a modified WG product to expand the application of WG.

Potential yeast growth and fermentation promoting activity of wheat gluten hydrolysates and soy protein hydrolysates during high-gravity fermentation

Wheat gluten hydrolysates (WGH) and soy protein hydrolysates (SPH) were used to examine their effects on the growth and fermentation performance of yeast during high-gravity fermentation. Results showed that both the kind and the addition amount of hydrolysates had significant impacts on the biomass, viability, fermentability and ethanol yield of yeast cells. Worts supplemented with WGH and SPH (with the hydrolysis time of 24 h and 12 h, and the addition amount of 1.0% and 0.1%, respectively) increased 5.5% and 12.6% of net cell growth, 0.3% and 1.1% of fermentability, and 19.3% (v/v) and 23.7% (v/v) of ethanol yields, respectively. All these results indicated that both hydrolysates were effective and preferential nitrogen sources for yeast growth and fermentation. The moderate molecular weight distribution, the complexity of nitrogen source and the higher hydrophilic and basic amino acids contents in hydrolysates might be responsible for their specific bioactivity.

Improvement of Multiple-Stress Tolerance and Ethanol Production in Yeast during Very-High-Gravity Fermentation by Supplementation of Wheat-Gluten Hydrolysates and Their Ultrafiltration Fractions.

The effects of wheat-gluten hydrolysates (WGH) and their ultrafiltration fractions on multiple-stress tolerance and ethanol production in yeast during very-high-gravity (VHG) fermentation were examined. The results showed that WGH and WHG-ultrafiltration-fraction supplementations could significantly enhance the growth and viability of yeast and further improve the tolerance of yeast to osmotic stress and ethanol stress. The addition of MW < 1 kDa fractions led to 51.08 and 21.70% enhancements in cell-membrane integrity, 30.74 and 10.43% decreases in intracellular ROS accumulation, and 34.18 and 26.16% increases in mitochondrial membrane potential (ΔΨm) in yeast under osmotic stress and ethanol stress, respectively. Moreover, WGH and WHG-ultrafiltration-fraction supplementations also improved the growth and ethanol production of yeast during VHG fermentation, and supplementation with the <1 kDa fraction resulted in a maximum biomass of 16.47 g/L dry cell and an ethanol content of 18.50% (v/v) after VHG fermentation.

Enzymatically Hydrolyzed Wheat Gluten as a Foaming Agent in Food: Incorporation in a Meringue Recipe as a Proof‐of‐Concept

Replacing animal proteins with plant protein sources in the food industry is desirable from an economic and environmental perspective. Enzymatic hydrolysis serves as a tool to improve the foaming properties of water-insoluble wheat gluten proteins. We conclude that wheat gluten hydrolysates can be a valid functional alternative for egg white proteins in meringues, and possibly other food systems.

Identification of food-derived peptides in human blood after ingestion of corn and wheat gluten hydrolysates

Bioactive peptides in the body after ingestion of plant protein hydrolysates have been speculated but not identified. We aimed to establish an approach to identify small amounts of food-derived peptides in humans after ingestion of non-extracellular matrix protein hydrolysates. Corn and wheat gluten hydrolysates were digested using pancreatin and leucine aminopeptidase; the resultant peptides were identified via size-exclusion chromatography and reverse-phase HPLC-tandem mass spectrometry (MS/MS). Structures of indigestible peptides were confirmed via LC-MS/MS in multi-reaction monitoring mode. All indigestible peptides in the exopeptidase digest were diprolyl and di- and tripyroglutamyl peptides. Blood collected from healthy volunteers (n = 4) before and after ingestion of 9 g of the hydrolysates was assessed for the indigestible peptides via LC-MS/MS. Six peptides (Pro-Ala, Pro-Gly, Pro-Gln, pyroGlu-Pro, pyroGlu-Leu-Pro, and pyroGlu-Gln-Pro) significantly increased in human plasma up to 10–100 nM compared to the baseline. This may hence be a powerful tool for identifying foodderived peptides in blood.

Nanomagnetic wheat gluten hydrolysates a new carrier for nanoimmobilization of inulinase

Functionalized magnetic nanoparticles are effective enzyme carriers since they have several advantages such as easily separation under external magnetic fields as well as reusability of enzymes. In this study, it was tried to prepare a composite nanoparticle with Fe3O4 nanoparticles and wheat gluten hydrolysate nanoparticles for utilizing in biocatalyst production. Firstly, Fe3O4 nanoparticles were synthesized by chemical co-precipitation. Since these nanoparticles are easily aggregated, surface coating procedure was used. These nanoparticles were coated by wheat gluten hydrolysates (WGHs) using glutaraldehyde as crosslinking agent. WGHs were prepared by enzymatic hydrolysis of wheat gluten by endopeptidases with degree of hydrolysis (24.3%) and then, by desolvation method using ethanol as a desolvating agent. FE-SEM images and DLS analysis showed that Fe3O4 nanoparticles have spherical morphology with 30–40 nm in diameter. Also, wheat gluten hydrolysates were ranged 100–150 nm and their zeta potential was around −29 mV. It should be noted that the size of nanocomposite particles were about 120–160 nm. Inulinase was covalently and successfully immobilized through gluteraldehyde on Fe3O4@WGH nanoparticles. Moreover, The results implied that, the enzyme was loaded up to 75% onto functionalized nanoparticles.

Wheat gluten hydrolysates separated by macroporous resins enhance the stress tolerance in brewer’s yeast

Wheat gluten hydrolysates (WGH) were used to examine their adsorption–desorption kinetics and thermodynamics characteristics on six macroporous resins, and their effects on the stress tolerance in brewer’s yeast. Results showed that the pseudo second-order kinetics, Langmuir and Freundlich model could illuminate the adsorption mechanism, and the adsorption process was physical, spontaneous and exothermic. The 40% ethanol fraction separated by XAD-16 resin improved significantly the ethanol tolerance and the viability of brewer’s yeast, while the 0% ethanol fraction separated by XAD-16 resin increased obviously the osmotic stress tolerance and the viability of brewer’s yeast. Results from scanning electron microscopy showed that both these WGH fractions could increase budding rate and maintain normal morphology of yeast cells under various environmental stress. Thus, WGH separated by macroporous resin could be used in high gravity brewing to enhance the ethanol and osmotic stress tolerance in brewer’s yeast.

Inulin hydrolysis by inulinase immobilized covalently on magnetic nanoparticles prepared with wheat gluten hydrolysates

Inulinase can produce a high amount of fructose syrup from inulin in a one-step enzymatic process. Inulinase from Aspergillus niger was immobilized covalently on Fe3O4 magnetic nanoparticles functionalized with wheat gluten hydrolysates (WGHs). Wheat gluten was enzymatically hydrolyzed by two endopeptidases Alcalase and Neutrase and related nanoparticles were prepared by desolvation method. Magnetite nanoparticles were coated with WGHs nanoparticles and then inulinase was immobilized onto it using glutaraldehyde as crosslinking agent. Parallel studies employing differential scanning calorimetry and field emmision scanning electron microscopy were carried out to observe functional and structural variations in free inulinase during immobilization. Optimum temperature of immobilized inulinase was increased, while, pH and Km values were decreased compared to free enzyme. Overall, a 12.3 folds rise was detected in enzyme half-life value after Immobilization at 75 °C and enzyme preserved 70% of its initial activity after 12 cycles of hydrolysis with 75% of enzyme loading.

Effects of wheat gluten hydrolysates fractionated by different methods on the growth and fermentation performances of brewer's yeast under high gravity fermentation

Summary Wheat gluten hydrolysates (WGH) were fractionated through ultrafiltration membrane with molecular weight (Mw) cut-off of 3 kDa and ethanol precipitation, respectively. WGH and their fractions were used to examine their effects on the growth and fermentation performances of brewer's yeast under high gravity fermentation. Results showed that WGH and their fractions exhibited significant differences in biomass accumulation, viability, ethanol yield, free amino nitrogen and sugar consumptions under high gravity fermentation. Compared to WGH, the fractions with Mw < 3 kDa and the supernatant of WGH treated with ethanol precipitation showed better fermentation performance for brewer's yeast. The relatively lower molecular weight and the higher levels of Leu, Lys, His and Arg in these two fractions might be responsible for their bioactivity for brewer's yeast. Thus, both ultrafiltration and ethanol precipitation could be used as efficient methods for enriching peptides with significant growth- and fermentation-promoting activity for brewer's yeast under high gravity fermentation.

Controlled enzymatic hydrolysis for improved exploitation of the antioxidant potential of wheat gluten

The aim of the study was to find the optimal operational and process parameters for the enzymatic hydrolysis of wheat gluten in a batch stirred bioreactor regarding both degree of hydrolysis and antioxidant capacity of the obtained hydrolysates. It appeared that impeller geometry and agitation speed influenced the mass transfer resulting in enhanced gluten hydrolysis. The highest initial reaction rate (0.83 ± 0.02 min−1) and degree of hydrolysis (30.47%) were achieved with the pitched four-bladed impeller and agitation speed of 350–450 rpm, conditions which provided proper balance between requirements for adequate mass/heat transfer and low shear stress. The impact of other process conditions including gluten concentration, temperature, pH and enzyme-gluten (E/S) ratio on the enzymatic reaction was investigated by applying a Box-Behnken experimental design from the viewpoint of the degree of hydrolysis (DH) and antioxidant activity. Three models obtained allowed calculation of the hydrolysis degree, and both 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ABTS (2,2′-azino-bis (3-ethylbenzothiazoline-6-sulpfonic acid) radical scavenging activity from a given set of reaction conditions with good predictability. The statistical analysis showed that each variable had a significant effect on degree of hydrolysis and the antioxidant capacity of both tested systems. Hydrolysis up to around DH 15% improved DPPH radical scavenging activity, while excessive hydrolysis worsened it. The ABTS activity of the hydrolysates was not associated with the DPPH activity nor with the DH, revealing that it was not possible to fulfill all desirable quality requirements (maximum degree of hydrolysis and protein yield, maximum DPPH and ABTS scavenging activities) by using the same reaction conditions. Overall, the study might contribute to approve wheat gluten, a by-product of wheat starch industry, as an accessible and cheap source of bioactive compounds for the development of novel nutraceuticals, cosmetics and drugs.

Production of a novel wheat gluten hydrolysate containing dipeptidyl peptidase-IV inhibitory tripeptides using ginger protease.

Wheat gluten is a Pro-rich protein complex comprising glutenins and gliadins. Previous studies have reported that oral intake of enzymatic hydrolysates of gluten has beneficial effects, such as suppression of muscle injury and improvement of hepatitis. Here, we utilized ginger protease that preferentially cleaves peptide bonds with Pro at the P2 position to produce a novel type of wheat gluten hydrolysate. Ginger protease efficiently hydrolyzed gluten, particularly under weak acidic conditions, to peptides with an average molecular weight of<600Da. In addition, the gluten hydrolysate contained substantial amounts of tripeptides, including Gln-Pro-Gln, Gln-Pro-Gly, Gln-Pro-Phe, Leu-Pro-Gln, and Ser-Pro-Gln (e.g. 40.7mg/g at pH 5.2). These gluten-derived tripeptides showed high inhibitory activity on dipeptidyl peptidase-IV with IC50 values of 79.8, 70.9, 71.7, 56.7, and 78.9μM, respectively, suggesting that the novel gluten hydrolysate prepared using ginger protease can be used as a functional food for patients with type 2 diabetes.

Air-water interfacial properties of enzymatically hydrolyzed wheat gluten in the presence of sucrose

Enzymatically hydrolyzed wheat gluten proteins may be a valuable alternative to animal proteins as foaming agents in food. Studies of the air-water (A-W) interfacial properties of such hydrolysates in aqueous solutions contribute to the understanding of their functionality in food systems. We here studied the A-W interfacial characteristics of wheat gluten hydrolysates (GHs) in the absence and presence of sucrose. Sucrose increased (P < 0.05) the foaming capacity, which is the initial amount of foam formed, of GHs. This is probably related to an increased affinity of GHs for the A-W interface in the presence of sucrose, as could be observed by higher (P < 0.05) rates of diffusion to and adsorption at the A-W interface of the GH constituents in sucrose solution compared to those in water. Furthermore, the surface dilatational moduli of GH protein films at A-W interfaces were in most cases higher (P < 0.05) in a sucrose solution than in water. The latter could only partly be related to differences in foam stability. Surface hydrophobicity and intrinsic tryptophan fluorescence measurements revealed that protein conformational changes in the presence of sucrose might be at the basis of the observed differences. Another possibility is that the hydrophilic sucrose molecules in the bulk cause the more hydrophobic protein molecules to concentrate at the interface, more so than in water. In conclusion, it is crucial to investigate the foaming of plant protein hydrolysates in media more complex than water, as other non-surface-active food ingredients alter their interfacial behavior.

In-situ and real-time monitoring of enzymatic process of wheat gluten by miniature fiber NIR spectrometer

The degree of hydrolysis (DH), peptide content and angiotensin I-converting enzyme (ACE) inhibitory activity of hydrolysates are the three most important indexes for process control in proteins enzymatic hydrolysis and ACE inhibitory peptides preparation. In this study, a miniature fiber optical spectrometer in conjunction with multivariate analysis for in-situ and real-time monitoring of the parameters (DH, peptide content and ACE inhibitory activity) in wheat gluten (WG) hydrolysis process. Synergy interval partial least square (Si-PLS) algorithm was performed to variables selection and the regression model was calibrated. The performance of a model was evaluated by the correlation coefficient (Rp) and the root mean square error (RMSEP) in the prediction set. The results showed that Rp=0.9270, RMSEP=1.73% for DH; Rp=0.9673, RMSEP=0.79mg/ml for peptide content; Rp=0.9507, RMSEP=5.12% for ACE inhibitory. This work demonstrated that miniature fiber optical spectrometer combined Si-PLS model can be used as an alternative method for in-situ and real-time monitoring the enzymatic process of WG.