PREPARATION AND CHARACTERIZATION OF MODIFIED WHEAT GLUTEN BY ENZYMATIC HYDROLYSIS-ULTRAFILTRATION

A comparative study on properties of fish meat hydrolysates produced by an enzymatic process at high pressure

Fish meat hydrolysates (FMHs) were produced from nine fishes at a high pressure of 300 MPa using Flavourzyme 500MG and a protease mixture including Flavourzyme 500MG, Alcalase 2.4L, Protamex, and Marugoto E. The electropherograms of the FMHs showed major far-migrating peptide bands in the vicinity of 5 kDa. The total soluble solids (TSS) and soluble nitrogen content in the FMHs were species-specific and were mostly higher in the case of four-enzyme hydrolysis. Most of the HPLC peptide peaks of the rockfish meat hydrolysates appeared within 10 min of elution, and total free amino acids in the hydrolysate increased abruptly as a result of four-enzyme hydrolysis. The FMHs, which were high in TSS and soluble nitrogen, may be applicable for use in food as seasoning, and could be produced efficiently via the enzymatic process used in this study.

Effectiveness of proteolytic enzymes to remove gluten residues and feasibility of incorporating them into cleaning products for industrial purposes

The development of protocols for efficient gluten elimination is one of the most critical aspects of any allergen management strategy in the industry. The suitability of different proteolytic enzymes to be included in a cleaning formulation that allows the effective elimination of gluten residues was studied. Alcalase (ALC), neutrase (NEUT) and flavourzyme (FLAV) were selected from in silico analysis. The presence of 1% (v/v) of linear alkylbenzene sulphonate (LAS), a common anionic detergent, improved the gluten solubility, which may favour its elimination. Chromatographic analysis showed that the three enzymes studied were able to hydrolyse gluten in the presence of LAS. The highest percentage of short peptides (< 5 kDa) was achieved with ALC, what increases the probability of reducing the gluten antigenicity. Besides, in the presence of ALC and detergent LAS have detected the lowest levels of gluten with ELISA kits. So, effective amounts of ALC and LAS were added to a cleaning formulation, where its proteolytic activity was maintained above 90% after 37 days at 4 °C and 25 °C (under dark). Preliminary validation of the effectiveness enzymatic cleaning formulation to hydrolyse gluten was performed in a ready-to-eat/frozen food company, in which previous episodes of cross-contamination with gluten have been detected. The gluten content decreased to values below 0.125 μg/100 cm² when the cleaning formulation was tested on different surfaces with different cleaning protocols, demonstrating the high suitability of the enzymatic cleaning formulation developed.

Production of wheat gluten hydrolyzates by enzymatic process at high pressure

A novel process for producing wheat gluten enzyme hydrolyzates (WGEHs) was developed, using combinations of Flavourzyme 500MG, Alcalase 2.4L, Protamex, and Marugoto E at the high pressure of 300 MPa, and the resultant hydrolyzates were analyzed for electrophoretic and hydrolytic properties. It was found that multiple-enzyme treatments increased the proportion of the electrophoretic bands less than 5 kDa in the hydrolyzates greatly both at ambient pressure and 300 MPa compared with one-enzyme hydrolysis. The contents of total soluble solids in the WGEHs increased considerably up to 89.75% according to the increase in the number of enzymes used at 300 MPa compared with 79.37% found for the ambient-pressure hydrolysis. These characteristics together with the contents of soluble nitrogen and free amino acids clearly indicated that the high-pressure enzymatic process of this study is an efficient method for obtaining WGEHs with increased degree of hydrolysis.

Exploring the Relationship between Structural and Air-Water Interfacial Properties of Wheat (Triticum aestivum L.) Gluten Hydrolysates in a Food System Relevant pH Range

The relationship between structural and foaming properties of two tryptic and two peptic wheat gluten hydrolysates was studied at different pH conditions. The impact of pH on foam stability (FS) of the samples heavily depended on the peptidase used and the degree of hydrolysis reached. Surface dilatational moduli were in most, but not all, instances related to FS, implying that, although the formation of a viscoelastic protein hydrolysate film is certainly important, this is not the only phenomenon that determines FS. In contrast to what might be expected, surface charge was not a major factor contributing to FS, except when close to the point-of-zero-charge. Surface hydrophobicity and intrinsic fluorescence measurements suggested that changes in protein conformation take place when the pH is varied, which can in turn influence foaming. Finally, hydrolyzed gluten proteins formed relatively large particles, suggesting that protein hydrolysate aggregation probably influences its foaming properties.

Relevance of the Functional Properties of Enzymatic Plant Protein Hydrolysates in Food Systems

Proteins play a crucial role in determining texture and structure of many food products. Although some animal proteins (such as egg white) have excellent functional and organoleptic properties, unfortunately, they entail a higher production cost and environmental impact than plant proteins. It is rather unfortunate that plant protein functionality is often insufficient because of low solubility in aqueous media. Enzymatic hydrolysis strongly increases solubility of proteins and alters their functional properties. The latter is attributed to 3 major structural changes: a decrease in average molecular mass, a higher availability of hydrophobic regions, and the liberation of ionizable groups. We here review current knowledge on solubility, water- and fat-holding capacity, gelation, foaming, and emulsifying properties of plant protein hydrolysates and discuss how these properties are affected by controlled enzymatic hydrolysis. In many cases, research in this field has been limited to fairly simple set-ups where functionality has been assessed in model systems. To evolve toward a more widely applied industrial use of plant protein hydrolysates, a more thorough understanding of functional properties is required. The structure-function relationship of protein hydrolysates needs to be studied in depth. Finally, test model systems closer to real food processing conditions, and thus to real foods, would be helpful to evaluate whether plant protein hydrolysates could be a viable alternative for other functional protein sources.

Partial characterization of ultrafiltrated soy protein hydrolysates with antioxidant and free radical scavenging activities

Soy protein isolate (SPI) was hydrolyzed with Flavourzyme® (SHF) or chymotrypsin (SHC). Hydrolysates were sequencially fractionated by ultrafiltration using different membrane pore sizes (50, 10, and 3 kDa). The antioxidant ability of each hydrolysate protein fraction was tested in a liposome oxidizing system and their free radical scavenging activity (FRSA) was evaluated with the DPPH method (diphenylpicrilhydrazine radical). Molecular weight (MW) distribution, solubility, surface hydrophobicity, and amino acid composition of each SPI hydrolysate fraction were measured and their effect on antioxidant and scavenging activities was established by multivariate correlation. The most active ultrafiltrated peptide fractions (P < 0.05), from SHF and SHC, had of MW of <3 kDa (F3 and C3, respectively). These fractions decreased liposome oxidation by 83.2% and 84.5%, respectively, and also showed the highest FRSA (F3: 21.3% and C3: 24.4%). In addition to molecular size, the antioxidant activity and FRSA of soy protein fractions were related to their amino acid composition, especially to an increased content of Phe and a lowered content of Lys. Also, hydrophobicity of ultrafiltrated peptide fractions was an important characteristic (P < 0.001) associated with their ability to trap free radicals. Ultrafiltered peptide fractions with low MW have a high potential to be used as natural alternatives to prevent lipid oxidation in foods.

Continuous hydrolysis of modified wheat gluten in an enzymatic membrane reactor

BACKGROUND

The low solubility of wheat gluten is one of the major limitations to its use in food processing, and enzymatic hydrolysis has been found to be an effective way to prepare more soluble bioactive peptides from gluten. The aim of this study was to prepare bioactive peptides from modified wheat gluten (MWG) in a continuous enzymatic membrane reactor (EMR) that allowed rapid separation of low-molecular-weight peptides from hydrolysates, thus avoiding the disadvantages of batch reaction such as inefficient use of enzymes, inconsistent products due to batch-to-batch variation, substrate-product inhibition, low productivity and excessive hydrolysis.

RESULTS

Wheat gluten was modified to decrease its lipid and starch contents in order to prevent membrane fouling. The optimal working conditions for Alcalase to hydrolyse MWG in the EMR were a substrate concentration of 20 g L(-1) , an enzyme/substrate ratio of 0.03, an operating pressure of 0.04 MPa, a temperature of 40 °C and a pH of 9. The operating stability of the EMR (including residual enzyme activity, productivity and capacity) was high. The permeate fractions showed antioxidant activities that were mostly due to low-molecular-weight peptides. A simple theoretical kinetic model was successfully applied to the enzymatic hydrolysis of MWG in the EMR.

CONCLUSION

Modification of wheat gluten made the continuous enzymatic membrane reaction more efficient and the EMR proved to be an effective means of producing peptides with particular properties and bioactivities. The permeate fractions (mainly < 1000 Da) were homogeneous and stable and also showed strong antioxidant activities.

Enhanced water absorption of wheat gluten by hydrothermal treatment followed by microbial transglutaminase reaction

BACKGROUND

The water absorption of wheat gluten plays an important role in the weight, volume and form ratio of the breads. In this paper, hydrothermal treatment and microbial transglutaminase (MTGase) modification were combined to improve the water absorption ratio (WAR) of wheat gluten. To understand the increases in WAR, the changes in MTGase reaction after gluten hydrothermal treatment were also investigated.

RESULTS

The sole hydrothermal treatment improved the WAR of gluten. The gluten treated at 100 degrees C for 30 min exhibited the highest WAR value (2.03 g g(-1) gluten) while the WAR of the control without hydrothermal treatment was 1.5 g g(-1) gluten. When gluten was exposed to 90 degrees C for 30 min followed by incubation with MTGase for 5 h, its WAR reached 2.48 g g(-1) gluten. In contrast to control gluten, the surface hydrophobicity of the gluten preheated at 90 degrees C for 30 min increased and fluctuated in a different way during the following MTGase reaction. Meantime, the trend in the amount of soluble protein of preheated gluten was also changed in the progress of MTGase reaction.

CONCLUSION

Hydrothermal treatment followed by MTGase reaction is an efficient approach to improve the WAR of wheat gluten. The analysis of catalytic process, including determination of ammonia, gluten surface hydrophobicity, soluble protein and SDS-PAGE, suggested that hydrothermal pretreatment accelerated the cross-linking reaction and may alter the ratio of gluten deamidation catalysed by MTGase, which induced an increase in the WAR.

Fractionation and characterization of brewers' spent grain protein hydrolysates

Protein hydrolysates with a low and high degree of hydrolysis were enzymatically produced from brewers' spent grain (BSG), the insoluble residue of barley malt resulting from the manufacture of wort in the production of beer. To that end, BSG protein concentrate (BPC), prepared by alkaline extraction of BSG and subsequent acid precipitation, was enzymatically hydrolyzed with Alcalase during both 1.7 and 120 min. Because these hydrolysates contained many different peptides, fractionation of the hydrolysates with graded ammonium sulfate or ethanol precipitation was performed to obtain fractions homogeneous in terms of molecular weight (MW) and hydrophobicity. The emulsifying and foaming capacities of the resultant fractions were determined. MW distributions and surface hydrophobicities of fractions with protein contents exceeding 75% were investigated to determine relationships between technofunctional and physicochemical properties. It was found that the emulsifying and foaming properties are determined by different physicochemical properties of the proteins or peptides. Neither MW nor hydrophobicity alone determines the emulsifying and foaming properties of protein hydrolysates. BSG protein hydrolysates with good emulsifying properties contained less than 40% of fragments with MW exceeding 14 500. Moreover, these hydrolysates had a high surface hydrophobicity. BSG protein hydrolysates with good foaming properties contained less than 10% of material with MW lower than 1700. Hydrolysates with good foaming properties showed low surface hydrophobicities, except for protein hydrolysates with higher levels of protein fragments with MW exceeding 14 500 than of such fragments with MW in a 1700-14 500 range.