Oxidation of proline decreases immunoreactivity and alters structure of barley prolamin

The changes induced by hydrodynamic cavitation treatment in wheat gliadin and celiac-toxic peptides

Hydrodynamic cavitation (HC) is thought weaken the allergenicity of beer gluten proteins. However, the mechanism of action has not been thoroughly studied. In this study, an HC device was used to treat wheat gliadin and two specific celiac-toxic peptides, P1 and P2. FT-IR, MFS, HPLC, and CD were used to monitor the structural characteristics of gliadin and the two peptides. HC reduced the abundance of the coeliac toxic peptides P1 and P2 in solution and the contents of secondary structure β-turns and PPII, which are related to reduced allergen immunoreactivity. This meant that both the primary and secondary structures of P1 and P2 were affected by HC, leading to fewer allergic reactions. This study was focused on the impact of HC on the secondary structures of allergens produced from gluten raw materials, and it has positive implications for reducing product allergenicity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-05973-7.

How does a celiac iceberg really float? The relationship between celiac disease and gluten

Celiac disease (CD) is an autoimmune intestinal disease caused by intolerance of genetically susceptible individuals after intake of gluten-containing grains (including wheat, barley, etc.) and their products. Currently, CD, with "iceberg" characteristics, affects a large population and is distributed over a wide range of individuals. This present review summarizes the latest research progress on the relationship between CD and gluten. Furthermore, the structure and function of gluten peptides related to CD, gluten detection methods, the effects of processing on gluten and gluten-free diets are emphatically reviewed. In addition, the current limitations in CD research are also discussed. The present work facilitates a comprehensive understanding of CD as well as gluten, which can provide a theoretical reference for future research.

Recent development in evaluation methods, influencing factors and control measures for freeze denaturation of food protein

Frozen storage is most widely adopted preservation method to maintain food freshness and nutritional attributes. However, at low temperature, food is prone to chemical changes such as protein denaturation and lipid oxidation. In this review, we discussed the reasons and influencing factors that cause protein denaturation during freezing, such as freezing rate, freezing temperature, freezing method, etc. From the previous literatures, it was found that frozen storage is commonly used to prevent freeze induced protein denaturation by adding cryoprotectants to food. Some widely used cryoprotectants (for example, sucrose and sorbitol) have been reported with higher sweetness and weaker cryoprotective abilities. Therefore, this article comprehensively discusses the new cryopreservation methods and providing comparative study to the conventional frozen storage. Meanwhile, this article sheds light on the freeze induced alterations, such as change in functional and gelling properties. In addition, this article could be helpful for the prolonged frozen storage of food with minimum quality related changes. Meanwhile, it could also improve the commercial values and consumer satisfaction of frozen food as well.

Application of Mass Spectrometry-Based Proteomics to Barley Research

Barley (Hordeum vulgare) is the fourth most cultivated crop in the world in terms of production volume, and it is also the most important raw material of the malting and brewing industries. Barley belongs to the grass (Poaceae) family and plays an important role in food security and food safety for both humans and livestock. With the global population set to reach 9.7 billion by 2050, but with less available and/or suitable land for agriculture, the use of biotechnology tools in breeding programs are of considerable importance in the quest to meet the growing food gap. Proteomics as a member of the "omics" technologies has become popular for the investigation of proteins in cereal crops and particularly barley and its related products such as malt and beer. This technology has been applied to study how proteins in barley respond to adverse environmental conditions including abiotic and/or biotic stresses, how they are impacted during food processing including malting and brewing, and the presence of proteins implicated in celiac disease. Moreover, proteomics can be used in the future to inform breeding programs that aim to enhance the nutritional value and broaden the application of this crop in new food and beverage products. Mass spectrometry analysis is a valuable tool that, along with genomics and transcriptomics, can inform plant breeding strategies that aim to produce superior barley varieties. In this review, recent studies employing both qualitative and quantitative mass spectrometry approaches are explored with a focus on their application in cultivation, manufacturing, processing, quality, and the safety of barley and its related products.

Effects of Cold Jet Atmospheric Pressure Plasma on the Structural Characteristics and Immunoreactivity of Celiac-Toxic Peptides and Wheat Storage Proteins

The present research reported the effects of structural properties and immunoreactivity of celiac-toxic peptides and wheat storage proteins modified by cold jet atmospheric pressure (CJAP) plasma. It could generate numerous high-energy excited atoms, photons, electrons, and reactive oxygen and nitrogen species, including O₃, H₂O₂, •OH, NO₂^- and NO₃^- etc., to modify two model peptides and wheat storage proteins. The Orbitrap HR-LC-MS/MS was utilized to identify and quantify CJAP plasma-modified model peptide products. Backbone cleavage of QQPFP and PQPQLPY at specific proline and glutamine residues, accompanied by hydroxylation at the aromatic ring of phenylalanine and tyrosine residues, contributed to the reduction and modification of celiac-toxic peptides. Apart from fragmentation, oxidation, and agglomeration states were evaluated, including carbonyl formation and the decline of γ-gliadin. The immunoreactivity of gliadin extract declined over time, demonstrating a significant decrease by 51.95% after 60 min of CJAP plasma treatment in vitro. The CJAP plasma could initiate depolymerization of gluten polymer, thereby reducing the amounts of large-sized polymers. In conclusion, CJAP plasma could be employed as a potential technique in the modification and reduction of celiac-toxic peptides and wheat storage proteins.

Variation in the structure and emulsification of egg yolk high-density lipoprotein by lipid peroxide

To further clarify the effect of the oxidation of egg yolk high-density lipoprotein (EYHDL) on the protein structure and emulsification, 2,2'-azobis (2-methylpropionamidine) dihydrochloride (AAPH) was selected as a representative lipid peroxidation-derived peroxyl radical. The results of Raman spectroscopy indicated that, with the increase in the concentration of AAPH, the EYHDL carbonyl content increased significantly and the free sulfhydryl content declined sharply. Circular dichroism spectroscopy and intrinsic fluorescence indicated that exposure of EYHDL to AAPH led to destruction of the orderly structure and reduction of the structural stability. The particle size distribution and zeta potential indicated that the peroxyl radical caused molecular aggregation. Moderate oxidizing conditions can enhance the emulsification of EYHDL, and high-intensity oxidation decreased emulsification. The research results indicated that EYHDL made a significant change in the oxidation system and led to a change in its structure and emulsification, providing a theoretical basis to clarify the EYHDL oxidation mechanism. PRACTICAL APPLICATIONS: Egg yolk powder is prone to emulsification degradation during storage. The emulsification of egg yolk powder is mainly derived from high-density lipoprotein in egg yolk. Moreover, egg yolk powder contains a large amount of lipids, and, during the processing and storage of egg yolk powder, many lipid peroxyl radicals are inevitably generated. Therefore, it is desired to combine the lipid peroxyl radicals generated during the storage of egg yolk powder with the decrease in emulsifiability. In this paper, we first investigated the effects of peroxyl radicals on the structure and emulsifying properties of high-density lipoproteins and provided a theoretical basis to solve the problem that the emulsifiability of egg yolk powder is significantly reduced during storage.

Effects of Ultrasonic-Microwave-Assisted Technology on Hordein Extraction from Barley and Optimization of Process Parameters Using Response Surface Methodology

We investigated the process intensification of ultrasonic-microwave-assisted technology for hordein extraction from barley. Response surface methodology was utilized to optimize the extraction conditions and to analyze the interaction between four selected variables: temperature, microwave power, ultrasonic power, and extraction time. The validated extraction yield of hordein reached 8.84% at 78°C, microwave power 298 W, and ultrasonic power 690 W after 20 min as optimum conditions. Compared with traditional water-bath extraction (4.7%), the ultrasonic-microwave-assisted technology effectively increased the hordein extraction yield and shortened the extraction time. According to the obtained quadratic model (R2 = 0.9457), ultrasonic power and extraction time were the first two significant factors. However, temperature limited the effects of other factors during extraction. SDS-PAGE and scanning electron microscopy were used to identify the hordein extract and to clarify the difference between the two hordein fractions extracted with new and traditional methods, respectively. Ultrasonic-microwave-assisted technology provided a new way to improve hordein extraction yield from barley and could be a good candidate for industrial application of process intensification.

Reactivity of peptides within the food matrix

Numerous biological activities have been reported for peptides or peptide-rich fractions from hydrolyzed food proteins. Some of the properties of peptides include antioxidant, antimicrobial, anti-inflammation, antihypertensive, and immune system modulation. To evaluate the efficacy of peptides in vivo, foods have been used as carrier vehicles. However, there are many molecules in foods that can react or interact with peptides, thereby reducing the bioavailability or bioactivity of these peptides. The Schiff base reactions of peptides with reducing sugars are well established. Peptides can also react with oxidized lipids or reactive oxygen species. Secondary metabolites such as quinones in foods, can react as well with amine or thiol groups of peptides. All these reactions affect the concentration of peptides. This review summarizes and discusses some of the implication of those reactions on the availability of bioactive peptides within the food matrix. PRACTICAL APPLICATIONS: Bioactive peptides possess specific effects on foods like preventing oxidative rancidity. In human, they may lower blood pressure or reduce inflammation. The knowledge on the type of reactions these peptides may encountered when foods are used as transport vehicles is essential. This will prevent variability in intake and ensure proper dosage and reproducible results.