Effect of frozen storage on the foaming properties of wheat gliadin

Components and physicochemical properties of mill streams: Effects on freeze-thaw stability and quality of frozen steamed bread dough

This study investigated the influence of five mill streams on the freeze-thaw (FT) stability of dough and steamed bread quality. The 1M2 stream (1st reduction) exhibited the longest stability time (7.24 min), maximum dough height (36.1 mm), and the highest specific volume (1.93 mL/g) of steamed bread. The 1S stream (1st sizing) had the highest water-extractable arabinoxylan content (0.62 %), which contributed to frozen dough stability and maintained a high specific volume (1.85 mL/g) throughout FT treatment. In contrast, the 3M stream (3rd reduction) showed the shortest stability time (5.83 min) and lowest specific volume (1.39 mL/g). Protein subunit and rheological analyses revealed that higher gliadin content in the 1M2 and 1S streams promoted dough extensibility, facilitating expansion during fermentation and steaming. These results demonstrate the key role of mill stream characteristics in determining dough FT stability and provide valuable insights for the use of specific mill streams in frozen dough.

Regulation of ice crystal growth in frozen dough: From the effect of gluten and starch fractions interaction on water binding - A review

The formation and growth of ice crystals are critical factors affecting the quality of frozen dough. Gluten and starch are the primary components of dough, and their hydration properties and effects on dough structure are crucial in determining the type of ice crystals formed. Gliadins, glutenins, A-type starch, and B-type starch are their refined components, each with distinct hydration properties and impact on dough structure. This review examines the structural properties and hydration properties of protein and starch components in frozen dough, as well as their individual and interactive influences on water absorption and the structural properties of frozen dough. Additionally, it explores changes at different structural levels during the interaction between protein and starch components in frozen dough. The review provides theoretical support for wheat breeding aimed at frozen flour products, ultimately contributing to the improvement of frozen dough quality and final product outcomes.

Unveiling the dynamic interactions of gluten-starch-water in frozen dough: An in-depth review

In recent decades, frozen dough has become an attractive means of preserving and offering the convenience of fresh-tasting foods while retaining their nutritional benefits. However, the frozen dough industry still faces significant challenges related to processing, freezing, and storage that affect the dough's quality and stability during thawing. Understanding the complex interactions between proteins (gluten, glutenin, gliadin, and glutenin macropolymers), starch dynamics (gelatinization and retrogradation), and water distribution-particularly how ice crystals interact with the gluten-starch matrix-is essential for improving frozen dough quality. This review also delves into the rheological properties resulting from the interplay of these components, emphasizing their collective impact on dough texture and stability. Additionally, it explores various freezing mechanisms and innovative strategies to reduce freeze damage, as well as practical challenges in translating theoretical insights into industrial applications. Finally, it proposes future strategies for improving the shelf life and quality of frozen dough by optimizing freezing methods and water distribution. Through a comprehensive synthesis of current literature, this review underscores the critical importance of gluten-starch-water interactions in frozen dough and highlights promising strategies for enhancing product performance and quality.

Oil-water interfacial behaviour of different caseins and stability of emulsions: Effect of micelle content and caseins concentrations

This study aimed to investigate the interfacial behaviour of caseins in different micelle content and its effect on the stability of emulsions, including micellar casein concentrate (MCN), calcium caseinate (CaC) and sodium caseinate (NaC). Results revealed that at high protein concentrations (0.5 %-2.5 %), MCN, CaC and NaC exhibited similar interfacial behaviour as well as unfolding rate constants (k 1 ) of 3.11-3.41 × 10-4 (s-1), 2.96-3.35 × 10-4 (s-1) and 2.75-3.27 × 10-4 (s-1), respectively. The interfacial layer formed was dominated by non-micelles, and microscopic images revealed the thickness of the interfacial layer to be 10-20 nm. By contrast, at low concentrations, the differences in the slope of E-π curves and k 1 indicated that the micelle content of casein affects protein interfacial behaviour and properties and that micellar casein is involved in the formation of the interfacial layer. The formation of large numbers of droplets during emulsion preparation results in a similar low concentration environment. Cryo-TEM showed adsorption of micellar casein in all three casein-stabilised emulsions, and the amount of adsorption was proportional to the micelle content. NaC has faster adsorption and rearrangement rates due to fewer micelles and more non-micelles, so that NaC forms smaller droplets and more stable emulsions than those formed by MCN and CaC within the range of 0.5 % to 2.0 %.

Cereal dietary fiber regulates the quality of whole grain products: Interaction between composition, modification and processing adaptability

The coarse texture and difficulty in processing dietary fiber (DF) in cereal bran have become limiting factors for the development of the whole cereal grain (WCG) food industry. To promote the development of the WCG industry, this review comprehensively summarizes the various forms and structures of cereal DF, including key features such as molecular weight, chain structure, and substitution groups. Different modification methods for changing the chemical structure of DF and their effects on the modification methods on physicochemical properties and biological activities of DF are discussed systematically. Furthermore, the review focusses on exploring the interactions between DF and dough components and discusses the effects on the gluten network structure, starch gelatinization and retrogradation, fermentation, glass transition, gelation, and rheological and crystalline characteristics of dough. Additionally, opportunities and challenges regarding the further development of DF for the flour products are also reviewed. The objective of this review is to establish a comprehensive foundation for the precise modification of cereal DF, particularly focusing on its application in dough-related products, and to advance the development and production of WCG products.

Wheat gliadin hydrolysates based nano-micelles for hydrophobic naringin: Structure characterization, interaction, and in vivo digestion

In this study, enzymatic hydrolysis was used to fabricate wheat gliadin hydrolysates (WGHs) for the encapsulation and protection of naringin. The exposure of hydrophilic amino acids decreased the critical micelle concentration (from 0.53 ± 0.02 mg/mL to 0.35 ± 0.03 mg/mL) and improved solubility, which provided amphiphilic conditions for the delivery of naringin. The hydrolysates with a degree of hydrolysis (DH) of 9 % had the strongest binding affinity with naringin, and exhibited the smallest particle size (113.7 ± 1.1 nm) and the highest encapsulation rate (83.2 ± 1.3 %). The storage, heat and photochemical stability of naringin were improved via the encapsulation of micelles. Furthermore, the micelles made up of hydrolysates with a DH of 12 % significantly enhanced the bioavailability of naringin (from 19.4 ± 4.3 % to 46.8 ± 1.4 %). Our experiment provides theoretical support for the utilization of delivery systems based on water-insoluble proteins.

Determination and Analysis of Composition, Structure, and Properties of Teff Protein Fractions

To develop teff-based food products with acceptable quality, the composition, structure, and properties of teff protein fractions should be better understood. In this study, teff proteins were extracted, and their protein composition, structure, and properties were calculated, analyzed, and compared with those of wheat gliadin and glutenin. Results showed that teff flour contained 9.07% protein, with prolamin as its main protein fraction. The isoelectric points of albumin, globulin, prolamin, and glutelin were at pH 3.6, 3.0, 4.4, and 3.4, respectively. Teff prolamin and glutelin showed a significant difference in amino acids and free energy of hydration compared to wheat gliadins and glutenins. The protein chain length of teff prolamins was smaller than that of wheat gliadins, and teff glutelins lacked high molecular weight glutelin subunits. Teff prolamin had the highest α-helices content (27.08%), whereas no random coils were determined, which is different from wheat gliadin. Teff glutelin had a lower content of β-turn than wheat glutenin, and no α-helices were determined in it. Teff prolamin and glutelin had lower disulfide bond content and surface hydrophobicity. Teff prolamin had significantly higher thermal stability than wheat gliadin, whereas the thermal stability of teff glutelin was significantly lower than that of wheat glutenin.

The Effect of Freeze-Thaw Cycles on the Microscopic Properties of Dumpling Wrappers

Dumplings are a traditional Chinese food welcomed by Chinese people. Research has indicated that process of quick-frozen wheat cultivars and their gliadins are all related to the quality and shelf-life of dumplings. Therefore, the effect of freeze-thaw cycles on the textural properties and microscopic characteristics of two types of quick-frozen dumpling wrappers (Zhaomai and Wenmai 19) and conformation of their gliadins were investigated. Scanning electron microscopy showed that Wenmai 19 dumpling wrappers had apparent damage after the first cycle, but Zhaomai wrappers did not reveal significant changes until the fourth cycle. The particle size distribution in the starch granules of Wenmai 19 wrappers varied in terms of mechanical damage, but Zhaomai delayed or avoided such effects. FT-IR found a loose protein structure of the gliadins. Differential scanning calorimetry showed that gliadins of Wenmai 19 degenerated more than those of Zhaomai. The crosslinking of gliadin and glutenin maintained a high-quality gluten network, thus protecting the gliadin stability from ice crystals. In turn, the gliadin maintained the strength of the gluten network. Therefore, raw flours with high-quality protein networks are more suitable for frozen dumplings. Freeze-thaw cycles dramatically decreased the textural characteristics of dumpling wrappers and the microscopic characteristics of their gliadin proteins. Concerning wheat cultivars with weak gluten, flours with high-quality protein networks are more suitable as raw materials for frozen dumplings.

Relevance of the air-water interfacial and foaming properties of (modified) wheat proteins for food systems

A shift from animal protein- to plant protein-based foods is crucial in transitioning toward a more sustainable global food system. Among food products typically stabilized by animal proteins, food foams represent a major category. Wheat proteins are ubiquitous and structurally diverse, which offers opportunities for exploiting them for food foam and air-water interface stabilization. Notably, they are often classified into those that are soluble in aqueous systems (albumins and globulins) and those that are not (gliadins and glutenins). However, gliadins are at least to an extent water extractable and thus surface active. We here provide a comprehensive overview of studies investigating the air-water interfacial and foaming properties of the different wheat protein fractions. Characteristics in model systems are related to the functional role that wheat proteins play in gas cell stabilization in existing wheat-based foods (bread dough, cake batter, and beer foam). Still, to further extend the applicability of wheat proteins, and particularly the poorly soluble glutenins, to other food foams, their modification is required. Different physical, (bio)chemical, and other modification strategies that have been utilized to alter the solubility and therefore the air-water interfacial and foaming properties of the gluten protein fraction are critically reviewed. Such approaches may open up new opportunities for the application of (modified) gluten proteins in other food products, such as plant-based meringues, whippable drinks, or ice cream. In each section, important knowledge gaps are highlighted and perspectives for research efforts that could lead to the rational design of wheat protein systems with enhanced functionality and overall an increased applicability in food industry are proposed.

Impact of Wheat Arabinoxylan with Defined Substitution Patterns on the Heat-Induced Polymerization Behavior of Gluten

To further depict the interaction mechanism of wheat arabinoxylan (AX) and gluten proteins upon thermal processing, AX was enzymatically tailored with defined substitution patterns and the impact on the heat-induced polymerization behavior of gluten was comparatively studied. The results showed that tailormade AX promoted the formation of glutenin-glutenin and glutenin-gliadin macrocrosslinks upon heating, with the optimal effect detected for AX depleted of Araf of disubstituted Xylp. The tailormade AX, especially AX depleted of monosubstituted Xylp, facilitated the polymerization ability of α-gliadin into glutenin compared with untailored AX. The unfolding process of gluten was partially impeded by AX upon heating, while the tailormade AX promoted the unfolding process. AX could bury Trp and Tyr upon polymerization of glutenin and gliadin and induced the change of the disulfide bridge conformation to a less-stable state, while the effect was alleviated with tailormade AX. The enhanced polymerization with tailormade AX strengthened the gluten network and induced more heterogeneously distributed large protein aggregates.

Aggregation properties and structure of chia seed gum and gluten protein mixtures after freezing storage

Chia seed gum (CSG) plays an important role in the aggregation and structural properties of gluten protein. The experimental results showed that adding 1.0 % CSG increased the freezing rate and shortened the freezing time by 42.3 % compared with gluten without CSG. At the same time, CSG had no significant effect on the composition of the gluten subunit but could better control the change in binding water and delay the structural deterioration caused by the extension of time (30 d). The viscoelasticity of gluten was increased, but only with the addition of 0.2-0.6 % CSG. In addition, it increased the denaturation transition temperature (Tp) and the degradation temperature (Td) of gluten protein to reduce the occurrence of recrystallization and resist pyrolysis. During frozen storage, gluten can form fine ice crystals and inhibit the transformation of α-helices and β-turns to random coils and β-sheets, which is more conducive to long-term frozen storage.

Impact of non-covalent bound polyphenols on conformational, functional properties and in vitro digestibility of pea protein

This study investigated the effects of the non-covalent interaction of pea protein isolate (PPI) with epigallocatechin-3-gallate (EGCG), chlorogenic acid (CA) and resveratrol (RES) on the structural and functional properties of proteins. The conformational changes of the protein structure with EGCG, CA and RES were analyzed using fourier transform infrared spectroscopy. Polyphenols strongly quenched the intrinsic fluorescence of PPI mainly through static quenching. The main interaction force was hydrogen bonding and van der Waals forces for PPI-EGCG, the main interaction force of PPI-CA complex was electrostatic interaction, while RES and PPI were bound by hydrophobic interaction. Free sulfhydryl groups and surface hydrophobicity significantly decreased in PPI after binding with phenolic compounds. The presence of EGCG, CA and RES enhanced the emulsification, foaming and in vitro digestibility of PPI. These results illustrate the potential applications of PPI-polyphenol complexes in food formulations.

Surface tension of native and modified plant seed proteins

The present review, dedicated to Prof. Zbigniew Adamczyk on the occasion of his 70th anniversary, covers the literature data on surface tension and surface compression (dilational) rheology of the adsorbed layers of 21 plant seed proteins (10 leguminous and 11 non-leguminous plants). They are typically analyzed as protein concentrates or isolates, the latter usually obtained by isoelectric precipitation or diafiltration. Despite generally lower solubility, as compared to their animal counterparts (lactoglobulins, caseins, albumins, etc.), the plant seed proteins are also capable of lowering surface tension and forming viscoelastic adsorbed layers. Many seed proteins serve mostly as amino acids reservoirs for the future seedling (storage proteins), hence their instantaneous amphiphilicity is not always sufficient to induce strong adsorption at the aqueous-air interface. They can be, however, conveniently unfolded, hydrolyzed and/or chemically/enzymatically modified to expose more hydrophilic or hydrophobic patches. As shown in numerous contributions reviewed below, the resulting shift of the hydrophilic-lipophilic balance can boost their surface activity to the level comparable to that of many animal proteins or low molecular weight surfactants. An important advantage of the plant seed proteins over the animal ones is their much lower environmental cost and abundance in many plants (e.g. ~40% in sunflower or soybean seeds).

Changes of aggregation and structural properties of heat-denatured gluten proteins in fast-frozen steamed bread during frozen storage

The aim of this research was to clearly clarify the deterioration mechanism of heat-denatured gluten proteins by exploring the change of aggregation and structural characteristics of heat-denatured gluten proteins in the steamed bread system and the steamed gluten system during frozen storage. An increase in the total SDS-soluble protein content was determined, which mainly attributed to the soluble monomer protein content increased. Combined with the significant increase of free sulfhydryl, from 3.12 μmol/g to 5.06 μmol/g and 2.64 μmol/g to 3.29 μmol/g, respectively, it can be inferred that the proteins depolymerization induced by frozen storage was mainly involved in the breakdown of heat-induced glutenin-gliadin disulfide cross-linking. Frozen storage induced the conversion of random coil structure to β-sheet structure and a ruptured microstructure with small fragment was observed. Moreover, the protein of steamed bread system was easier to depolymerize than that of the steamed gluten system.

Interaction between A-type/B-type starch granules and gluten in dough during mixing

To explore the interaction between A/B starch and gluten, the rheological and structural properties of starch-gluten dough with varied A/B starch ratios during mixing were investigated. The G' and G″ values of under- and overdeveloped dough with an A/B starch ratio of 5:5 were higher than those of dough with other ratios and decreased as the A/B starch ratio increased in optimized dough. B starch enhanced extension resistance and dough firmness. Small B starch granules promoted continuous gluten network formation, while large A starch granules readily separate from the gluten network. B starch promoted GMP polymerization. Covalent bonds were the main force involved in A starch-gluten interactions. Hydrophobic interactions were the main force in the under- to optimum-mixing stages, whereas hydrogen and covalent bonds were involved in B starch-gluten interactions from the optimum- to over-mixing stages. A model describing the interactions between gluten and starch components was proposed.

The sol-gel-sol transformation behavior of egg white proteins induced by alkali

In the current study, we found an interesting phenomenon that fresh egg white (EW) undergo the sol-gel-sol transition with alkali treatment. The transformation behavior at different alkalinity (1.5%, 2.0%, and 2.5%) was investigated. As the gel formed, the hardness, lightness, surface hydrophobicity and the total number of identified peptides increased, and then, remarkable reduction when the gel collapsed. Rheological behavior indicated that the viscosity varied with shear rate. Fourier transform infrared spectroscopy (FTIR) showed that β-sheets gradually decreased as the α-helices increased during gel-sol transformation. The quantification of EW peptides analysis revealed that there was no dramatic correlation between the number of identified peptides and alkalinity. It was concluded that the sol-gel-sol transition was strongly dependent on alkali levels, moreover, high concentration promoted gel formation as well as liquefaction. The EW transformation behavior induced by alkali had a significant effect on protein aggregation and denaturation, and further changed physicochemical properties.

Mechanism of enhancing foaming properties of egg white by super critical carbon dioxide treatment

The effect of supercritical carbon dioxide (SCCD) treatment at varying processing time (30-90 min) on foaming and structure properties of egg white protein (EWP) were studied in this paper. The highest foaming ability (107.7%) was obtained after 60 min SCCD treatment, which was 3.6-fold to the control group. Foaming stability kept stable under the processing time of 75 min. Results of surface tension, surface hydrophobicity, rheological properties and particle size indicated that protein was easier to spread to the gas-liquid interface and generate molecular rearrangement. Circular dichroism (CD) and Endogenous fluorescence spectrum showed that there were slight changes on the secondary structure of EWP. The α-helical structure of the protein was destroyed and the particle size became uneven, which indicated that the protein structure became more flexible and loose. The results of this study indicate that SCCD treatment had a potential to be implemented to enhance foaming properties of EWP.

The Molecular Properties of Peanut Protein: Impact of Temperature, Relative Humidity and Vacuum Packaging during Storage

This study aimed to investigate the variation of molecular functional properties of peanut protein isolate (PPI) over the storage process and reveal the correlation between the PPI secondary structure and properties in the storage procedure. After storage, the molecular properties of PPI changed significantly (p < 0.05). Extending storage time resulted in a decrease in free sulfhydryl content, fluorescence intensity, surface hydrophobicity and emulsifying properties, which was accompanied by an increase in protein particle size. The results of infrared spectroscopy suggested the content decline of α-helix and β-sheet, and the content rise of β-turn and random coil. Based on bivariate correlation analysis, it was revealed that surface hydrophobicity and emulsifying activity of PPI was significantly affected by α-helix and by β-turn (p < 0.05), respectively. This research supplied more information for the relationship between the peanut protein’s secondary structure and functional properties over the stored process.

Plant protein-based hydrophobic fine and ultrafine carrier particles in drug delivery systems

For thousands of years, plants and their products have been used as the mainstay of medicinal therapy. In recent years, besides attempts to isolate the active ingredients of medicinal plants, other new applications of plant products, such as their use to prepare drug delivery vehicles, have been discovered. Nanobiotechnology is a branch of pharmacology that can provide new approaches for drug delivery by the preparation of biocompatible carrier nanoparticles (NPs). In this article, we review recent studies with four important plant proteins that have been used as carriers for targeted delivery of drugs and genes. Zein is a water-insoluble protein from maize; Gliadin is a 70% alcohol-soluble protein from wheat and corn; legumin is a casein-like protein from leguminous seeds such as peas; lectins are glycoproteins naturally occurring in many plants that recognize specific carbohydrate residues. NPs formed from these proteins show good biocompatibility, possess the ability to enhance solubility, and provide sustained release of drugs and reduce their toxicity and side effects. The effects of preparation methods on the size and loading capacity of these NPs are also described in this review.

Effects of multiple freeze–thaw treatments on physicochemical and biological activities of egg phosvitin and its phosphopeptides

Multiple freeze–thaw treatments improved the emulsifying and biological activities of egg phosvitin.

Adsorption and Distribution of Edible Gliadin Nanoparticles at the Air/Water Interface

Edible gliadin nanoparticles (GNPs) were fabricated using the anti-solvent method. They possessed unique high foamability and foam stability. An increasing concentration of GNPs accelerated their initial adsorption speed from the bulk phase to the interface and raised the viscoelastic modulus of interfacial films. High foamability (174.2 ± 6.4%) was achieved at the very low concentration of GNPs (1 mg/mL), which was much better than that of ovalbumin and sodium caseinate. Three stages of adsorption kinetics at the air/water interface were characterized. First, they quickly diffused and adsorbed at the interface, resulting in a fast increase of the surface pressure. Then, nanoparticles started to fuse into a film, and finally, the smooth film became a firm and rigid layer to protect bubbles against coalescence and disproportionation. These results explained that GNPs had good foamability and high foam stability simultaneously. That provides GNPs as a potential candidate for new foaming agents applied in edible and biodegradable products.