Influence of Maillard reaction extent on acid induced gels of whey proteins and dextrans

Structural and functional properties of Maillard-reacted casein phosphopeptides with different carbohydrates

This study used glucose, fructose, maltose and dextran to explore the effects of different carbohydrates on the Maillard reaction of casein phosphopeptides (CPP). The color parameter results showed that heating time from 1 to 5 h led to brown color, which was consistent with the observed increased in browning intensity. Fourier transform infrared spectroscopy results verified that four carbohydrates reacted with CPP to produce Maillard conjugates. Fluorescence spectroscopy showed that the Maillard reaction changed the tertiary structure of CPP by decreasing the intrinsic fluorescence intensity and surface hydrophobicity compared with the CPP-carbohydrate mixture. At the same time, the Maillard reaction effectively improved the emulsifying properties, reducing power and DPPH radical scavenging activity of CPP. Furthermore, this study also found that glucose and fructose improved CPP more than maltose and dextran. Therefore, monosaccharides have good potential in modifying CPP via the Maillard reaction.

Graphical Abstract

Effect of ultrasound-assisted Maillard reaction on glycosylation of goat whey protein: Structure and functional properties

Goat whey protein (GWP) has a rich amino acid profile and good techno-functional attributes but still has limited functional performance for certain applications. This study introduces an innovative ultrasound-assisted Maillard reaction to enhance GWP's functional properties by conjugating it with either gum Arabic (GA) or citrus pectin (CP). Sonication accelerated the Maillard reaction, and the glycosylation of GWP was significantly enhanced after optimization of the conjugation conditions. Gel electrophoresis examination verified the creation of GWP-polysaccharide conjugates, while scanning electron microscopy analysis revealed structural modifications caused by polysaccharide grafting and sonication. The use of ultrasound in the Maillard reaction notably enhanced the solubility, foaming capacity, and emulsifying attributes of the GWPs. Among the conjugates, the GWP-GA ones exhibited the best functional properties. Our findings suggest that this approach can notably improve the functional attributes of GWPs, thus broadening their potential uses in the food sector and beyond.

Constructing network structures to enhance stability and target deposition of selenium nanoparticles via amphiphilic sodium alginate and alkyl glycosides

Dietary selenium (Se) supplementation has recently received increasing attention; however, Selenium nanoparticles (SeNPs) exhibit poor stability and tend to aggregate in aqueous solution. Therefore, enhancing the stability of SeNPs and their effective delivery to plants remain challenging. In this study, sodium alginate (SA) and lysozyme (LZ) were reacted via the wet-heat Maillard reaction (MR) to obtain amphiphilic alginate-based polymers (SA-LZ). Alkyl glycosides (APG) were introduced into SA-LZ to enhance the deposition of SeNPs in leaves. Thus, a renewable and degradable polysaccharide-based material (SA-LZ/APG) loaded with Se formed an amphiphilic alginate-based-based shell with a Se core. Notably, the encapsulation of SeNPs into a polysaccharide base (SA-LZ/APG) increased the stabilization of SeNPs and resulted in orange-red, zero-valent, monoclinic and spherical SeNPs with a mean diameter of approximately 43.0 nm. In addition, SA-LZ/APG-SeNPs reduced the interfacial tension of plant leaves and increased the Se content of plants compared to the blank group. In vitro studies have reported that SA-LZ/APG-SeNPs and SA-LZ-SeNPs have significantly better clearance of DDPH and ABTS than that of APG-SeNPs. Thus, we believe that SA-LZ/APG is a promising smart delivery system that can synergistically enhance the stability of SeNPs in aqueous solutions and improve the bioavailability of Se nutrient solutions.

Enhancement mechanism of glycation with l-arabinose and xylose on texture properties of silver carp mince gel

BACKGROUND

Glycation is a green processing technology. Based on our previous studies, glycation with l-arabinose and xylose was beneficial to enhance the texture properties of silver carp mince (SCM) gels. However, the possible enhancement mechanism remained unclear. Therefore, in this study, SCM gels with different types of reducing sugar (glucose, l-arabinose, and xylose) were prepared based on our previous study. The possible mechanism of texture enhancement of SCM gels was analyzed by investigating the changes in water distribution, protein structures, and microstructure in the gel system.

RESULTS

The glycation of l-arabinose and xylose enhanced the hardness, cohesiveness, chewiness, and resilience of SCM gels. Hardness increased from 1883.04 (control group) to 3624.54 (l-arabinose group) and 4348.18 (xylose group). Low-field nuclear magnetic resonance (LF-NMR) showed that glycation promoted the tight binding of immobilized water to proteins. Raman spectroscopic analysis showed that glycation increased the surface hydrophobicity and promoted the formation of disulfide bonds. Scanning electron microscopy (SEM) showed that glycation promoted the formation of uniform and dense three-dimensional network structure in SCM gels.

CONCLUSION

In summary, glycation enhanced the binding ability of immobilized water to proteins, improved the surface hydrophobicity, promoted the formation of disulfide bonds, and led to a more uniform and dense gel network structure of proteins, thus enhancing the texture properties of SCM gels. This research provided a theoretical basis for a better understanding of the mechanism of the effect of glycation on the quality of gel products and also provided technical support for the application of l-arabinose and xylose in new functional gel foods. © 2024 Society of Chemical Industry.

Enhancing Stability and Antioxidant Activity of Resveratrol-Loaded Emulsions by Ovalbumin-Dextran Conjugates

A reliable strategy for improving the stability and shelf life of protein-stabilized systems is by covalently attaching the protein onto a polysaccharide. In this study, ovalbumin (OVA) was modified with dextran (DEX) of different molecular weights by the Maillard reaction, and was used to enhance the stability of emulsions loaded with resveratrol. The surface hydrophobicity, thermal stability, and FT-IR spectroscopy of the OVA-DEX conjugates were evaluated. The results showed that the surface hydrophobicity of OVA decreased, while the thermal stability of OVA was significantly improved after DEX covalent modification. The OVA-DEX1k-stabilized emulsion exhibited high encapsulation efficiency of resveratrol, with the value of 89.0%. In addition, OVA-DEX was considerably more effective in droplet stabilization against different environmental stresses (heat, pH, and ionic strength). After 28 days of storage at 25 °C, the OVA-stabilized emulsion showed faster decomposition of resveratrol, whereas the OVA-DEX-conjugate-stabilized emulsion had approximately 73% retention of resveratrol. Moreover, the antioxidant activity of resveratrol-loaded emulsions stabilized by OVA-DEX was higher during storage under different temperatures. These results proved that the OVA-DEX conjugates had the potential to form stable, food-grade emulsion-based delivery systems against environmental stresses, which strongly supports their potential in the field of food and biomedical applications.

Study on the structural characteristics and emulsifying properties of chickpea protein isolate-citrus pectin conjugates prepared by Maillard reaction

Chickpea protein isolate (CPI) typically exhibits limited emulsifying properties under various food processing conditions, including pH variations, different salt concentrations, and elevated temperatures, which limits its applications in the food industry. In this study, CPI-citrus pectin (CP) conjugates were prepared through the Maillard reaction to investigate the influence of various CP concentrations on the structural and emulsifying properties of CPI. With the CPI/CP ratio of 1:2, the degree of graft reached 35.54 %, indicating the successful covalent binding between CPI and CP. FT-IR and intrinsic fluorescence spectroscopy analyses revealed alterations in the secondary and tertiary structures of CPI after glycosylation modification. The solubility of CPI increased from 81.39 % to 89.59 % after glycosylation. Moreover, freshly prepared CPI emulsions showed an increase in interfacial protein adsorption (70.33 % to 92.71 %), a reduction in particle size (5.33 μm to 1.49 μm), and a decrease in zeta-potential (-34.9 mV to -52.5 mV). Simultaneously, the long-term stability of the emulsions was assessed by employing a LUMiSizer stability analyzer. Furthermore, emulsions prepared with CPI:CP 1:2 exhibited excellent stability under various environmental stressors. In conclusion, the results of this study demonstrate that the glycosylation is a valuable approach to improve the emulsifying properties of CPI.

Stability of a novel glycosylated peanut protein isolate delivery system loaded with gallic acid

To overcome the shortcomings of gallic acid (GA) application, a novel glycosylated PPI delivery system was prepared for the first time in this study using the interaction between peanut protein isolate (PPI) and GA. The effects of glycosylation on the structural and functional properties of PPI and the functional properties of nanoparticles were investigated. The optimal nanoparticles were prepared at a mass ratio 1:3 of glycosylated PPI to GA with a particle size of 338.351 ± 18.823 nm and a PDI of 0.222 ± 0.039. Hydrophobic interactions were the main force maintaining the nanoparticle structure. The nanoparticles remained stable when exposed to different environmental factors. In addition, the DPPH and ABTS radical scavenging activities of nanoparticle-embedded GA were 35.94 ± 3.24 % and 62.59 ± 5.07 % after 108 h, which were significantly higher than those of the free GA group (P < 0.05). This study is important for developing GA and hydrophilic polyphenol delivery systems.

Influence of dextrans on the textural, rheological, and microstructural properties of acid-induced faba bean protein gels

Dextrans (DXs) are a group of natural polysaccharides with different branching patterns. Previous studies examining the effects of DXs on plant protein gels have only focused on α-(1 → 3)-branched DXs. Here, we compared the effects of α-(1 → 3)-branched DX L12 with those of two α-(1 → 2)-branched DXs on the properties of glucono-δ-lactone-induced faba bean protein isolate (FPI) gels. DX L12 showed stronger effects in decreasing gel hardness and enhancing gel viscoelasticity than the other two DXs. Moreover, DX L12 decreased the water-holding capacity of FPI gels, whereas the other DXs enhanced it. Microstructural analysis revealed that DX addition promoted phase separation during gel formation. However, FPI/L12 gels exhibited greater phase separation than the other two gels and contained larger void spaces. These differences could be attributed to the varying water adsorption and self-association properties of the DXs. These findings could guide the application of DX in the tailored preparation of plant protein gels.

Insight on the emulsifying mechanisms of low-salt type emulsions stabilized by Maillard conjugates: Myofibrillar protein peptide-dextrin with different degrees of hydrolysis

In this study, we investigated the emulsifying properties and stabilisation mechanisms of low-salt type emulsions stabilised by MP-base conjugates prepared via the Maillard reaction between DX and MP peptides (MPP). Mild hydrolysis by Alcalase promoted a well-controlled Maillard reaction in dry conditions. Combining hydrolysis and Maillard reaction caused the dissociation and unfolding of highly aggregated MP structures; the ordered secondary structure was lost and the hydrophobic residue was exposed. The MPP-DX conjugates greatly improved the emulsifying ability and stability in the low-salt system; the resulting emulsion exhibited a small droplet size and homogeneous microstructure with desirable storage stability. Further, the glycation products were found to effectively suppress gravity-induced creaming. The MPP-DX glycoconjugate developed with 5% DG, exhibiting strongest flocculation and creaming stability, was determined as the optimal emulsifying agent for low-salt type emulsions. These findings provide a theoretical basis for developing low-salt meat products and/or emulsion-based foods.

Physicochemical and functional characteristics of glycated collagen protein from giant salamander skin induced by ultrasound Maillard reaction

Chinese giant salamander skin collagen (CGSSC) was successfully conjugated with glucose (Glu)/xylose (Xy) by ultrasound Maillard reaction (MR) in nature deep eutectic solvents (NADES). The effects of ultrasound and reducing sugar types on the degree graft (DG) of MR products (MRPs), as well as the influence of DG on the structure and functional properties of MRPs were investigated. The results indicated that the ultrasound assisted could markedly enhance the MR of CGSSC, and low molecular weight reducing sugars were more reactive in MR. The ultrasound MR significantly changed the microstructure, secondary and tertiary structures of CGSSC. Moreover, the free sulfhydryl content of MRPs were increased, thus enhancing the surface hydrophobicity, emulsifying properties and antioxidant activity, which were positively correlated with DG. These findings provided theoretical insights into the effects of ultrasound assisted and different sugar types on the functional properties of collagen induced by MR.

Effects of caramelization and Maillard reaction products on the physiology of Saccharomyces cerevisiae

The thermal treatment the sugarcane juice undergoes during its processing alters the medium's chemical composition through the so-called Maillard reactions and its products, which can affect the alcohol-producing yeast's physiology in steps following the processing. This study aims to describe and characterize the reactivity of the primary amino acids present in sugarcane with sucrose, as well as demonstrate the physiological effects of the reaction's products on the yeast Saccharomyces cerevisiae. The main amino acids in sugarcane (glutamine, asparagine, and aspartic acid) were chosen to be reacted with sucrose under similar conditions to the industrial sugarcane processing (pH 5 and temperature 100-120 °C). The physiological effect of Maillard and caramelization reaction on the S. cerevisiae CEN.PK-122 and PE-2 strains were tested in microplate experiments using a modified mineral media containing both the reacted and unreacted amino acid-sucrose systems and four modified synthetic molasses media. The results have shown that the presence of any amino acids drastically increases product formation. Furthermore, among the amino acids, aspartic acid was the most reactive. Meanwhile, asparagine and glutamine had similar results. In S. cerevisiae physiology, aspartic acid had the most significant effect on culture growth by reducing the maximum specific growth rate and optical density. The increase in the Maillard product concentration for synthetic molasses also evidenced the inhibitory effect on yeast growth compared to media in the absence of these products. We conclude that this initial investigation clarifies the inhibitory effect of the Maillard products on yeast physiology.

Effect of Oat β-Glucan on the Structure and Properties of Soybean Protein Isolate During Maillard Reaction

Maillard reaction (MR) with oat β-glucan changed the structure of soybean protein isolate (SPI), further leading to the enhancement of its functional properties. SPI was unfolded by MR, and the SPI conjugates with high molecular weight were identified. The water solubility of SPI was improved by cross-linking with hydrophilic β-glucan, while the hydrophobicity also increased along with the unfolding of the SPI. Cross-linking with β-glucan elevated the viscosity of SPI, thus enhancing viscosity-related physiological activities, including bile acid binding ability, fat binding capacity, and hypoglycemic activity, and the functional properties increased as the βG content involved in MR increased.

Utilization of different by-products to produce nutritionally rich gelled products

Yellow corn cooking water with yerba mate (Ilex paraguariensis) extract, obtained as a by-product of snack manufacture, was combined with whey protein concentrate (7 g/100 g), flaxseed (Linum usitatissimum L.) flour (2 g/100 g), and honey (8 g/100 g) to obtain different gelled products. The effect of the composition on the physicochemical parameters was analyzed. Flaxseed flour was added directly or with a previous pre-heating, and, in both cases, it increased the solid behavior of gels. On the contrary, honey increased the gel liquid-like behavior, and both ingredients modified the color of the gels. Elastic and loss modulus decreased after storage for 7 and 14 days. Some of the textural parameters also changed during storage. Principal component analysis and cluster analysis revealed three groups of formulations according to their composition, and those samples containing only flaxseed flour were best described with the textural and rheological parameters. Yerba mate extract, mainly, flaxseed flour, and honey increased the phenolic composition of gels but decreased the sensory acceptability, despite the sweetness of honey. A variety of gelled products with different textures and flavors was obtained using by-products of the food industry. These gels could be used either for dessert formulations or as a matrix for gelled products.

Developing radio frequency (RF) heating protocol in packed tofu processing by computer simulation

Packed tofu was produced by reheating the mixture of preheated soymilk and coagulant in a sealed container. This study aimed to replace the conventional heating method with RF heating during the reheating of soymilk for packed tofu production. In this study, dielectric properties (DPs), thermal properties (TPs), and rheological properties of soymilk were determined. A mathematical model was developed to simulate the RF heating process of soymilk to determine the appropriate packaging geometry. Water holding capacity (WHC), texture analysis, color measurement, and microstructure observation were performed to evaluate the quality of RF-heated packed tofu. Results showed that soymilk added with Glucono-Delta-Lactone (GDL) coagulated at the temperature above 60 °C, and the loss factor (ε″) was slightly reduced when soymilk was converted to tofu at coagulation temperature. Based on the simulation results, the cylindrical vessel (φ50 mm × 100 mm) was chosen as the soymilk container for desired heating rate (5.9 °C/min) and uniformity (λ = 0.0065, 0.0069, 0.0016 for top, middle, and bottom layers). The texture analysis revealed that the hardness and chewiness of packed tofu prepared by RF heating were enhanced (maximum 1.36 times and 1.21 times) compared with commercial packed tofu, while the springiness were not significantly changed. Furthermore, the denser network structure was observed inside RF-heated packed tofu by SEM. These results indicated that packed tofu prepared by RF heating was of higher gel strength and sensory quality. RF heating has the potential to be applied in packed tofu production.

Ultra-stable high internal phase emulsions stabilized by protein-anionic polysaccharide Maillard conjugates

This paper reports the production of O/W high internal phase emulsions (HIPEs) using protein-anionic polysaccharide Maillard conjugates. First, Maillard conjugates were prepared from soy protein isolate (SPI) or sodium caseinate (SC) proteins and Alyssum homolocarpum seed gum (AHSG) or kappa-carrageenan (kC) polysaccharides. The conjugation process was confirmed and monitored by UV spectrophotometry, Fourier transform infrared, circular dichroism, fluorescence spectroscopies, and differential scanning calorimetry. Under the optimized reaction conditions, SC-AHSG conjugates exhibited the highest glycation degree and emulsifying properties. Next, HIPEs were made using the optimized conjugates, and their microstructure, droplet size, and physical stability were evaluated. The emulsion stabilized by SC-AHSG conjugate had the lowest mean droplet size (363.07 ± 34.56 nm), orderly-packed oil droplets with monomodal distribution, the highest zeta potential (-27.70 ± 0.70 mV), high storage stability (no creaming or oil-off) and was ultra-stable against environmental stresses. Results of this research are helpful for development of emulsion-based foods with novel functionality.

Development of fish gelatin-chitooligosaccharide conjugates through the Maillard reaction for the encapsulation of curcumin

The poor water solubility, bioavailability and stability of bioactive compounds have become the bottleneck restricting their wide application, thus developing a functional carrier to realize the efficient encapsulation and activity improvement of active hydrophobic substances has become a research hotspot. In this work, a functional glycosylated fish gelatin (called FG-COS conjugates) carrier based on fish gelatin (FG) and chitooligosaccharide (COS) via Maillard reaction was developed. The functional carrier exhibited good antioxidant activity and high encapsulation of curcumin (Cur). Enhanced antioxidant effect of Cur loaded in FG-COS conjugates (called FG-COS-Cur nanoparticles) was achieved, showing remarkable UV protection on Cur and enhanced intracellular antioxidant activity of FG-COS-Cur nanoparticles. Remarkably, FG-COS-Cur nanoparticles increased the cell viability of H2O2-induced oxidative damage Caco-2 cells, drastically reduced the levels of reactive oxygen species (ROS) and lactate dehydrogenase (LDH), and significantly increased intracellular antioxidant enzyme activities, which all exhibited a dose-response relationship. These findings suggested that the FG-COS conjugates with intrinsic antioxidant activity could effectively encapsulate Cur and improved bioavailability for hydrophobic active molecules in functional food field.

Insights into flavor and key influencing factors of Maillard reaction products: A recent update

During food processing, especially heating, the flavor and color of food change to a great extent due to Maillard reaction (MR). MR is a natural process for improving the flavor in various model systems and food products. Maillard reaction Products (MRPs) serve as ideal materials for the production of diverse flavors, which ultimately improve the flavor or reduce the odor of raw materials. Due to the complexity of the reaction, MR is affected by various factors, such as protein source, hydrolysis conditions, polypeptide molecular weight, temperature, and pH. In the recent years, much emphasis is given on conditional MR that could be used in producing of flavor-enhancing peptides and other compounds to increase the consumer preference and acceptability of processed foods. Recent reviews have highlighted the effects of MR on the functional and biological properties, without elaborating the flavor compounds obtained by the MR. In this review, we have mainly introduced the Maillard reaction-derived flavors (MF), the main substances producing MF, and detection methods. Subsequently, the main factors influencing MF, from the selection of materials (sugar sources, protein sources, enzymatic hydrolysis methods, molecular weights of peptides) to the reaction conditions (temperature, pH), are also described. In addition, the existing adverse effects of MR on the biological properties of protein are also pointed out.

Effect of ultrasound on the glycosylation reaction of pea protein isolate-arabinose: Structure and emulsifying properties

This study investigated the effects of different ultrasonic power and ultrasonic time on the structure and emulsifying properties of pea protein isolate (PPI)-arabinose conjugates. An examination of the absorbance and color development of PPI-d-arabinose (Ara) conjugates found that compared with traditional heating, the degree of glycosylation of protein reached the maximum when the ultrasonic treatment power was 150 and the treatment time was 30 min. Structural analysis revealed that the content of disordered structures (β-turn and random coil) of the protein conjugates increased, the maximum emission wavelength of the fluorescence spectrum was red-shifted, and the UV second-order derivative values decreased. The protein structure unfolded, exposing more hydrophobic groups on the molecular surface. Ultrasonic treatment improved the emulsification of protein conjugates. The emulsifying activity index (EAI) increased to 19.7 and 19.3 m²/g, and the emulsifying stability index (ESI) also increased. The contact angle and zeta potential also demonstrate that ultrasonic power has a positive effect on emulsion stability. Based on examining the thermal stability of the emulsion, the ultrasonic treatment increased the thermal denaturation resistance of the protein. This result confirms that mild sonication can increase the degree of glycosylation reaction and improve the emulsification properties of protein-Ara conjugates, providing a theoretical basis for developing foods with excellent emulsification properties.

The Protein Composition Changed the Quality Characteristics of Plant-Based Meat Analogues Produced by a Single-Screw Extruder: Four Main Soybean Varieties in China as Representatives

Plant-based meat analogues (PBMs) are increasingly interesting to customers because of their meat-like quality and contribution to a healthy diet. The single-screw extruder is an important method for processing PBMs, and the characteristics of the product are directly affected by the composition of the raw materials; however, little research focuses on this issue. To explore the effect of protein composition on the quality characteristics of PBMs produced by a single-screw extruder, four soybean varieties used in China (Heihe 43 (HH 43), Jiyu 86 (JY 86), Suinong 52 (SN 52), and Shengfeng 5 (SF 5)) were selected. The 11S/7S ratios for these varieties ranged from 1.0: 1 to 2.5: 1 in order to produce PBMs with different protein compositions. The structure, processing, nutrition, and flavor characteristics were explored to analyze their differences. The results showed that protein composition affected the structure of PBMs, but the correlation was not significant. Meanwhile, a lower 11S/7S ratio (HH 43) did not prove to be a favorable characteristic for the processing of PBMs. From the perspective of nutrition and flavor, it seems acceptable to use a moderate 11S/7S ratio (JY 86 and SN 43) to produce PBMs. This study proved that the protein composition of raw materials affects the characteristics of PBM products produced by a single-screw extruder. To produce PBMs of higher quality, soybeans with a markedly different 11S/7S ratio should not be selected.

Protein-polysaccharide interactions for the fabrication of bioactive-loaded nanocarriers: Chemical conjugates and physical complexes

As unique biopolymeric architectures, covalently and electrostatically protein-polysaccharide (PRO-POL) systems can be utilized for bioactive delivery by virtue of their featured structures and unique physicochemical attributes. PRO-POL systems (i. e, microscopic /nano-dimensional multipolymer particles, molecularly conjugated vehicles, hydrogels/nanogels/oleogels/emulgels, biofunctional films, multilayer emulsion-based delivery systems, particles for Pickering emulsions, and multilayer coated liposomal nanocarriers) possess a number of outstanding attributes, like biocompatibility, biodegradability, and bioavailability with low toxicity that qualify them as powerful agents for the delivery of different bioactive ingredients. To take benefits from these systems, an in-depth understanding of the chemical conjugates and physical complexes of the PRO-POL systems is crucial. In this review, we offer a comprehensive study concerning the unique properties of covalently/electrostatically PRO-POL systems and introduce emerging platforms to fabricate relevant nanocarriers for encapsulation of bioactive components along with a subsequent sustained/controlled release.

Effects of Grafting Degree on the Physicochemical Properties of Egg White Protein-Sodium Carboxymethylcellulose Conjugates and Their Aerogels

To improve the mechanical strength and oil-loading performances of egg white protein (EWP) aerogel, the effects of different grafting degrees on the modification of EWP by sodium carboxymethylcellulose (CMC-Na) were investigated. After different dry-heat treatment durations (0, 12, 24, 36, and 48 h), the EWP/CMC-Na conjugates with different grafting degrees (noted as EC0, EC12, EC24, EC36, and EC48, respectively) were obtained. Subsequently, the physicochemical properties of the conjugates, as well as the microstructure, mechanical properties, pore parameters, emulsification properties and oil-carrying properties of the conjugated aerogels, were characterized. The results showed that EC12 (with a grafting degree of 8.35%) aerogel possessed a uniform structure, the largest specific surface area, and the best emulsification performance. This facilitated a more robust aerogel (2.05 MPa) with nearly three times the mechanical strength of EWP aerogel. Moreover, this had a positive influence on the efficient loading and stable retention of oil. EC12 aerogel thus achieved an oil absorption capacity of 5.46 g/g aerogel and an oil holding capacity of 31.95%, and both values were nearly 1.7 times higher than those of EWP aerogel. In general, the EWP-based aerogel with a grafting degree of 8.35% had the best mechanical and oil-loading properties.

Application of protein-polysaccharide Maillard conjugates as emulsifiers: Source, preparation and functional properties

The protein-polysaccharide conjugates formed by Maillard reaction can be used as novel emulsifiers in the food industry. Proteins and polysaccharides have extensive sources, and their emulsifying properties are highly dependent on their structural features. The Maillard conjugates can be prepared from conventional and novel methods, and these methods have different advantages and limitations in industrial applications. After an appropriate glycation, the conjugates show some modified or enhanced functional properties, including solubility, emulsifying property, thermal stability, foaming capacity, and gelation property. However, the research on the structure-function relationship of both proteins and polysaccharides is limited. It is necessary to well understand the characteristics of these biopolymers, and select appropriate conditions to control the process of Maillard reaction. Overall, the Maillard conjugates show great potential as the emulsifiers and stabilizers in the emulsion system. This review introduces the sources and structural characteristics of commonly used proteins and polysaccharides for Maillard reaction, outlines the methods (dry-heating, wet-heating, electrospinning, ultrasound, pulsed electric field, and microwave) for preparing Maillard conjugates and focuses on the improved functional properties (solubility, emulsifying, foaming and thermal properties) and the potential mechanisms.

Rheological and textural properties of acid-induced soybean protein isolate gel in the presence of soybean protein isolate hydrolysates or their glycosylated products

Enzymatic hydrolysis and glycosylation were successively applied to modify soybean protein isolate (SPI) and rheological and textural properties of acid-induced SPI gel added with the obtained SPI hydrolysates and their glycosylated products were then investigated. The incorporation of SPI hydrolysates decreased the elastic modulus (G') and hardness of SPI gel, which might be related to the random aggregation between SPI hydrolysates and native SPI molecules via hydrophobic interactions. In addition, as the molecular weight of SPI hydrolysates decreased, the reduction in G' and hardness became more significant. Although glycosylation of SPI hydrolysates weakened the adverse effects of hydrolysates on the SPI gel formation to some extent, the glycosylated SPI hydrolysates were still unable to improve the gel quality compared with the control. However, results of this research may provide important information for understanding the influencing mechanism of SPI hydrolysates and their glycosylated products on the formation of SPI gel.

Astaxanthin-loaded emulsion gels stabilized by Maillard reaction products of whey protein and flaxseed gum: Physicochemical characterization and in vitro digestibility

In order to evaluate the effect of ultrasound and Maillard reaction on the physicochemical properties and gastrointestinal fate of astaxanthin-loaded emulsion gels, the Maillard reaction products (MRPs) of whey protein and flaxseed gum (FG) were prepared by traditional or ultrasonic assisted wet-heating. The MRPs obtained by ultrasonic assisted wet-heating had higher grafting degree and more expanded structures evidenced by the browning intensity, fluorescence intensity and circular dichroism (CD) analysis, thus enhancing its functional properties like solubility and emulsifying capacity. The MRPs improved the water holding capacity, encapsulation efficiency, stability of emulsion gels, in which astaxanthin was wrapped as a model bioactive compound. During the simulated digestion process, the bioaccessibility of loaded astaxanthin reached 72.08% for the emulsion gels stabilized by MRPs. The results highlighted the potential of MRPs in improving functionality of protein and as a delivery carrier of bioactive compounds in food industry.

Structural characteristics and emulsifying properties of myofibrillar protein-dextran conjugates induced by ultrasound Maillard reaction

In this study, we investigated the effect of the ultrasound-assisted Maillard reaction on the structural and emulsifying properties of myofibrillar protein (MP) and dextran (DX) conjugates with different molecular weights (40, 70 and 150 kDa). Compared with classical heating, mild and moderate ultrasound-assisted methods (100-200 W) could accelerate the later stage of the Maillard reaction, which increased the degree of graft (DG) and the content of advanced Maillard reaction products (MPRs). Structural analysis revealed conjugates obtained by Maillard reaction induced the loss of ordered secondary structures (α-helix, β-sheets) and red-shift of maximum emission wavelength of intrinsic fluorescence spectrum. The conjugate containing 40 kDa DX exhibited higher extent of Maillard reaction compared to those containing 70 kDa and 150 kDa DX under various treating methods. Moreover, the ultrasound-assisted Maillard reaction could effectively improve the emulsifying behaviors. 100 W ultrasound-induced conjugates grafted by 70 kDa DX produced the smallest emulsion size with optimum storage stability. Confocal laser scanning microscopy and analytical centrifugal analyzer further confirmed MP grafted by 70 kDa DX with the assistance of 100 W ultrasound field could produce the smallest and most homogeneous MP-base emulsion with no flocculation. Our study demonstrated that mild ultrasound treatment resulted in well-controlled Maillard reaction, and the related glycoconjugate grafted with 70 kDa DX showed the greatest improvements in emulsifying ability and stability. These findings provided a theoretical foundation for the development of emulsion-based foods with excellent characteristics.

Effect of temperature and pH on the gelation, rheology, texture, and structural properties of whey protein and sugar gels based on Maillard reaction

This study aimed to determine the effect of initial pH and temperature on whey protein gel formation via the Maillard reaction, including changes in gel structure, rheological and texture properties. The color changes in the whey protein and glucose gels were not significant with increasing heat temperature. High temperature and alkaline conditions promoted exposure to hydrophobic groups such as -SH, which accelerated protein aggregation and gel formation. Moreover, the increased particle size and additional hydrophobic groups contributed to higher elastic modulus (G') in the whey protein gel. Fluorescence measurements revealed that more tryptophan on the protein surface decreased with increasing temperature, which indicated that exposure to tryptophan could increase the hydrophobicity of the protein gels. Whey proteins formed stronger, gummier, more elastic, and more cohesive gels at 70 ℃ under initial pH 9 conditions, which also increased with the addition of fructose.

Effect of pullulan concentration and pH on the interactions between whey protein concentrate and pullulan during gelation

BACKGROUND

Whey protein concentrate (WPC)/pullulan (PUL) hydrogel is applied as a microencapsulation wall material to protect probiotics. However, the interactions between WPC and PUL during gelation have not been clarified. In the present study, the effects of PUL concentration and pH on the interactions between WPC and PUL during gelation were evaluated with respect to appearance, zeta-potential, sulfhydryl group amount, surface hydrophobicity and infrared spectroscopy measurements. The rheological properties of WPC/PUL gels were also determined.

RESULTS

The results obtained showed that a proper concentration (0.40 g mL^-1 ) of PUL could improve the gel by enhancing the strength of hydrogen bonding, electrostatic interactions and exposure of hydrophobic groups, whereas too much PUL inhibited the formation of disulfide bonds. Furthermore, hydrophobic interactions, disulfide bonds and hydrogen bonds were destroyed in varying degrees under an alkaline environment. The rheological results also demonstrated a similar effect of PUL concentration and pH on the storage modulus (G') of WPC/PUL gels.

CONCLUSION

When the WPC/PUL gel was formed at PUL concentration of 0.40 g mL^-1 and pH 7.0, the interaction between WPC and PUL could be enhanced, which is beneficial for the future application of WPC/PUL gels in the food industry. © 2020 Society of Chemical Industry.

Glycation of soy proteins leads to a range of fractions with various supramolecular assemblies and surface activities

Dry and subsequent wet heating were used to glycate soy proteins with dextran or glucose, followed by fractionation based on size and solubility. Dry heating led to protein glycation (formation of furosine, Nε-(carboxymethyl)-l-lysine, Nε-(carboxyethyl)-l-lysine, and protein-bound carbonyls) and aggregation (increased particle size); while subsequent wet heating induced partial unfolding and de-aggregation. The measurable free amino group content of soy proteins changed from 0.77 to 0.14, then to 0.62 mmol/g upon dry and subsequent wet heating; this non-monotonic evolution is probably due to protein structural changes, and shows that this content should be interpreted with caution as a glycation marker. After both heating steps, the smaller-sized water-soluble fractions showed higher surface activity than the larger insoluble ones, and dextran conjugates exhibited a higher surface activity than their glucose counterparts. We thereby achieved a comprehensive understanding of the properties of various fractions in plant protein fractions, which is essential when targeting applications.