Mechanical Properties, Microstructure, and In Vitro Digestion of Transglutaminase-Crosslinked Whey Protein and Potato Protein Hydrolysate Composite Gels

Spectral analysis of the impact of various polysaccharides on the entrapment of curcumin by whey protein isolate

This study employed spectroscopic methods to investigate the interactions between whey protein isolate/polysaccharide (WPI/PS) complexes and curcumin. The UV-visible absorption spectra and fluorescence spectra indicated effective binding of curcumin to WPI and its complexes with chitosan (CS), carrageenan (CAR) and carboxymethylcellulose (CMC). This binding significantly increased the UV-visible absorption intensity of curcumin, with its maximum fluorescence emission peak shifting from 552 nm to 510 nm. Fluorescence kinetics analysis suggested that the binding constant between curcumin and WPI/CS complexes reached a maximum of 4.0794 × 105 L/mol. Circular dichroism and infrared spectroscopy indicated that the higher binding constant was attributed to the binding of CS, which reduced the α-helix structure and exposed hydrophobic groups of WPI. Curcumin entrapped by WPI/CS complexes showed the highest DPPH radical scavenging activities, UV and thermal stability. In summary, the WPI/CS complexes effectively protect curcumin against various environmental stresses and maintain its antioxidant properties.

Enhancing the Functional and Emulsifying Properties of Potato Protein via Enzymatic Hydrolysis with Papain and Bromelain for Gluten-Free Cake Emulsifiers

In recent years, plant-derived food proteins have gained increasing attention due to their economic, ecological, and health benefits. This study aimed to enhance the functional properties of potato protein isolate (PPI) through enzymatic hydrolysis with papain and bromelain, evaluating the physicochemical and emulsifying characteristics of the resulting potato protein hydrolysates (PPHs) for their potential use as plant-based emulsifiers. PPHs were prepared at various hydrolysis times (0.25-2 h), resulting in reduced molecular weights and improved solubility under acidic conditions (pH 4-6). PPHs exhibited higher ABTS radical-scavenging activity than PPI. The foaming stability (FS) of bromelain-treated PPI was maintained, whereas papain-treated PPI showed decreased FS with increased hydrolysis. Bromelain-treated PPHs demonstrated a superior emulsifying activity index (EAI: 306 m2/g), polydispersity index (PDI), higher surface potential, and higher viscosity compared to papain-treated PPHs, particularly after 15 min of hydrolysis. Incorporating PPHs into gluten-free chiffon rice cake batter reduced the batter density, increased the specific volume, and improved the cake's textural properties, including springiness, cohesiveness, and resilience. These findings suggest that bromelain-treated PPHs are promising plant-based emulsifiers with applications in food systems requiring enhanced stability and functionality.

The impact of ultrasound synergized with salt on the structure and loading characteristics of whey protein isolate-chitosan complexes

This study examined the impact of ultrasound synergized with salt on the structure and loading properties of whey protein isolate (WPI)-chitosan (CS) complexes. A higher curcumin loading value was obtained when WPI and CS were combined at a 10:6 mass ratio with a complex concentration of 8 g/L. The synergistic effect of ultrasound combined with salt treatment directly applied to WPI was more effective in enhancing the loading capacity of curcumin than when applied to WPI/CS complexes. Different NaCl concentrations affected the structure of WPI and its complexing ability with CS differently. High NaCl concentrations could cause aggregation of WPI and its complexes. After ultrasonic treatment with 0.4 % NaCl, the particle size of WPI decreased from 330.4 to 213.3 nm, its hydrophobicity increased, and the α-helix structure unfolded. The complexes formed by modified WPI and CS had higher viscosity and a looser structure, enhancing curcumin loading capacity to 36.3 mg/g, an improvement of 25.8 % over the control. The curcumin encapsulated in the modified WPI/CS complexes showed greater radical scavenging activity compared to free curcumin. The results of this study offer valuable insights in the design and preparation of WPI/CS complexes with good loading capacity.

Synergistic effect of edible salts on the physicochemical properties of whey protein isolate-carrageenan complexes and their application as foam and emulsion stabilizers

NaCl and CaCl2 are commonly used edible salts in food. The synergistic influences of these two salts on the physicochemical properties of whey protein isolate-carrageenan (WPI-Car) complexes were investigated in relation to their foaming and emulsifying properties. The results showed that as the ratio of NaCl: CaCl2 decreased from 6:0 to 3:3, the turbidity of the complexes increased from 0.51 to 0.77 and the absolute zeta potential decreased from 28.86 to 9.05 mV (P < 0.05). NaCl caused the exposure of hydrophobic groups, whereas CaCl2 caused hydrophobic groups to be buried within the molecule. The transformation between the α-helix structure and β-sheet structure of WPI was closely related to the ratios of NaCl to CaCl2. The electrostatic force, hydrophobic interaction, and hydrogen bond were significantly influenced by the synergistic influence of NaCl and CaCl2. The foaming capacity of WPI-Car complexes reached a maximum of 90.0 % at a NaCl: CaCl2 ratio of 3:3. Compared to the individual effects of monovalent NaCl and divalent CaCl2, the mixture of NaCl and CaCl2 (5:1) produced suitable refolding due to their synergistic effect, which improved the emulsifying properties of WPI-Car complexes. The findings of this study provide useful information for designing and preparing WPI-Car complexes for food applications.

Development and characterization of soy protein-based custard-like soft foods for elderly individuals with swallowing difficulties

There is growing interest in developing protein-rich foods for the elderly using plant proteins. The application of soy protein isolate (SPI) as a model protein to create protein-rich, custard-like soft foods presents a unique opportunity for innovative formulations tailored to those within the aging population suffering from swallowing difficulties. This study investigated the physicochemical and textural properties of custard-type soft food formulations developed using SPI for dysphagic elderly individuals, with the goal of achieving characteristics similar to those of optimal milk protein-based counterparts. The protein content in the SPI-based custards varied from 8.9 % to 13.9 % and the milk-protein based custards had 8.9 % protein content. There was a substantial difference in textural, rheological and creep resistance and other properties between SPI and milk protein-based formulations. The SPI-based custards also had lower water-holding capacity, looser structure, and higher level of insoluble protein aggregates. The SPI-based custards imparted a more spreadable mouthfeel suitable for the aging population. The custards containing 13.9 % SPI had higher gel strength, viscosity, texture, and product stability. All of these custards were classified as Level 6 - Soft & Bite-sized dysphagia diet, based on International Dysphagia Diet Standardisation Initiative (IDDSI) tests. Instrumental IDDSI tests for Level 6 foods corroborated these observations, yielding reliable and consistent data. This research provides insights for developing protein-rich plant-based soft foods intended for the elderly population that have characteristics close to milk protein-based custards and comply with IDSSI criteria.

Formation and Characterization of Mycelium-Potato Protein Hybrid Materials for Application in Meat Analogs or Substitutes

There is increasing interest in the development of meat analogs due to growing concerns about the environmental, ethical, and health impacts of livestock production and consumption. Among non-meat protein sources, mycoproteins derived from fungal fermentation are emerging as promising meat alternatives because of their natural fibrous structure, high nutritional content, and low environmental impact. However, their poor gelling properties limit their application in creating meat analogs. This study investigated the potential of creating meat analogs by combining mycoprotein (MCP), a mycelium-based protein, with potato protein (PP), a plant-based protein, to create hybrid products with meat-like structures and textures. The PP-MCP composites were evaluated for their physicochemical, rheological, textural, and microstructural properties using electrophoresis, differential scanning calorimetry, dynamic shear rheology, texture profile analysis, confocal fluorescence microscopy, and scanning electron microscopy analyses. The PP-MCP hybrid gels were stronger and had more fibrous structures than simple PP gels, which was mainly attributed to the presence of hyphae fibers in mycelia. Dynamic shear rheology showed that the PP-MCP hybrids formed irreversible heat-set gels with a setting temperature of around 70 °C during heating, which was attributed to the unfolding and aggregation of the potato proteins. Confocal and electron microscopy analyses showed that the hybrid gels contained a network of mycelia fibers embedded within a potato protein matrix. The hardness of the PP-MCP composites could be increased by raising the potato protein content. These findings suggest that PP-MCP composites may be useful for the development of meat analogs with more meat-like structures and textures.

Hydroxyl radical-induced oxidation boosts the gelation of ginkgo seed protein in the presence of hyaluronic acid

Hydroxyl radical-induced oxidation can modify gelling properties of food proteins. In this study, a hydroxyl radical generating system (HRGS), consisting of 0.1 mM Fe3+, 0.1 mM ascorbic acid, and 1, 10, or 20 mM H2O2, was used to oxidize ginkgo seed protein isolate (GSPI) for 4 h at ambient temperature in the presence of 0.3 % (w/v) hyaluronic acid (HA) to enhance its gelation properties. HRGS treatment led to increased protein hydrophobicity, reduced sulfhydryl content, and disulfide bond-mediated protein crosslinking. Moreover, the secondary structure of GSPI varied with H2O2 concentrations. Moderate oxidation (approximately 10 mM H2O2) promoted GSPI aggregation and improved mechanical strength, rheological properties, water holding capacity, and whiteness of GSPI gels. However, excessive oxidation disrupted hydrogen bonding, generated excessive disulfide bonds, hindered active group interaction, inhibited gel network formation, and reduced gel strength. Hence, hydroxyl radical-induced oxidation holds potential for enhancing GSPI gelation within specific concentration ranges. This study suggests that controlled oxidation could be a novel approach for developing protein-based gel products.

Effect of Multi-Mode Divergent Ultrasound Pretreatment on Hardness, Microstructure and Digestion of Acid-Induced Whey Protein Gels

Whey protein was pretreated with multi-frequency ultrasound in mono-, dual-, and tri-frequency modes. The effect of multi-frequency ultrasound pretreatment on the hardness, chemical forces, and microstructure of acid-induced whey protein gel was investigated. Whey protein gels pretreated with dual- and tri-frequency ultrasound showed higher hardness (p < 0.05) and a denser network than mono-frequency ultrasound and control. Moreover, they had higher hydrophobic interaction and lower disulfide bonds than the control (p < 0.05). The effect of gel properties on digestion was evaluated using an in vitro static model. Whey protein gels pretreated with dual- and tri-frequency ultrasound had a higher proportion of large fragments in the oral boluses than in the control. Large fragments (>3.35 mm) in those samples were resistant to gastric digestion. Moreover, the tri-frequency ultrasound pretreatment of whey protein gel released the least free amino group during gastric digestion. In contrast, whey protein gel with the mono-frequency ultrasound pretreatment released the highest amount of free amino acid group during intestinal digestion. Findings from this study suggests that gel hardness and network density could modulate the digestion behaviors of protein gels.

L-Theanine Improves the Gelation of Ginkgo Seed Proteins at Different pH Levels

L-theanine (L-Th), a non-protein amino acid naturally found in teas and certain plant leaves, has garnered considerable attention due to its health benefits and potential to modify proteins such as ginkgo seed proteins, which have poor gelling properties, thereby expanding their applications in the food industry. The objective of this study was to investigate the impact of varying concentrations of L-Th (0.0%, 0.5%, 1.0%, and 2.0%) on the gelling properties of ginkgo seed protein isolate (GSPI) at various pH levels (5.0, 6.0, and 7.0). The GSPI gels exhibited the highest strength at a pH of 5.0 (132.1 ± 5.6 g), followed by a pH of 6.0 (95.9 ± 3.9 g), while a weak gel was formed at a pH of 7.0 (29.5 ± 0.2 g). The incorporation of L-Th increased the hardness (58.5-231.6%) and springiness (3.0-9.5%) of the GSPI gels at a pH of 7.0 in a concentration-dependent manner. However, L-Th did not enhance the gel strength or water holding capacity at a pH of 5.0. The rheological characteristics of the GSPI sols were found to be closely related to the textural properties of L-Th-incorporated gels. To understand the underlying mechanism of L-Th's effects, the physicochemical properties of the sols were analyzed. Specifically, L-Th promoted GSPI solubilization (up to 7.3%), reduced their hydrophobicity (up to 16.2%), reduced the particle size (up to 40.9%), and increased the ζ potential (up to 21%) of the sols. Overall, our findings suggest that L-Th holds promise as a functional ingredient for improving gel products.

Characterizations of emulsion gel formed with the mixture of whey and soy protein and its protein digestion under in vitro gastric conditions

Partially replacing animal proteins with plant proteins to develop new products has much attention. To get knowledge of their application in emulsion gels, heat-induced composite protein emulsion gels were fabricated using the mixtures of whey protein isolate (WPI) and soy protein isolate (SPI) with the final total protein concentration of 10% (w/w). The water holding capacity (WHC), mechanical and rheological properties and microstructure of mixed protein emulsion gels prepared at different WPI to SPI ratios (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, 0:100, w/w) were investigated. The ratios of WPI to SPI showed little effect on the WHC of the mixed protein emulsion gels (p > 0.05). Increasing the ratio of SPI decreased the hardness and storage modulus (G') of mixed protein emulsion gels, whereas the porosity of mixed protein emulsion gels in the microstructure increased, as shown by CLSM. Both β-lactoglobulin and α-lactalbumin from WPI and 7 S and 11 S from SPI participated in forming the gel matrix of mixed protein emulsion gels. More protein aggregates existed as the gel matrix filler at the high soy protein levels. Interestingly, the G' of mixed protein emulsion gels at the WPI to SPI ratio of 50:50 was higher than the sum of G' of individual WPI and SPI emulsion gels. The whey protein network predominated the gel matrix, while soy protein predominated in the active filling effect. When subjected to an in vitro dynamic gastric digestion model, soy protein in the gels (WPI:SPI = 50:50) degraded faster than whey protein during gastric digestion. This study provided new information on the characteristics of composite protein emulsion gel fabricated with the WPI and SPI mixture.

Development of high internal phase emulsions with noncovalent crosslink of soy protein isolate and tannic acid: Mechanism and application for 3D printing

In this study, we propose a design strategy using soy protein isolate (SPI)-tannic acid (TA) complexes crosslinked through noncovalent interactions to develop high internal phase emulsions (HIPEs) for 3D printing materials. The results of Fourier transform infrared spectroscopy, intrinsic fluorescence, and molecular docking analyses indicated that the dominant interactions occurring between the SPI and TA were mediated by hydrogen bonds and hydrophobic interactions. The secondary structure, particle size, ζ-potential, hydrophobicity and wettability of SPI was significantly altered by the addition of TA. The microstructure of HIPEs stabilized by SPI-TA complexes exhibited more regular and even polygonal shapes, thereby allowing the protein to form a dense self-supporting network structure. When the concentration of TA exceeded 50 μmol/g protein, the formed HIPEs remained stable after 45 days of storage. Rheological tests revealed that the HIPEs exhibited a typical gel-like (G' > G'') and shear-thinning behavior, which contributed to preferable 3D printing behavior.