Whey Protein Isolate Solutions Research Articles

Adsorption Layer Properties and Foam Behavior of Aqueous Solutions of Whey Protein Isolate (WPI) Modified by Vacuum Cold Plasma (VCP)

For years, cold plasma processing has been used as a non-thermal technology in industries such as food. As interfacial properties of protein play a remarkable role in many processes, this study investigates the effect of cold plasma on the foaming and interfacial behavior of WPI. The objective of this study is to evaluate the effect of different gases (air, 1:1 argon–air mixture, and sulfur hexafluoride (SF6)) used in low-pressure cold plasma (VCP) treatments of whey protein isolate (WPI) on the surface and foaming behavior of aqueous WPI solutions. Dynamic surface dilational elasticity, surface tension isotherms, surface layer thickness, and the foamability and foam stability were investigated in this study. VCP treatment did not significantly affect the adsorption layer thickness. However, an increase in induction time, surface pressure equilibrium value, and aggregated size is observed after SF6VCP treatment, which can be attributed to the reaction of WPI with the reactive SF6 species of the cold plasma. The surface dilational elastic modulus increased after VCP treatment, which can be related to the increased mechanical strength of the protein layer via sulfonation and aggregate formation. VCP treatment of WPI increases the foam stability, while the average diameter of foam bubbles and liquid drainage in the foam depends on the gas used for the cold plasma.

KARANFİL VE KAYISI ESANSİYEL YAĞLARI İLE AKTİF HALE GETİRİLMİŞ PEYNİIR ALTI SUYU PROTEİNİ İZOLAT BAZLI YENİLEBİLİR FİLMLER

The aim of this research is to investigate the effects of essential oils on the mechanical and antimicrobial properties of protein-based edible films. Clove and apricot oils were added to whey protein isolate (WPI) solutions and were named C-WPI and A-WPI, respectively. Kaşar cheese was chosen as a food sample to investigate the behavior of modified films on a food product. It was observed that the oil-protein interaction increased the elasticity but decreased the strength of the emulsified films. The incorporation of oil into the film matrix resulted in a more opaque appearance but also increased thermal stability. It was detected that both types of essential oils impart antimicrobial properties of the films, but clove oil is more effective than apricot oil. In conclusion, the successful antimicrobial properties of the modified WPI film make it a potential packaging material, especially for food products prone to microbiological spoilage.

Combination of Machine Learning and Raman Spectroscopy for Determination of the Complex of Whey Protein Isolate with Hyaluronic Acid.

Macromolecules and their complexes remain interesting topics in various fields, such as targeted drug delivery and tissue regeneration. The complex chemical structure of such substances can be studied with a combination of Raman spectroscopy and machine learning. The complex of whey protein isolate (WPI) and hyaluronic acid (HA) is beneficial in terms of drug delivery. It provides HA properties with the stability obtained from WPI. However, differences between WPI-HA and WPI solutions can be difficult to detect by Raman spectroscopy. Especially when the low HA (0.1, 0.25, 0.5% w/v) and the constant WPI (5% w/v) concentrations are used. Before applying the machine learning techniques, all the collected data were divided into training and test sets in a ratio of 3:1. The performances of two ensemble methods, random forest (RF) and gradient boosting (GB), were evaluated on the Raman data, depending on the type of problem (regression or classification). The impact of noise reduction using principal component analysis (PCA) on the performance of the two machine learning methods was assessed. This procedure allowed us to reduce the number of features while retaining 95% of the explained variance in the data. Another application of these machine learning methods was to identify the WPI Raman bands that changed the most with the addition of HA. Both the RF and GB could provide feature importance data that could be plotted in conjunction with the actual Raman spectra of the samples. The results show that the addition of HA to WPI led to changes mainly around 1003 cm-1 (correspond to ring breath of phenylalanine) and 1400 cm-1, as demonstrated by the regression and classification models. For selected Raman bands, where the feature importance was greater than 1%, a direct evaluation of the effect of the amount of HA on the Raman intensities was performed but was found not to be informative. Thus, applying the RF or GB estimators to the Raman data with feature importance evaluation could detect and highlight small differences in the spectra of substances that arose from changes in the chemical structure; using PCA to filter out noise in the Raman data could improve the performance of both the RF and GB. The demonstrated results will make it possible to analyze changes in chemical bonds during various processes, for example, conjugation, to study complex mixtures of substances, even with small additions of the components of interest.

Co-encapsulation of curcumin and piperine in whey protein isolate fibrils improves their water dispersibility and antioxidant activity

In this study, whey protein isolate (WPI) fibrils prepared by acid heat treatment for different times (5, 10, 15, or 20 h) were used for the co-encapsulation and co-delivery of curcumin (Cur) and piperine (Pip). Co-encapsulation of both nutraceuticals in the fibrils significantly improved their water dispersibility, chemical stability, and antioxidant activity. For instance, the water dispersibility of Cur and Pip in native WPI solutions was around 47.0% and 47.5%, respectively. In contrast, the water dispersibility of the same two nutraceuticals in WPI fibrils (15 h treatment) was 94.3% and 66.6%, respectively. The nutraceutical-loaded WPI fibrils did not undergo significant flocculation or precipitation after 14 d storage at 25 °C. After encapsulation, the DPPH free radical scavenging ability of the Cur-Pip combination experienced a surge, rising from approximately 35.4% to 72.0%. The Stern-Volmer quenching constants (Ksv) of Cur-WPI (3.03 × 104 M−1) and Pip-WPI (7.08 × 104 M−1) were much smaller than those of Cur-WPI fibrils (3.88 × 104–4.69 × 104 M−1) and Pip-WPI fibrils (8.26 × 104–9.41 × 104 M−1), indicating that the nutraceuticals bind stronger to the protein fibrils than to the native protein molecules. In summary, WPI fibrils have the capability to encapsulate, protect, and deliver hydrophobic nutraceuticals, suggesting their suitability for application in functional foods and beverages.

Milk Whey Protein Fibrils—Effect of Stirring and Heating Time

Milk whey proteins, which are derived from skim milk through membrane filtration, exhibit valuable functional properties when transformed into a fibrillar form. This conversion enhances their suitability for various applications, including thickening, gelling, emulsification, and foaming. However, reported fibrillation methods have longer heating times, which may not be economical for the dairy industry. To address these challenges, the current study was undertaken with the objective of reducing the time required for fibril formation. In this study, 2% milk whey protein isolate (mWPI) solution at pH 2 was heated with static and stirring heating conditions at 80 °C for 20 h to convert milk whey proteins into fibrils. Fibrils were observed using the thioflavin T value, transmission electron microscopy, Tricine SDS-PAGE, rheology, and protein oxidation. Results suggest that stirring heating conditions with 14 h heating time produced fibrils with good morphology compared to static heating, showing a 6 h reduction compared to an earlier reported 80 °C for 20 h heating time. Also, stirring heating produced a uniform and homogeneous fibril solution compared to the static heating method. Gentle stirring during heating can also help to scale up fibril production in an industrial setup. The fibrillation method with processing intervention will help to produce fibrils with enhanced functionality at the pilot and industrial scales.

Effects of Various Types of Vacuum Cold Plasma Treatment on the Chemical and Functional Properties of Whey Protein Isolate with a Focus on Interfacial Properties

Vacuum cold plasma (VCP), a novel non-thermal processing technology used to modify the physicochemical properties and functionalities of food materials, was applied to whey protein isolate (WPI). The treatment affects the protein chemistry and, as a result, leads to differences in the behavior in solution and at interfaces. To minimize the undesirable effects of high oxidation and to increase the effectiveness of reactive species, the VCP treatment was applied at low pressure using different types of gases (air, combination of argon and air, and sulfur hexafluoride (SF6)). The treatment led to a decrease in the sulfur content and an increase in the carbonyl content, evidenced by oxidation reactions and enhanced disulfide bond formation, as well as cross-linking of protein molecules. Fluorescence-based indicators suggest that the hydrophobicity of the proteins as well as their aggregation increase after VCP treatment with an argon–air gas mixture; however, it decreases after VCP treatments with air and SF6. The chemical modifications further lead to changes in the pH of aqueous WPI solutions, as well as the average size and ζ-potential of WPI aggregates. Moreover, the dynamic surface tension, surface dilational elasticity, and the thickness of the WPI adsorption layers at the air/water interface depend on the VCP type. SF6 plasma treatment leads to a significant decrease in pH and an increase in the ζ-potential, and consequently to a significant increase in the aggregate size. The dynamic surface tension as well as the adsorption rates increase after SF6VCP treatment, but decrease after air–VCP and argon–air–VCP treatments. The adsorbed WPI aggregates form strong viscoelastic interfacial layers, the thickness of which depends on the type of VCP treatment.

Evaluation of ionic calcium and protein concentration on heat- and cold-induced gelation of whey protein isolate gels as a potential food formulation for 3D food printing

3D food printing (3DFP) is an innovative food process, but developing foods with ideal printability can prove challenging. Whey protein isolate (WPI) gels can be difficult to print due to their rigidity. This study evaluated the cold- and heat-induced gelation properties of WPI for use in 3DFP. Initially, the effect of WPI concentration ([WPI]) (8–12% (w/w)) and ionic calcium concentration ([Ca2+]) (0–8 mM) was evaluated on the heat-induced gelation capability and thermal reversibility. Treatments were categorised into three groups: thermo-irreversible, thermo-reversible, and non-gelling. Non-gelling treatments were used for cold-induced gelation by mixing the denatured WPI solution with 150 mM Ca2+ solution. Thermo-reversibility and cold-induced gelation properties were assessed using oscillatory rheometry. Finally, thermo-irreversible gels (TIRG) were characterised using extrudability and texture profile analysis. The thermo-reversible gels had an unsuitable range of G' (5–60 Pa) and δ (40–60°) for obtaining a self-standing object. Cold gelation using [WPI] = 10%, G' > 500 Pa and δ < 10°, may be suitable for 3DFP but requires an adapted extrusion-based 3D printer, i.e., co-extrusion, cooling or support bath. The extrusion force of TIRG decreased during heating and was mainly affected by [WPI]. Upon re-cooling, the force recovered (>85%) with the addition of [Ca2+] > 4 mM. TIRG using the following treatments [WPI]-[Ca2+] = 12% - 2 mM, 11% - 4 mM, and 10% - 6 mM demonstrated good printability. Principal component analysis showed TIRG with low hardness, resilience, and extrusion force loss during heating are potentially suitable for 3DFP.

The Effect of Erythritol on the Physicochemical Properties of Reformulated, High-Protein, and Sugar-Free Macarons Produced from Whey Protein Isolate Intended for Diabetics, Athletes, and Physically Active People

This study reports the possibility of obtaining sugar-free WPI-based macarons with erythritol addition. The whey protein isolate (WPI) solution (20%, w/v) was whipped, and erythritol was added to the foam at concentrations of 20, 40, and 60 g, with 125 g of almond flour. The rheological properties (τ, G', G″, and tan (δ)) and stability of the macaron batters before baking were evaluated. In order to produce the macarons, the batters were solidified at 147 °C for 12 min. The textural and surface properties (roughness and color), as well as the microstructures and water activities, were determined for the macarons. It was feasible to produce macarons over the entire range of the tested erythritol content. Even the smallest amount of erythritol (20 g) facilitated the preservation of the macaron structure. The medium erythritol concentration (40 g) improved the stability of the batters and their rheology and was the most effective for air pocket stabilization during baking; however, its largest addition (60 g) resulted in an increase in the final macaron volume. The increased erythritol addition improved mechanical properties and shelf life, producing a smoothing effect on the macaron surfaces and having a significant effect on their color co-ordinates.

The effect of different edible fungal polysaccharides on the stability of whey protein isolate solution near isoelectric point

SummaryWhey protein isolate (WPI) is unstable near isoelectric point with simultaneous precipitation or phase separation, which negatively affects its application. In the current study, four kinds of edible fungal polysaccharides were selected to improve the WPI stability through non‐covalent interaction. The addition of edible fungal polysaccharides significantly improved the WPI stability. Zeta potential analysis showed that edible fungal polysaccharides reduced the zeta potential of WPI. The analysis of rheological properties showed that complex solutions exhibited higher viscosity and behaved as pseudoplastic fluids. Bio‐layer interferometry demonstrated the interactions between edible fungal polysaccharides and WPI, and the KD between Tremella fuciformis (TFP) and WPI was the lowest. LC–MS/MS results indicated that the peptide fragments “VGINYWLAHK” and “TPEVDDEALEKFDK” in α‐lactalbumin and β‐lactoglobulin were probably binding regions interacted with the four kinds of edible fungal polysaccharides. Furthermore, molecular docking results inferred GLN43 and GLU127 were the major residues in the α‐lactalbumin and β‐lactoglobulin.

Formation, physicochemical properties, and comparison of heat- and enzyme-induced whey protein-gelatin composite hydrogels

Hydrogels are widely used in the food industry due to their desirable physicochemical and functional attributes. The combination of two or more biopolymers can be used to formulate hydrogels with novel or improved attributes. In this study, whey protein isolate (WPI) and gelatin were used to prepare composite hydrogels using either heat- or enzymatic-crosslinking methods. For heat-induced gelation, gelatin-WPI mixtures were heated above the thermal denaturation temperature of the whey proteins to unfold and crosslink them. For enzyme-induced gelation, transglutaminase was added to crosslink both the gelatin and heat-denatured whey proteins in the gelatin-WPI mixtures. The effects of pH and crosslinking methods on the formation and properties of the hydrogels were investigated. The initial pH of the WPI solution influenced the thermal aggregation of the proteins by affecting the electrostatic interactions between them, thereby influencing the macroscopic properties of the hydrogels formed. For instance, heat-induced hydrogels with a higher elastic modulus were formed at pH 6 (1767 Pa) than at pH 7 (866 Pa) or pH 8 (735 Pa). The enzyme-induced hydrogels set more rapidly and had a considerably higher elastic modulus at pH 7 (2566 Pa) and pH 8 (1566 Pa) than the heat-induced ones. The enzyme-induced hydrogels also exhibited greater hardness and swelling, but the heat-induced ones exhibited better freeze-thaw stability. By changing the pH and crosslinking methods, the structure and texture of the composite hydrogels could be controlled, which may allow these systems to be used for a broad range of commercial applications in food and other industries.

Mechanistic study on in vitro disintegration and proteolysis of whey protein isolate gels: Effect of the strength of sodium ions

In this study, the influence of the strength of sodium ions on the mechanical properties, microstructure and proteolysis of whey protein isolate (WPI) gels during in vitro gastrointestinal digestion was investigated. The results showed that heat treatment of 15% (w/v) WPI solutions in the presence of 0–0.1 M NaCl resulted in fine-stranded gels with a smaller coarseness length scale, while the presence of higher salt concentrations (0.15–0.5 M) induced coarse-stranded gels with larger particle sizes of the protein aggregates. The elastic shear modulus was found to increase with increasing NaCl concentration, followed by a reduction under higher ionic strength. During in vitro gastrointestinal digestion, the kinetics of disintegration of all the gels were dominated by a surface erosion mechanism. The half disintegration time ( t 1/2 ) significantly increased from 136.2 min to 416.0 min with the increase of NaCl concentration from 0 to 0.5 M, respectively. The coarse-stranded gels were more resistant to digestion with less mass loss and a lower rate and extent of proteolysis throughout the in vitro digestion than the fine-stranded gels. This could be attributed to the limited swelling and more severe protein aggregation found in the coarser gels with more compact structures, which would retard the accessibility of acids and enzymes during digestion. The present work has provided mechanistic insights into the microstructural changes induced by sodium salts on disintegration and proteolysis of WPI gels during in vitro digestion. This is meaningful for future designing protein-based structured food products with designated digestion rates for targeted dietary demands. • Formation of coarse-stranded WPI gels with protein aggregation at higher NaCl concentration. • Elastic shear modulus of WPI gels showed an optimum at 0.15 M NaCl. • All gels were disintegrated by surface erosion mechanism during in vitro digestion. • Half disintegration time increased with increasing NaCl concentration in WPI gels. • Coarser gels showed less mass loss and a lower extent and rate of proteolysis.

Effect of whey protein isolate-based edible films containing amino acids on the PhIP level and physicochemical properties of pan-fried chicken breasts.

This study was conducted to investigate the inhibitory effects of edible films containing amino acids (AAs) on the formation of 2-amino-1-methyl-6-phenylimidazo [4,5-b] pyridine (PhIP) in chicken breasts and to evaluate the physicochemical properties of the chicken. Heated whey protein isolate (HWPI) solution (100 g) was made by heating 5 g whey protein isolate (WPI) solution at 90°C for 30 min in a water bath and subsequently mixed with 2.5 g glycerol (GLY), and tryptophan (Trp) or lysine (Lys) at 0.25%, 0.5%, and 0.75% concentrations. Unheated whey protein isolate (UHWPI)-based casting solution was prepared with the same method but without heating of WPI solution. Chicken breasts were cut at the same weights and were covered with the prepared edible films and fried at 195°C for 7.5 min. For edible films, total soluble matter (TSM%), color (calorimeter), radical scavenging activity (DPPH), and Fourier transform infrared spectroscopy (FTIR) were conducted. For chicken breasts, PhIP level, color before and after frying (calorimeter), cooking loss percentage (weigh loss before after frying), and tenderness (texture analyzer) were evaluated. The average PhIP level decreased from 78.47 ppb to 6.69-8.31 ppb for chicken covered with Lys-containing HWPI edible films, and to 25.82-46.80 ppb for chicken covered with Trp-containing ones. For chicken covered with UHWPI edible films, the PhIP decreased 28.4-56.04 ppb for Trp-containing ones and 19.67-40.32 ppb for Lys-containing ones. Moreover, chicken breasts covered with HWPI edible films had lower cooking loss and improved tenderness compared to the chicken breasts with no edible film. This study provides a new approach to decrease the PhIP levels in fried chicken breast.

Effects of Radiation on Cross-Linking Reaction, Microstructure, and Microbiological Properties of Whey Protein-Based Tissue Adhesive Development.

Whey proteins are mainly a group of small globular proteins. Their structures can be modified by physical, chemical, and other means to improve their functionality. The objectives of this study are to investigate the effect of radiation on protein–protein interaction, microstructure, and microbiological properties of whey protein–water solutions for a novel biomaterial tissue adhesive. Whey protein isolate solutions (10%, 27%, 30%, 33%, and 36% protein) were treated by different intensities (10–35 kGy) of gamma radiation. The protein solutions were analyzed for viscosity, turbidity, soluble nitrogen, total plate count, and yeast and mold counts. The interactions between whey proteins were also analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and scanning electron microscopy. The viscosity of protein solution (27%, w/w) was increased by the treatment of gamma radiation and by the storage at 23 °C. The 35 kGy intensity irradiated soluble nitrogen (10%, w/w) was reduced to about half of the sample treated by 0 kGy gamma radiation. The effects of gamma radiation and storage time can significantly increase the viscosity of whey protein solutions (p < 0.05). Radiation treatment had significant impact on soluble nitrogen of whey protein solutions (p < 0.05). SDS-PAGE results show that the extent of oligomerization of whey protein isolate solutions are increased by the enhancement in gamma radiation intensity. Photographs of SEM also indicate that protein–protein interactions are induced by gamma radiation in the model system. Consistent with above results, the bonding strength increases by the addition of extent of gamma radiation and the concentration of glutaraldehyde. Our results revealed that the combination of gamma-irradiated whey protein isolate solutions and glutaraldehyde can be used as a novel biomaterial tissue adhesive.

Ionic strength and buffering capacity of emulsifying salts determine denaturation and gelation temperatures of whey proteins

Ionic conditions affect the denaturation and gelling of whey proteins, affecting the physical properties of foods in which proteins are used as ingredients. We comprehensively investigated the effect of the presence of commonly used emulsifying salts on the denaturation and gelling properties of concentrated solutions of β-lactoglobulin (β-LG) and whey protein isolate (WPI). The denaturation temperature in water was 73.5°C [coefficient of variation (CV) 0.49%], 71.8°C (CV 0.38%), and 69.9°C (CV 0.41%) for β-LG (14% wt/wt), β-LG (30% wt/wt), and WPI (30% wt/wt), respectively. Increasing the concentration of salts, except for sodium hexametaphosphate, resulted in a linear increase in the denaturation temperature of WPI (kosmotropic behavior) and an acceleration in its gelling rate. Sodium chloride and tartrate salts exhibited the strongest effect in protecting WPI against thermal denaturation. Despite the constant initial pH of all solutions, salts having buffering capacity (e.g., phosphate and citrate salts) prevented a decrease in pH as the temperature increased above 70°C, resulting in a decline in denaturation temperature at low salt concentrations (≤0.2 mol/g). When pH was kept constant at denaturation temperature, all salts except sodium hexametaphosphate, which exhibited chaotropic behavior, exhibited similar effects on denaturation temperature. At low salt concentration, gelation was the controlling step, occurring up to 10°C above denaturation temperature. At high salt concentration (>3% wt/wt), thermal denaturation was the controlling step, with gelation occurring immediately after. These results indicate that the ionic and buffering properties of salts added to milk will determine the native versus denatured state and gelation of whey proteins in systems subjected to high temperature, short time processing (72°C for 15 s).

The effects of whey protein fibrils on the linear and non-linear rheological properties of a gluten-free dough.

The increasing awareness of the celiac disease, an autoimmune disorder caused by the consumption of products containing gluten, has led to a growing interest in the development of gluten-free bakery products. In this study, whey protein fibrils (WPFs) were incorporated to mimic the fibrous network of gluten. The rheological properties and microstructure of the developed gluten-free doughs were evaluated and compared with gluten doughs. Protein fibrils were prepared by heating a whey protein isolate (WPI) solution at 80°C in an acidic environment with low salt concentration, and then the fibril lengths were adjusted by leveling up the solution pH to 3.5 and 7. The dimensions of the fibrils were measured by atomic force microscopy (AFM). Rice and potato starches were mixed with fibrils, WPI, gluten, or without protein, to form different doughs for further investigation. Shear tests, including stress sweep, frequency sweep, and creep recovery, were performed to study the viscoelastic properties of doughs under small or large deformation. The strain-hardening properties of doughs under biaxial extension were studied by the lubricated squeezing flow method. The microstructure of the doughs was characterized by cryo-scanning electron microscopy (cryo-SEM). Compared with doughs prepared with WPI and no proteins, doughs incorporating fibrils showed comparable linear viscoelasticity to gluten dough tested with stress sweep, frequency sweep, and creep recovery in the linear viscoelastic region. More differences between the protein fibril doughs were revealed in the rheological properties in the non-linear region. Creep recovery parameters, such as compliance, elastic moduli during the creep, and recovery stages of gluten dough, were like those of WPF pH7 dough, but significantly different from those of the WPF pH3.5 dough. Strain-hardening properties were found in the WPF pH7 dough, although not in WPF pH3.5 dough. Microstructural characterization showed that both fibrils prepared with the different conditions formed a continuous protein phase for the improvement of dough cohesiveness, but the structure of the phase was different between the two fibrils. To summarize, whey protein fibril at pH 7 seemed to have the potential of being used as an ingredient with similar functions to gluten in gluten-free bakery products.

Lubrication properties of model dairy beverages: Effect of the characteristics of protein dispersions and emulsions

In this study we investigated the individual contribution of different ingredients to the lubrication properties of dairy-based model beverages containing whey protein (native or aggregated), micellar casein and emulsified oil in different combinations. In single-component systems, whey protein isolate (WPI) solutions showed the lowest friction coefficients of all protein samples. Whey protein aggregates (WPA, ∼247 nm, irregular morphology) led to higher friction coefficients than micellar casein isolate (MCI) with comparable size (∼207 nm, near spherical shape). When protein particles were combined, i.e. WPA and MCI, lubrication was not much affected. However, when WPI was added to either WPA or MCI, higher friction coefficients were observed compared to single-component systems. Emulsions (droplet size ∼ 440 nm) provided better lubrication than the protein samples. Oil droplets stabilized by soy lecithin (SL) were more efficient at reducing friction than those stabilized by WPI. The friction coefficient of SE strongly increased in the presence of WPI. In comparison, lubrication of WE was less affected by the addition of WPI. These results show that different proteins affect the lubrication properties of emulsions stabilized with different emulsifiers in a different way. Our research also indicates that multicomponent systems are complex, and that control over the lubrication properties requires a better understanding of the contribution of individual components.

The Influence of Whey Protein Heating Parameters on Their Susceptibility to Digestive Enzymes and the Antidiabetic Activity of Hydrolysates.

The inhibition of dipeptidyl peptidase-IV (DPP-IV) and the release of glucagon-like peptide-1 (GLP-1) could normalize blood glucose levels in diabetic patients. This study evaluated the susceptibility of whey proteins to enzyme hydrolysis and the antidiabetic properties of protein hydrolysates from β-lactoglobulin (β-LG) and α-lactalbumin (α-LA) solutions compared with whey protein isolate (WPI) solution treated at different heating temperatures (65, 75, and 85 °C). α-LA hydrolysate provided the lowest degree of hydrolysis (DH). Those heating temperatures did not significantly affect the DH of all protein hydrolysates. α-LA hydrolysate significantly increased GLP-1 levels and DPP-IV inhibitory activity more than β-LG hydrolysate. WPI hydrolysate inhibited DPP-IV activity less than an α-LA hydrolysate, but they were no significant differences for GLP-1 release activity. Heat treatment could affect the antidiabetic properties of all protein hydrolysates. Heating at 75 °C resulted in greater inhibition of the activity of DPP-IV than at 65 and 85 °C. The highest increase in GLP-1 release was also observed by heating at 75 °C. The recently obtained information is useful for the utilization of α-LA, heated at 75 °C for 30 min, in the preparation of antidiabetic food supplements.

Complexation behavior of Auricularia auricula polysaccharide and whey protein isolate: Characterization and potential beverage application

The formation of soluble complexes between whey proteins and polysaccharides has potentially useful applications in the beverage industry. In this study, Auricularia auricula polysaccharides (AP) and A. auricula extract (EAA) were prepared and their complexation behavior with whey protein isolate (WPI) was studied at pH 4.7 in order to ensure protein dispersal and avoid precipitation to achieve enhanced WPI stability. Both AP and EAA enhanced stability of 2%–4% WPI via the formation of complexes. WPI-AP and WPI-EAA solutions exhibited characteristics resembling steady pseudoplastic fluid. Heat treatment further resulted in altered structures of formed complexes which improved stability. Sensory evaluation by electronic tongue indicated that AP and EAA could relieve astringency of the WPI solution induced in acidic pH. This study provided the theoretical basis and demonstrated the potential application of a novel WPI-enriched beverage. Practical applications Functional Auricularia auricula polysaccharides and an A. auricula extract were shown to enhance stability of high concentrated whey protein isolate solutions. In this study, a potential commercially exploitable healthy beverage was developed. Furthermore, the foundation for its production is provided, which does not involve polysaccharide extraction steps thereby preserving the nutritional value of polysaccharide-rich ingredients.

Freeze − thaw induced structuration of whey protein − alfalfa (Medicago sativa L.) galactomannan binary systems

The cryotropic gelation of food biopolymers is an alternative method to impart bespoke structural, textural, and functional characteristics to food colloids. The present work aims to explore the structuring performance of whey protein isolate (WPI) in the presence of alfalfa (Medicago sativa L.) galactomannan (AAG) under cryogenic processing. Aqueous WPI solutions (10% wt.) fortified with AAG (0–1% wt.) were subjected to five consecutive freeze – thaw cycles from 25 to −28 °C with an isothermal hold at −28 °C for 20 h. The development of the elastic modulus G′ in the WPI – AAG solutions was monitored throughout the cryogenic processing, and the cryogels obtained were characterised rheologically, structurally and physically. The addition of AAG in heat-treated WPI solutions induced an extensive microscopic phase separation, which was driven via a depletion – flocculation mechanism. Cryostructuration was governed by WPI, whilst AAG modulated the development of the microstructural features, the rheological behaviour and the stability of the cryogels when confronted with spontaneous and forced syneresis phenomena. It was postulated that the mechanisms of action of AAG were associated primarily with its ability to enhance the macroviscosity of the unfrozen water phase controlling the ripening of ice crystals (porogens) during the freezing step, and secondarily to its direct contribution via the partially structured hydrogel segments interpenetrating the formed protein network. Since the extent of phase separation eminently affected the cryogelation process, it was suggested that the use of at least 0.75% wt. of AAG was required in order to enhance the structural, rheological and physical stability of the WPI cryogels.

Unraveling the nature of ohmic heating effects in structural aspects of whey proteins – The impact of electrical and electrochemical effects

Electric field (EF) variables and electrode material are fundamental factors in ohmic heating (OH) processing. In this study, stainless steel, titanium and graphite were used as electrodes in conventional and OH (at 50 Hz and 20 kHz) treatments of whey protein isolate solutions at pH 3 and pH 7. The treated solutions were characterized in terms of UV absorbance, changes in intrinsic fluorescence, binding of a conformational probe and secondary structure (evaluated by circular dichroism). Differentiated structural features were induced by the different treatment conditions and were more evident at pH 7 and OH at 50 Hz. The metal leakage (quantified with ICP-MS) from the electrodes revealed to influence the equilibrium of early stages of protein aggregation, with stainless steel demonstrating to be the most electro-active material followed by titanium and finally graphite (that did not release metal). These findings highlight that structural properties of whey proteins may not only be influenced by the EF action but also by the leakage of metals from the electrodes. Industrial relevanceOH is a recognized emerging processing technology and has a recognized potential to control and enhance protein functionality due its ability to influence protein structural features. Both electrode stability and protein structural changes are related with the EF operational parameters such as voltage, current or frequency. These parameters are decisive in the occurrence and extension of electrochemical phenomena and in the EF action mechanisms over protein structure. The confirmation of EF non-thermal effects at high and low frequencies (independently of the electrochemical phenomena) dissipated previous doubts regarding its effectiveness to modulate protein functionality. The understanding of the electrode material stability and influence of different electric parameters on the product's functionality, stability and safety are fundamental to design OH devices and to the establishment of operational protocols. The stability and material release from the electrodes is a fundamental factor during OH processing, imposing serious implications in equipment costs, maintenance, as well as in product quality and safety. This study highlights the influence of different electrode materials during OH at different electrical frequencies and its impacts on protein structural aspects.