Effect of different iron ratios on interaction and thermodynamic stability of bound whey protein isolate.

Whey protein isolates (WPI) are known to have mineral-binding capacity to promote iron absorption. The aim of this study was to investigate the effect of iron ratio on the conformational structure of iron-bound whey protein isolate (WPI-Fe) and its thermodynamic stability. It was shown that the iron to protein ratio affects both the iron binding capacity of WPI and the iron valence state on the surface of WPI-Fe complexes. As the iron content increases, aggregation between protein molecules occurs. In addition, WPI-Fe nanoparticles have thermodynamic stability and Fe2+ has a high affinity with WPI for spontaneous exothermic reactions. This study demonstrates that WPI-Fe complexes can be used to efficiently deliver high-quality iron source (Fe2+) for future iron supplements.

An Apple and Acáchul Berry Snack Rich in Bioaccessible Antioxidants and Folic Acid: A Healthy Alternative for Prenatal Diets.

A fruit leather (apple and acáchul berry) oriented toward women of reproductive age was developed. The snack was supplemented with an ingredient composed of folic acid (FA) and whey proteins (WPI) to ensure the required vitamin intake to prevent fetal neural tube defects. In order to generate a low-calorie snack, alternative sweeteners were used (stevia and maltitol). The fruit leather composition was determined. Also, an in vitro digestion process was carried out to evaluate the bioaccessibility of compounds with antioxidant capacity (AC), total polyphenols (TPCs), total monomeric anthocyanins (ACY), and FA. The quantification of FA was conducted by a microbiological method and by HPLC. The leather contained carbohydrates (70%) and antioxidant compounds, mainly from fruits. Bioaccessibility was high for AC (50%) and TPCs (90%), and low for ACY (17%). Regarding FA, bioaccessibility was higher for WPI-FA (50%) than for FA alone (37%), suggesting that WPI effectively protected the vitamin from processing and digestion. Furthermore, the product was shown to be non-cytotoxic in a Caco-2 cell model. The developed snack is an interesting option due to its low energy intake, no added sugar, and high content of bioactive compounds. Also, the supplementation with WPI-FA improved the conservation and bioaccessibility of FA.

Whey protein isolate and inulin-glycosylated conjugate affect the physicochemical properties and oxidative stability of pomegranate seed oil emulsion.

Glycosylated protein was obtained by the reaction of whey protein isolate(WPI) with inulin of different polymerization degrees and was used to stabilize a pomegranate seed oil emulsion. The physicochemical and antioxidative properties of the emulsions were assessed, and the impacts of accelerated oxidation on pomegranate seed oil were examined. The interfacial tension of WPI and short-chain inulin (SCI)-glycosylated conjugate (WPI-SCI) gradually decreased with increasing glycosylation reaction time. Emulsions stabilized by WPI-SCI (72 h) were the most stable, with a thick interfacial film on the surface of the droplets. After accelerated oxidation for 72 h, WPI-SCI inhibited the oxidation of oil in the emulsion. GC-IMS results showed that the production of harmful volatile components in oil was inhibited, and the peroxide strength was less than 30 mmol/kg oil. This study contributes to understanding of stable storage of lipids.

Pectin-coated whey protein isolate/zein self-aggregated nanoparticles as curcumin delivery vehicles: Effects of heating, pH, and adding sequence.

In this work, pectin was employed as a coating material to fabricate zein/whey protein isolate (WPI)/pectin complex nanoparticles via a pH-adjusted and heat-induced electrostatic adsorption process for potential oral administration applications of curcumin. Factors such as the order of raw material addition, heating temperature and pH, and zein concentration were comprehensively examined. In addition to electrostatic interactions, Fourier transform infrared and fluorescence spectroscopy indicated that hydrophobic interactions and hydrogen bonds were also involved in the development of complex nanoparticles. The complex nanoparticles obtained not only improved the antioxidant activity of curcumin in aqueous phase, but also contributed to its controlled release under gastrointestinal conditions. Our findings revealed that the heating pH and adding sequence of raw materials had a notable impact on the properties of complex nanoparticles, and that pectin coating had an exceptional stabilizing effect on complex nanoparticles under gastrointestinal circumstances. This study provides novel insights and perspectives for the preparation of polysaccharide-protein complex nanoparticles, signifying the potential use of zein/WPI/pectin complex nanoparticles as delivery vehicles in the functional food and pharmaceutical industries.

Effects of whey protein isolate and ferulic acid/phloridzin/naringin/cysteine on the thermal stability of mulberry anthocyanin extract at neutral pH.

In this study, the effects of whey protein isolate (WPI) and four copigments, including ferulic acid (FA), phloridzin, naringin, and cysteine (Cys), on the thermal stability (80 °C/2h) of mulberry anthocyanin extract (MAE) pigment solution at pH 6.3 were studied. WPI addition or copigment (except for Cys) addition alone could protect anthocyanin from degradation to a certain degree, and FA exhibited the best effect among copigments. Compared with the MAE-WPI and MAE-FA binary systems, ΔE of the MAE-WPI-FA ternary system decreased by 20.9% and 21.1%, respectively, and the total anthocyanin degradation rate decreased by 38.0% and 39.3%, respectively, indicating the best stabilizing effect. Remarkably, interactions between anthocyanins and Cys, which generate four anthocyanin derivatives with 513-nm UV absorption during heat treatment, did not alter the color stability of MAE solution; however, they accelerated anthocyanin degradation. These results favor the combined use of multiple methods to stabilize anthocyanins at neutral conditions.

Quality Improvement of Garlic Paste by Whey Protein Isolate Combined with High Hydrostatic Pressure Treatment.

Garlic, one of the most popular spices and medical herbs, has a unique pungent flavor and taste. Conventional homogenization and thermal treatment commonly lead to flavor and color deterioration in garlic paste, because allicin is highly susceptible to degradation and reaction. The present study was to investigate the effects of whey protein isolate (WPI) and different levels of high hydrostatic pressure (HHP, 200, 300, 400, 500, and 600 MPa) on the quality of garlic paste. Results showed that the addition of WPI in the homogenization of garlic significantly prevented green discoloration. Furthermore, WPI plus HHP under 500 MPa could better protect the color of garlic paste. Higher pressure (600 MPa) led to WPI aggregation, resulting in higher green color chroma of garlic paste. GC-MS results revealed that the application of WPI and HHP in garlic paste increased the relative level of pungent flavor compounds and decreased those of unpleasant odor compounds. The correlation analysis results revealed that WPI efficiently prevented garlic green discoloration, which is attributed to the thiol group in WPI exchanging the sulfonyl groups in allicin. In consideration of the microbial load, flavor and color quality of garlic paste, the optimal processing conditions were found at 500 MPa for 5 min with 2% WPI addition, extending shelf life to 25 days.

The effect of sweet tea polysaccharide on the physicochemical and structural properties of whey protein isolate gels.

In this study, we investigated the effect of sweet tea polysaccharide (STP) on the physicochemical and structural properties of heat-induced whey protein isolate (WPI) gels, and explored the potential mechanism. The results indicated that STP promoted the unfolding and cross-linking of WPI to form a stable three-dimensional network structure, and significantly improved the strength, water-holding capacity and viscoelasticity of WPI gels. However, the addition of STP was limited to 2 %, too much STP would loosen the gel network and affect the gel properties. The results of FTIR and fluorescence spectroscopy suggested that STP affected the secondary and tertiary structures of WPI, promoted the movement of aromatic amino acids to the protein surface and the conversion of α-helix to ß-sheet. In addition, STP reduced the surface hydrophobicity of the gel, increased the free sulfhydryl content, and enhanced the hydrogen bonding, disulfide bonding, and hydrophobic interactions between protein molecules. These findings can provide a reference for the application of STP as a gel modifier in the food industry.

Stabilization of anthocyanins by simultaneous encapsulation-copigmentation via protein-polysaccharide polyelectrolyte complexes.

This study prepared a series of polyelectrolyte complexes (PECs) composed of heated whey protein isolate (HWPI) and different polysaccharides for simultaneous encapsulation and copigmentation of anthocyanins (ATC) and their ultimate stabilization. Four polysaccharides including chondroitin sulfate, dextran sulfate, gum arabic, and pectin were chosen due to their abilities to simultaneously complex with HWPI and copigment ATC. At pH 4.0, these PECs were formed with an average particle size of 120-360 nm, the ATC encapsulation efficiency of 62-80%, and the production yield of 47-68%, depending on the type of polysaccharides. The PECs effectively inhibited the degradation of ATC during storage and when exposed to neutral pH, ascorbic acid, and heat. Pectin had the best protection, followed by gum arabic, chondroitin sulfate, and dextran sulfate. The stabilizing effects were associated with the hydrogen bonding, hydrophobic and electrostatic interactions between HWPI and polysaccharides, conferring dense internal network and hydrophobic microenvironment in the complexes.

Milk Protein Hydrolysis by Actinidin-Kinetic and Thermodynamic Characterisation and Comparison to Bromelain and Papain.

Plant proteases, including actinidin, papain and bromelain, have been widely used in the food industry but with limited application in dairy systems. This research aimed to establish and compare operational parameters (kinetics, temperature, enzyme type, time and thermodynamics) relevant to the applications of these enzymes in the hydrolysis of whey protein isolates (WPI), whey protein concentrates (WPC) or milk protein concentrates (MPC). The degree of hydrolysis (DH) increased with the rise in temperature, and the maximum DH was achieved at 60 °C for all three dairy systems. The addition of papain resulted in a greater %DH of whey proteins in comparison to bromelain. The cleavage of proteins was clearly time-dependent (p < 0.05), while the pH did not change significantly (p > 0.05) during this time. PAGE analysis revealed that all three enzymes mainly acted on α-lactalbumin and αs-casein in WPI and MPC, respectively. Kinetic parameters from the Lineweaver-Burk plot at 60 °C using WPC and MPC as a substrate varied widely, establishing that WPC hydrolysis was characterised by a lower KM, higher kcat, kcat/KM and Vmax compared to MPC in the case of all three enzymes. The difference in kcat/KM values amongst all enzymes (actinidin > papain > bromelain) indicated the difference in the strength of substrate binding sites. The thermodynamic parameters of these enzymes with MPC and WPC were also determined at a temperature range of 15-60 °C, and the results indicate the potential application of papain and actinidin in the dairy industry.

Physicochemical and Sensory Properties Colored Whey Protein-Cellulose Nanocrystal Edible Films after Freeze-Thaw Treatment.

Balancing physicochemical properties and sensory properties is one of the key points in expanding edible packaging applications. The work consisted of two parts, one was to investigate the effects of cellulose nanocrystals (CNC) on the packaging-related properties of whey protein isolate films with natural colorants (curcumin, phycocyanin, and lycopene) under freeze-thaw (FT) conditions; the other was to test oral tactility and visual sensory properties of the edible films and their overall acceptability in packed ice cream. FT treatment reduced the mechanical strength and moisture content and increased the water vapor permeability of the films, as water-phase transformation not only disrupted hydrogen bonds but also the film network structure through physical stress. The oral tactility produced by CNC and the visual effect produced by colorants could affect participants' preference for edible films. This study provides a good reference for the consumer-driven product development of packaged low-temperature products.

Preparation of alginate-whey protein isolate and alginate-pectin-whey protein isolate composites for protection and delivery of Lactobacillus plantarum.

Probiotics are sensitive to external conditions, resulting in low survival rates after being ingested or during food production, transportation and storage. In order to improve the survival rate of Lactobacillus plantarum (LP) during gastrointestinal digestion, storage, and freeze-drying, alginate-whey protein isolate (ALG-WPI) and alginate-pectin-whey protein isolate (ALG-PEC-WPI) composites were employed to encapsulate LP. The encapsulation efficiency of ALG-WPI-LP and ALG-PEC-WPI-LP beads both reached more than 99 %. Scanning electron microscopy (SEM) indicated that dense and rough aggregates were formed on the surface of both composites, and attached LP cells could be observed inside the beads. The ALG-WPI and ALG-PEC-WPI composites can protect the viability of LP in simulated gastric fluid (SGF) and release the probiotics in simulated intestinal fluid (SIF). The storage stability of LP at 4 °C was improved by about 15 % in comparison with bare LP and the survival rates of LP in ALG-WPI-LP and ALG-PEC-WPI-LP powders after freeze-drying were increased by 65.37 % and 72.06 %, respectively. The formation mechanism of ALG-WPI and ALG-PEC-WPI composites was further explored by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The ALG-WPI and ALG-PEC-WPI composites have great potential to protect and deliver probiotics in food systems.

Development of whey protein isolate-phytosterols complexes stabilized oil-in-water emulsion for ß-carotene protection and delivery.

Although ß-carotene (BC) exerts beneficial effects on human health, the direct use of this compound as a nutritional supplement is hindered by its low water solubility and oxidation stability. Herein, we develop an oil-in-water emulsion stabilized by whey protein isolate (WPI)-phytosterols (PS) complexes as a delivery system for BC to overcome the above limitations. The rheology and stability of the emulsion were characterized, and the influence of the emulsion on the chemical stability and bioaccessibility of BC was discussed. The results showed that the PSs promoted the adsorption of WPI at the oil-water interface and improved the viscosity and viscoelasticity of the emulsion. The emulsion with a WPI:PS mass ratio of 25:2 (EWPI-PS) featured the highest fraction of interfacial adsorbed protein (88.73 %), excellent stability during 21-day storage at 25 °C. The BC retention rate of EWPI-PS (61.48 %) was significantly higher than that of the emulsion stabilized by WPI only (EWPI, 31.90 %) after 21-day storage at 50 °C. In addition, BC-loaded EWPI-PS showed higher freeze-thaw and thermal stability than BC-loaded EWPI, and a lower free fatty acid release rate and BC bioaccessibility than BC-loaded EWPI in simulated gastrointestinal digestion experiments. These results provide a theoretical basis for the WPI-PS complexes-stabilized emulsion as BC delivery system.

Cholecalciferol- and α-tocopherol-loaded walnut oil emulsions stabilized by whey protein isolate and soy lecithin for food applications.

BACKGROUND: To overcome the limitations in the use of protein as an emulsifier, soy lecithin, a natural surfactant, was used along with whey protein isolate (WPI) to produce o/w emulsions containing cholecalciferol and α-tocopherol. The physical stability of the emulsions prepared with WPI and varying concentrations of lecithin (0, 1, 2, and 3% w/w) was measured in different heat, pH, and ionic-strength food environmental conditions. RESULTS: All emulsions were shown to be less than 250 nm in size and less than 0.3 in polydispersity index (PDI). The morphology of the emulsions was spherical, and the droplets of the emulsion containing lecithin were thicker and larger than those of the emulsion without lecithin (WPI_L0). After autoclaving, WPI_L0 increased in size from 197.8 ± 1.7 nm to 528.5 ± 28.4 nm, and the retention of cholecalciferol and α-tocopherol decreased to 40.83 ± 0.63% and 49.68 ± 1.84%, respectively. At pH 5.5, near the isoelectric point of WPI, WPI_L0 increased in size due to aggregation, but emulsions containing lecithin remained stable at a PDI under 0.3. Turbiscan stability index of the emulsion prepared with WPI and 3% lecithin was the lowest, indicating good storage stability. In addition, it was confirmed that the higher the lecithin content, the higher the viscosity, and the higher the amount of free fatty acids released in the in vitro digestion model. CONCLUSION: This study can provide theoretical evidence for enhancing the physical stability of protein emulsions by co-stabilization with lecithin, promoting their application in various foods. © 2022 Society of Chemical Industry.

Study on the mechanism of non-covalent interaction between rose anthocyanin extracts and whey protein isolate under different pH conditions.

The non-covalent interaction between anthocyanin and dietary protein had an impact on their physicochemical property. The purpose of this study was to study the non-covalent interaction mechanism between rose anthocyanin extract (RAEs) and whey protein isolate (WPI), and further compare the interaction mechanism with pure anthocyanin (PC) and WPI. At pH 3.0 and pH 7.0, RAEs and WPI had non-covalent interactions in the two systems with two types of unequal and mutually influencing binding sites, and the interaction forces were both hydrogen bonds and van der Waals forces. Interestingly, PC and WPI also had non-covalent interactions in both systems, the number of which binding sites was about one type, and the forces were hydrogen bonds and van der Waals forces. In addition, a variety of spectral combination techniques indicated that RAEs and PC caused similar changes in the secondary structure of WPI.

Effect of whey protein isolate and phenolic copigments in the thermal stability of mulberry anthocyanin extract at an acidic pH.

This study investigated the effect of whey protein isolate (WPI) and phenolic copigments on the color and anthocyanin stability of mulberry anthocyanin extract (MAE) subjected to heat treatment (80℃/120 min) at pH 3.6. Results showed that four phenolic compounds, including gallic acid, ferulic acid, (-)-epigallocatechin gallate (EGCG), and rutin, significantly affected the color enhancement of MAE solution, among which the strongest copigmentation effect on MAE was observed for rutin at 0.08-0.8 mg/ml. WPI (0.16 mg/ml) and rutin (0.8 mg/ml) reduced the thermal degradation rate of total anthocyanins by 27.1% and 50%, respectively. WPI-MAE-rutin ternary mixtures improved the color stability of MAE solution and decreased the anthocyanin's thermal degradation rate by 18.1% and 10.6%, respectively, compared with the corresponding binary systems (MAE-WPI and MAE-rutin). The results implied the MAE-WPI-rutin had a better protective effect on the thermal stability of MAE than the binary systems.

Structural and foaming properties of whey and soy protein isolates in mixed systems before and after heat treatment.

The partial replacement of proteins from animal sources by plant proteins in formulated food products has been proposed as useful to improve sustainability aspects of the products without dramatically changing their techno-functional properties. Although several research groups have published on the gelling properties of mixed systems containing whey and soy protein isolates (WPI and SPI), their foaming properties are much less described. In this context, the main objective of this paper was to evaluate the structural and foaming properties of samples containing different mass ratios of WPI:SPI (100:0, 75:25, 50:50, 25:75 and 0:100) before and after heat treatment. The samples were evaluated according to their solubility, foaming capacity (FC), foam microstructure and foam stability (FS). Before heat treatment, mixing SPI to WPI did not affect the solubility of whey proteins, but, after heat treatment, insoluble co-aggregates were formed. Similar FC was measured for all samples despite their WPI:SPI ratio and the applied heat treatment. The partial replacement of WPI by SPI changed the microstructure of the foams and had an antagonistic effect on the FS of the samples, due to the negative effect of insoluble soy protein aggregates and/or insoluble co-aggregates on the reinforcement of the air-water interfacial film.

Whey protein isolate-gum Acacia Maillard conjugates as emulsifiers for nutraceutical emulsions: Impact of glycation methods on physicochemical stability and in vitro bioaccessibility of ß-carotene emulsions.

The physicochemical stability and in vitro bioaccessibility of ß-carotene emulsions stabilized by the whey protein isolate (WPI)-gum Acacia (GA) conjugates prepared by dry-heating (Con WPI (D)) and ultrasound (Con WPI (U)) Maillard reaction were investigated in this study. The conjugate-stabilized emulsions have a larger mean size than the WPI-stabilized emulsion. The stability of emulsions under freeze-thaw treatment, high ionic strength conditions, thermal treatment and pH conditions near the isoelectric point of WPI were improved by glycation. The chemical stability of ß-carotene in emulsions was also enhanced by WPI-GA conjugates. The WPI-GA conjugate-stabilized emulsions have better stability for droplet aggregation during in vitro simulated gastrointestinal digestion, which increased ß-carotene bioaccessibility. However, the Con WPI (U)-stabilized emulsion shows poor thermal stability and lower ß-carotene bioaccessibility than the Con WPI (D)-stabilized emulsion, which may be attributed to ultrasound-induced structural changes during the process of glycation.

Grape seed proanthocyanidin-loaded gel-like W/O/W emulsion stabilized by genipin-crosslinked alkaline soluble polysaccharides-whey protein isolate conjugates: Fabrication, stability, and in vitro digestion.

The present work aims to fabricate the genipin-crosslinked alkaline soluble polysaccharides-whey protein isolate conjugates (G-AWC) to stabilize W/O/W emulsions for encapsulation and delivery of grape seed proanthocyanidins (GSP). After crosslinking reaction, the molecular weight was increased and surface hydrophobicity was decreased. Then, the G-AWC and polyglycerol polyricinoleate (PGPR, a lipophilic emulsifier) were employed to prepare a GSP-loaded W/O/W emulsion with the addition of gelatin and sucrose in W1 phase via a two-step procedure. Creamed emulsion could be fabricated at W1/O volume fraction (Φ) of 10%-70% and further increased Φ to 75% or even up to 90% could obtain gel-like emulsion with notably elastic behaviors. In the W1/O/W2 emulsion with Φ of 80%, the encapsulation efficiency (EE) of GSP reached up to 95.86%, and decreased by ca. 10% after a week of storage. Moreover, the encapsulated GSP in the emulsion showed a remarkably higher bioaccessibility (40.72%) compared to free GSP (13.11%) in the simulated gastrointestinal digestion. These results indicated that G-AWC-stabilized W/O/W emulsions could be an effective carrier to encapsulate water-soluble bioactive compounds with enhanced stability and bioaccessibility.

Structural characterization of modified whey protein isolates using cold plasma treatment and its applications in emulsion oleogels.

Cold plasma as a green and expeditious tool was used to modify whey protein isolate (WPI) in order to improve its emulsion capability. The emulsion-based oleogels with antibacterial functions were then constructed using the modified WPI. The modified WPI treated with cold plasma under 10 s at 50 W power significantly lowered the oil-water interface tension. Meanwhile, the fluorescence intensity and the α-helix content of WPI reduced with the cold plasma treatment. It is noted that SEM results showed that the treated WPI had more regular dendritic structures. Such modified WPI was applied to construct oleogels loaded with thyme essential oil and coconut oil, which showed a porous uniform network structure and excellent antimicrobial activities against E.coli. As a proof of concept, this study demonstrated cold plasma could be as a new facile tool to modify food-sourced proteins and expected to enlarge their applications in oleogel productions.

Fabrication and characterization of whey protein isolates- lotus seedpod proanthocyanin conjugate: Its potential application in oxidizable emulsions.

Emulsified ω-3 polyunsaturated fatty acid have expanding application in different food matrix with improved water solubility while still prone to oxidation. Lotus seedpod proanthocyanidin (LSPC) was grafted to whey protein isolate (WPI) to create nature-derived antioxidant emulsifiers. 1HNMR, SDS-PAGE and multiple spectrometry showed that the structure of protein was changed after grafting. DPPH and FRAP measurements showed that WPI-LSPC conjugate (90.53 ± 1.48% of DPPH scavenging, 691.85 ± 4.54 µg/mL for FRAP assay) possessed a much better antioxidant ability than WPI (17.06 ± 3.34% of DPPH scavenging, 10.43 ± 0.26 µg/mL for FRAP assay). Ultrasonic emulsification and DSC experiments showed that WPI-LSPC conjugate were more effective at forming and stabilizing the flaxseed oil emulsions than pure WPI, with higher thermostability. Likewise, low levels of primary and secondary oxidation products were formed for the conjugate than the pure protein in O/W systems after storage, again suggesting WPI-LSPC could be used as fine antioxidant emulsifiers in oxidizing delivery systems.