Effect of heat treatment on physicochemical and emulsifying properties of polymerized whey protein concentrate and polymerized whey protein isolate

Improvement of branched-chain amino acid production by isolated high-producing protease from Bacillus amyloliquefaciens NY130 on isolated soy/whey proteins and their muscle cell protection

Branched-chain amino acids (BCAAs) are vital components of human and animal nutrition that contribute to the building blocks of proteins. In this study, 170 protease-producing strains were isolated and screened from soy-fermented foods. Bacillus amyloliquefaciens NY130 was obtained from Cheonggukjang with high production of BCAAs. Optimal production of protease from B. amyloliquefaciens NY130 (protease NY130) was achieved at 42 °C and pH 6.0 for 21 h. It was purified and determined as 27- and 40 kDa. Protease NY130 showed maximum activity at pH 9.0 and 45 °C with Km value of 10.95 mg for ISP and 1.69 mg for WPI. Protease-treated ISP and WPI showed increased sweetness and saltiness via electronic tongue analysis and enhanced the protective effect against oxidative stress in C2C12 myocytes by increasing p-mTOR/mTOR protein expression to 160%. This work possesses potential in producing BCAAs by using protease for utilization in food.

Effects of thermal treatment on the formation and properties of whey protein isolate/whey protein hydrolysate-sodium hyaluronate complexes

In dairy products, the added sodium hyaluronate may form complexes with proteins, thereby affecting product properties. In the present study, the interaction between whey protein isolate (WPI)/ whey protein hydrolysate (WPH) and sodium hyaluronate (SH) was characterized under thermal treatment at different temperatures (25 ℃, 65 ℃, 90 ℃ and 121 ℃) after studying effects of protein/SH ratio and pH on complex formation. The addition of SH reduced the particle size of WPI/WPH and increased potential value in the system, with greater variation with increasing treatment temperature. The structural properties of complexes were studied. The binding with SH decreased the contents of free amino group and free thiol group, as well as the fluorescence intensity and surface hydrophobicity. FTIR results and browning intensity measurement demonstrated the formation of Maillard reaction products. Moreover, the attachment of SH improved the thermal stability of WPI/WPH and decreased their antigenicity.

New perspective on protein-based microcapsules as delivery vehicles for sensitive substances: A review

Sensitive substances have attracted wide attention due to their rich functional activities, such as antibiosis activities, antioxidant activities and prevent disease, etc. However, the low stability of sensitive substances limits their bioavailability and functional activities. Protein-based microcapsules can encapsulate sensitive substances to improve their adverse properties due to their good stability, strong emulsifying ability and wide source. Therefore, it is necessary to fully elaborate and summarize protein-based microcapsules to maximize their potential benefits in nutritional interventions. The focus of this review is to highlight the classification of protein-based microcapsules. In addition, the principles, advantages and disadvantages of preparation methods for protein-based microcapsules are summarized. Some novel preparation methods for protein-based microcapsules are also emphasized. Moreover, the mechanism of protein-based microcapsules that release sensitive substances in vitro is elucidated and summarized. Furthermore, the applications of protein-based microcapsules are outlined. Protein-based microcapsules can effectively encapsulate sensitive substances, which improve their bioavailability, and provide protective effects during storage and gastrointestinal digestion. In addition, microcapsules can improve the sensory quality of food and enhance its stability. The performance of protein-based microcapsules for delivering sensitive substances is influenced by factors such as protein type, the ratio between protein ratio and the other wall material, the preparation process, etc. Future research should focus on the new composite protein-based microcapsule delivery system, which can be applied to in vivo research and have synergistic effects and precise nutritional functions. In summary, protein-based microcapsules have broader research prospects in the functional foods and nutrition field.

Study on stabilized mechanism of high internal phase Pickering emulsions based on commercial yeast proteins: Modulating the characteristics of Pickering particle via sonication

The primary significance of this work is that the commercial yeast proteins particles were successfully used to characterize the high internal phase Pickering emulsions (HIPPEs). The different sonication time (0,3,7,11,15 min) was used to modulate the structure and interface characteristics of yeast proteins (YPs) that as Pickering particles. Immediately afterward, the influence of YPs particles prepared at different sonication time on the rheological behavior and coalescence mechanism of HIPPEs was investigated. The results indicate that the YPs sonicated for 7 min exhibited a more relaxed molecular structures and conformation, the smallest particle size, the highest H0 and optimal amphiphilicity (the three-phase contact (θ) was 88.91°). The transition from extended to compact conformations of YPs occurred when the sonication time exceeded 7 min, resulting in an augmentation of size of YPs particles, a reduction in surface hydrophobicity (H0), and an elevation in hydrophilicity. The HIPPEs stabilized by YPs particles sonicated for 7 min exhibited the highest adsorption interface protein percentage and a more homogeneous three-dimensional (3D) protein network, resulting in the smallest droplet size and the highest storage (G'). The HIPPEs sample that stabilized by YPs particles sonicated for 15 min showed the lowest adsorption protein percentage. This caused a reduction in the thickness of its interface protein layer and an enlargement in the droplet diameter (D [3,2]). It was prone to droplet coalescence according to the equation used to evaluate the coalescence probability of droplets (Eq (2)). And the non-adsorbed YPs particles form larger aggregation structures in the continuous phase and act as "structural agents" in 3D protein network. Therefore, mechanistically, the interface protein layer formed by YPs particles sonicated 7 min contributed more to HIPPEs stability. Whereas the "structural agents" contributed more to HIPPEs stability when the sonication time exceeded 7 min. The present results shed important new light on the application of commercial YPs in the functional food fields, acting as an available and effective alternative protein.

Effect of high moisture extrusion on the structure and physicochemical properties of Tartary buckwheat protein and its in vitro digestion

Tartary buckwheat is rich in nutrients and its protein supports numerous biological functions. However, the digestibility of Tartary buckwheat protein (TBP) poses a significant limitation owing to its inherent structure. This study aimed to assess the impact of high moisture extrusion (HME, 60 % moisture content) on the structural and physicochemical attributes, as well as the in vitro digestibility of TBP. Our results indicated that TBP exhibited unfolded and amorphous microstructures after HME. The protein molecular weight of TBP decreased after HME, and a greater degradation was observed at 70 °C than 100 °C. In particular, HME at 70 °C caused an almost complete disappearance of bands near 35 kDa compared with HME at 100 °C. In addition, compared with native TBP (NTBP, 44.53 µmol/g protein), TBP subjected to HME at 70 °C showed a lower disulfide bond (SS) content (42.67 µmol/g protein), whereas TBP subjected to HME at 100 °C demonstrated a higher SS content (45.70 µmol/g protein). These changes endowed TBP with good solubility (from 55.96 % to 83.31 % at pH 7), foaming ability (20.00 %-28.57 %), and surface hydrophobicity (8.34-23.07). Furthermore, the emulsifying activity (EA) and in vitro digestibility are closely related to SS content. Notably, extruded TBP (ETBP) obtained at 70 °C exhibited higher EA and digestibility than NTBP, whereas ETBP obtained at 100 °C showed the opposite trend. Consequently, HME (especially at 70 °C) demonstrated significant potential as a processing technique for improving the functional and digestive properties of TBP.

Constructing a strongly interacting Pea-Cod binary protein system by introducing metal cations toward enhanced gelling properties

Developing prospective plant-animal binary protein systems with desirable nutritional and rheological properties stands as a significant and challenging pursuit within the food industry. Our understanding of the effect of adding salt on the aggregation behavior of food proteins is currently based on single model protein systems, however, this knowledge is rather limited following binary protein systems. Herein, various ionic strength settings are used to mitigate the repulsive forces between pea-cod mixed proteins during the thermal process, which further benefits the construction of a strengthened gel network. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) collectively demonstrated that larger heat-induced protein aggregates were formed, which increased in size with higher ionic strength. In the presence of 2.5 mM CaCl2 and 50 mM NaCl, the disulfide bonds significantly increased from 19.3 to 27.53 and 30.5 μM/g, respectively. Notably, similar aggregation behavior could be found when introducing 2.5 mM CaCl2 or 25 mM NaCl, due to the enhanced aggregation tendency by specific binding of Ca2+ to proteins. With relevance to the strengthened cross-links between protein molecules, salt endowed composite gels with preferable gelling properties, evidenced by increased storage modulus. Additionally, the gelling temperature of mixed proteins decreased below 50 °C at elevated ionic strength. Simultaneously, the proportion of network proteins in composite gels increased remarkably from 82.05 % to 93.61 % and 92.31 % upon adding 5.0 mM CaCl2 and 100 mM NaCl, respectively. The findings provide a valuable foundation for designing economically viable and health-oriented plant-animal binary protein systems.

Characterization of yeast protein isolates extracted via high-pressure homogenization and pH shift: A promising protein source enriched with essential amino acids and branched-chain amino acids

In the global food industry, plant-based protein isolates are gaining prominence as an alternative to animal-based counterparts. However, their nutritional value often falters due to insufficient essential amino acids. To address this issue, our study introduces a sustainable protein isolate derived from yeast cells, achieved through high-pressure homogenization (HPH) and alkali pH-shifting treatment. Subjected to HPH pressures ranging from 60 to 120 MPa and 1 to 10 cycles, higher pressure and cycle numbers resulted in enhanced disruption of yeast cells. Combining HPH with alkali pH-shifting treatment significantly augmented protein extraction. Four cycles of HPH at 100 MPa yielded the optimized protein content, resulting in a yeast protein isolate (YPI) with 75.3 g protein per 100 g powder, including 30.0 g of essential amino acids and 18.4 g of branched-chain amino acids per 100 g protein. YPI exhibited superior water and oil-holding capacities compared to pea protein isolate, whey protein isolate (WPI), and soy protein isolate. Although YPI exhibited lower emulsifying ability than WPI, it excelled in stabilizing protein-stabilized emulsions. For foaming, YPI outperformed others in both foaming ability and stabilizing protein-based foam. In conclusion, YPI surpasses numerous plant-based protein alternatives in essential amino acids and branched-chain amino acids contents, positioning it as an excellent candidate for widespread utilization as a sustainable protein source in the food industry, owing to its exceptional nutritional advantages, as well as emulsifying and foaming properties. PRACTICAL APPLICATION: This study introduces a sustainable protein isolate derived from yeast cells. YPI exhibited considerable promise as a protein source. Nutritionally, YPI notably surpassed plant-based protein isolates in EAA and BCAA contents. Functionally, YPI demonstrated superior water-holding and oil-holding capacities, as well as an effective emulsion and foam stabilizer.

Chitin nanocrystals as natural gel modifier for yielding stronger acid-induced soy protein isolate gel

This study aimed to enhance the rheological properties and thermal stability of acid-induced soy protein isolate (SPI) gels by incorporating chitin nanocrystals (ChNCs) and proposing a gelation mechanism. SPI gels exhibited pseudo-plastic behavior. Increasing ChNCs concentration from 0.00 % to 1.00 % improved G' values, recovery rate, and initial degradation temperature: from 75.6 Pa to 1024.3 Pa, 80.27 % to 85.47 %, and 261.5 °C to 275.8 °C, respectively. FTIR analysis confirmed electrostatic and hydrogen bonding interactions between SPI and ChNCs. Adding 1.00 % ChNCs reduced α-helix content from 19.7 % to 12.1 % while increasing β-sheet content from 46.5 % to 52.6 %. This led to protein unfolding, exposure of Trp residues, and orderly aggregation, forming a dense cross-linked gel network. Gel particle size increased from 185.5 nm (no ChNCs) to 504.4 nm (1.00 % ChNCs), with reduced surface charges. Hydrophobic and electrostatic interactions were key forces stabilizing SPI-ChNCs gels. These findings offer a practical approach to enhancing traditional acid-induced protein gel-based functional foods using naturally sourced chitin nanocrystals.

Aggregation studies of alpha-lactalbumin induced by edible azo dyes with different sulfonyl group numbers: A comparative study

As an opaque and complex colloidal mixture, milk is usually present as a positively charged colloid under acidic conditions. Adding negatively charged colloids can lead to protein aggregation in milk. Alpha-lactalbumin (α-La) is an essential component of whey protein and has good physicochemical properties for functional food development. We combined spectroscopy, computer simulations, and other techniques to comparative analyze the mechanisms and characteristics of isolated α-La aggregation induced by CI Acid Red 27 (C27)/CI Acid Red 14 (FB) containing different sulfonyl groups in vitro. The results showed that C27/FB (5.25 × 10-5 mol·L-1 to 3.15 × 10-4 mol·L-1) induced the formation of fibril-like aggregates under acidic conditions (pH 2.0 and 4.0) mainly benefit from hydrophobic and electrostatic forces. Weakening and redshift of α-La's characteristics negative peak were observed (208 nm to 218 nm) on circular dichroism. β-Crosslinks self-assembly and reorganization of disulfide bonds occurred during protein fibrillation. Moreover, the different redshift intensity of Congo red binding to amyloid fibrils was observed to be induced by C27 (>551 nm) and FB (>536 nm), and the direct observation by TEM demonstrated the ability to induce protein fibrillation is C27 > FB. Edible azo dyes with more sulfonyl groups would possess a stronger ability to induce protein fibrillation.

Unraveling the Role of Flavor Structure and Physicochemical Properties in the Binding Phenomenon with Commercial Food Protein Isolates

Food protein-flavor binding influences flavor release and perception. The complexity of the binding phenomenon lies in the flavor and protein properties. Thus, molecular interactions between commercial whey- or plant-based protein isolates (PI) such as pea, soy, and lupin, with carbonyl and alcohol flavor compounds were assessed by static headspace (HS) GC-MS. HS results showed that not only the displacement of the carbonyl group from the inner part of the flavor structure toward the edge promoted binding up to 52.76% ± 4.65 but also the flavor's degree of unsaturation. Similarly, thermal treatment led to a slight increase in hexanal-protein binding because of possible protein conformational changes. Protein's residual fat (<1%) seemed insufficient to promote significant flavor binding to PI. Despite the complexity of commercial food protein isolates, the results displayed that binding is predominantly influenced by the flavor structure and physicochemical properties, with the protein source and residual fat playing a secondary role.

Use of high-intensity ultrasound as a pre-treatment for complex coacervation from whey protein isolate and iota-carrageenan

The aim of this work was to evaluate the influence of high intensity ultrasound (HIUS) treatment on the molecular conformation of whey protein isolated (WPI) as a previous step for complex coacervation with iota carrageenan (IC) and its effect on the surface functional properties of complex coacervates (CC). Both biopolymers were hydrated (1% w/w) separately. A WPI suspension was treated with an ultrasonic bath (40 kHz, 600 W, 30 and 60 min, 100% amplitude). A non-sonicated protein was used as a control. Coacervation was achieved by mixing WPI and IC dispersions (10 min). FTIR-ATR analysis (400-4000 cm-1) detected changes after sonication on WPI secondary structure (1600-1700 cm-1), electrostatic interaction between WPI and IC by electronegative IC charged groups like sulfate (1200-1260 cm-1), anhydrous oxygen of the 3.6 anhydro-D-galactose (940-1066 cm-1) and the electropositive regions of WPI. Rheology results showed pseudoplastic behavior of both IC and WPI-IC with a significant change in viscosity level. Further, HIUS treatment had a positive effect on the emulsifying properties of the WPI-IC coacervates, increasing the time foaming (30 min) and emulsion stability (1 month) percentage. HIUS and complex coacervation proved to be an efficient tool to improve the surface functional properties of WPI.

Physicochemical and Functional Properties of Thermal-Induced Polymerized Goat Milk Whey Protein

Goat milk whey protein products are a hard-to-source commodity. Whey protein concentrate was directly prepared from fresh goat milk. The effects of the heating temperature (69-78 °C), time (15-30 min), and pH (7.5-7.9) on the physicochemical and functional properties of the goat milk whey protein were investigated. The results showed that the particle size of the samples significantly increased (p < 0.05) after heat treatment. The zeta potential of polymerized goat milk whey protein (PGWP) was lower than that of native goat milk whey protein. The content of the free sulfhydryl groups of PGWP decreased with increasing heating temperature and time, while an increase in surface hydrophobicity and apparent viscosity of PGWP were observed after heat treatment. Fourier Transform Infrared Spectroscopy analysis indicated that heat treatment and pH had considerable impacts on the secondary structure of goat milk whey protein. Transmission electron microscope images revealed that heat induced the formation of a large and uniform protein network. Additionally, the changes in the physicochemical and structural properties contributed to the improvement of the emulsifying and foaming properties of goat milk whey protein after heat treatment. The results may provide a theoretical basis for the applications of polymerized goat milk whey protein in related products.

Effect of Heat Treatment on Yellow Field Pea (Pisum sativum) Protein Concentrate Coupled with Membrane Ultrafiltration on Emulsification Properties of the Isolated >50 kDa Proteins

The aim of this paper was to determine the emulsification properties of protein aggregates obtained from heat pretreated yellow field pea protein concentrate (PPC). PPC dispersions were prepared in distilled water (adjusted to pH 3.0, 5.0, 7.0, or 9.0), heated in a water bath (100 °C) for 30 min, centrifuged and the supernatant passed first through a 30 kDa membrane and, then, the first retentate (>30 kDa) through a 50 kDa membrane. The 50 kDa membrane separation yielded a second retentate (>50 kDa proteins), which was isolated for emulsification studies. The near UV circular dichroic spectra of the protein samples showed more unfolded structures at pH 3.0 and 5.0 than at pH 7.0 and 9.0. The presence of small and spherical oil droplets of emulsions stabilized by the >50 kDa proteins at pH 3.0, 7.0, and 9.0 was confirmed by confocal laser scanning microscopy images. Emulsions stabilized at pH 7.0 and 9.0 had a narrower size distribution range than at pH 3.0 and 5.0. A narrow oil droplet size distribution range and lower interfacial protein concentrations of the emulsions stabilized by the >50 kDa proteins were observed at the corresponding pH of the heat treatment when compared to other pH values. Emulsions stabilized by the >50 kDa proteins exhibited a relatively low flocculation and coalescence index, which infers relative stability. The results from this work suggest that heat pretreatment of the PPC led to the formation of new protein aggregates, especially FT9 with enhanced emulsification properties, at some of the test conditions when compared to the unheated PPC.

Effects of Heat Treatment on the Structural and Functional Properties of Phaseolus vulgaris L. Protein

The paper presents the effect of heat treatment at 80 °C at different times (3, 5, 7, and 9 min) on the structural and functional properties of Phaseolus vulgaris L. protein (PVP, bean protein powder). Surface and structure properties of PVP after heat treatment were analyzed using a Fourier transform infrared spectrometer (FTIR), a fluorescence spectrophotometer, a visible light spectrophotometer, a laser particle size analyzer, and other equipment. The secondary structure and surface hydrophobicity (H0) of PVP changed significantly after heat treatment: the β-sheet content decreased from 25.32 ± 0.09% to 24.66 ± 0.09%, the random coil content increased from 23.91 ± 0.11% to 25.68 ± 0.08%, and the H0 rose by 28.96-64.99%. In addition, the functional properties of PVP after heat treatment were analyzed. After heat treatment, the emulsifying activity index (EAI) of PVP increased from 78.52 ± 2.01 m2/g to 98.21 ± 1.33 m2/g, the foaming ability (FA) improved from 87.31 ± 2.56% to 95.82 ± 2.96%, and the foam stability (FS) rose from 53.23 ± 1.72% to 58.71 ± 2.18%. Finally, the degree of hydrolysis (DH) of PVP after gastrointestinal simulated digestion in vitro was detected by the Ortho-Phthal (OPA) method. Heat treatment enhanced the DH of PVP from 62.34 ± 0.31% to 73.64 ± 0.53%. It was confirmed that heat treatment changed the structural properties of PVP and improved its foamability, emulsification, and digestibility. It provides ideas for improving PVP's potential and producing new foods with rich nutrition, multiple functions, and easy absorption.

Effects of spray drying and freeze drying on the structure and emulsifying properties of yam soluble protein: A study by experiment and molecular dynamics simulation

This study focused on the effects of freeze drying (FD) and sprays drying (SD) on the structure and emulsifying properties of yam soluble protein (YSP). The results showed that the surface hydrophobicity (Ho) value, free sulfhydryl group (SH) content, turns content, denaturation temperature and enthalpy value of spray-dried YSP (SD-YSP) were higher than freeze-dried YSP (FD-YSP), but the apparent hydrodynamic diameter (Dh) value of SD-YSP was smaller. The smaller Dh, higher Ho and free SH led to higher percentage of adsorbed proteins and stronger binding between protein and oil droplet in emulsions. Thus, the emulsifying properties of SD-YSP were better, and the SD-YSP-stabilized emulsion had better dynamical rheological properties. Molecular dynamics (MD) simulations suggested that some intramolecular disulfide bonds and hydrogen bonds of dioscorin were broken, and some helices transformed into turns during the SD process. These structural changes resulted in better thermal stability and emulsification properties of SD-YSP.

Synergistic effect of microfluidization and transglutaminase cross-linking on the structural and oil-water interface functional properties of whey protein concentrate for improving the thermal stability of nanoemulsions

Generally, whey protein concentrate (WPC) undergoes high-temperature denaturation and aggregation, which reduces its emulsifying properties and is not conducive to as an emulsifier to maintain the thermal stability of emulsions. In this study, dynamic high-pressure microfluidization technology (DHPM) combined with TGase (TG) cross-linking was applied to prepare DHPM-TG-WPC, and the thermal stabilization mechanism of nanoemulsions prepared with DHPM-TG-WPC was explored. Results showed DHPM treatment could promote the formation of TG-crosslinked WPC polymers. Compared to WPC, the free sulfhydryl and free amino group content of DHPM-TG-WPC was significantly decreased (P < 0.05), the surface hydrophobicity and interfacial tension of DHPM-TG-WPC were increased by 45.23 % and 62.34 %, respectively. And its emulsifying stability index and interface protein adsorption was significantly enhanced (P < 0.05). Furthermore, compared to WPC, DHPM-WPC and TG-WPC, DHPM-TG-WPC-stabilized nanoemulsions showed the best 15 days of storage stability after thermal sterilization. This study provides a theoretical basis for the application of modified-WPC emulsion.

Complex coacervation and freeze drying using whey protein concentrate, soy protein isolate and arabic gum to improve the oxidative stability of chia oil

BACKGROUND

Chia oil (CO) is popular for being the richest vegetable source of α-linolenic acid (60-66%). However, this content of polyunsaturated fatty acids (PUFA) limits the incorporation of bulk CO in food products due to its high probability of oxidation. This justifies the study of alternative wall materials for microencapsulation. No reports regarding the use of dairy protein/vegetable protein/polysaccharide blends as wall material for the microencapsulation of CO have been published. Therefore, this work analyzed the behavior of a whey protein concentrate (WPC)/soy protein isolate (SPI)/arabic gum (AG) blend as wall material. The complex coacervation (CC) process was studied: pH, 4.0; total solid content, 30% w/v; WPC/SPI/AG ratio, 8:1:1 w/w/w; stirring speed, 600 rpm; time, 30 min; room temperature.

RESULTS

The oxidative stability index (OSI) of CO (3.25 ± 0.16 h) was significantly increased after microencapsulation (around four times higher). Furthermore, the well-known matrix-forming ability of AG and WPC helped increase the OSI of microencapsulated oils. Meanwhile, SPI contributed to the increase of the encapsulation efficiency due to its high viscosity. Enhanced properties were observed with CC: encapsulation efficiency (up to 79.88%), OSIs (from 11.25 to 12.52 h) and thermal stability of microcapsules given by the denaturation peak temperatures of WPC (from 77.12 to 86.00 °C). No significant differences were observed in the fatty acid composition of bulk and microencapsulated oils.

CONCLUSION

Microcapsules developed from complex coacervates based on the ternary blend represent promising omega-3-rich carriers for being incorporated into functional foods.

Modified whey protein isolate gel prepared by thermal aggregation combined with transglutaminase crosslinking achieves Casein-like slow digestion in vitro and in vivo

Our study aimed to fabricate a modified slow-digestive whey protein isolate (WPI), which can supply enough branched-chain amino acids (BCAAs) during long-term fasting. The WPI aqueous solution (10 % w/v) was treated by heat (80 ℃) to unfold the protein tertiary structure, and subsequently treated with transglutaminase to form a gel via cross-linking. The powder of the WPI gel was obtained by spray drying, which can dissolve in water easily and self-assemble into gels again. This modified WPI contained protein aggregates with high molecular weight, and kept a stable gel-like structure under simulated gastric digestion conditions (pH = 3, 37 ℃). A dense honeycomb internal microstructure of the freeze-dried gel was observed. Further, we found that the WPI gel successfully achieved a casein-like digestible ratio (37.37 %) and released more BCAAs (0.18 mg/mL) than casein during the 4 h of in vitro simulated digestion based on the INFOGEST method. Finally, our results showed that the C57BL/6 mice oral administrated with the modified WPI gel had consistently higher BCAAs concentration (0.052 mg/mL) in their blood serum than the mice with normal WPI intake during the 6 h of in vivo digestion.

Separation of α-Lactalbumin Enriched Fraction from Bovine Native Whey Concentrate by Combining Membrane and High-Pressure Processing

Whey exhibits interesting nutritional properties, but its high β-Lactoglobulin (β-Lg) content could be a concern in infant food applications. In this study, high-pressure processing (HPP) was assessed as a β-Lg removal strategy to generate an enriched α-Lactalbumin (α-La) fraction from bovine native whey concentrate. Different HPP treatment parameters were considered: initial pH (physiological and acidified), sample temperature (7-35 °C), pressure (0-600 MPa) and processing time (0-490 s). The conditions providing the best α-La yield and α-La purification degree balance (46.16% and 80.21%, respectively) were 4 min (600 MPa, 23 °C), despite the significant decrease of the surface hydrophobicity and the total thiol content indexes in the α-La-enriched fraction. Under our working conditions, the general effects of HPP on α-La and β-Lg agreed with results reported in other studies of cow milk or whey. Notwithstanding, our results also indicated that the use of native whey concentrate could improve the β-Lg precipitation degree and the α-La purification degree, in comparison to raw milk or whey. Future studies should include further characterization of the α-La-enriched fraction and the implementation of membrane concentration and HPP treatment to valorize cheese whey.

Foaming and Physicochemical Properties of Commercial Protein Ingredients Used for Infant Formula Formulation

Protein, as one of the main ingredients for infant formula, may be closely related to the undesirable foam formed during the reconstitution of infant formula. Demineralized whey powder (D70 and D90), whey protein concentrate (WPC), and skimmed milk powder (SMP) are the four protein ingredients commonly used in infant formula formulation. The foaming and physicochemical properties of these four protein ingredients from different manufacturers were analyzed in the present study. Significant differences (p < 0.05) in foaming properties were found between the samples from different manufacturers. SMP showed a highest foaming capacity (FC) and foam stability (FS), followed by D70, D90, and WPC. Although the protein composition was similar based on reducing SDS-PAGE, the aggregates varied based on non-reducing SDS-PAGE, probably resulting in the different foaming properties. Particle size, zeta potential, and solubility of the protein ingredients were assessed. The protein structure was evaluated by circular dichroism, surface hydrophobicity, and free sulfhydryl. Pearson’s correlation analysis demonstrated that FC and FS were positively correlated with random coil (0.55 and 0.74), β-turn (0.53 and 0.73), and zeta potential (0.55 and 0.51) but negatively correlated with β-strand (−0.56 and −0.71), free sulfhydryl (−0.56 and −0.63), particle size (−0.45 and −0.53), and fat content (−0.50 and −0.49). The results of this study could provide a theoretical guidance for reducing formation of foam of infant formula products during reconstitution.

Fabrication and Characterization of Chitosan-Pea Protein Isolate Nanoparticles

Chitosan (CS) and pea protein isolate (PPI) were used as raw materials to prepare nanoparticles. The structures and functional properties of the nanoparticles with three ratios (1:1, 1:2 1:3, CS:PPI) were evaluated. The particle sizes of chitosan-pea protein isolate (CS-PPI) nanoparticles with the ratios of 1:1, 1:2, and 1:3 were 802.95 ± 71.94, 807.10 ± 86.22, and 767.75 ± 110.10 nm, respectively, and there were no significant differences. Through the analysis of turbidity, endogenous fluorescence spectroscopy and Fourier transform infrared spectroscopy, the interaction between CS and PPI was mainly caused by electrostatic mutual attraction and hydrogen bonding. In terms of interface properties, the contact angles of nanoparticles with the ratio of 1:1, 1:2, and 1:3 were 119.2°, 112.3°, and 107.0°, respectively. The emulsifying activity (EAI) of the nanoparticles was related to the proportion of protein. The nanoparticle with the ratio of 1:1 had the highest potential and the best thermal stability. From the observation of their morphology by transmission electron microscopy, it could be seen that the nanoparticles with a ratio of 1:3 were the closest to spherical. This study provides a theoretical basis for the design of CS-PPI nanoparticles and their applications in promoting emulsion stabilization and the delivery of active substances using emulsions.

Strategies for Improving Bioavailability, Bioactivity, and Physical-Chemical Behavior of Curcumin

Curcumin (CCM) is one of the most frequently explored plant compounds with various biological actions such as antibacterial, antiviral, antifungal, antineoplastic, and antioxidant/anti-inflammatory properties. The laboratory data and clinical trials have demonstrated that the bioavailability and bioactivity of curcumin are influenced by the feature of the curcumin molecular complex types. Curcumin has a high capacity to form molecular complexes with proteins (such as whey proteins, bovine serum albumin, β-lactoglobulin), carbohydrates, lipids, and natural compounds (e.g., resveratrol, piperine, quercetin). These complexes increase the bioactivity and bioavailability of curcumin. The current review provides these derivatization strategies for curcumin in terms of biological and physico-chemical aspects with a strong focus on different type of proteins, characterization methods, and thermodynamic features of protein–curcumin complexes, and with the aim of evaluating the best performances. The current literature review offers, taking into consideration various biological effects of the CCM, a whole approach for CCM-biomolecules interactions such as CCM-proteins, CCM-nanomaterials, and CCM-natural compounds regarding molecular strategies to improve the bioactivity as well as the bioavailability of curcumin in biological systems.

Effects of Heat Treatment Duration on the Electrical Properties, Texture and Color of Polymerized Whey Protein

In this research effects of heat treatment duration on the electrical properties (zeta potential and conductivity), texture and color of polymerized whey protein (PWP) were analyzed. Whey protein solutions were heated for 30 min to obtain single-heated polymerized whey protein (SPWP). After cooling to room temperature, the process was repeated to obtain double-heated polymerized whey protein (DPWP). The largest agglomeration was demonstrated after 10 min of single-heating (zeta potential recorded as -13.3 mV). Single-heating decreased conductivity by 68% and the next heating cycle by 54%. As the heating time increased, there was a significant increase in the firmness of the heated solutions. Zeta potential of the polymerized whey protein correlated with firmness, consistency, and index of viscosity, the latter of which was higher when the zeta potential (r = 0.544) and particle size (r = 0.567) increased. However, there was no correlation between zeta potential and color. This research has implications for future use of PWP in the dairy industry to improve the syneretic, textural, and sensory properties of dairy products.

Complexation of Anthocyanin-Bound Blackcurrant Pectin and Whey Protein: Effect of pH and Heat Treatment

A complexation study between blackcurrant pectin (BCP) and whey protein (WP) was carried out to investigate the impact of bound anthocyanins on pectin−protein interactions. The effects of pH (3.5 and 4.5), heating (85 °C, 15 min), and heating sequence (mixed-heated or heated-mixed) were studied. The pH influenced the color, turbidity, particle size, and zeta-potential of the mixtures, but its impact was mainly significant when heating was introduced. Heating increased the amount of BCP in the complexes—especially at pH 3.5, where 88% w/w of the initial pectin was found in the sedimented (insoluble) fraction. Based on phase-separation measurements, the mixed-heated system at pH 4.5 displayed greater stability than at pH 3.5. Heating sequence was essential in preventing destabilization of the systems; mixing of components before heating produced a more stable system with small complexes (<300 nm) and relatively low polydispersity. However, heating WP before mixing with BCP prompted protein aggregation—producing large complexes (>400 nm) and worsening the destabilization. Peak shifts and emergence (800−1200 cm−1) in infrared spectra confirmed that BCP and WP functional groups were altered after mixing and heating via electrostatic, hydrophobic, and hydrogen bonding interactions. This study demonstrated that appropriate processing conditions can positively impact anthocyanin-bound pectin−protein interactions.

Impact of Heat Treatment on the Structure and Properties of the Plant Protein Corona Formed around TiO2 Nanoparticles

Titanium dioxide (TiO₂) nanoparticles are utilized within the food industry as an additive to alter food brightness and whiteness. Amphiphilic food ingredients, like proteins, can adsorb on to the surfaces of TiO₂ nanoparticles and form protein coronas that could alter their gastrointestinal fate. At present, our understanding of the factors influencing the formation and properties of protein coronas was limited. In this study, we explored the influence of thermal treatments of proteins on the physicochemical properties of protein coronas formed on TiO₂ nanoparticles. Four plant proteins (glutenin, soy protein isolate, gliadin, and zein) were heat-treated at different temperatures for 30 min. Heat treatment (100 °C) disrupted the structure of the original proteins and changed the structure properties of the protein and formed coronas. Quartz crystal microbalance with dissipation results showed that for the heat-sensitive proteins, such as glutenin, a high temperature treatment (100 °C) weakened the binding affinity between the protein and the nanoparticle surfaces. In contrast, for more heat-resistant proteins, such as gliadin, a high-temperature treatment had much less effect. In summary, this study showed that the structural properties of plant proteins affected by heat were an important factor affecting the formation of protein coronas on food nanoparticles.

Microencapsulation of curcumin by spray drying: Characterization and fortification of milk

Curcumin, the major bioactive component of turmeric (Curcuma longa), was microencapsulated by spray drying in the matrix of HI-CAP 100 (resistant starch)/ maltodextrin and whey protein isolate to improve its oral bioavailability and solubility. Taguchi orthogonal array design (L₁₈) was used to optimize the spray drying conditions. The optimal conditions for microencapsulation were inlet drying air temperature of 185 °C, feed rate of 6 mL/min and HI-CAP 100 as wall material. The moisture content, encapsulation efficiency and bulk density at these conditions were 4.65%, 82.42% and 358.40 kg/m³, respectively. The spray-dried microcapsules were spherical-shaped with folds and vacuoles. The yellowness index and a^* value of curcumin decreased after microencapsulation. FTIR spectroscopy indicated that the curcumin after microencapsulation presumably retained its chemical structure. DSC thermograms confirmed that the microcapsules were heat stable up to 200 °C. The microcapsules had better heat stability and sustained in-vitro release as compared to that of pure curcumin. The DPPH free radical scavenging activity of curcumin was 61.43%, which was largely unaffected after microencapsulation. Fortification of milk with HI-CAP 100-based microcapsules at the selected dose had no adverse effect on organoleptic properties as compared to normal milk.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05142-0.

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.

Effect of solid-state fermentation by three different Bacillus species on composition and protein structure of soybean meal

BACKGROUND

Fermentation efficiency of thermophiles of Bacillus licheniformis YYC4 and Geobacillus stearothermophilus A75, and mesophilic Bacillus subtilis 10 160 on soybean meal (SBM), was evaluated by examining the nutritional and protein structural changes.

RESULTS

SBM fermentation by B. licheniformis YYC4, B. subtilis 10 160 and G. stearothemophilus A75 increased significantly the crude and soluble protein from 442.4 to 524.8, 516.1 and 499.9 g kg-1 , and from 53.9 to 203.3, 291.3 and 74.6 g kg-1 , and decreased trypsin inhibitor from 8.19 to 3.19, 2.14 and 5.10 mg g-1 , respectively. Bacillus licheniformis YYC4 and B. subtilis 10 160 significantly increased phenol and pyrazine content. Furthermore, B. licheniformis YYC4 fermentation could produce abundant alcohols, ketones, esters and acids. Surface hydrophobicity, sulfhydryl groups and disulfide bond contents of SBM protein were increased significantly from 98.27 to 166.13, 173.27 and 150.71, from 3.26 to 4.88, 5.03 and 4.21 μmol g-1 , and from 20.77 to 27.95, 29.53 and 25.5 μmol g-1 after their fermentation. Fermentation induced red shifts of the maximum absorption wavelength (λmax ) of fluorescence spectra from 353 to 362, 376 and 361 nm, while significantly reducing the fluorescence intensity of protein, especially when B. subtilis 10 160 was used. Moreover, fermentation markedly changed the secondary structure composition of SBM protein. Analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and atomic force microscopy showed that macromolecule protein was degraded into small-sized protein or peptide during fermentation of SBM.

CONCLUSION

Bacillus licheniformis YYC4 fermentation (without sterilization) improved nutrition and protein structure of SBM as B. subtilis 10 160, suggesting its potential application in the SBM fermentation industry. © 2021 Society of Chemical Industry.

The interactions between anthocyanin and whey protein: A review

Anthocyanins (ACN) are natural pigments that produce bright red, blue, and purple colors in plants and can be used to color food products. However, ACN sensitivity to different factors limits their applications in the food industry. Whey protein (WP), a functional nutritional additive, has been shown to interact with ACN and improve the color, stability, antioxidant capacity, bioavailability, and other functional properties of the ACN-WP complex. The WP's secondary structure is expected to unfold due to heat treatment, which may increase its binding affinity with ACN. Different ACN structures will also have different binding affinity with WP and their interaction mechanism may also be different. Circular dichroism (CD) spectroscopy and Fourier transform infrared (FTIR) spectroscopy show that the WP secondary structure changes after binding with ACN. Fluorescence spectroscopy shows that the WP maximum fluorescence emission wavelength shifts, and the fluorescence intensity decreases after interaction with ACN. Moreover, thermodynamic analysis suggests that the ACN-WP binding forces are mainly hydrophobic interactions, although there is also evidence of electrostatic interactions and hydrogen bonding between ACN and WP. In this review, we summarize the information available on ACN-WP interactions under different conditions and discuss the impact of different ACN chemical structures and of WP conformation changes on the affinity between ACN and WP. This summary helps improve our understanding of WP protection of ACN against color degradation, thus providing new tools to improve ACN color stability and expanding the applications of ACN and WP in the food and pharmacy industries.

Inhibition of Lipid and Protein Oxidation in Whey-Protein-Stabilized Emulsions Using a Natural Antioxidant: Black Rice Anthocyanins

The food industry is exploring the natural environment to identify botanical extracts that can be used as functional ingredients that can replace synthetic ingredients in foods. In the present study, the ability of black rice anthocyanins as natural antioxidants to inhibit both lipid and protein oxidation in protein-stabilized oil-in-water emulsions was examined. Whey-protein-stabilized emulsions were prepared containing 0, 0.02, 0.04, and 0.06% (w/v) anthocyanins, and then the impact of this plant-based extract on their physical and chemical stabilities was evaluated. The addition of the anthocyanins improved the physical stability of the emulsions in a dose-dependent manner by inhibiting droplet aggregation during storage (35 °C for 5 days). The anthocyanins also exhibited good antioxidant activity in a dose-dependent manner, as seen by their capacity for inhibiting both lipid oxidation (reduced lipid hydroperoxides and malondialdehyde) and protein oxidation (reduced carbonyl and Schiff base formation, intrinsic fluorescence loss, and molecular weight changes). Black rice anthocyanins may therefore be an effective botanical extract for improving the stability of protein-stabilized food emulsions by inhibiting oxidative reactions.