Effect of two-step enzymatic hydrolysis on the antioxidant properties and proteomics of hydrolysates of milk protein concentrate

Effect of ultrasound on the characterization and peptidomics of foxtail millet bran protein hydrolysates

Protein hydrolysates have attracted much attention for their high biological activity and are a crucial product form for the utilization of foxtail millet bran by-products. In this study, changes in the structure, functionality, activity and peptide profile of foxtail millet bran protein hydrolysates (FMBPHs) at different ultrasound powers (0 - 600 W) were investigated. The results showed that ultrasound promoted the transformation of α-helix and β-sheet to random coils and β-turn, and the exposure of hydrophobic groups and sulfhydryl groups in FMBPHs. The average particle size of the samples decreased, and the absolute value of the ζ-potential increased significantly. Simultaneously, smaller porous particles and loose fragments appeared on the surface of FMBPHs when the ultrasonic power was increased to 450 W. Additionally, 450 W ultrasound treatment improved solubility, foaming properties, emulsifying properties, thermal stability of FMBPHs. The DPPH, ABTS and hydroxyl radical scavenging ability (IC50, 2.65, 1.06 and 3.02 mg/mL), Fe2+ chelating activity (IC50, 2.62 mg/mL), and reducing power of the samples were also enhanced. The peptidomics results demonstrated that ultrasonication increased the number of active peptides in the hydrolysate, and the relative abundance of 17 active peptides was obviously elevated at 450 W. Peptide map analysis showed that ultrasound-induced structural modifications affected the peptide profiles of Ubiquitin-like domain-containing protein, Cupin type-1 domain-containing protein, 40S ribosomal protein S19, and Oleosin 1, showing changes in the abundance of certain peptides, which may be related to changes in the characterization of FMBPHs.

Effects of ultrasound pretreatment on the structure, IgE binding capacity, functional properties and bioactivity of whey protein hydrolysates via multispectroscopy and peptidomics revealed

Whey protein is an important food ingredient, but it is also considered a major food allergen. The aim of this study was to investigate the effect of ultrasound pretreatment on the structure, IgE binding capacity, functional properties and biological activity of whey protein isolate (WPI) hydrolysates (WPH), including WPI hydrolyzed by a combination of enzymes from Bromelain and ProteAXH (BA-WPI) and WPI hydrolyzed by a combination of enzymes from Papain W-40 and ProteAXH (PA-WPI). The IgE binding capacity of BA-WPI and PA-WPI was reduced to 40.28% and 30.17%, respectively, due to disruption/exposure/shielding of conformational and linear epitopes. The IgE binding capacity of sonicated WPI was increased, but ultrasound pretreatment further reduced the IgE binding capacity of the hydrolysates to 32.89% and 28.04%. This is due to the fact that ultrasound pretreatment leads to conformational changes including increased α-helix and β-sheet structure, exposure of aromatic amino acids, surface hydrophobicity, and increased sulfhydryl content, which increases the accessibility of allergenic epitopes to WPI by the enzyme. Multispectral and LC-MS/MS results further indicated that ultrasound pretreatment altered the conformational and primary structural changes of the hydrolysates. The thermograms showed that ultrasound pretreatment mainly altered the epitope spectra of β-lactoglobulin hydrolysates, while it had less effect on the epitope spectra of α-lactalbumin hydrolysates. Additionally, ultrasound pretreatment significantly improved the foaming properties, antioxidant activity, and α-glucosidase inhibition of the hydrolysates without impairing the solubility and emulsification properties of the hydrolysates. Therefore, ultrasound pretreatment is a feasible method to reduce the allergenicity of WPH and to improve their functional properties and bioactivity. Notably, ultrasonic pretreatment improved the effectiveness and efficiency of WPI hydrolysis, which is a feasible method to produce high-quality protein feedstock in a green, efficient, and economical way.

Effect of bi-enzyme hydrolysis on the properties and composition of hydrolysates of Manchurian walnut dreg protein

Walnut dreg (WD) active peptides are an important source of dietary antioxidants; however, the products of conventional hydrolysis have limited industrial output owing to poor flavour and low bioactivity. To this end, in this study, we aimed to employ bvLAP, an aminopeptidase previously identified in our research, as well as commercially available Alcalase for bi-enzyme digestion. The flavour, antioxidant activity, and structures of products resulting from various digestion methods were compared. The results showed that the bi-enzyme digestion products had enhanced antioxidant activity, increased β-sheet content, and reduced bitterness intensity from 9.65 to 6.93. Moreover, bi-enzyme hydrolysates showed a more diverse amino acid composition containing 1640 peptides with distinct sequences. These results demonstrate that bi-enzyme hydrolysis could be a potential process for converting WD into functional food ingredients. Additionally, our results provide new concepts that can be applied in waste processing and high-value utilisation of WD.

Functional chia (Salvia hispanica L.) co-product protein hydrolysate: An analysis of biochemical, antidiabetic, antioxidant potential and physicochemical properties

Protein hydrolysates with antioxidant potential have been reported to act as adjuvants in preventing and treating type-2 diabetes (T2D). This work investigated the biochemical, antidiabetic, antioxidant potential, and physicochemical properties of chia meal protein hydrolysate (CMPH). Bands smaller than 14 kDa were observed in the electrophoretic profile. The predominant amino acids were hydrophobic and aromatic. CMPH had the potential to inhibit α-amylase (IC50: 1.76 ± 0.13 mg/mL), α-glucosidase (IC50: 0.42 ± 0.13 mg/mL), and DPP-IV (IC50: 0.46 ± 0.14 mg/mL). Antioxidant activity for ABTS (IC50: 0.236 mg/mL), DPPH (8.83 ± 0.52%), and ORAC (IC25: 0.115 mg/mL). Against chia meal protein isolate (CMPI), CMPH has a broad solubility (pH 2-12.46). Particle size (624.5 ± 247.3 nm), low PDI (0.22 ± 0.06), ζ-potential (-31.1 ± 2.5 mV), and surface hydrophobicity (11,183.33 ± 2024.11) and the intrinsic fluorescence peak of CMPH was lower than that of CMPI. CMPH represents an alternative to add value to the agri-food co-product of the chia seed oil industry, generating food ingredients with outstanding antidiabetic and antioxidant potential.

Effect of enzymatic hydrolysis with Alcalase or Protamex on technological and antioxidant properties of whey protein hydrolysates

The aim of this study was to evaluate the effect of the enzymatic hydrolysis, performed using Alcalase and Protamex enzymes, on the technological functionalities and the antioxidant capacity of whey protein hydrolysates (WPHs) to identify the conditions allowing to obtain target functionality/ies. Samples were characterized for hydrolysis degree (DH), molecular weight distribution, structural properties, and food-related functionalities. Free sulfhydryl groups and surface hydrophobicity significantly decreased with the increase in DH, regardless of the used enzyme. The foaming and antioxidant properties of Alcalase WPHs were higher as compared to those of WPI, reaching the maximum value at DH = 18-20 %, while higher DH resulted in impaired functionality. Gelling properties were guaranteed when WPI was hydrolysed by Protamex at DH < 15 % while foaming and antioxidant abilities were fostered at 15 < DH < 21 %. These results were well correlated with MW distribution and were rationalized into a road map which represents a useful tool in the selection of proper hydrolysis conditions (time, DH, enzyme type) to obtain WPHs with tailored functionalities. Research outcomes highlighted the possibility to drive protein hydrolysis to optimize the desired functionality/ies.

Proteomic analysis of milk fat globule membrane proteins in mature human milk of women with and without gestational diabetes mellitus

Milk fat globule membrane proteins (MFGMP) in human milks have positive effects on infant's health. As gestational diabetes mellitus (GDM) causes variations in MFGMP, it is essential to understand the effects of GDMon MFGMP. This study aims to investigate and compare the MFGMP (>3 months postpartum) of GDM and non-GDM (NGDM) women using four-dimensional-data-independent-acquisition proteomics technology. Principal component analysis shows significant differences in the MFGMP of GDM and NGDM women. A total of 4747 MFGMP were identified in maturehuman milk of GDM and NGDM women. Among these proteins, 174 differentially expressed proteins (DEPs) were identified in MFGM of GDM and NGDM women. Albumin (FC = 7.96) and transthyretin (FC = 2.57) which are related to insulin resistance and involved in thyroid hormone synthesis, are significantly up-regulated in MFGMP of GDM mothers indicating insulin resistance, imbalance of glucose homeostasis and poor glucose metabolism might persist in postpartum period.

Effect of different salts on the foaming properties of model protein systems for infant formula

This multiscale study aimed to evaluate the effects of different salts (NaCl, KCl, MgCl2, and CaCl2) on the foaming capacity (FC) and foam stability (FS) of model protein systems (MPS) for infant formula via changes in surface and structural properties. Our results showed that the FC and FS of MPS were increased with the addition of NaCl, KCl, and MgCl2, whereas CaCl2 significantly decreased FC (79.5 ± 10.6%) and increased FS (93.2 ± 2.2%). The surface hydrophobicity was increased and the net charge and surface tension were reduced after the addition of salts. Structural analysis revealed the reduction of intensity of intrinsic fluorescence spectroscopy and UV absorption, and the conversion of α-helix into β-strand, which was attributed to protein agglomeration. Additionally, MgCl2 and CaCl2 exhibited larger size and lower net charge compared with NaCl and KCl, indicating a greater ability to bind to charged amino acids and form larger aggregates. Correlation analysis indicated that FC was positively related to adsorbed protein and β-turn and negatively correlated with particle size. In addition, FS showed a positive correlation with β-strand, apparent viscosity, and zeta potential. However, it exhibited a negative correlation with β-turn, α-helix, and sulfhydryl content. These results provide a theoretical reference for further understanding of the effect of salts on the foaming properties of MPS.

In silico prediction aided preparation of antioxidant soybean peptides by enzymatic hydrolysis for ameliorating lead exposure-induced toxicity

Food derived bioactive peptides are prominent dietary supplements to protect against oxidative stress induced by lead (Pb) exposure. This study aimed to develop a new strategy for rapid preparation of highly active antioxidant soybean polypeptides (ASPs) against Pb toxicity. In silico enzymatic hydrolysis simulation and antioxidant activity prediction showed that pepsin, chymotrypsin and bromelain can produce peptides with the highest activity. The preparation process was then optimized, and the obtained ASP showed good antioxidant and metal-chelating activities in vitro. An in vivo study showed that ASP exerted prominent protective effects against Pb-induced cognitive impairment and tissue damage in mice by reducing Pb deposition and enhancing the antioxidant capacity in tissues and was superior to Vc, DMSA or their combination in some aspects. ASP composition analysis demonstrated that its prominent antioxidant activity might be attributed to the high proportion of amino acid residues E, L, P and V in the peptide sequence and L, V and A at the C- and N-termini. In conclusion, in silico prediction could facilitate the preparation of ASP. And the ASP prepared with the new strategy exerted prominent protective effects against Pb toxicity.

Advances in separation and identification of biologically important milk proteins and peptides

Milk is a rich source of biologically important proteins and peptides. In addition, milk contains a variety of extracellular vesicles (EVs), including exosomes, that carry their own proteome cargo. EVs are essential for cell-cell communication and modulation of biological processes. They act as nature carriers of bioactive proteins/peptides in targeted delivery during various physiological and pathological conditions. Identification of the proteins and protein-derived peptides in milk and EVs and recognition of their biological activities and functions had a tremendous impact on food industry, medicine research, and clinical applications. Advanced separation methods, mass spectrometry (MS)-based proteomic approaches and innovative biostatistical procedures allowed for characterization of milk protein isoforms, genetic/splice variants, posttranslational modifications and their key roles, and contributed to novel discoveries. This review article discusses recently published developments in separation and identification of bioactive proteins/peptides from milk and milk EVs, including MS-based proteomic approaches.

pH-induced physiochemical and structural changes of milk proteins mixtures and its effect on foaming behavior

Milk proteins are well known to produce aerated food due to the amphiphilicity. However, milk proteins are commonly added in blends for the desirable properties in food industry. In this study, the foaming properties of milk protein mixtures (MPM), a mixtures of whey protein isolated (WPI) and milk protein concentrate (MPC), was studied through foaming capacity (FC), foam stability (FS), and foam morphology at pH 3.0-9.0. Physiochemical, structural, surface properties, and Pearson correlation analysis were measured to gain insight into foaming behavior. Results indicated that MPM showed excellent FC (113.0-114.3 %) and FS (90.7-93.0 %) at pH 6.0-9.0, and foam displayed a smaller size and uniform distribution. MPM solutions showed smaller particles, higher solubility, and lower apparent viscosity at pH 6.0-9.0, which resulted in an increase in surface pressure and adsorption rate (Kdiff), facilitating more protein absorbed to interface. To further investigate structural changes, various spectral methods were used, in which the structure of MPM was changed with pH. Correlation analysis further suggests that Kdiff and solubility positively affect the formation of foam, while free sulfhydryl and β-sheet contributed to stabilizing foams. These findings provide valuable information on MPM as ingredients for aerated foods under acidic, neutral, and alkaline conditions.

Dynamic microfluidic-assisted transglutaminase modification of soy protein isolate-chitosan: Effects on structural and functional properties of the adduct and its antioxidant activity after in vitro digestion

In this study, soy protein isolate (SPI)-chitosan (CS) adducts were prepared by using dynamic microfluidic-assisted transglutaminase (TGase) modification. It was shown that the solubility and degree of binding of SPI-CS adducts prepared by dynamic microfluidic-assisted TGase modification were better. After the samples were treated twice at 400 bar, the degree of binding for SPI-CS adducts increased to 31.97 ± 1.31%, and the solubility increased to 66.25 ± 1.10%. With the increase of microfluidic pressure, the exposed free sulfhydryl groups increased, the particle size reduced, and the surface hydrophobicity first increased and then decreased. Under the action of the pressure generated by microfluidics, the structure of the protein in the SPI-CS adduct was unfolded and transformed from an ordered structure to a disordered one. The SPI-CS adducts prepared with assisted dynamic microfluidic treatment showed significantly higher ABTS radical scavenging rate, DPPH radical scavenging rate and reducing power after in vitro digestion compared with that of SPI-CS adducts prepared with TGase alone. This result indicated that appropriate dynamic microfluidic treatment improved the structural and functional properties of TGase-modified SPI-CS adducts and significantly increased the antioxidant activity after in vitro digestion.

Functionalization of pine kernel protein by pH-shifting combined with ultrasound treatments: Further improvement with increasing acidity

As a novel plant protein, developing various aspects of pine kernel protein (PKP) functionality is essential to meet the demand for protein-rich foods. To achieve this, the PKP was functionalized by a combination of pH-shifting and ultrasound techniques. The solubility, emulsification and droplet stability of the PKP in the pH range suitable to food (pH 3 to 7) were further investigated. The pH 12-shifting was an effective strategy to increase the solubility of PKP under extreme acidic and neutral conditions, characterized by a higher content of β-sheets and random coils, a greater exposure of free sulfhydryl and hydrophobic groups. Furthermore, appropriate ultrasonic power (250 W) further improved the solubility of PKPs by disrupting intermolecular hydrogen and hydrophobic bonds. As the ambient acidity increased, the emulsions exhibited higher viscoelasticity and stronger protein interactions. Especially at pH 3, the oil droplets stabilized by U250-PKP-12 (PKP treated with 250 W ultrasound-assisted pH 12-shifting) were homogeneously dispersed and surrounded by dense protein, maintaining small particle size and large electrostatic repulsion, and there was no apparent creaming or phase separation in the emulsions after 10 days of storage. Thus, the functionality of PKP after pH-shifting combined with ultrasonic treatments is further enhanced by increasing the environmental acidity.

Kinetics of Egg-Yolk Protein Hydrolysis and Properties of Hydrolysates

Lecithin-free egg yolk (LFEY) is a byproduct of the extraction of egg-yolk phospholipids, which contain approximately 46% egg yolk proteins (EYPs) and 48% lipids. The enzymatic proteolysis is the alternative to increase the commercial value of LFEY. The kinetics of proteolysis in full-fat and defatted LFEY with Alcalase 2.4 L was analyzed in terms of the Weibull and Michaelis-Menten models. A product inhibition effect was also studied in the full-fat and defatted substrate hydrolysis. The molecular weight profile of hydrolysates was analyzed by gel filtration chromatography. Results pointed out that the defatting process did not importantly affect the maximum degree of hydrolysis (DH_max) in the reaction but rather the time at which DH_max is attained. The maximum rate of hydrolysis (V_max) and the Michaelis-Menten constant K_M were higher in the hydrolysis of the defatted LFEY. The defatting process might have induced conformational changes in the EYP molecules, and this affected their interaction with the enzyme. Consequently, the enzymatic reaction mechanism of hydrolysis and the molecular weight profile of peptides were influenced by defatting. A product inhibition effect was observed when adding 1% hydrolysates containing peptides lower than 3 kDa at the beginning of the reaction with both substrates.

Improving the biological activity, functional properties, and emulsion stability of soybean meal hydrolysate via covalent conjugation with polyphenol

The use of by-products as functional components in food production is gaining popularity. This study investigated the structure, biological activity, interaction force, and emulsion stability of soybean meal hydrolysate (SMHs) after covalent conjugation with proanthocyanidin (PC), epigallocatechin (EGCG), gallic acid (GA), and caffeic acid (CA). SDS-PAGE confirmed the formation of SMHs-polyphenol conjugates. Structural analysis indicates unfolding and disordered-structure formation. This transformation directly influenced the antioxidant activity and emulsification of SMHs. The antioxidant and emulsifying properties of all covalent complexes were superior to SMHs, in order of SMHs-PC, SMHs-EGCG, SMHs-GA, and SMHs-CA. Among, SMHs-PC conjugates displayed the highest antioxidant activity (ABTS^•+ and DPPH radical scavenging capacities of 89.33% and 52.71%, respectively), total polyphenol content (235.10 mg/g), and emulsification activity (EAI) and stability (ESI) values (109.27 m²/g and 135.05 min, respectively). Moreover, SMHs-PC emulsion showed the smallest particle size (467.20 nm), highest viscosity (520.19 Pa.s), highest protein adsorption (94.33%), and lowest release rate of free fatty acids (FFAs) (18.61%) after digestion. These results provided valuable information for the use of modified SMHs as emulsifiers, which is a promising approach for increasing the value of soybean meal.

Effects of Heating Treatment on Functional and Structural Properties of Liquid Whole Egg

Liquid whole egg (LWE) products have many advantages such as convenient transportation, easy production and are safe. However, LWE has a short shelf life and high thermal sensitivity, so suitable heating treatment is the key to the production of LWE products. The aim of this study is to investigate the effects of heating treatments conditions (at 55–67 °C for 0–10 min) on the emulsification, foaming activity and rheological properties of LWE. The results indicated that the emulsifying activity of LWE had no significant change after 55–64 °C heating treatment, while it decreased significantly after heating treatment at 67 °C. The foaming property of LWE increased significantly after 55 °C to the 64 °C heating treatment; while the foaming property showed a downward trend with the increase in heat treatment temperature, it can significantly improve the foam stability of LWE. The heating treatment thoroughly changed the molecular weight distribution of LWE protein, thus promoted the protein surface hydrophobicity, hydrophobicity activity and rheological properties. The heating treatment at 61 °C for 6 min had a better effect on the functional properties than that of the other heating groups. In addition, the results of this study provide the change in rules of LWE under different heating treatment conditions and provide theoretical guidance for the production and processing of LWE.

Soy protein nanoparticles prepared by enzymatic cross-linking with enhanced emulsion stability

Particle-stabilized emulsions have shown increasing potential application in food emulsion systems. Here, soy protein, an abundant and inexpensive plant-based protein, was used to develop nanoparticles for emulsion stabilizer applications. An enzymatic cross-linking method based on microbial transglutaminase (mTG) was developed for the fabrication of soy protein nanoparticles (SPNPs). The emulsion stability was compared between soy protein isolate (SPI) and three different nanoparticles. The size of SPNPs ranged from 10 nm to 40 nm, depending on the production conditions. The emulsions stabilized by SPNPs were stable for at least 20 days at room temperature, whereas the emulsion that was stabilized by SPI showed a significant creaming and phase separation phenomenon. The SPNPs also showed a higher antioxidant and reducing effect compared to SPI. The use of mTG induced cross-linking resulted in the formation of covalent bonding between protein molecules, and led to the formation of nanoparticles with higher stability. The approaches support the utilization of inexpensive and abundant plant-based resources as emulsion stabilizers in food applications.

Physicochemical, antioxidant, antimicrobial, and in vitro cytotoxic activities of corn pollen protein hydrolysates obtained by different peptidases

The applications of protein hydrolysates as food preservatives and nutraceutical ingredients have attracted much attention because of their beneficial effects. The interest in these ingredients has shifted toward their biological activities with benefits to human health. Bioactive peptides are known as antioxidant agents that could promote health-promoting effects and prolong food shelf-life beyond their basic nutritional value. Thus, the aim of this study was to investigate antioxidant, antimicrobial, and in vitro cytotoxic properties of corn pollen protein (CPP) hydrolysates obtained by different enzymes. Proteolytic activity in terms of degree of hydrolysis (DH) and SDS-PAGE analysis was measured in pancreatin (H-Pan), pepsin (H-Pep), and trypsin (H-Tri) hydrolysates. Amino acid composition, antioxidant and antimicrobial activities, and cytotoxicity of hydrolysates were evaluated. DH and SDS-PAGE revealed higher proteolytic activity of pepsin compared to other enzymes. Amino acid analysis showed that the functional amino acids such as antioxidant types were most predominant in H-Pep compared to two other samples. Antioxidant activity of hydrolysates was found to be affected by the type of enzyme and the concentration of hydrolysates. There was a significant difference (p < 0.05) between antioxidant activity of different hydrolysates. The highest antioxidant activity in terms of Trolox equivalent antioxidant capacity (0.23-2.75 mM), DPPH (33.3%-64.8%), and hydroxyl (33.7%-63.2%) radical scavenging activities, chelation of iron (33.2%-62.5%) and copper (30.2%-50.5%) metals, and total antioxidant activity (0.65-0.85) was obtained for H-Pep followed by H-Pan and H-Tri samples. Antibacterial tests showed that pepsin-hydrolyzed protein was not significantly (P > 0.05) effective against E. coli at any concentrations, however, it showed significant (P < 0.05) concentration-dependent effect against S. aureus (with inhibition zones of 15-25 mm). Cytotoxicity results revealed that CPP, as a nonhydrolyzed protein, did not generally show antiproliferative activity, however, a significant (P < 0.05) ability of H-Pep hydrolysate in decreasing HT-29 colon cancer cell line viability was seen in a concentration-dependent manner (the lowest cell viability of 32% at 5 mg/mL). Overall, investigating the application of protein-based hydrolysates is one of the possible strategies that govern their applied intentions as preservatives and nutraceuticals in the food and pharmaceutical industries.

Purification, Identification and Molecular Docking of Novel Antioxidant Peptides from Walnut (Juglans regia L.) Protein Hydrolysates

Walnut protein isolate (WPI) was hydrolyzed using Alcalase for 0, 30, 60, 90, 120 and 150 min to investigate the effect of different hydrolysis times on the structure and antioxidant properties of walnut proteins. The identified peptides HADMVFY, NHCQYYL, NLFHKRP and PSYQPTP were used to investigate the structure-activity relationship by using LC-MS/MS and molecular docking. The kinetic equations DH = 3.72ln [1 + (6.68 E₀/S₀ + 0.08) t] were developed and validated to explore the mechanism of WIP hydrolysis by Alcalase. Structural characteristics showed that the UV fluorescence intensity and endogenous fluorescence intensity of the hydrolysates were significantly higher than those of the control. FTIR results suggested that the secondary structure gradually shifted from an ordered to a disordered structure. Enzymatic hydrolysis containing much smaller molecule peptides than WPI was observed by molecular weight distribution. In vitro, an antioxidant test indicated that Alcalase protease hydrolysis at 120 min showed more potent antioxidant activity than hydrolysates at other hydrolysis times. In addition, four new antioxidant peptides were identified by LC-MS/MS. Molecular docking indicated that these peptides could interact with ABTS through interactions such as hydrogen bonding and hydrophobic interactions. Thus, WPI hydrolysates could be used as potential antioxidants in the food and pharmaceutical industries.

Effects of high-pressure homogenization on physicochemical and functional properties of enzymatic hydrolyzed soybean protein concentrate

This paper investigates the effect on the physicochemical and functional properties of soybean protein concentrate (SPC) by using Alcalase protease and high-pressure homogenization (HPH) (0, 20, 40, 60, 80, and 100 MPa) for the combined modification. The results showed that the degree of hydrolysis of SPC was 4.1% and the antigen protein was degraded after Alcalase hydrolysis, when the homogenization pressure (HP) was 6 0Mpa, the particle size of the SPC was the smallest, the zate potential absolute value up to 33.45 mV, the secondary structure has the lowest β-sheet content, the highest random coil content, and the highest surface hydrophobicity (H0), the size of protein fragments on the microstructure surface is the smallest, the lowest denaturation temperature (T d ) and enthalpy (△H) are 72.59°C and 1.35 J/g, the highest solubility is 80.54%, and the highest water and oil holding capacities are 7.73 g/g and 6.51 g/g, respectively. The best emulsifying activity and emulsifying stability were 43.46 m2/g and 190.35 min, the most even distribution of emulsion droplets. This indicates that the HPH treatment destroys the structure of enzymatic hydrolyzed SPC, changes its physicochemical properties, and improves its functional properties. In this study, SPC was modified by HPH and enzyme combined treatment, in order to improve the functionality and application range of SPC, and provide a theoretical basis for its high-value utilization in the food field.

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.

Boosting Hydrolysis of Cellulose at High Temperature by β-Glucosidase Induced Metal-Organic Framework In-Situ Co-Precipitation Encapsulation

Due to the poor enzyme thermal stability, the efficient conversion of high crystallinity cellulose into glucose in aqueous phase over 50 °C is challenging. Herein, an enzyme-induced MOFs encapsulation of β-glucosidase (β-G) strategy was proposed for the first time. By using various methods, including SEM, XRD, XPS, NMR, FTIR and BET, the successful preparation of a porous channel-type flower-like enzyme complex (β-G@MOFs) was confirmed. The prepared enzyme complex (β-G@MOFs) materials showed improved thermal stability (from 50 °C to 100 °C in the aqueous phase) and excellent resistance to ionic liquids (the reaction temperature was as high as 110 °C) compared to the free enzyme (β-G). Not only the catalytic hydrolysis of cellulose by single enzyme (β-G) in ionic liquid was realized, but also the high-temperature continuous reaction performance of the enzyme was significantly improved. Benefiting from the significantly improved heat resistance, the β-G@MOFs exhibited 32.1 times and 34.2 times higher enzymatic hydrolysis rate compared to β-G for cellobiose and cellulose substrates, respectively. Besides, the catalytic activity of β-G@MOFs was retained up to 86 % after five cycles at 110 °C. This was remarkable because the fixation of the enzyme by the MOFs ensured that the folded structure of the enzyme would not expand at high temperatures, allowing the native conformation of the encapsulated protein well-maintained. Furthermore, we believe that this structural stability was caused by the confinement of flower-like porous MOFs.

Effect of radio frequency, ultrasound, microwave-assisted papain, and alcalase hydrolysis on the structure, antioxidant activity, and peptidomic profile of Rosa roxburghii Tratt. seed protein

Traditional enzymatic hydrolysis methods have defects such as low efficiency and poor bioactivity in the production of active peptides. In this study, radio frequency (RF) technology was innovatively used to assist the hydrolysis of Rosa roxburghii Tratt. seed protein (RTSP) by papain and alcalase. RF-assisted hydrolysis was compared with ultrasound-(US) and microwave (MW)-assisted techniques in terms of the degree of hydrolysis, structure, antioxidant properties, and changes in the peptidome of the hydrolysates to clarify the mechanism of functional change of physically-assisted hydrolysate. All three methods improved hydrolysis efficiency. The degree of hydrolysis (DH) of papain group increased from 6.38% to 7.97%, 9.97% and 8.37% after US-, MW- and RF-assisted hydrolysis, respectively, while the DH of alcalase-treated group increased from 21.13% to 25.66%, 26.03%, and 23.01%, respectively. The in vitro antioxidant capacity and intracellular antioxidant capacity of RTSP and its hydrolysates were measured and evaluated by fuzzy statistical evaluation, and MW-assisted alcalase hydrolysis had the highest in vitro and intracellular antioxidant activity scores of 0.713 and 0.820, respectively. Fourier transform infrared and amino acid composition analysis explained the enhanced antioxidant properties of the hydrolysates. Further peptide profiling showed the physical assistance led to an increase in the species and contents of small molecule antioxidant peptides compared to enzyme treatment alone. Pearson's linear correlation analysis showed that AY, LY, IY, PHW, SVL, LHL, YYV, VYY, and NHAV were significantly correlated with the antioxidant properties of hydrolysates. Our data suggested that physical assistance such as US, MW, and RF were effective to improve the efficiency of enzymatic hydrolysis and produce novel antioxidant peptides. PRACTICAL APPLICATION: In this study, it was found that electromagnetic wave-assisted enzymatic hydrolysis could improve the efficiency of hydrolysis and enhance the antioxidant activity of hydrolysates compared to unassisted means. Compared with MW treatment, RF has the comparable hydrolysis effect, but has the advantages of high penetration ability, good uniformity, and low energy consumption and has greater potential for the production of bioactive peptides.

Antiaging function of Chinese pond turtle (Chinemys reevesii) peptide through activation of the Nrf2/Keap1 signaling pathway and its structure-activity relationship

Chinese pond turtle is a traditional nourishing food with high nutritional value and bioactivity and has been considered a dietary remedy for prolonging the lifespan since ancient times. However, only limited information about their effects on longevity is available. This study was performed to assess the antioxidant activities and antiaging potential of Chinese pond turtle peptide (CPTP) using Drosophila melanogaster model and uncover the possible mechanisms underlying the beneficial effects. CPTP exhibited excellent antioxidant capability in vitro with IC₅₀ values of 3.31, 1.93, and 9.52 mg/ml for 1,1-diphenyl-2-pycryl-hydrazyl (DPPH), 2,2-azinobis (3-ethylbenzothiazo-line-6-sulfonic acid) diammonium salt (ABTS), and hydroxyl radical scavenging, respectively. In vivo, 0.8% of CPTP significantly extended the mean and median lifespan of female flies by 7.66 and 7.85%, followed by enhanced resistance to oxidative and heat stress. Besides, CPTP remarkably increased the antioxidant enzyme activities and diminished the peroxide product accumulation. Furthermore, CPTP upregulated the relative mRNA expression of antioxidant-related genes, including nuclear factor-erythroid-2-like 2 (Nrf2) and its downstream target genes, while downregulated the expression of Kelch-like ECH-associated protein 1 (Keap1). Taken together, CPTP displayed promising potential in both antioxidant and antiaging effects on flies by targeting the Nrf2/Keap1 pathway. Further peptide sequence determination revealed that 89.23% of peptides from the identified sequences in CPTP could exert potential inhibitory effects on Keap1. Among these peptides, ten representative peptide sequences could actively interact with the binding sites of Keap1-Nrf2 interaction through hydrogen bonds, van der Walls, hydrophobic interactions, and electrostatic interactions. Conclusively, CPTP could be utilized as health-promoting bioactive peptide with antioxidant and antiaging capacities.

Differences in Protein Profiles of Kefir Grains from Different Origins When Subcultured in Goat Milk

Proteins not only serve as a nitrogen source for microorganisms but are the main skeleton of kefir grains. After subculturing in goat milk for 4 months, proteins and peptides in three kefir grains from China, Germany, and the United States were analyzed. Except for the S-layer protein from special Lactobacillus sp., α_s1-casein, α_s2-casein, and β-casein from goat milk were found in kefir grains. These proteins could form aggregates through a covalent interaction with polysaccharides to maintain the morphological stability of the grains. Furthermore, they were highly related to the microbiota in kefir grains. Additionally, a number of hydrophilic/hydrophobic peptides that were hydrolyzed by extracellular proteases were found from kefir grains. A correlation may exist between peptides and Lactobacillus sp. in kefir grains. Bioactive peptides, including DKIHPF, LGPVRGPFP, and QEPVLGPVRGPFP, were found from these kefir grains. The results indicated that goat milk as a substrate affects the protein and peptide composition of kefir grains.

Cardioprotective Peptides from Milk Processing and Dairy Products: From Bioactivity to Final Products including Commercialization and Legislation

Recent research has revealed the potential of peptides derived from dairy products preventing cardiovascular disorders, one of the main causes of death worldwide. This review provides an overview of the main cardioprotective effects (assayed in vitro, in vivo, and ex vivo) of bioactive peptides derived from different dairy processing methods (fermentation and enzymatic hydrolysis) and dairy products (yogurt, cheese, and kefir), as well as the beneficial or detrimental effects of the process of gastrointestinal digestion following oral consumption on the biological activities of dairy-derived peptides. The main literature available on the structure–function relationship of dairy bioactive peptides, such as molecular docking and quantitative structure–activity relationships, and their allergenicity and toxicity will also be covered together with the main legislative frameworks governing the commercialization of these compounds. The current products and companies currently commercializing their products as a source of bioactive peptides will also be summarized, emphasizing the main challenges and opportunities for the industrial exploitation of dairy bioactive peptides in the market of functional food and nutraceuticals.

Probing the antioxidant activity of functional proteins and bioactive peptides in Hermetia illucens larvae fed with food wastes

Food waste is becoming more prevalent, and managing it is one of the most important issues in terms of food safety. In this study, functional proteins and bioactive peptides produced from the enzymatic digestion of black soldier fly (Hermetia illucens L., BSF) fed with food wastes were characterized and quantified using proteomics-based analysis. The results revealed approximately 78 peptides and 57 proteins, including 40S ribosomal protein S4, 60S ribosomal protein L8, ATP synthase subunit alpha, ribosomal protein S3, Histone H2A, NADP-glutamate dehydrogenase, Fumarate hydratase, RNA helicase, Chitin binding Peritrophin-A, Lectin C-type protein, etc. were found in BSF. Furthermore, functional analysis of the proteins revealed that the 60S ribosomal protein L5 (RpL5) in BSF interacted with a variety of ribosomal proteins and played a key role in the glycolytic process (AT14039p). Higher antioxidant activity was found in peptide sequences such as GYGFGGGAGCLSMDTGAHLNR, VVPSANRAMVGIVAGGGRIDKPILK, AGLQFPVGR, GFKDQIQDVFK, and GFKDQIQDVFK. It was concluded that the bioconversion of food wastes by BSF brought about the generation of a variety of functional proteins and bioactive peptides with strong antioxidant activity. However, more studies are required to exploit BSF's potential in the value addition of food wastes.