Physicochemical properties and antioxidant activities of tree peony (Paeonia suffruticosa Andr.) seed protein hydrolysates obtained with different proteases

A new technique for antioxidant walnut peptide preparation directly from walnut cake: Enzymatic preparation process optimization coupled with enzyme membrane reactor and kinetic analysis

The lack of scalable production methods limits the commercial production viability of walnut peptides. To overcome this obstacle, enzyme membrane reactors (EMRs) were used to continuously produce bioactive peptides (called CEMR) directly from walnut cake. The optimum operating conditions were pH 10.7, an [E/S] ratio of 11 %, and a temperature of 44 °C, which resulted in a peptide yield of 256.0 ± 4.66 mg/g cake and a protein conversion degree reaching 63.49 ± 0.82 %. Kinetic analysis showed that affinity between alkaline protease and walnut cake can be enhanced by EMR (km decreased, kA increased). The antioxidant results showed that the strongest antioxidant activity was detected in CEMR. The composition of amino acids and molecular weight distribution results showed that the highest content of Glu (20.20 ± 0.48 %), Asp (20.70 ± 0.95 %), and peptides with molecular weight < 1KD (51.92 %) were detected in CEMR. The results of CEMR provide a new option for simplifying the production process of walnut peptide.

Physicochemical and functional properties of two kinds of Schisandra proteins and their antioxidant activity in H2O2-treated HepG2 cells

Schisandra chinensis protein (SCP) and Schisandra sphenantherae protein (SSP) were extracted by alkali extraction and isoelectric precipitation, and the amino acid compositions, structures, and physicochemical properties of the two proteins were analyzed to evaluate their functional properties. The effects of SCP and SSP on proliferation, protection, and anti-apoptosis of H2O2-treated HepG2 cells after oxidative stress were investigated. The results showed that SCP had a higher content of essential amino acids (16.27 ± 0.76) than SSP. Scanning electron microscopy and Fourier-transform infrared spectroscopy analyses, as well as substituent distribution in electrophoresis, revealed the structural differences between the two proteins; in particular, the disulfide bond content is higher in SCP, which was also found to be more stable in terms of heat tolerance (114.7 °C), solubility (47.18 %), emulsification (158.57 m2/g), emulsion stability (89.53 %), foaming (226 %), and foaming stability (90.32 %). In an in vitro experiment, SSP was more effective in protecting HepG2 cells from H2O2-treated oxidative damage, effectively inhibiting the levels of reactive oxygen species and malondialdehyde, maintaining the stability of cell membranes, promoting antioxidant mechanisms, and decreasing apoptosis by regulating the expression of genes and proteins related to the mitochondrial apoptotic pathway. These results suggest that both SCP and SSP are suitable as novel food additives, and that the excellent functional properties and thermal stability of SCP make it a potential nutritional resource in the food industry. In addition, SSP has potential as a protein resource with antioxidant activity.

Germination affects structural and techno-functional properties of proteins from quinoa seeds with increased realease of antioxidant peptides by gastrointestinal digestion

This study investigated the impact of germination on quinoa protein (QP) composition, techno-functional properties, and the release of antioxidant peptides during gastrointestinal digestion. Germinated QP (GQP) at 36 and 48 h showed significant degradation of storage proteins. GQP12 and GQP24 exhibited increased surface hydrophobicity but decreased solubility, foaming, and emulsifying properties, while that of GQP60 and GQP72 were improved. Both QP and GQP demonstrated good digestibility, with over 90 % of their gastrointestinal digests smaller than 1 kDa. Gastrointestinal digests of GQP12 (QPGI12) exhibited excellent antioxidant activity, attributed to higher hydrophobic amino acid content of GQP12 and peptides of QPGI12 digests. Eight antioxidant peptides with strong binding affinity to Keap1 were identified, with peptides FGDL, FGGL, and FDGL interacting through hydrogen bonding and hydrophobic interactions. Findings gained in this study indicated that germination might serve as an efficient strategy for improving techno-functionality and bioactivity of QP for antioxidant peptides production.

Preparation, separation and identification of novel hypocholesterolemic peptides from wheat germ: An in vitro and in silico study

The aim of this study was to prepare, isolate, and identify hypocholesterolemic peptides from wheat germ protein and explore their efficacy. Wheat germ protein was hydrolyzed using four commercial enzymes. Hydrolysate, with the highest in vitro hypocholesterolemic activity was isolated using ultrafiltration and macroporous resin. The fractions with highest binding affinity to sodium taurocholate were evaluated for cholesterol-lowering activity and resistance to digestion using Caco-2 monolayers. Fraction III had the highest cholesterol-lowering activity, reducing the subcutaneous transport and absorption of cholesterol and resisted digestion. Nano-LC-MS/MS and molecular docking were used to identify cholesterol-lowering peptides from Fraction III. Three cholesterol-lowering peptides, FAAGAPP, GAGDIPGGIG, and GPVPDTGIFS, were identified. These peptides exhibited cholesterol micelle solubility, specifically by 76.2 %, 68.3 %, and 64.7 %, respectively. In summary, wheat germ peptides exhibited significant cholesterol-lowering activity in vitro, suggesting their potential for application in functional foods.

Reducing the allergenicity of whey proteins while improving their functional properties and bioactivity using combined enzymes

The aim of this study was to investigate the changes in functional properties, bioactivity and allergenicity of whey protein hydrolysates (WPH) prepared by combinations of endopeptidases and exopeptidases. The immunoglobulin E-binding capacity of WPH made by combining pineapple protease and papain with the exopeptidase ProteAXH was reduced by 47.62 % and 51.91 %, respectively, and the emulsification performance was improved by about 40 % in both cases. Multispectral results indicated that the addition of ProteAXH increased the disruption of protein conformation. Liquid chromatography coupled with tandem mass spectrometry analysis revealed that the exopeptidase altered the hydrolysis sites of the protein. Further combination with bioinformatics revealed that increased conformational disruption and altered linear epitope hydrolysis sites decreased the allergenicity of WPH. Meanwhile, the structural changes also increased the release of emulsifying peptides and bioactive peptides, thus improving the functional properties. In conclusion, these two WPHs combine hypoallergenicity with excellent functional properties and bioactivity.

Composite gel based on κ-carrageenan-soybean isolate protein/soy protein fibrils: Focus on structural differences and gel properties

The effects of different concentrations of κ-carrageenan (κC) on the structure and gel properties of soybean protein isolate (SPI) and soybean protein fibrils (SPF) were investigated in this work. The interaction between κC and SPI/SPF was explored by SDS-PAGE, FTIR, fluorescence spectroscopy, surface hydrophobicity (H0). Results indicated that the binding of κC to SPI and SPF is mainly hydrogen bonding and hydrophobic interactions. With the increase of κC concentration, the fluorescence intensity and H0 of SPI/SPF-κC decrease. When κC was 8 mg/mL, the H0 of SPI/SPF-κC decreased by 53.56 % and 57.23 % respectively. The addition of κC increased the particle size and turbidity of SPI, while the opposite results for SPF. The gel properties of SPI/SPF-κC were evaluated by texture, rheology and LF-NMR. The results showed that the gel properties of SPF were better than those of SPI, and the addition of κC significantly increased the G', apparent viscosity and resistance to denaturation of the gel. When κC concentration was 8 mg/mL, the hardness of SPI/SPF-κC was 127.2 ± 5.82 g and 134.23 ± 5.89 g, respectively. In conclusion, the fibrillation of proteins and κC can effectively improve the gel properties of SPI gels, which provides a theoretical basis for expanding the high-value utilization of SPI and SPF.

Discovery of two novel ACE inhibitory peptides from soybeans: Stability, molecular interactions, and in vivo antihypertensive effects

Functional peptides that are derived from natural protein-rich foods possess a wide range of physiological and pharmacological properties and have become ideal alternatives to chemical drugs. In this study, two novel ACE inhibitory peptides, GKGLW (IC50 = 34.96 μM) and GDGLKW (IC50 = 33.98 μM), were screened and identified from soybeans through sequential stepwise double enzymolysis, and their molecular mechanisms were explored by combining computational simulation. Initially, the optimal combination of alkaline protease and chymotrypsin was determined through the analysis of the enzymatic preferences of five different proteases and the ACE inhibitory activity of their hydrolyzed products. Following purification by ultrafiltration and Sephadex G-25 gel chromatography, the amino acid sequences of the peptides were identified by LC-MS/MS and selectively synthesized based on binding energy. Molecular docking and dynamics simulation/generalized born surface area calculation indicated that the peptides mainly interacted with key residues Ala354, Tyr523, and His353 in the ACE active pocket through hydrogen bonds, and hydrophobic and aromatic amino acids were beneficial to the ACE inhibitory activity of the peptides. Additionally, the two peptides showed good stability in simulating the gastrointestinal digestion process. The antihypertensive effects of these two peptides were further verified in a spontaneously hypertensive rats (SHRs) model. In conclusion, this study successfully identified two ACE inhibitory peptides, GKGLW and GDGLKW, from soybeans by combining proteases with different characteristics for stepwise degradation of soy protein, revealing their potential application value as antihypertensive functional foods.

Enhancement on the solubility of polyploid and diploid rice proteins by enzymatic hydrolysis: From structural and functional characteristics of rice protein hydrolysates

Polyploid rice protein (PRP) has the advantage of high nutritional value, but its functional properties are minimal due to its poor solubility. This work aims to improve the solubility of PRP through enzymatic hydrolysis and assess the effect of hydrolysis time (5-330 min) and protease type (Alcalase, Neutrase, and Trypsin) on the structural, functional, and antioxidant properties of PRP hydrolysates (PRPHs). Compared to PRP, PRPHs exhibited significantly decreased free sulfhydryl content and surface hydrophobicity and improved structural flexibility, regardless of the protease used. With increasing time, the nitrogen solubility index of the hydrolysates increased by 25.01 %, which was attributed to the reduction in molecular weight (< 15 kDa). The highest emulsifying activity (48.81 m2/g) and hydroxyl radical scavenging activity (IC50 of 5.49 mg/mL) were observed from Neutrase hydrolysates at 210 min and 330 min, respectively. Trypsin hydrolysate at 210 min demonstrated the lowest IC50 (0.17 mg/mL) in ABTS+. Moreover, compared to diploid rice protein hydrolysates (DRPHs) obtained under the same conditions, PRPHs by all proteases exhibited superior functional and antioxidant properties and richer amino acid content. This study showed the potential of PRPHs applied to functional foods with favorable functional and antioxidant properties.

Influence of Supercritical Fluid Extraction Process on Techno-Functionality of Enzymatically Derived Peptides from Filter-Pressed Shrimp Waste

This study explored how combining supercritical fluid extraction (SFE) and enzymatic hydrolysis influences the structure and functionality of peptides recovered from filter-pressed shrimp waste. Freeze-dried press cake (PC) was defatted via SFE and hydrolyzed using Alcalase (ALC) and trypsin (TRYP). ALC-treated PC achieved the highest protein recovery (63.49%), extraction yield (24.73%), and hydrolysis degree (18.10%) (p < 0.05). SFE-treated hydrolysates showed higher zeta potential (-47.23 to -49.93 mV) than non-SFE samples (-25.15 to -38.62 mV) but had larger droplet sizes, indicating lower emulsion stability. SC-ALC displayed reduced fluorescence intensity and a red shift in maximum wavelength. TRYP hydrolysates reduced interfacial tension (20 mN/m), similar to sodium caseinate (Na-Cas, 13 mN/m), but with lesser effects. Dilatational rheology showed TRYP hydrolysates formed stronger, solid-like structures. These results emphasize protease efficacy over SFE for extracting functional compounds, enhancing shrimp waste valorization.

A novel iron fortifier prepared through quinoa protein peptides hydrolyzed with different proteases

Iron deficiency is a widespread global issue that leads to nutritional disorders and iron deficiency anemia (IDA). In this study, quinoa protein peptide (QPP) was selected to design a novel iron supplement, quinoa protein peptide‑iron chelate (QPP-Fe). Notably, QPP with a molecular weight of <2000 Da, prepared using Alcalase, exhibited the highest iron chelation ratio of 79.2 ± 0.36 mg/g. Furthermore, FTIR, UV-Vis, CD, and fluorescence spectroscopy results indicated that the addition of Fe2+ significantly altered the secondary structure of QPP. This alteration was primarily attributed to the interaction of Fe2+ with carboxyl, amino, and imidazole groups. Moreover, we observed that the QPP-Fe form compact spherical structures, leading to reduced and much more uniform particle sizes. The molecular docking results revealed that Fe2+ formed ligand bonds with Glu, His, Ala, and Gly through electrostatic interactions. Then a pocket structure that wrapped Fe2+ around the peptide was formed, which changed the peptide from a free and disordered state to a more stable state. These results can provide a reference for the development of iron-fortified functional foods.

Identification of two novel α-amylase inhibitory activity peptide from Russian sea cucumber body wallprotein hydrolysate

This study aimed to identify novel α-amylase inhibitory peptides from Russian sea cucumbers and elucidate their inhibitory mechanisms. Among the 52 identified sea cucumber peptide (SCP), two peptides with potential α-amylase inhibitory activity, FPSPPLVA (SCP1) and GPPMPPPPLP (SCP2), were selected from the sequences researched. The results showed that both SCP1 and SCP2 exhibited α-amylase inhibitory activity with IC50 of 0.92 ± 0.03 mg/mL (SCP1) and 2.01 ± 0.02 mg/mL (SCP2), respectively. Molecular docking studies revealed the potential interaction mechanism between these inhibitors and α-amylase. Two peptides interacted with Gln63, Tyr151, Thr163, Lys200, His201, His305, and Ala307 within the α-amylase active site. The formation of hydrogen bonds and hydrophobic interactions between the inhibitors and α-amylase impedes the formation of enzyme-substrate complexes and subsequent glycosylation. Lineweaver-Burk plot indicated that both SCP1 and SCP2 act as reversible mixed inhibitors of α-amylase. Furthermore, the results of infrared and circular dichroism spectroscopy confirmed the formation of non-covalent binding complexes between SCP and amylase, leading to alterations in the secondary structure of the enzyme.

Ursolic acid- betulinic acid-CCM NPs: A delivery system for improving the stability and bioavailability of CCM

The research constructed a co-assembly nanoparticles (NPs) of ursolic acid (UA) and betulinic acid (BA) as carriers to load the active substance curcumin (CCM) by co-precipitation method, aiming to improve the stability and bioavailability of CCM in the human body and enabling CCM to play more functions in the production of functional foods. The average particle size of UA-BA-CCM NPs was 222.6 nm and zeta potential was -26.63 mV. The UA-BA-CCM NPs had small size and great stability. The drug loading was up to 20.42 %. Moreover, the hydrogen bonds and π-π stacking existed in the three molecules. The result was verified by Molecular Dynamics Simulation, FITR, and UV experiments. In simulated in vitro release experiments, the release rate of the NPs was lower than free CCM in gastric phase, improving CCM bioavailability. Meanwhile, the UA-BA-CCM NPs performed better clearing free radicals than free CCM. Thus, UA-BA-CCM NPs delivery system not only could improve stability and bioavailability of CCM, but also might make CCM play a role in the functional food.

Characteristics, Antioxidant Activity Stability, and Anti-Fatigue Activity of Hydrolysates from Cucumaria frondosa Tentacles

This study aimed to assess the impact of alcalase, trypsin, flavourzyme, and neutrase on the characteristics, antioxidant activity stability, and anti-fatigue activity of hydrolysates derived from Cucumaria frondosa tentacles (CFTHs). The results demonstrate that favourzyme hydrolysates exhibited the highest degree of hydrolysis (DH). Zeta potential and particle size measurements indicated that hydrolyzed peptides treated with favourzyme appeared aggregated and exhibited larger particle sizes. The antioxidant properties of CFTHs demonstrated good thermal stability, pH stability, and enhanced simulated gastrointestinal digestive stability. The anti-fatigue activity of CFTHs was examined using an acute exercise fatigue model. The results indicate that CFTHs extended the exhaustive swimming time of mice to 17.81 min. Additionally, CFTHs significantly elevated (p < 0.01) blood glucose (Glu) and liver glycogen (LG) levels, while also decreasing (p < 0.05) the concentrations of metabolites such as lactic acid (LA), urea nitrogen (BUN), creatine kinase (CK), lactate dehydrogenase (LDH), and ammonia (NH3). This reduction contributed to the alleviation of fatigue in the body. Furthermore, the levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were significantly increased (p < 0.05), which aided in mitigating oxidative damage induced by strenuous exercise. These findings strongly support the potential utilization of CFTHs in food products as natural antioxidant and anti-fatigue alternatives.

Optimizing β-Lactoglobulin antigenicity through single enzyme hydrolysis: Exploring structural changes and effects on linear epitopes

β-lactoglobulin (β-LG) is the major allergen in dairy products, but research on the optimal conditions for antigen reduction in β-LG using different enzymes remains limited. Therefore, this study aims to investigate the antigenicity, structural characteristics, and peptide distribution of advantageous protease hydrolysates capable of eliminating the allergenic epitopes of β-LG selected via bioinformatics tools. The results showed that under optimal enzymatic hydrolysis conditions, the antigen reduction rates for the four advantageous proteases acting on β-LG were 47.37 % (pepsin), 33.54 % (chymotrypsin A), 38.71 % (papain), and 45.91 % (stem bromelain), respectively. The four proteases effectively degraded β-LG, causing shorter peptide chain formation, reduced content of highly ordered α-helix, decreased fluorescence intensity, and lower surface hydrophobicity. Furthermore, they cleaved the linear epitopes of β-LG into peptides of varying sizes, leading to different antigen reduction rates among the hydrolysates. These findings provide a theoretical basis for developing targeted enzymatic hydrolysis technologies and low-allergenicity dairy-based materials.

Discovery of selective ROCK2 inhibitors with free radical scavenging ability for the treatment of gouty arthritis

ROCK inhibitors can inhibit IL-1β and NLRP3, and their therapeutic potential for osteoarthritis and rheumatoid arthritis has been confirmed, but their impact on gouty arthritis has not been reported yet. By hybridization the structure of Edaravone, a series of ROCK inhibitors with pyrazolone scaffold were designed and synthesized. RM-04 has acceptable selective ROCK2 inhibitory activity with an IC50 of 4.62 µM, and its IC50 values for scavenging DPPH• and ABTS•+ are 16.72 µM and 23.15 µM, respectively, which is equivalent to that of Edaravone. Furthermore, RM-04 exhibits good pharmacokinetic properties and good safety in vivo. Meanwhile, in sodium urate-induced acute gout model, RM-04 at a dose of 5 mg/kg exhibited the alleviating effect approximately equivalent to that of Celecoxib, indicating that ROCKs inhibitors with antioxidation activity could reduce the damage caused by gouty arthritis.

Tailoring Structural, Emulsifying, and Interfacial Properties of Rice Bran Protein Through Limited Enzymatic Hydrolysis After High-Hydrostatic-Pressure Pretreatment

We carried out limited enzymatic hydrolysis with trypsin on rice bran protein (RBP) pretreated by high hydrostatic pressure (HHP) in this study. The effects of the degree of hydrolysis (DH) on the structural and emulsifying properties were investigated. The results indicated that the molecular structure of RBP changed after limited enzymatic hydrolysis. The rice bran protein hydrolysate (RBPH, DH8) exhibited a better molecular distribution, a smaller particle size (200.4 nm), a better emulsifying activity index (31.82 m2/g), and an improved emulsifying stability index (24.69 min). RBPH emulsions with different DH (0-12) values were prepared. The interfacial properties, such as particle size, the ζ-potential, and the interfacial tension of the emulsions, were measured. Compared to the control, the interfacial properties of the RBPH emulsions were significantly improved after limited enzymatic hydrolysis. The RBPH emulsion at DH8 showed better stability with a smaller emulsion droplet size (2.31 μm), a lower ζ-potential (-25.56 mV), and a lower interfacial tension. This study can provide a theoretical basis for the application of RBP as the plant protein-based emulsifier in the beverage industry.

Structure, antioxidant activity, and neuroprotective effect of black soybean (Glycine max (L.) merr.) protein hydrolysates

The potential biological properties of protein hydrolysates have generated considerable research interest. This study was to hydrolyze black soybean protein (BSP) using five different commercial enzymes, and elucidate the influence of these enzymes on the structure and biological activities of the resulting hydrolysates. Enzymatic treatment changed secondary and tertiary structures of BSP, decreased particle size, α-helix and β-sheet. Alcalase hydrolysate had the highest hydrolytic degree (29.84 %), absolute zeta potential (38.43 mV), the smallest particle (149.87 nm) and molecular weight (<3 kDa). In silico revealed alcalase hydrolysate had the strongest antioxidant potential. This finding was further validated through the lowest IC50 (mg/mL) in DPPH (2.67), ABTS (0.82), Fe2+ chelating (1.33) and·OH (1.12). Moreover, cellular antioxidant assays showed alcalase hydrolysate had the strongest cytoprotective effects on H2O2-induced PC12 cells. These results suggest BSPEHs, especially those prepared by alcalase, have potential as bioactive ingredients for nutrition, healthcare and food industry.

Formation of self-assembled fibril aggregates of trypsin-controllably hydrolyzed soy protein and its regulation on stability of high internal phase Pickering emulsions

The mechanisms of trypsin hydrolysis time on the structure of soy protein hydrolysate fibril aggregates (SPHFAs) and the stability of SPHFAs-high internal phase Pickering emulsions (HIPPEs) were investigated. SPHFAs were prepared using soy protein hydrolysate (SPH) with different trypsin hydrolysis time (0 min-120 min) to stabilize SPHFAs-HIPPEs. The results showed that moderate trypsin hydrolysis (30 min, hydrolysis degree of 2.31 %) induced SPH unfolding and increased the surface hydrophobicity of SPH, thereby promoting the formation of flexible SPHFAs with maximal thioflavin T intensity and ζ-potential. Moreover, moderate trypsin hydrolysis improved the viscoelasticity of SPHFAs-HIPPEs, and SPHFAs-HIPPEs remained stable after storage at 25 °C for 80 d and heating at 100 °C for 1 h. Excessive trypsin hydrolysis (> 30 min) decreased the stability of SPHFAs-HIPPEs. In conclusion, moderate trypsin hydrolysis promoted the formation of flexible SPHFAs with high surface charge by inducing SPH unfolding, thereby promoting the stability of SPHFAs-HIPPEs.

Enhancing Digestibility and Intestinal Peptide Release of Pleurotus eryngii Protein: An Enzymatic Approach

Pleurotus eryngii is a tasty and low-calorie mushroom containing abundant high-quality protein. This study aims to improve the digestibility of P. eryngii protein (PEP) and hence to facilitate its development as a healthy alternative protein. The extracted PEP was pretreated with 1000-5000 U of papain, neutral protease and alkaline protease. The Chyme collected from in vitro simulated gastrointestinal digestion was analyzed by fluorescence microscopy and protein particle analyzer, and the endpoint profiles of peptides and amino acids were determined by UHPLC-MS/MS and NanoLC-MS/MS. The particle size curve and fluorescence microscopy images jointly supported that protease hydrolysis improved decomposition and dispersion of PEP during digestion, particularly in the gastric phase. The impact on Zeta potential was minimal. Proteases effectively increased the abundance of amino acids after digestion, particularly L-isomer Lys and Arg Maximum release was achieved when pretreated with 5000 U of alkaline protease, reaching 7.54 times that of control. Pretreatments by proteases also notably increased digestive yields of 16,736-19,870 peptides, with the maximum reaching 1.70 times that of the control, which mainly consisted of small peptides composed of 7-15 amino acids with molecular weight below 800 Da. The findings indicated that protease hydrolysis, especially pretreatment with 5000 U of alkaline protease, effectively enhanced the digestibility of PEP, which shed light on providing enzymatic approaches for improving bioavailability and developing healthy fungal proteins.

Extraction, structural characteristics and antioxidant activity of hemp seeds glycoprotein

The extraction process of hemp seeds glycoprotein (HGP) was optimized by using response surface methodology based on the single-factor experiments, and the structure characteristic and antioxidant activity of HGP were evaluated. The optimum conditions were extracting temperature of 58.54 °C, material-liquid ratio of 1:22.21 and ultrasonic power of 344.53 W. The molecular weight of HGP was identified by SDS-PAGE to be about 35 kDa. The FT-IR results demonstrated the presence of uronic acid and pyranose in the HGP structure. UV spectral scanning results confirmed the presence of a polypeptide skeleton structure and aromatic amino acids in HGP. TGA analysis revealed two weight loss intervals for HGP, with a thermal degradation temperature of 341.6 °C. Moreover, HGP demonstrated good antioxidant activity in vitro, with IC50 values of all antioxidant indexes below 0.5 mg/mL. These findings provide a basis for in-depth exploration of functional characteristics of hemp seeds glycoprotein.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01583-3.

Changes in ficin specificity by different substrate proteins promoted by enzyme immobilization

Ficin extract has been immobilized using different supports: glyoxyl and Aspartic/1,6 hexamethylenediamine (Asp/HA) agarose beads. The latter was later submitted to glutaraldehyde modification to get covalent immobilization. The activities of these 3 kinds of biocatalysts were compared utilizing 4 different substrates, casein, hemoglobin and bovine serum albumin and benzoyl-arginine-p-nitroanilide at pH 7 and 5. Using glyoxyl-agarose, the effect of enzyme-support reaction time on the activity versus the four substrates at both pH values was studied. Reaction time has been shown to distort the enzyme due to an increase in the number of covalent support-enzyme bonds. Surprisingly, for all the substrates and conditions the prolongation of the enzyme-support reaction did not imply a decrease in enzyme activity. Using the Asp/HA supports (with different amount of HA) differences in the effect on enzyme activity versus the different substrates are much more significant, while with some substrates the immobilization produced a decrease in enzyme activity, with in other cases the activity increased. These different effects are even increased after glutaraldehyde treatment. That way, the conformational changes induced by the biocatalyst immobilization or the chemical modification fully altered the enzyme protein specificity. This may also have some implications when following enzyme inactivation.

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.

A composite enzyme derived from papain and chymotrypsin reduces the Allergenicity of Cow's Milk allergen casein by targeting T and B cell epitopes

Casein, the major allergen in cow's milk, presents a significant challenge in providing nutritional support for children with allergies. To address this issue, we investigated a composite enzyme, comprising papain and chymotrypsin, to reduce the allergenicity of casein. Enzymatic hydrolysis induced substantial structural changes in casein, diminishing its affinity for specific IgE and IgG antibodies. Additionally, in a BALB/c mouse model, casein hydrolysate alleviated allergic symptoms, evidenced by lower serum IgE and IgG levels, reduced plasma histamine, and decreased Th2 cytokine release during cell co-culture. Peptidomic analysis revealed a 52.38% and 60% reduction in peptides containing IgE epitopes in casein hydrolyzed by the composite enzyme compared to papain and chymotrypsin, respectively, along with a notable absence of previously reported T cell epitopes. These results demonstrate the potential of enzyme combinations to enhance the efficiency of epitope destruction in allergenic proteins, providing valuable insights into the development of hypoallergenic dairy products.

Effects of ultrasonic waves of different powers on the physicochemical properties, functional characteristics, and ultrastructure of bovine liver peptides

In recent years, ultrasound has emerged as a widely used technology for modifying proteins/peptides. In this study, we focused on the intrinsic mechanism of ultrasound-induced modification of bovine liver peptides, which were treated with ultrasound power of 0, 100, 200, 300, 400, and 500 W, and their physicochemical and functional properties, as well as ultrastructures, were investigated. The results show that ultrasound mainly affects hydrogen bonding and hydrophobic interactions to change the conformation of proteins and unfolds proteins through a cavitation effect, leading to an increase in biological activity. Fourier infrared spectroscopy showed that ultrasound inhibited the formation of hydrogen bonds and reduced intermolecular cross-linking. Molecular weight distribution showed that the antioxidant components of bovine liver polypeptides were mainly concentrated in fractions of 500-1,000 Da. Maximum values of ABTS (82.66 %), DPPH (76.02 %), chelated iron (62.18 %), and reducing power (1.2447) were obtained by treating bovine liver polypeptides with 500 W ultrasound. Combined with the scanning electron microscopy results, with the intervention of ultrasound, the impact force generated by ultrasonication may lead to the loosening of the protein structure, which further promotes the release of antioxidant peptides, and these findings provide new insights into the application of ultrasound in the release of antioxidant peptides from bovine liver.

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.

Advancing protein hydrolysis and phytosterol encapsulation: Emerging trends and innovations in protein-based microencapsulation techniques - A comprehensive review

Phytosterols represent a diverse and complex category of lipophilic bioactive compounds, exhibiting excellent pro-healthy properties. However, their consumption in daily diets is insufficient, and their application in food production is hindered by challenges such as low water solubility, high reactivity, and rapid degradation. The adoption of different protein or their structural modification as hydrolysates as wall material into microencapsulation techniques can be associated with improved solubility, enhanced bioaccessibility, increased bioavailability, and an extension of shelf life. This contribution provides an overview of advancements in modifying functional properties through various protein isolation methods and structural changes resulting from enzymatic hydrolysis. Additionally, the paper considers the state of the art in the utilization of various techniques and the composition of wall material in the encapsulation of phytosterols and other common lipophilic phytochemicals incorporated into delivery systems. Protein isolates obtained through novel methods of extraction may be characterized by an enhancement of their functional properties, which is crucial for the microencapsulation process. It entails not only recognizing their role as protective barriers for core materials against environmental conditions but also acknowledging their potential health-promoting attributes. These attributes encompass antioxidant properties and enhanced functional characteristics compared to native proteins. Moreover, the exploration of protein hydrolysates as versatile wall materials holds significant promise. These hydrolysates offer exceptional protective features for core materials, extending beyond mere environmental shielding. The envisioned impact extends beyond conventional delivery systems, offering transformative potential for the future of drug delivery and nutraceutical formulations.

Preparation of umami peptides from chicken breast by batch coupled enzymatic hydrolysis and membrane separation mode and the taste mechanism of identified umami peptides

Batch coupled enzymatic hydrolysis and membrane separation mode (BCEH-MSM) is efficient in preparing active peptides due to enzyme being more purposeful in hydrolysing macromolecular. Therefore, BCEH-MSM probably could be an alternative option to the traditional enzymatic hydrolysis and offline membrane separation mode (TEH-OMSM). This work aimed to explore the potential of BCEH-MSM in enhancing the enzymatic hydrolysis (EH) efficiency and the umami of the enzymatic hydrolysate. The EH efficiency was valuated based on product yields. Amino acid analyzer and HPLC were used to analyze tasting compounds. Electronic-tongue was used to determine umami intensity. The results showed that BCEH-MSM exhibited superior EH efficiency and higher umami intensity compared to TEH-OMSM. LC-MS/MS was used to identify peptides with higher umami intensity in the enzymatic hydrolysate. LGEETF, VNFDGEI, and QLSELLRAGSSPNL had umami profile verified by electronic-tongue. Molecular docking further showed that crucial amino acid residues involved in the binding to T1R1/T1R3 was His145.

Structural, antioxidant activity, and stability studies of jellyfish collagen peptide-calcium chelates

The aim of this study was to prepare and characterize jellyfish collagen peptide (JCP)-calcium chelates (JCP-Ca) using peptides with different molecular weights. Further analysis revealed that the low-molecular-weight jellyfish collagen peptide (JCP1) had a higher chelation rate. Structural characterization showed that functional groups such as N-H, C[bond, double bond]O, and -COO were involved in the formation of JCP-Ca, which shifted towards a more ordered and regular structure, and smaller-molecular-weight peptides were more likely to form a denser structure. In addition, JCPs chelated with calcium ions showed excellent antioxidant capacity. JCP-Ca showed good stability in heat-treated and gastrointestinal environments, whereas the antioxidant activity was significantly reduced under highly acidic conditions. The present study addresses the knowledge gap regarding the physicochemical properties of JCP-Ca and establishes a solid research foundation for its associated products.

Structural changes and functional characteristics of common vetch isolate proteins altered by different pH-shifting treatments

To investigate protein structure and functional changes, common vetch protein isolate (CVPI) during pH-shifting were performed. Results showed secondary and tertiary structures of CVPI were improved during these treatments compared with the pH 7.0. Scanning electron microscopy showed the microstructure was changed from lamellar to spherical granular and rod-like structure during pH - shifting. Under 8 pH treatments (pH 2.0, 3.0, 12.0, 2.0 → 7.0, 3.0 → 7.0, 12.0 → 7.0, 11.0 → 9.0 and 11.0 → 7.0), the average particle sizes were smaller and from 82 to 146 nm. Under 8 pH treatments (pH 2.0, 3.0, 11.0, 12.0, 11.0 → 9.0, 11.0 → 7.0,12.0 → 9.0 and 12.0 → 7.0), the protein solubility was higher and from 63 to 86 %. Under 3 pH treatments (pH 2.0, 11.0 and 12.0), the emulsion activity index and emulsion stability index was higher and from 40 to 60 m2/g and from 54 to 97 min. Under 5 pH treatments (pH 2.0, 12.0, 11.0 → 9.0, 12.0 → 9.0 and 12.0 → 7.0), the foaming capacity and foaming stability was higher and from 145 to 185 % and from 67 to 82 %. Therefore, the pH - shifting treatment gave the CVPI improved characteristics in structural and functional properties.

Structure, functional and physicochemical properties of lotus seed protein under different pH environments

BACKGROUND

The present study investigated the structure, functional and physicochemical properties of lotus seed protein (LSP) under different pH environments. The structures of LSP were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Fourier transform infrared spectroscopy (FTIR), zeta potential, particle size distributions, free sulfhydryl and rheological properties. The functional and physicochemical properties of LSP were characterized by color, foaming property, emulsification property, solubility, oil holding capacity, water holding capacity, differential scanning calorimetry analysis and surface hydrophobicity.

RESULTS

LSP was mainly composed of eight subunits (18, 25, 31, 47, 51, 56, 65 and 151 kDa), in which the richest band was 25 kDa. FTIR results showed that LSP had high total contents of α-helix and β-sheet (44.81-46.85%) in acidic environments. Meanwhile, there was more β-structure and random structure in neutral and alkaline environments (pH 7.0 and 9.0). At pH 5.0, LSP had large particle size (1576.98 nm), high emulsion stability index (91.43 min), foaming stability (75.69%) and water holding capacity (2.21 g g-1), but low solubility (35.98%), free sulfhydryl content (1.95 μmol g-1) and surface hydrophobicity (780). DSC analysis showed the denaturation temperatures (82.23 °C) of LSP at pH 5.0 was higher than those (80.10, 80.52 and 71.82 °C) at pH 3.0, 7.0 and 9.0. The analysis of rheological properties showed that LSP gel had high stability and great strength in an alkaline environment.

CONCLUSION

The findings of the present study are anticipated to serve as a valuable reference for the implementation of LSP in the food industry. © 2024 Society of Chemical Industry.

Physicochemical properties, antioxidant and antidiabetic activities of different hydrolysates of goat milk protein

There is growing interest in the origin, preparation, and application of bioactive peptides. This study investigated the impact of 6 enzymes on the structural, physicochemical properties, antioxidant activities, and antidiabetic potential of defatted fresh goat milk. Structural and functional changes resulting from enzymatic hydrolysis were assessed using gel electrophoresis, laser particle size analysis, multi-spectroscopy, and evaluations of foaming and emulsification properties. Antioxidant capacity was determined through free radical scavenging, Fe2+ chelation, and reducing ability experiments. Additionally, the inhibitory effects of the hydrolysates on α-glucosidase and α-amylase were measured to evaluate antidiabetic activity. Results showed that enzymatic hydrolysis disrupted the spatial structure of goat milk protein and reduced its molecular weight. Papain hydrolysate exhibited the highest degree of hydrolysis (32.87 ± 0.11%) and smallest particle size (294.75 ± 3.33 nm), followed by alcalase hydrolysate (29.12 ± 0.09%, 302.03 ± 7.28 nm). Alcalase hydrolysate showed the best foaming properties, while papain hydrolysate demonstrated the strongest DPPH and hydroxyl radical scavenging activity, Fe2+ chelation, and antidiabetic potential. These findings provide solid theoretical basis for utilizing defatted goat milk as functional ingredients or excipients in the food, medical, and cosmetic industries.

Recent advances in mung bean protein: From structure, function to application

With the surge in protein demand, the application of plant proteins has ushered in a new wave of research. Mung bean is a potential source of protein due to its high protein content (20-30 %). The nutrition, structure, function, and application of mung bean protein have always been a focus of attention. In this paper, these highlighted points have been reviewed to explore the potential application value of mung bean protein. Mung bean protein contains a higher content of essential amino acids than soybean protein, which can meet the amino acid values recommended by FAO/WHO for adults. Mung bean protein also can promote human health due to its bioactivity, such as the antioxidant, and anti-cancer activity. Meanwhile, mung bean protein also has well solubility, foaming, emulsification and gelation properties. Therefore, mung bean protein can be used as an antioxidant edible film additive, emulsion-based food, active substance carrier, and meat analogue in the food industry. It is understood there are still relatively few commercial applications of mung bean protein. This paper highlights the potential application of mung bean proteins, and aims to provide a reference for future commercial applications of mung bean proteins.

Sour orange (Citrus aurantium) seed, a rich source of protein isolate and hydrolysate - A thorough investigation

Sour orange (Citrus aurantium) seeds are typically discarded by juice processors as waste. This study aimed to extract protein isolates, produce hydrolysates from de-oiled sour orange seeds (SOS), and characterize their physicochemical properties. Previous studies have described methods to obtain protein isolates and hydrolysates from agricultural residues. However, there is limited data on the SOS. This research characterized protein isolates and hydrolysates from SOS, emphasizing yield, purity, and amino acid composition. Protein isolates were extracted using borate saline buffer, saline, and distilled water. Enzymatically hydrolysis was conducted using Protamex® (a commercial protease) at concentrations ranging from 0.2 to 5 g enzyme/100g protein isolate. Differential scanning calorimetry, electrophoresis, and FT-IR spectroscopy were utilized to characterize the isolates and hydrolysates. Data showed that using 5 % saline resulted in protein extraction with a yield and purity of 30 and 86 %, respectively. DSC analysis revealed that the denaturation temperature of the protein isolate was 68 °C, while the hydrolysates exhibited structural instability, as indicated by a decrease in enthalpy change compared to the isolate. The protein isolate had a 76° contact angle. The amino acid profile showed a significant presence of glutamic acid (130.530 mg/g) and arginine (70.210 mg/g). Electrophoresis analysis exhibited four major bands of the protein. The bands' intensity decreased, and new bands appeared after hydrolysis. The enzyme hydrolysis was confirmed using the O-phthaldialdehyde method and FTIR. Findings revealed that based on the free amine group quantity, the hydrolysate obtained using 5 g enzyme/100g protein isolate was 14.220 ± 0.299 μmol/mg protein. The study concluded that sour orange seeds are a good source of protein, with protein isolates and hydrolysates exhibiting desirable characteristics. More research needs to be conducted to acquire further information about their functional properties and potential applications.

Characterisation and comparison of enzymatically prepared donkey milk whey protein hydrolysates

This study evaluated the structural characteristics, processing properties, and antioxidant properties of hydrolysates prepared from donkey milk (DM) whey protein using different proteases (Alcalase, Neutrase, papain, and Flavourzyme). The results showed that enzymatic hydrolysis significantly increased hydrolysate solubility and reduced average particle size compared to those of DM whey protein. Neutrase and Flavourzyme hydrolysates exhibited higher degrees of hydrolysis (DH), along with elevated emulsification properties and surface hydrophobicity. The choice of protease influenced secondary and tertiary protein structures and amino acid composition. Enzymatic hydrolysis led to decreased molecular weight of DM whey proteins. Moreover, all hydrolysates exhibited higher fluorescence intensity at λmax compared to DM whey protein, implying distinct properties due to the varied impacts of the four proteases on DM whey protein structure. The preparation of hydrolysates from DM whey proteins using proteases contributes to the development of integrated-value DM products.

Euglena gracilis Protein: Effects of Different Acidic and Alkaline Environments on Structural Characteristics and Functional Properties

Due to the growing demand for human-edible protein sources, microalgae are recognized as an economically viable alternative source of proteins. The investigation into the structural characteristics and functional properties of microalgin is highly significant for its potential application in the food industry as an alternative source of protein. In this research, we extracted protein from Euglena gracilis by using alkaline extraction and acid precipitation and investigated its structural characteristics and functional properties in different acidic and alkaline environments. The molecular weight distribution of Euglena gracilis protein (EGP), as revealed by the size exclusion chromatography results, ranges from 152 to 5.7 kDa. EGP was found to be rich in hydrophobic amino acids and essential amino acids. Fourier infrared analysis revealed that EGP exhibited higher α-helix structure content and lower β-sheet structure content in alkaline environments compared with acidic ones. EGP exhibited higher foaming properties, emulsifying activity index, solubility, free sulfhydryl, and total sulfhydryl in pH environments far from its isoelectric point, and lower fluorescence intensity (2325 A.U.), lower surface hydrophobicity, larger average particle size (25.13 µm), higher emulsifying stability index, and water-holding capacity in pH environments near its isoelectric point. In addition, X-ray diffraction (XRD) patterns indicated that different acidic and alkaline environments lead to reductions in the crystal size and crystallinity of EGP. EGP exhibited high denaturation temperature (Td; 99.32 °C) and high enthalpy (ΔH; 146.33 J/g) at pH 11.0, as shown by the differential scanning calorimetry (DSC) results. The findings from our studies on EGP in different acidic and alkaline environments provide a data basis for its potential commercial utilization as a food ingredient in products such as emulsions, gels, and foams.

Ultrasound-assisted complex enzyme extraction, structural characterization, and biological activity of polysaccharides from Ligustrum robustum

Ligustrum robustum is one of the traditional teas in China with a long history of drinking and medicinal use. Through Response surface optimization, the yield of polysaccharides extracted by ultrasonic-assisted complex enzyme (UAE-EN) method was increased to 14.10 ± 0.56 %. Neutral homogeneous polysaccharide (LRNP) and acidic homogeneous polysaccharide (LRAP-1, LRAP-2, LRAP-3) from L. robustum were purified. The molecular weights of them were 5894, 4256, 4621 and 3915 Da. LRNP was composed of glucose (Glc), galactose (Gal), arabinose (Ara) with molar percentage of 24.97, 42.38 and 30.80. Structure analysis revealed that the backbone of LRNP consisted of 1,5-linked α-Araf, 1,4-linked β-Galp, 1,6-linked β-Galp, and 1,4-linked β-Glcp with the branches of 1,2-linked α-Araf, 1,3-linked α-Araf, 1,3-linked β-Glcp and 1,6-linked β-Galp residues, some terminal residues of α-Araf, β-Glcp and α-Galp were also included. In vitro experiments showed that the four polysaccharides possessed excellent antioxidant, antitumor and hypoglycemic activities. LRNP possessed the protective effect against oxidative stress. The studies provide a basis for further exploitation of L. robustum.

Screening, separation and identification of metal-chelating peptides for nutritional, cosmetics and pharmaceutical applications

Metal-chelating peptides, which form metal-peptide coordination complexes with various metal ions, can be used as biofunctional ingredients notably to enhance human health and prevent diseases. This review aims to discuss recent insights into food-derived metal-chelating peptides, the strategies set up for their discovery, their study, and identification. After understanding the overall properties of metal-chelating peptides, their production from food-derived protein sources and their potential applications will be discussed, particularly in nutritional, cosmetics and pharmaceutical fields. In addition, the review provides an overview of the last decades of progress in discovering food-derived metal-chelating peptides, addressing several screening, separation and identification methodologies. Furthermore, it emphasizes the methods used to assess peptide-metal interaction, allowing for better understanding of chemical and thermodynamic parameters associated with the formation of peptide-metal coordination complexes, as well as the specific amino acid residues that play important roles in the metal ion coordination.

Structure, physicochemical properties, and biological activities of protein hydrolysates from Zanthoxylum seed

BACKGROUND

Zanthoxylum seed, as a low-cost and easily accessible plant protein resource, has good potential in the food industry. But protein and its hydrolysates from Zanthoxylum seed are underutilized due to the dearth of studies on them. This study aimed to investigate the structure and physicochemical and biological activities of Zanthoxylum seed protein (ZSP) hydrolysates prepared using Protamex®, Alcalase®, Neutrase®, trypsin, or pepsin.

RESULTS

Hydrolysis using each of the five enzymes diminished average particle size and molecular weight of ZSP but increased random coil content. ZSP hydrolysate prepared using pepsin had the highest degree of hydrolysis (24.07%) and the smallest molecular weight (<13 kDa) and average particle size (129.80 nm) with the highest solubility (98.9%). In contrast, ZSP hydrolysate prepared using Alcalase had the highest surface hydrophobicity and foaming capacity (88.89%), as well as the lowest foam stability (45.00%). Moreover, ZSP hydrolysate prepared using Alcalase exhibited the best hydroxyl-radical scavenging (half maximal inhibitory concentration (IC50 ) 1.94 mg mL-1 ) and ferrous-ion chelating (IC50 0.61 mg mL-1 ) activities. Additionally, ZSP hydrolysate prepared using pepsin displayed the highest angiotensin-converting enzyme inhibition activity (IC50 0.54 mg mL-1 ).

CONCLUSION

These data showed that enzyme hydrolysis improved the physicochemical properties of ZSP, and enzymatic hydrolysates of ZSP exhibited significant biological activity. These results provided validation for application of ZSP enzymatic hydrolysates as antioxidants and antihypertensive agents in the food or medicinal industries. © 2023 Society of Chemical Industry.

The structural characteristics and physicochemical properties of mung bean protein hydrolysate of protamex induced by ultrasound

BACKGROUND

The limited physicochemical properties (such as low foaming and emulsifying capacity) of mung bean protein hydrolysate restrict its application in the food industry. Ultrasound treatment could change the structures of protein hydrolysate to accordingly affect its physicochemical properties. The aim of this study was to investigate the effects of ultrasound treatment on the structural and physicochemical properties of mung bean protein hydrolysate of protamex (MBHP). The structural characteristics of MBHP were evaluated using tricine sodium dodecylsulfate-polyacrylamide gel electrophoresis, laser scattering, fluorescence spectrometry, etc. Solubility, fat absorption capacity and foaming, emulsifying and thermal properties were determined to characterize the physicochemical properties of MBHP.

RESULTS

MBHP and ultrasonicated-MBHPs (UT-MBHPs) all contained five main bands of 25.8, 12.1, 5.6, 4.8 and 3.9 kDa, illustrating that ultrasound did not change the subunits of MBHP. Ultrasound treatment increased the contents of α-helix, β-sheet and random coil and enhanced the intrinsic fluorescence intensity of MBHP, but decreased the content of β-turn, which demonstrated that ultrasound modified the secondary and tertiary structures of MBHP. UT-MBHPs exhibited higher solubility, foaming capacity and emulsifying properties than MBHP, among which MBHP-330 W had the highest solubility (97.32%), foaming capacity (200%), emulsification activity index (306.96 m2  g-1 ) and emulsion stability index (94.80%) at pH 9.0.

CONCLUSION

Ultrasound treatment enhanced the physicochemical properties of MBHP, which could broaden its application as a vital ingredient in the food industry. © 2023 Society of Chemical Industry.

Integrated extraction, structural characterization, and activity assessment of squid pen protein hydrolysates and β-chitin with different protease hydrolysis

Squid pen (SP) is a valuable source of protein and β-chitin. However, current research has primarily focused on extracting β-chitin from SP. This study innovatively extracted both SP protein hydrolysates (SPPHs) and SP β-chitin (SPC) simultaneously using protease hydrolysis. The effects of different proteases on their structural characteristics and bioactivity were evaluated. The results showed that SP alcalase β-chitin (SPAC) had the highest degree of deproteinization (DP, 98.19 %) and SP alcalase hydrolysates (SPAH) had a degree of hydrolysis (DH) of 24.47 %. The analysis of amino acid composition suggested that aromatic amino acids accounted for 17.44 % in SPAH. Structural characterization revealed that SP flavourzyme hydrolysates (SPFH) had the sparsest structure. SPC exhibited an excellent crystallinity index (CI, over 60 %) and degree of acetylation (DA, over 70 %). During simulated gastrointestinal digestion (SGD), the hydroxyl radical scavenging activity, ABTS radical scavenging activity, Fe2+ chelating activity, and reducing power of the SPPHs remained stable or increased significantly. Additionally, SPFC exhibited substantial inhibitory effects on Staphylococcus aureus and Escherichia coli (S. aureus and E. coli), with inhibition circle diameters measuring 2.4 cm and 2.1 cm. These findings supported the potential use of SPPHs as natural antioxidant alternatives and suggested that SPC could serve as a potential antibacterial supplement.

Multifunctional apple seed protein hydrolysates: Impact of enzymolysis on the biochemical, techno-functional and in vitro α-glucosidase, pancreatic lipase and angiotensin-converting enzyme inhibition activities

The work was designed to assess the amelioration effect of papain hydrolysis on the biochemical, techno-functional, and biological properties of apple seed protein isolate (API) after 0-90 min of hydrolysis. Hydrolysis significantly enhanced the nutritional value (protein content ˃ 90 %) while decreasing the average particle size. With increasing hydrolysis time, FTIR analysis revealed a transition from α-helix to β-turn structure, indicating the unfolding of protein structure. This structural alteration positively influenced the functional characteristics, with samples hydrolyzed for 90 min exhibiting excellent solubility, higher water and oil absorption capacity, foaming capacity, and increased emulsifying activity index. Moreover, samples hydrolyzed for 90 min displayed the highest α-glucosidase (29.62-57.43 %), pancreatic lipase inhibition (12.87-31.08 %), and ACE inhibition (25.32-62.70 %) activity. Interestingly, the inhibiting ability of protein hydrolysates against α-glucosidase and ACE was more effective than pancreatic lipase, suggesting their usefulness as a functional ingredient, particularly in type II diabetes and hypertension management.

Physicochemical, functional, and antioxidant properties of black soldier fly larvae protein

This study explores the multifaceted attributes of black soldier fly larvae protein (BSFLP), focusing on its physicochemical, functional, and antioxidant properties. BSFLP is characterized by 16 amino acids, with a predominant random coil secondary structure revealed by circular dichroism spectra. Differential scanning calorimetry indicates a substantial thermal denaturation temperature of 97.63°C. The protein exhibits commendable solubility, emulsification, and foaming properties in alkaline and low-salt environments, albeit with reduced water-holding capacity and foam stability under elevated alkaline and high-temperature conditions. In vitro assessments demonstrate that BSFLP displays robust scavenging proficiency against 2,2-diphenyl-1-picrylhydrazyl, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), and hydroxyl radicals, with calculated EC50 values of 1.90 ± 0.57, 0.55 ± 0.01, and 1.14 ± 0.02 mg/mL, respectively, along with notable reducing capabilities. Results from in vivo antioxidant experiments reveal that BSFLP, administered at doses of 300 and 500 mg/kg, significantly enhances the activities of antioxidant enzymes (superoxide dismutase, catalase, and glutathione peroxidase) (p < 0.05) while simultaneously reducing malondialdehyde levels in both serum and tissues of d-galactose-induced oxidative stress in mice. Moreover, the protein effectively attenuates oxidative damage in liver and hippocampal tissues. These findings underscore the potential utility of BSFLP as a natural antioxidant source, with applications spanning the food, pharmaceutical, and cosmetic industries. PRACTICAL APPLICATION: Black soldier fly larvae protein emerges as an environmentally sustainable reservoir of natural antioxidants, holding significant promise for the food, pharmaceutical, and cosmetic sectors. Its advantageous amino acid composition, robust thermal resilience, and impressive functional attributes position it as a compelling subject for continued investigation and advancement in various applications.

Nitrogen regulates the synthesis of hydrophobic amino acids to improve protein structural and gel properties in common buckwheat

Nitrogen (N) fertilizer impacts the grain quality of common buckwheat, but the effects and regulatory mechanisms of N on various protein parameters of buckwheat are not fully understood. The purpose of this study was to investigate the particle morphology, structural and gel properties, and regulation mechanism of buckwheat protein under four N levels. The bulk density, surface hydrophobicity, particle size, and thermal properties of the buckwheat protein were maximized through the optimal N application (180 kg N/ha), further enhancing the thermal stability of the protein. N application increased the β-sheet content and reduced the random coil content. Appropriate N fertilizer input enhanced the tertiary structure stability and gel elasticity of buckwheat protein by promoting hydrophobic interactions, disulfide bonds, ionic bonds, storage modulus and loss modulus. The differentially expressed proteins induced by N are primarily enriched in small ribosomal subunit and ribosome, improving protein quality mainly by promoting the synthesis of hydrophobic amino acids. Future agriculture should pay attention to the hydrophobic amino acid content of buckwheat to effectively improve protein quality. This study further advances the application of buckwheat protein in the field of food processing and provides a theoretical basis for the extensive development and utilization of buckwheat protein.

Characterization of the structure, antioxidant activity and hypoglycemic activity of soy (Glycine max L.) protein hydrolysates

This study aimed to hydrolyze soy isolate protein (SPI) using five enzymes (alcalase, pepsin, trypsin, papain, and bromelain) in order to obtain five enzymatic hydrolysates and to elucidate the effect of enzymes on structural and biological activities of the resulting hydrolysates. The antioxidant and hypoglycemic activities of the soy protein isolate hydrolysates (SPIEHs) were evaluated through in silico analysis, revealing that the alcalase hydrolysate exhibited the highest potential, followed by the papain and bromelain hydrolysates. Subsequently, the degree of hydrolysis (DH), molecular weight distribution (MWD), amino acid composition, structure, antioxidant activities, and hypoglycemic activity in vitro of SPIEHs were analyzed. After enzymatic treatment, the particle size, polymer dispersity index (PDI), ζ-potentials, β-sheet content and α-helix content of SPIEHs was decreased, and the maximum emission wavelength of all SPIEHs exhibited red-shifted, which all suggesting the structure of SPIEHs was unfolded. More total amino acids (TAAs), aromatic amino acids (AAAs), and hydrophobic amino acids (HAAs) were found in alcalase hydrolysate. For 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, metal ion chelating activity, α-glucosidase inhibitory activity and α-amylase inhibitory activity, alcalase hydrolysate had the lowest IC50; alcalase hydrolysate and papain hydrolysate had the lowest IC50 for hydroxyl radical scavenging activity. Physiological activity of SPIEHs was evaluated thoroughly by 5-Axe cobweb charts, and the results revealed that alcalase hydrolysate exhibited the greatest biological activities.

Structural properties of Kudzu protein enzymatic hydrolysate and its repair effect on HepG2 cells damaged by H2O2 oxidation

We investigated the structural properties, foaming capacity and foaming stability, antioxidant activity, and amino acid composition of Kudzu protein (KP) and Kudzu protein hydrolysate (KPH). The peptide sequence of KPH was analyzed using ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS), and the binding ability of the peptide sequence to Keap1 was predicted through molecular docking simulations. The electrophoresis and molecular weight distribution analysis results showed that the molecular weight of KPH was significantly lower than that of KP, with a mean molecular weight of approximately 2000-5000 Da. The structures and properties were characterized using Fourier transform infrared spectroscopy, relative fluorescence, and circular dichroism. The results showed that KP exposed a large number of hydrophobic groups after enzymatic hydrolysis, and its structure changed from α-helical to random coils. KPH has a higher foaming capacity (200%) and foaming stability (97.5%) than KP, which may be related to the change in structure. These results indicate that moderate hydrolysis can improve the functional properties of KP, providing a new opportunity for its application as a food ingredient. The antioxidant assay results showed that KP and KPH had a good hydroxyl radical, superoxide anion, 1,1-diphenyl-2-picrylhydrazyl (DPPH), and 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) scavenging capacity and a high reducing capacity. KPH exerted better antioxidant effects than KP. The scavenging rates for DPPH, ABTS, hydroxyl radicals, and superoxide anions were 89.31%, 93.14%, 85.74%, and 58.29%, respectively, and its reducing capacity was 2.191, which may be related to the increase in amino acids with antioxidant activity after enzymolysis. In vitro, KP and KPH could significantly repair H2O2-induced oxidative damage in HepG2 cells, reduce the apoptosis rate, activate the Nrf2-Keap1 signaling pathway, reduce the accumulation of reactive oxygen species and malondialdehyde after oxidative damage, increase the activities of superoxide dismutase and glutathione (GSH) peroxidase, and increase the content of GSH and the total antioxidant capacity. Twenty-one peptide components were identified in KPH using UPLC-MS/MS, and the binding ability of 21 peptide components to Keap1 was analyzed through molecular docking technology. The results showed that all 21 peptides in KPH had good antioxidant activity, and real-time quantitative PCR (qRT-PCR) analysis was conducted to further explain the high antioxidant activity of KPH at the genetic level. These results show that KP and KPH are suitable for preparing antioxidant foods and related health foods to prevent oxidation-related diseases. KPH has more beneficial effects than KP.

Functional, physicochemical, and structural properties of the hydrolysates derived from the abalone (Haliotis discus subsp hannai Ino) foot muscle proteins

This study was conducted to investigate functional, physicochemical, and structural properties of abalone foot muscle proteins (AFPs) and their hydrolysates (HAFPs) obtained using animal protease (HA), papain (HPP), and Protamex® (HP) at different time points. The HA-hydrolysate obtained after 0.5 h of treatment demonstrated the highest solubility at pH 7.0 (84.19%); the HPP-hydrolysate at 4 h exhibited the highest degree of hydrolysis (11.4%); the HPP-hydrolysate at 0.5 h had the highest oil holding capacity (2.62 g/g) and emulsion stability index (39.73 min), and the HP-hydrolysate at 4 h had the highest emulsifying activity index (93.23 m2/g) and foaming stability (91.45%); Regarding the physicochemical properties, the HPP-hydrolysates revealed the largest particle size, higher absolute zeta potential, and superior interfacial activity. Structural characterization demonstrated the enzymolysis-based changes in the composition and the secondary structure of the AFPs. These results provide practical support for the theoretical basis of the use of AFPs as a source of nutritive proteins in the food industry.

Flexible processing technology of coix seed prolamins by combined heat-ultrasound: Effects on their enzymatic hydrolysis characteristics and the hypoglycemic activities of derived peptides

The self-assembled structures of coix seeds affected the enzymatic efficiency and doesn't facilitate the release of more active peptides. The influence of heating combined with ultrasound pretreatment (HT + US) on the structure, enzymatic properties and hydrolysates (CHPs) of coix seed prolamin was investigated. Results showed that the structural of coix seed prolamins has changed after HT + US, including increased surface hydrophobicity, reduced α-helix and random coil content, and a decrease in particle size. So that, leads to changes in thermodynamic parameters such as an increase in the reaction rate constant and a decrease in activation energy, enthalpy and enthalpy. The fractions of <1000 Da, degree of hydrolysis and α-glucosidase inhibitory were increased in the HT + US group compared to single pretreatment by 0.68%-17.34%, 12.69%-34.43% and 30.00%-53.46%. The peptide content and α-glucosidase inhibitory activity of CHPs could be maintained at 72.21 % and 57.97 % of the initial raw materials after in vitro digestion. Thus, the findings indicate that HT + US provides a feasible and efficient approach to can effectively enhance the enzymatic hydrolysis efficiency and hypoglycaemic efficacy of CHPs.

Immunomodulatory activity of semen Ziziphi Spinosae protein: a potential plant protein functional food raw material

Semen Ziziphi Spinosae protein (SZSP) is a new plant protein resource with good food functional properties and health care function. However, the biological activity of SZSP has not been further studied, which greatly limits the development and utilization of SZSP in the food industry. The aim of this study was to investigate the protective effect of SZSP on immunosuppressed mice and its inhibitory effect on immune-stimulated RAW264.7 cells. The results demonstrated that SZSP remarkably improved the immunomodulatory secretion in serum (interleukin-2, tumor necrosis factor-α [TNF-α], interferon-γ, immunoglobulin-A, immunoglobulin-G, immunoglobulin-M) and primary macrophages (nitric oxide, interleukin-1β, TNF-α) and promoted the NK-cell killing activity of primary splenocytes in CTX-induced immunosuppression mice. Immunohistochemical analysis results indicated that the secretion of CD₄⁺ and CD₈⁺ in the spleen and thymus can be regulated by SZSP, leading to inhibition of the damage induced by cyclophosphamide in mice. Meanwhile, in order to clarify the immunomodulatory mechanism of SZSP, we showed that SZSP significantly inhibited the secretion of NO, interleukin-6, and TNF-α and reduced the phosphorylation expression of p-ERK, p-JNK, and p-IκBα in lipopolysaccharide-stimulated RAW264.7 cells. Therefore, the immunomodulatory effect of SZSP may be related to the activation of MAPKs and NF-κB signaling pathways. Based on the above studies, the preliminary purification of SZSP was continued, and S1F2G1 with immunomodulatory activity was obtained. Taken together, SZSP has an immunoregulatory effect in vivo and in vitro and may be a favorable candidate of functional food raw material for regulating immune responses.

Development of lentil peptides with potent antioxidant, antihypertensive, and antidiabetic activities along with umami taste

Lentil peptides have shown promising bioactive properties regarding the antioxidant activity and also inhibitory activity of angiotensin-I-converting enzyme (ACE). Sequential hydrolysis of proteins has shown a higher degree of hydrolysis with enhanced antioxidant and ACE-inhibitory activities. The lentil protein concentrate (LPC) was sequentially hydrolyzed using Alcalase and Flavourzyme at 2% w/w. The hydrolysate (LPH) was cross-linked (LPHC) or sonicated (LPHUS) and sequentially cross-linked (LPHUSC). Amino acid profile, molecular weight (MW) distribution, DPPH and ABTS radical scavenging activities (RSA; 7 mg/mL), ACE (0.1-2 mg/mL), α-glucosidase, and α-amylase inhibitory activities (10-500 μg/mL), and umami taste were determined. The highest DPPH RSA was obtained for LPH (68.75%), followed by LPHUSC (67.60%), and LPHUS (67.49%) while the highest ABTS RSA values were obtained for LPHC (97.28%) and LPHUSC (97.20%). Cross-linking and sonication led to the improvement of the ACE-inhibitory activity so that LPHUSC and LPHC had IC50 values of 0.23 and 0.27 mg/mL, respectively. LPHC and LPHUSC also indicated higher α-glucosidase inhibitory activity (IC50 of 1.2 and 1.23 mg/mL) compared to LPH (IC50 of 1.74 mg/mL) and LPHUS (IC50 of 1.75 mg/mL) while the IC50 value of acarbose indicated 0.51 mg/mL. Moreover, LPHC and LPHUSC exhibited higher α-amylase inhibitory activities (IC50 of 1.35 and 1.16 mg/mL) than LPHUS (IC50 of 1.95 mg/mL), and LPH (IC50 of 2.51 mg/mL) while acarbose had an IC50 value of 0.43 mg/mL. Umami taste analysis revealed that LPH and LPHC due to MW of 1.7 and 2.3 kDa and also high umami amino acids could be well considered as representative of meaty and umami analog flavors while indicating stronger antioxidant, antihypertension, and antidiabetic attributes.