Solubility, functional properties, ACE-I inhibitory and DPPH scavenging activities of Alcalase hydrolysed soy protein hydrolysates

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.

Modification of the physicochemical, functional, biochemical and structural properties of a soursop seed (Annona muricata L.) protein isolate treated with high-intensity ultrasound

The obtained seeds from fruit processing are considered by-products containing proteins that could be utilized as ingredients in food manufacturing. However, in the specific case of soursop seeds, their usage for the preparation of protein isolates is limited. In this investigation a protein isolate from soursop seeds (SSPI) was obtained by alkaline extraction and isoelectric precipitation methods. The SSPI was sonicated at 200, 400 and 600 W during 15 and 30 min and its effect on the physicochemical, functional, biochemical, and structural properties was evaluated. Ultrasound increased (p < 0.05) up to 5 % protein content, 261 % protein solubility, 60.7 % foaming capacity, 30.2 % foaming stability, 86 % emulsifying activity index, 4.1 % emulsifying stability index, 85.4 % in vitro protein digestibility, 423.4 % albumin content, 83 % total sulfhydryl content, 316 % free sulfhydryl content, 236 % α-helix, 46 % β-sheet, and 43 % β-turn of SSPI, in comparison with the control treatment without ultrasound. Furthermore, ultrasound decreased (p < 0.05) up to 50 % particle size, 37 % molecular flexibility, 68 % surface hydrophobicity, 41 % intrinsic florescence spectrum, and 60 % random coil content. Scanning electron microscopy analysis revealed smooth structures of the SSPI with molecular weights ranging from 12 kDa to 65 kDa. The increase of albumins content in the SSPI by ultrasound was highly correlated (r = 0.962; p < 0.01) with the protein solubility. Improving the physicochemical, functional, biochemical and structural properties of SSPI by ultrasound could contribute to its utilization as ingredient in food industry.

Changes in the structure and functional properties of soybean isolate protein: Effects of different modification methods

Soybean protein isolate (SPI) is an important plant protein in food processing; however, its spherical structure prevents the exposure of its hydrophobic residues and affects its functional properties. In this study, we elucidate the effects of deamidation, phosphorylation, and glycosylation on the structure (Fourier-transform infrared spectroscopy, circular dichroism, fluorescence, and scanning electron microscopy) and functional properties (solubility, emulsifying activity index (EAI), and emulsifying stability index (ESI)) of SPI. The zeta potentials of the deamidated, phosphorylated, and glycosylated (DSPI, PSPI, and MSPI, respectively) samples decreased significantly (p < 0.05) relative to those of SPI. The functional properties of the modified SPI samples were improved, with MSPI-2 showing the best solubility (86.73 ± 0.34%), EAI (118.89 ± 0.73 m2/g), and ESI (273.33 ± 0.59 min). Moreover, the effects of the three modifications on the SPI functional properties increase in the order MSPI > PSPI > DSPI. These results provide a theoretical understanding the relationship between the modifications and SPI structure.

Ultrasound-assisted limited enzymatic hydrolysis of high concentrated soy protein isolate: Alterations on the functional properties and its relation with hydrophobicity and molecular weight

The effects of power ultrasound (US) pretreatment on the preparation of soy protein isolate hydrolysate (SPIH) prepared at the same degree of hydrolysis (DH) of 12 % were measured. Cylindrical power ultrasound was modified into mono-frequency (20, 28, 35, 40, 50 kHz) ultrasonic cup coupled with an agitator to make it applicable for high density SPI (soy protein isolate) solutions (14 %, w/v). A comparative study of the alterations of the hydrolysates molecular weight, hydrophobics, antioxidants and functional properties change as well as their relation were explored. The results showed that under the same DH, ultrasound pretreatment decelerated the degradation of protein molecular mass and the decrease rate of the degradation lessened with the increase of ultrasonic frequency. Meanwhile, the pretreatments improved the hydrophobics and antioxidants properties of SPIH. Both surface hydrophobicity (H0) and relative hydrophobicity (RH) of the pretreated groups increased with the decrease of ultrasonic frequency. Lowest frequency (20 kHz) ultrasound pretreatment had the most improved emulsifying properties and water holding capacities, although decrease in the viscosity and solubility were found. Most of these alterations were correspondence toward the change in hydrophobics properties and molecular mass. In conclusion, the frequency selection of ultrasound pretreatment is essential for the alteration of SPIH functional qualities prepared at the same DH.

Enzymatic hydrolysis of soy and chickpea protein with Alcalase and Flavourzyme and formation of hydrogen bond mediated insoluble aggregates

Food applications involving plant proteins require modification of their functionality to mimic the unique properties of animal proteins. Enzymatic hydrolysis is commonly used to alter the functionality of plant proteins, particularly to improve their solubility near the isoelectric point. Current methodological approaches mostly indicate improved solubility upon hydrolysis. However, published methods include the removal of insoluble material before analysis, and calculations are based on only the solubilized material as a percentage of the filtered protein. This approach artificially increases solubility estimation and gives an incorrect assessment of the efficacy of hydrolysis. By using the total amount of protein, this study aims to determine the effect of two microbial proteases, Flavourzyme and Alcalase, on the solubility and structural and thermal properties of soy and chickpea proteins. Protein isolates were first extracted from soy and chickpea flour and hydrolyzed from 0 to 3 h. Then, their degree of hydrolysis and solubility at a range of pHs were determined using the o-phthaldialdehyde (OPA) and Lowry methods, respectively. Proteins' electrophoretic mobility, protein-protein interactions, thermal properties, and protein secondary structures were also determined. Solubility decreased over time though the solubility of the hydrolysate improved near the isoelectric point. Soy Flavourzyme hydrolysates remained the most soluble and chickpea Flavourzyme hydrolysates showed the least solubility. Thermal data suggested that Alcalase reduced the protein denaturation temperature, leading to a loss of solubility upon thermal enzyme inactivation. The loss of solubility of hydrolysates was strongly associated with hydrogen bonding, which may result from the formation of polar peptide termini. These results challenge commonly accepted beliefs that hydrolysis inevitably improves solubility of plant proteins. Instead, it is shown that hydrolysis causes structural changes that result in aggregation, thus potentially limiting the application of enzymatic hydrolysis without the addition of further processing methods.

Effects of soy protein hydrolysates on antioxidant activity and inhibition of muscle loss

Peptides show biological activity, and are more easily digested than complex proteins. In the present work, we evaluated the effects of soy hydrolysate on skeletal muscle. Soy protein isolate (SPI) was hydrolysed using 2% Alcalase (SPHA) and Flavourzyme (SPHF) at pH 8 for 3 h at 60°C, and at pH 7 for 3 h at 55°C, respectively. Antioxidant properties (total phenolic content and DPPH activity) and inhibition of muscle loss (myogenin, myosin heavy chain [MyHC], creatine kinase, and myostatin) by the SPI hydrolysates in C2C12 cells were compared with those of SPI. Alcalase produced more hydrolysed soy oligopeptides than Flavourzyme. Enzymatic hydrolysis increased the levels of essential amino acids, particularly in SPHF (2,466.85 mg/L) as compared to SPI (56.08 mg/L). The total phenolic contents of hydrolysates increased from 12.02 mg GAE/g in SPI to 22.87 and 18.67 mg GAE/g in SPHA and SPHF, respectively. The IC50 value of DPPH activity decreased four times after hydrolysis (SPI: 124.38, SPHA: 32.18, and SPHF: 30.21 mg/mL). SPHA and SPHF treatments increased the expression levels of both MyHC1 and MyHC3, as well as creatine kinase activity. A significant increase in MyHC3 expression was observed in SPHF at 10 µg/mL. Soy hydrolysates (SPHA: 93.5% and SPHF: 61%) induced a greater decrease in the expression of myostatin, a muscle reduction marker, than SPI (30.4%). In conclusion, soy hydrolysates may inhibit muscle loss, showing particularly better effects when Alcalase is used for hydrolysis.

Development of energy-rich protein bars and in vitro determination of angiotensin I-converting enzyme inhibitory antihypertensive activities

Three energy-rich protein (ERP) bars were prepared to meet the daily recommended dietary allowance (RDA) for the protein of Pakistani athletes. The bars were developed using dates, cheddar cheese (CC), whey protein isolate (WPI), roasted chickpea flour, and rice flour in different proportions. Bar #1 contained 64 g dates, 16 g dried apricots, 12 g WPI, and 8 g ripened CC. Bar #2 contained the same proportion of these ingredients with an addition of 12.5 g roasted chickpea flour, while bar #3 contained 6.25 g roasted rice and 6.25 g roasted chickpea flour. All the ingredients were homogeneously mixed into paste to form bars weighing 100-110 g per serving size. These bars were studied for the compositional analysis (moisture, protein, and lipid content), protein characterization through sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and in vitro determination of the angiotensin I-converting enzyme (ACE-I) antihypertensive activity. Moisture and lipid content in bars were 22% and 0.057%-0.313%, respectively, while protein, fiber, and ash contents varied from 22.3% to 23.6%, 6.66 to 5.81, and 2.12% to 2.44%, respectively. The minimum energy content was recorded (272.70 Kcal/100 g) in bar #1 while bar #3 showed the highest energy content 274.65 Kcal/110 g with the addition of (5%) roasted chickpea and rice flour, respectively. Electrophoresis analysis of proteins in bar # 1 (cheese +WPI) showed the four bands at 62, 24, 20, and 12 kDa. Bar #2 (10% roasted chickpea flour) showed some additional bands at 40, 36, 34, and 28 kDa while relatively lower antihypertensive activity than bars #1 and 3. The study revealed that adding 10% roasted chickpea flour (bar #2) increased the protein content and diversity in proteins. It provided 40% proteins to athletes and could be helpful to meet their R.D.A. by consuming two bars/day.

Limited hydrolysis of glycosylated whey protein isolate ameliorates the oxidative and physical stabilities of conjugated linoleic acid oil-in-water emulsions

Conjugated linoleic acid contains unsaturated fatty acids with multiple bioactivities, but it has poor oxidative and physical stabilities. Its emulsion was fabricated with glycosylated whey protein isolate and hydrolysates of glycosylated whey protein isolate to enhance its stability. An obvious decrease in peroxide value, thiobarbituric acid-reactive substances, particle size and creaming index of emulsion loaded by hydrolysates of glycosylated protein isolate with the increase of hydrolysis time. However, the absolute value of zeta-potential and interfacial adsorption rate of emulsion stabilized by hydrolysates of glycosylated whey protein isolate, were increased by 10.99 and 16.94% at hydrolysis time of 120 min, compared with emulsion loaded by glycosylated whey protein isolate. Thus, limited hydrolysis of glycosylated whey protein isolate as an effective method, remarkably improved the oxidative and physical stability of emulsion.

Use of Alcalase in the production of bioactive peptides: A review

This review aims to cover the uses of the commercially available protease Alcalase in the production of biologically active peptides since 2010. Immobilization of Alcalase has also been reviewed, as immobilization of the enzyme may improve the final reaction design enabling the use of more drastic conditions and the reuse of the biocatalyst. That way, this review presents the production, via Alcalase hydrolysis of different proteins, of peptides with antioxidant, angiotensin I-converting enzyme inhibitory, metal binding, antidiabetic, anti-inflammatory and antimicrobial activities (among other bioactivities) and peptides that improve the functional, sensory and nutritional properties of foods. Alcalase has proved to be among the most efficient proteases for this goal, using different protein sources, being especially interesting the use of the protein residues from food industry as feedstock, as this also solves nature pollution problems. Very interestingly, the bioactivities of the protein hydrolysates further improved when Alcalase is used in a combined way with other proteases both in a sequential way or in a simultaneous hydrolysis (something that could be related to the concept of combi-enzymes), as the combination of proteases with different selectivities and specificities enable the production of a larger amount of peptides and of a smaller size.

Effect of high-pressure processing enzymatic hydrolysates of soy protein isolate on the emulsifying and oxidative stability of myofibrillar protein-prepared oil-in-water emulsions

BACKGROUND

Oil-in-water (O/W) emulsions are thermodynamically unstable and are easily oxidized. Recently, protein hydrolysates have been used to enhance the emulsifying and oxidative stability of emulsions. High-pressure processing (HPP) enzymatic hydrolysates of soy protein isolate have higher bioactivities. The objective of the study was to investigate the effects of various soy protein isolate hydrolysate (SPIH) concentrations obtained during different 4 h pressure treatments on improving the emulsifying and oxidative stability of myofibrillar protein (MP) emulsions.

RESULTS

Emulsions with 4 mg mL^-1 SPIH obtained at 200 MPa had the highest emulsifying activity index and emulsion stability index (P ≤ 0.05). This increase in emulsion stability was related to increased zeta potential and reduced average particle size. Optical microscopy and confocal laser scanning microscopy observations confirmed that emulsions with 4 mg mL^-1 SPIH possessed relatively small oil droplets. The addition of SPIH obtained at 200 MPa significantly reduced thiobarbituric acid reactive substance values (P ≤ 0.05) of emulsions during 8 days of storage. Concurrently, the carbonyl content remained the lowest and the sulfhydryl content remained the highest, which indicated that the emulsions had higher protein oxidative stability.

CONCLUSIONS

SPIH obtained under HPP could improve the emulsifying and oxidative stability of MP-prepared O/W emulsions.

Ultrasound-assisted modification of functional properties and biological activity of biopolymers: A review

In this review, the recent applications of power ultrasound technology in improving the functional properties and biological activities of biopolymers are reviewed. The basic principles of ultrasonic technology are briefly introduced, and its main effects on gelling, structural, textural, emulsifying, rheological properties, solubility, thermal stability, foaming ability and foaming stability and biological activity are illustrated with examples reviewing the latest published research papers. Many positive effects of ultrasound treatment on these functional properties of biopolymers have been confirmed. However, the effectiveness of power ultrasound in improving biopolymers properties depends on a variety of factors, including frequency, intensity, duration, system temperature, and intrinsic properties of biopolymers such as macromolecular structure. In order to obtain the desired outcomes, it is best to apply optimized ultrasound processing parameters and use the best conditions in terms of frequency, amplitude, temperature, time, pH, concentration and ionic strength related to the inherent characteristics of each biopolymer. This will help employ the full potential of ultrasound technology for generating innovative biopolymers functionalities for various applications such as food, pharmaceuticals, and other industries.

Characteristics, Functional Properties, and Antioxidant Activities of Water-Soluble Proteins Extracted from Grasshoppers, Patanga succincta and Chondracris roseapbrunner

Water-soluble proteins extracted from two species of grasshoppers, Patanga succincta (WSPP) and Chondracris roseapbrunner (WSPC), were characterized as well as their functional properties and antioxidant activities were investigated. The extraction yield, on a wet weight basis, was 7.35% and 7.46% for WSPP and WSPC, respectively. The most abundant amino acid in both proteins was glutamic acid, followed by aspartic, alanine, and leucine, in that order. The electrophoretic study revealed that proteins with MW of 29, 42, 50, 69, and 146 kDa were the major protein components in WSPP and WSPC. FTIR analysis showed that those proteins remained their structural integrity. The surface hydrophobicity at pH 7 of WSPC was higher than WSPP, but the sulfhydryl group content did not show significant difference between the proteins from two species. Both grasshopper proteins were mostly soluble in strong acidic and alkaline aqueous solutions with a minimum value at pH 4. Those proteins exhibited poor emulsifying properties and foaming capacity, but they had greater foaming stability compared with bovine serum albumin (BSA) (p<0.05). WSPC showed greater DPPH• and ABTS•+ scavenging activities and ferric-reducing antioxidant power (FRAP) than did WSPP (p<0.05). Therefore, based on characteristics and functional properties, water-soluble proteins from both edible grasshoppers can be used as an ingredient in food applications.

High angiotensin-I converting enzyme (ACE) inhibitory activity of Alcalase-digested green soybean (Glycine max) hydrolysates

As a protein-rich, underutilized crop, green soybean could be exploited to produce hydrolysates containing angiotensin-I converting enzyme (ACE) inhibitory peptides. Defatted green soybean was hydrolyzed using four different food-grade proteases (Alcalase, Papain, Flavourzyme and Bromelain) and their ACE inhibitory activities were evaluated. The Alcalase-generated green soybean hydrolysate showed the highest ACE inhibitory activity (IC50: 0.14 mg/mL at 6 h hydrolysis time) followed by Papain (IC50: 0.20 mg/mL at 5 h hydrolysis time), Bromelain (IC50: 0.36 mg/mL at 6 h hydrolysis time) and Flavourzyme (IC50: 1.14 mg/mL at 6 h hydrolysis time) hydrolysates. The Alcalase-generated hydrolysate was profiled based on its hydrophobicity and isoelectric point using reversed phase high performance liquid chromatography (RP-HPLC) and isoelectric point focusing (IEF) fractionators. The Alcalase-generated green soybean hydrolysate comprising of peptides EAQRLLF, PSLRSYLAE, PDRSIHGRQLAE, FITAFR and RGQVLS, revealed the highest ACE inhibitory activity of 94.19%, 99.31%, 92.92%, 101.51% and 90.40%, respectively, while their IC50 values were 878 μM, 532 μM, 1552 μM, 1342 μM and 993 μM, respectively. It can be concluded that Alcalase-digested green soybean hydrolysates could be exploited as a source of peptides to be incorporated into functional foods with antihypertensive activity.