Influence of Degree of Hydrolysis on Chemical Composition, Functional Properties, and Antioxidant Activities of Chinese Sturgeon (Acipenser sinensis) Hydrolysates Obtained by Using Alcalase 2.4L

Enzyme-free method for preparation of sturgeon extracts with antioxidant, hepatoprotective and immune-enhancing functions

Sturgeon has a long lifespan and slow evolutionary rate due to their powerful endogenous antioxidant system. This work aimed to assess the in vitro and in vivo antioxidant activity of sturgeon extracts from both muscle and roe. The extraction process without enzyme hydrolysis is not only simple, but also can produce extracts with better free radicals scavenging abilities than enzymatic hydrolysates in both cellular and in vivo experiments. Moreover, in mouse models with liver injury and immunosuppression treatment, the sturgeon extracts demonstrated strong hepatoprotective and immune-enhancing functions, comparable to vitamin C and ginseng extract supplements, which were attributed to abundant antioxidant peptides of the extracts. The 15 isolated peptides exhibited diverse free radical scavenging ability. Therefore, the sturgeon extracts showed high potential to be applied in food and biomedical industries.

Exploring the Physicochemical Characteristics of Marine Protein Hydrolysates and the Impact of In Vitro Gastrointestinal Digestion on Their Bioactivity

Fish protein hydrolysates (FPHs) were obtained from different fish sources using a combination of microbial enzymes. The industrially produced FPHs from blue whiting (Micromesistius poutassou) and sprat (Sprattus sprattus) were compared to freeze-dried FPHs generated in-house from hake (Merluccius merluccius) and mackerel (Scomber scombrus) in terms of their physicochemical composition and functionality. Significant differences (p < 0.05) were observed in the protein, moisture, and ash contents of the FPHs, with the majority having high levels of protein (73.24-89.31%). Fractions that were more extensively hydrolysed exhibited a high solubility index (74.05-98.99%) at different pHs. Blue whiting protein hydrolysate-B (BWPH-B) had the highest foaming capacity at pH 4 (146.98 ± 4.28%) and foam stability over 5 min (90-100%) at pH 4, 6, and 8. The emulsifying capacity ranged from 61.11-108.90 m2/g, while emulsion stability was 37.82-76.99% at 0.5% (w/v) concentration. In terms of peptide bioactivity, sprat protein hydrolysate (SPH) had the strongest overall reducing power. The highest Cu2+ chelating activity was exhibited by hake protein hydrolysate (HPH) and mackerel protein hydrolysate (MPH), with IC50 values of 0.66 and 0.78 mg protein/mL, respectively, while blue whiting protein hydrolysate-A (BWPH-A) had the highest activity against Fe2+ (IC50 = 1.89 mg protein/mL). SPH scavenged DPPH and ABTS radicals best with IC50 values of 0.73 and 2.76 mg protein/mL, respectively. All FPHs displayed noteworthy scavenging activity against hydroxyl radicals, with IC50 values ranging from 0.48-3.46 mg protein/mL. SPH and MPH showed the highest scavenging potential against superoxide radicals with IC50 values of 1.75 and 2.53 mg protein/mL and against hydrogen peroxide with 2.22 and 3.66 mg protein/mL, respectively. While inhibition of α-glucosidase was not observed, the IC50 values against α-amylase ranged from 8.81-18.42 mg protein/mL, with SPH displaying the highest activity. The stability of FPHs following simulated gastrointestinal digestion (SGID) showed an irregular trend. Overall, the findings suggest that marine-derived protein hydrolysates may serve as good sources of natural nutraceuticals with antioxidant and antidiabetic properties.

Investigation of Antioxidant Activity of Protein Hydrolysates from New Zealand Commercial Low-Grade Fish Roes

The objective of this study was to investigate the nutrient composition of low-grade New Zealand commercial fish (Gemfish and Hoki) roe and to investigate the effects of delipidation and freeze-drying processes on roe hydrolysis and antioxidant activities of their protein hydrolysates. Enzymatic hydrolysis of the Hoki and Gemfish roe homogenates was carried out using three commercial proteases: Alcalase, bacterial protease HT, and fungal protease FP-II. The protein and lipid contents of Gemfish and Hoki roes were 23.8% and 7.6%; and 17.9% and 10.1%, respectively. The lipid fraction consisted mainly of monounsaturated fatty acid (MUFA) in both Gemfish roe (41.5%) and Hoki roe (40.2%), and docosahexaenoic (DHA) was the dominant polyunsaturated fatty acid (PUFA) in Gemfish roe (21.4%) and Hoki roe (18.6%). Phosphatidylcholine was the main phospholipid in Gemfish roe (34.6%) and Hoki roe (28.7%). Alcalase achieved the most extensive hydrolysis, and its hydrolysate displayed the highest 2,2-dipheny1-1-picrylhydrazyl (DPPH)˙ and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging activities and ferric reducing antioxidant power (FRAP). The combination of defatting and freeze-drying treatments reduced DPPH˙ scavenging activity (by 38%), ABTS˙ scavenging activity (by 40%) and ferric (Fe3+) reducing power by18% (p < 0.05). These findings indicate that pre-processing treatments of delipidation and freeze-drying could negatively impact the effectiveness of enzymatic hydrolysis in extracting valuable compounds from low grade roe.

Characterization and Molecular Dynamics Simulation of a Lipase Capable of Improving the Functional Characteristics of an Egg-Yolk-Contaminated Liquid Egg White

Lipase has great application potential in hydrolyzing residual yolk lipid in egg white liquid to restore its functional properties. In this study, a lipase gene from Bacillus subtilis was expressed in E. coli BL21 (DE3) and named Lip-IM. Results showed that although Lip-IM has stronger specificity for medium- and short-chain substrates than long-chain substrates (C16, C18), due to its excellent enzyme activity, it also has strong hydrolysis activity for long-chain substrates and maintained over 80% activity at 4-20 °C, but significantly reduced when the temperature exceeds 40 °C. The addition of 0.5% Lip-IM enhanced foaming ability by 26% (from 475 to 501%) and reduced liquid precipitation rate by 9% (from 57 to 48%). Furthermore, molecular dynamics (MD) simulations were run to investigate the conformational stability of Lip-IM at different temperatures. Results showed that Lip-IM maintained a stable conformation within the temperature range of 277-303 K. Fluctuations in the flexible area and backbone movement of proteins were identified as the main reasons for its poor thermal stability.

Bioactivities of Garcinia kola enzymatic hydrolysates at different enzyme-substrate ratios

Natural products, such as enzymatic hydrolysates and bioactive peptides from dietary sources, are safe alternatives to synthetic compounds linked to various deleterious effects. The purpose of this study is to determine the in vitro bioactivities (antioxidant and anti-inflammatory activities) of Garcinia kola seeds enzymatic hydrolysates (GKPHs) at different enzyme (pepsin)-substrate ratios. G. kola protein, isolated by alkaline solubilization and acid precipitation, was hydrolyzed with pepsin at varying enzyme-substrate (E:S) ratios. The antioxidant parameters investigated include 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging, hydrogen peroxide scavenging and ferrous ion (Fe²⁺) chelating activities. For anti-inflammatory properties, membrane stabilization and protein denaturation activities tests were used. GKPH produced at 1:32 had the highest degree of hydrolysis (66.27 ± 4.21%). All GKPHs had excellent in vitro anti-inflammatory properties. However, only enzymatic hydrolysates produced at 1:16 (E:S) ratio chelated iron (II) and as well had the highest percentage hemolysis inhibition of 84.45 ± 0.007%, percentage protein denaturation inhibition of 53.36 ± 0.01% at maximum concentration and exhibited highest DPPH scavenging activity (87.24 ± 0.10%). The enzymatic hydrolysates had excellent solubility, emulsifying and foaming properties. It could be deduced from this study that pepsin at a ratio of 1:16 of G. kola protein produced the most effective enzymatic hydrolysates in terms of their antioxidant and anti-inflammatory activities. G. kola pepsin enzymatic hydrolysates, thus, have potential in development as functional foods and as therapeutics pharmaceutical industries in the management of diseases associated with oxidative stress and inflammation owing to their excellent functional, antioxidant and anti-inflammatory properties.

Recent Advances in In Vitro and In Vivo Studies of Antioxidant, ACE-Inhibitory and Anti-Inflammatory Peptides from Legume Protein Hydrolysates

Consumption of legumes has been shown to enhance health and lower the risk of cardiovascular disease and specific types of cancer. ACE inhibitors, antioxidants, and synthetic anti-inflammatories are widely used today; however, they have several undesirable side effects. Thus, researchers have focused on finding ACE inhibitors, antioxidant, and anti-inflammatory peptides from natural sources, such as legumes. Recently, in vitro and in vivo research has shown the bioactive peptides generated from legume protein hydrolysates, such as antioxidant, anti-hypertensive, anticancer, anti-proliferative, anti-inflammatory, etc., in the context of different disease mitigation. Therefore, this review aims to describe the recent advances in in vitro and in vivo studies of antioxidant, anti-hypertensive and anti-inflammatory peptides isolated from legume-derived protein hydrolysates. The results indicated that antioxidant legumes peptides are characterized by short-chain sequence amino acids and possess anti-hypertensive properties by reducing systolic blood pressure (SBP) in spontaneously hypertensive rats (SHR).

In vitro antioxidant and anti-inflammatory properties of Artocarpus altilis (Parkinson) Fosberg (seedless breadfruit) fruit pulp protein hydrolysates

Protein hydrolysates from dietary sources possess many physiological and biological properties. Artocarpus altilis is an evergreen multipurpose plant with many benefits. Therefore, this study evaluates in vitro antioxidant and anti-inflammatory properties of A. altilis protein hydrolysates. Protein was isolated from A. altilis and hydrolysed with pepsin and trypsin separately using different enzyme: substrate ratios (1:8, 1:16, 1:32). Antioxidant properties investigated included Fe²⁺-chelating, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and hydrogen peroxide radical scavenging activities. Anti-inflammatory activities were determined using effects on hypotonic solution-induced cell lysis on red blood cell membrane stabilisation and heat-induced protein denaturation. The degree of hydrolysis of trypsin hydrolysate increased with increasing enzyme-substrate ratio, while pepsin hydrolysate decreased as the enzyme-substrate ratio increased. The dominant amino acids in A. altilis protein and hydrolysates were glutamate, aspartate and leucine. Protein hydrolysates obtained from pepsin and trypsin digestion had DPPH scavenging abilities of 43.0 ± 0.01% and 22.2 ± 0.01%, respectively. However, trypsin-hydrolysed protein had a high Fe²⁺-chelating ability, while pepsin-hydrolysed protein had high hydrogen peroxide scavenging ability. Trypsin-hydrolysed protein showed good membrane stability and inhibition of protein denaturation. The results indicated that A. altilis protein hydrolysates possess significant antioxidant and anti-inflammatory effects and can further lend support to food industries as functional foods.

Influence of the Enzymatic Hydrolysis Using Flavourzyme Enzyme on Functional, Secondary Structure, and Antioxidant Characteristics of Protein Hydrolysates Produced from Bighead Carp (Hypophthalmichthys nobilis)

In the current study, bighead carp fish were used in conjunction with the flavourzyme enzyme to obtain (FPH) fish protein hydrolysates. The optimum conditions of the hydrolysis process included an enzyme/substrate ratio of 4% and a temperature of 50 °C and pH of 6.5. The hydrolysis time was studied and investigated at 1, 3, and 6 h, and the (DH) degree of hydrolysis was recorded at 16.56%, 22.23%, and 25.48%, respectively. The greatest yield value was 17.83% at DH 25.48%. By increasing the DH up to 25.48%, the crude protein and total amino acid composition of the hydrolysate were 88.19% and 86.03%, respectively. Moreover, more peptides with low molecular weight were formed during hydrolysis, which could enhance the functional properties of FPH, particularly the solubility property ranging from 85% to 97%. FTIR analysis revealed that enzymatic hydrolysis impacted the protein's secondary structure, as indicated by a remarkable wavelength of amide bands. Additionally, antioxidant activities were investigated and showed high activity of DDPH radical scavenging, and hydroxyl radical scavenging demonstrated remarkable activity. The current findings demonstrate that the functional, structural, and antioxidant characteristics of FPH might make it an excellent source of protein and suggest potential applications in the food industry.

Gryllus bimaculatus De Geer hydrolysates alleviate lipid accumulation, inflammation, and endoplasmic reticulum stress in palmitic acid-treated human hepatoma G2 cells

ETHNOPHARMACOLOGICAL RELEVANCE

Nonalcoholic fatty liver disease (NAFLD) is one of the most common hepatic diseases closely intertwined with saturated fatty acids intake. Therefore, various studies are being conducted to find natural substances to prevent either the onset or progression of NAFLD. According to traditional medicinal literature, it has been reported that Gryllus bimaculatus De Geer (GB) has systemic detoxifying activity; however, the preventive effects of GB on NAFLD have not been elucidated to date.

AIM OF STUDY

To evaluate the potential of GB as a material for the mitigation of NAFLD, we investigated the effects of GB hydrolysates on the hepatic lipid accumulation, inflammation, and endoplasmic reticulum (ER) stress in human hepatoma G2 (Hep G2) cells treated with palmitic acid (PA).

METHODS

Steamed and dried GB was defatted, pulverized, and then lyophilized following hydrolyzation using Neutrase® (GB-N) or Flavourzyme® (GB-F). Hep G2 cells were incubated with GB-N or GB-F at various concentrations (0, 0.25, 0.5, and 1 mg/mL) for 24 h, and then PA was treated for another 24 h.

RESULTS

The GB-N and GB-F significantly prevented the PA-induced intracellular lipid accumulation in the human liver cells (p < 0.05). Moreover, the GB-N and GB-F increased the hepatic cellular viability against the PA-treatment (p < 0.05). In addition, the GB-N and GB-F significantly ameliorated the PA-inducible proinflammatory cytokines mRNA expression, such as tumor necrosis factor-α and interleukin-1β, compared to the PA-treated hepatic cells (p < 0.05). Furthermore, the GB-N and GB-F inhibited the PA-inducible lipogenic mRNA expression, such as fatty acid synthase, sterol regulatory element-binding protein 1c, and peroxisome proliferator-activated receptor-γ (p < 0.05). Moreover, the GB-N and GB-F alleviated the ER stress-related mRNA expression, such as glucose regulatory protein 78 and X-box binding protein increased in PA-treated cells (p < 0.05).

CONCLUSIONS

These results indicate that GB-N and GB-F could be used as materials to prevent the NAFLD onset or progression with alleviating hepatic lipid accumulation, inflammation, and ER stress.

Effect of the Degree of Hydrolysis on Nutritional, Functional, and Morphological Characteristics of Protein Hydrolysate Produced from Bighead Carp (Hypophthalmichthys nobilis) Using Ficin Enzyme

The production of fish protein hydrolysates from bighead carp (Hypophthalmichthys nobilis) using ficin enzymes was achieved in optimal conditions of 3% enzyme/substrate ratio, 40 °C temperature, and pH 6. Three different hydrolysis times, 1, 3, and 6 h, were investigated, and their degree of hydrolysis (DH) values were 13.36%, 17.09%, and 20.15%, respectively. The hydrolysate yield values increased with DH increase, and the highest yield was obtained at DH 20.15%. The crude protein content increased from 80.58% to 85.27%, and amino acid compositions increased from 78.33% to 83.07%. The peptides formed during hydrolysis indicated low molecular weight that might improve functional characteristics of fish protein hydrolysates, including protein solubility, which ranged from 84.88% to 95.48% for all hydrolysates. The thermal degradation of hydrolysates occurred from 160 to 168 °C with intensive endothermic peaks. Results revealed that oil holding capacity was higher at DH 13.36%; water holding capacity was higher when DH increased. Hence, fish protein hydrolysates (FPH) from bighead carp have improved functional properties, and can be utilized as supplements and excellent protein sources in various uses in food applications.

Study of biological activities and physicochemical properties of Yamú (Brycon siebenthalae) viscera hydrolysates in sodium alginate-based edible coating solutions

The fishing industry produces waste such as viscera, which is an environmental problem for many countries. Obtaining protein from these wastes are useful for the food industry. In this study, the chemical composition, amino acid profile, solubility, digestibility and thermal properties of Yamú protein isolate (PI) and its hydrolysates obtained by enzymatic hydrolysis were characterized. The hydrolysates (0.05, 0.1, 0.5, 1 and 2% w/v) were mixed with a sodium alginate-based solution to form an edible coating solution (ECS). Antioxidant capacity antimicrobial activity, Zeta potential (ζ) and adsorption kinetics properties were determined. PI contains 88% (w/w) protein showing better solubility, digestibility and thermal stability properties. The hydrolysate concentrations with DPPH inhibitory ECS were 0.1 and 0.5% (w/v). The kinetic properties of ECS showed good stability and excellent adsorption. These results suggest that this Yamú protein has high nutritional potential as an ingredient for the production of functional foods.

Enzymatic hydrolysis: Sialylated mucin (SiaMuc) glycoprotein of edible swiftlet's nest (ESN) and its molecular weight distribution as bioactive ESN SiaMuc-glycopeptide hydrolysate

Bioactive edible swiftlet's nest (ESN) sialylated-mucin (SiaMuc) hydrolysate is produced by alcalase hydrolysis. Enzymatic hydrolysis of ESN breakdown high-valued ESN SiaMuc-glycoprotein into bioactive SiaMuc-glycopeptide. This is a breakthrough for the issue of insolubility and low extraction rate in ESN, and even increases the bioavailability of ESN nutritional functionality and health benefits. Hydrolysis of ESN SiaMuc-glycoprotein was performed for 1 to 4 h and its effect on physicochemical properties, molecular weight (MW) distribution, SiaMuc-glycoprotein and glycopeptide integrity were determined. Other than improvement in solubility and bioavailability as SiaMuc-glycopeptide, results from SDS-PAGE revealed that MW of SiaMuc-glycoprotein decreased from 42.0-148.8 kDa to 17.7-142.7 kDa with increasing hydrolysis period. Further hydrolysis from maximized DH (90 min) showed an insignificant effect on the MW of ESN SiaMuc-glycopeptide and remained constant at 15.2 kDa. This highlights that enzymatic hydrolysis only influences macro SiaMuc-glycoprotein fractions (142.7, 115.3 and 102.7 kDa), while the majority of SiaMuc-glycopeptide fractions from 36.6-98.6 kDa remained intact. Conclusively, alcalase hydrolysis of ESN showed high recovery in the form of bioactive ESN SiaMuc-glycopeptide. Therefore, enzymatic biotechnology is an economic alternative applicable on ESN that broaden industrial utilization by reducing the MW without destroying the quality of bioactive SiaMuc-glycoprotein.

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.

Structural and physicochemical characteristics of lyophilized Chinese sturgeon protein hydrolysates prepared by using two different enzymes

The structural and physicochemical characteristics of protein hydrolysates prepared from Chinese sturgeon through the enzymatic hydrolysis process were evaluated. Two different enzymes including papain and alcalase 2.4L were used in the hydrolysis process. The papain enzyme significantly increased the degree of hydrolysis (20.62%) and decreased the ζ-potential (12.4 ± 1.31 mV) as compared to the alcalase enzyme, which represented 15.55% and 15.53 ± 0.77 mV, respectively. Alcalase 2.4L hydrolysate exhibited smaller particle size (822.047 ± 61.26 nm) than papain hydrolysate (1425.39 ± 44.82 nm). Hydrolysis by papain and alcalase 2.4L enzymes decreased the molecular weights (MW ≤ 1,000 Da) to 98.27% and 86.84%, respectively. The surface hydrophobicity and turbidity of the hydrolysates significantly affected by enzyme type and protein concentrations. By using the X-ray diffraction analysis, the papain hydrolysate showed a higher relative crystallinity degree (30.33%) than alcalase 2.4L hydrolysate (29.40%), whereas the Fourier transform infrared spectroscopy showed more clearly peaks for the amide bands of alcalase hydrolysate. The thermal properties also affected by enzymatic hydrolysis conditions, since the melting temperatures were 159.17 and 149.58 °C, whereas the rate of mass loss was 67.04% and 62.8%, for papain and alcalase hydrolysates, respectively. PRACTICAL APPLICATION: The enzymatic hydrolysis process of proteins is employed to obtain the nutritionally and functionality important peptides that result during the preparation of fish protein hydrolysate. The objective of this study was to investigate the structural and physicochemical characteristics of protein hydrolysate prepared from Chinese sturgeon. This study showed that these characteristics were affected by enzymatic hydrolysis conditions especially enzyme type. The finding of this study may be useful in terms of providing new information on the properties of the protein hydrolysate and the structural changes resulting from controlled enzymatic hydrolysis conditions. Overall, these conditions could potentially alter the secondary structure of the protein hydrolysates or peptides and enhance their functional properties.

Optimization of Oyster (Crassostrea talienwhanensis) Protein Hydrolysates Using Response Surface Methodology

Oyster (Crassostrea talienwhanensis) protein was hydrolyzed by trypsin to produce peptides with different response values, and response surface methodology (RSM) was applied to optimize the hydrolysis conditions. The highest degree of hydrolysis (DH) of the oyster peptide (OP) was obtained at an enzyme concentration of 1593.2 U/g, a pH of 8.2, a hydrolysis temperature of 40.1 °C, a hydrolysis time of 6.0 h, and a water/material ratio of 8.2. The greatest hydroxyl-radical-scavenging activity of OP was obtained at an enzyme concentration of 1546.3 U/g, a pH of 9.0, a hydrolysis temperature of 50.2 °C, a hydrolysis time of 5.1 h, and a water/material ratio of 5.6. The largest branched-chain amino acid (BCAA) content of OP was obtained at an enzyme concentration of 1323.8 U/g, a pH of 8.3, a hydrolysis temperature of 41.7 °C, a hydrolysis time of 6.7 h, and a water/material ratio of 4.8. The three experimental values were significantly in agreement with the predicted values within the 95% confidence interval. Furthermore, ultrafiltration and chromatographic methods were used to purify the OP, and 13 peptides that were rich in Lys, Arg, His, and Thr were identified by LC-MS/MS. The results of this study offer different optimum hydrolysis conditions to produce target peptides from oyster protein by using RSM, and this study provide a theoretical basis for the high-value utilization of oyster protein.

Effects of ultrasonic, microwave, and combined ultrasonic-microwave pretreatments on the enzymatic hydrolysis process and protein hydrolysate properties obtained from Chinese sturgeon (Acipenser sinensis)

Degree of hydrolysis (DH), yield, amino acid profile, protein solubility, and antioxidant activity of Chinese sturgeon protein hydrolysates, as influenced by thermal pretreatment, ultrasonic (US), microwave (MW), and combined US-microwave pretreatments were investigated. Initially, the samples were subjected to thermal pretreatments in order to measure their effect on DH, which increased at 55°C. The DH recorded 7.63, 5.55, and 6.02% for US, MW, and combined US-MW pretreatment (US + MW), respectively, at the optimal time (8 min). The enzymatic hydrolysis (EN) of pretreated samples increased the DH to 19.41, 14.18, and 16.91% for US + EN, MW + EN, and US + MW + EN, respectively. The US + EN treatment was most effective for obtaining higher DH and yield, which were 19.41% and 18.62%, respectively. The use of US + EN also resulted in an increase in the percentage of molecular weights (≤1,000 Da), amino acid content and protein solubility, which reached 89.24, 80.08, and 98.58%, respectively. While, US + MW + EN pretreatment has achieved the highest antioxidant activities by IC₅₀ of 1,1-diphenyl-2-picrylhydrazyl and 2,2-Azinobis (3-ehtylbenzothiazoli- 6-sulfnic acid), which were 3.01 and 1.85 mg/ml, respectively, in addition to the reducing power assay, which was 0.528 at a protein concentration of 5 mg/ml. Therefore, US and combined US-MW techniques can play a promising role in the production of protein hydrolysates and the improvement of their antioxidant properties. PRACTICAL APPLICATIONS: Nowadays, interest in Chinese sturgeon production has increased as a promising source of protein and antioxidant peptides. The optimal thermal pretreatment can be used to enhance the degree of hydrolysis. The results indicated that the use of ultrasound as a pretreatment enhanced the degree of hydrolysis, which could be useful in the preparation of protein hydrolysate with higher yields. The use of combined US-MW significantly improved the antioxidant properties of the protein hydrolysate. The combined US-MW technique is a novel method for obtaining valuable peptides and protein hydrolysates that can be applied as antioxidant constituents in the food products.

Frationation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity

In the present work, defatted corn germ was hydrolyzed by three proteases and further separated by sequential ultrafiltration with different molecular weight cutoff (100, 10, 2 kDa). Corn germ protein hydrolysate (CGPH) and their fractions were investigated for antioxidant activity, α-glucosidase, α-amylase, and DPP-IV inhibitory activity. The degree of hydrolysis (DH) after 2 hr was 17.5%, 11.14%, and 2.05% for alcalase, trypsin, and flavourzyme, respectively. Trypsin hydrolysate showed the highest DPPH and ABTS+ radical scavenging and Fe2+ chelating activity, but a lower α-glucosidase inhibitory activity. F1 fraction (<2 kDa) exhibited highest radical scavenging and α-glucosidase inhibitory activity. While F2 fraction (2-10 kDa) showed the higher Fe2+ chelating and α-amylase inhibitory activity, F1 fraction of flavourzyme showed the highest α-glucosidase inhibitory and F2 fraction of alcalase and flavourzyme exhibited highest α-amylase inhibitory activity. Hydrolysate and F1 fraction of alcalase and F2 fraction of trypsin showed the highest DPP-IV inhibitory activity. RP-HPLC results showed that trypsin hydrolysate had higher levels of high-hydrophobic peptides. The amino acid composition of the F1 fractions showed high levels of hydrophobic amino acids. Thus, CGPHs may be used as a potential source of antioxidant and antidiabetic peptides in food industry and pharmaceutical application.