Antioxidative and Functional Properties of Pumpkin Oil Cake Globulin Hydrolysates

Cucurbitin extracted from pumpkin (Cucurbita pepo) oil cake was enzymatically hydrolysed with three different enzymes viz. alcalase, flavourzyme and pepsin. Antioxidative and functional properties of cucurbitin hydrolysates with different degrees of hydrolysis (DH) were investigated. The antioxidant activity of the hydrolysates was strongly dependent on the enzyme used. The hydrolysates obtained by alcalase and pepsin showed antioxidative potential whereas flavourzyme hydrolysates did not demonstrate these activities. Reducing power and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity of cucurbitin hydrolysate were positively related to DH. The highest antioxidant activity was found in the hydrolysate obtained by alcalase at DH 25.6 % [reducing power of 0.25 ± 0.01 A700 nm and ABTS scavenging activity of 3.34 ± 0.02 mmol/L Trolox equivalent antioxidant coefficients (TEAC)]. Hydrolysis by all enzymes increased the protein solubility within the studied pH range. The best emulsion activity and stability index (EAI = 143.28 ± 3.05 m²/g and ESI = 87.5 ± 1.96 min) have hydrolysates produced by flavourzyme (DH 9.2 %) whereas alcalase produced hydrolysates with the best foaming capacity (FC = 242 ± 3.21). The results demonstrate that hydrolysates produced in the present study have good functional properties as well as antioxidant activity indicating their possible use in different food systems.     

Ultrasonic pretreatment of corn gluten meal proteins and neutrase: Effect on protein conformation and preparation of ACE (angiotensin converting enzyme) inhibitory peptides

The impact of ultrasound pretreatment of corn gluten meal (CGM) protein and neutrase on the ACE (angiotensin converting enzyme) inhibitory activity of hydrolysate was studied. The UV–vis differential spectra and fluorescence spectra of the CGM protein and neutrase were determined. The neutrase activity and the ACE inhibitory activity of the CGM protein hydrolysates were analyzed. The highest ACE inhibitory activity was obtained at 10 min hydrolysis when the CGM protein was pretreated at 20 kHz for 10–30 min and at a power of 1000 W. The neutrase activity and ACE inhibitory activity were at their maxima at sonication of 250 W and sonication time of 15 min. The fluorescence and UV differential spectra of the proteins of CGM and neutrase reflected molecular unfolding due to sonication. Sonication of the protein substrate and the enzyme before hydrolysis may be an effective way to enhance the ACE inhibition attributes of the hydrolysate.     

Enzymatic modification of sesame seed protein,sourced from waste resource for nutraceutical application

The functional characteristics which include protein solubility at different pH, emulsifying and foaming properties, degree of hydrolysis, molecular weight distribution, antioxidant and ACE inhibitory activity of sesame protein hydrolysates prepared with pepsin, papain and alcalase enzymes were evaluated. The rate of degree of hydrolysis was found to reach maximum (25–30%) within the first time fragment i.e 10 min but 80% of hydrolysis was obtained in 120 min with alcalase. SDS-PAGE of hydrolysates with papain, pepsin and alcalase evinced bands of low molecular weight protein of 14.3 kDa and even lower for alcalase treatment of 120 min. Hydrolysates so formed were of improved functional properties as evident from emulsifying and foaming property. Hydrolysis with different proteases enhanced the protein solubility significantly at pH 7.0. Antioxidative assay revealed radical scavenging activity of the hydrolysates with papain hydrolysates showing maximum antioxidative efficacy. The ultra-filtered peptide fractions which showed comparable ACE inhibitory activity were sequenced by MALDI-TOF and matched to that of previously identified ACE inhibitory peptides. The results corroborate the ACE inhibitory effect of the peptides. Hence, these highly bioactive protein hydrolysates produced from waste sesame meals can be successfully employed in various functional food formulations.     

Amino Acid Profiles of 44 Soybean Lines and ACE‐I Inhibitory Activities of Peptide Fractions from Selected Lines

Soybeans are cultivated in the United States chiefly for cooking oil, while the residue after oil extraction (soybean meal) is mostly used in animal feed formulations. High protein content in the defatted soybean meals led to the extraction of pure protein and its application in food products. We selected 44 soybean lines to determine their moisture and protein contents, and their amino acid composition was investigated. Soybean lines with high protein content, one high yielding (R95‐1705), and two high oleic acid (N98‐4445A, S03‐543CR), were selected for protein isolate preparation, hydrolysis using alcalase and gastro‐intestinal (GI) resistance. Furthermore, the GI resistant hydrolysates were fractionated and tested for angiotensin‐I‐converting enzyme (ACE‐I) inhibition activity. The amino acid analysis showed high methionine in the high protein and fatty acid lines (R05‐4494 and R05‐5491), and high cysteine content in one of the high oleic acid soybean line CRR05‐188 in comparison to the check lines (UA‐4805 and 5601‐T). The protein isolate with the highest purity (90–93 %) was derived from the selected lines N98‐4445A and S03‐543CR, and hydrolyzed using alcalase enzyme. The protein hydrolysates (500 µg/mL) showed inhibition of the ACE‐I by 49 %. The results from this study will promote the use of high oleic acid soybeans as a source of protein and peptides with functional activities.     

Production of defatted palm kernel cake protein hydrolysate as a valuable source of natural antioxidants

The aim of this study was to produce a valuable protein hydrolysate from palm kernel cake (PKC) for the development of natural antioxidants. Extracted PKC protein was hydrolyzed using different proteases (alcalase, chymotrypsin, papain, pepsin, trypsin, flavourzyme, and bromelain). Subsequently, antioxidant activity and degree of hydrolysis (DH) of each hydrolysate were evaluated using DPPH• radical scavenging activity and O-phthaldialdehyde spectrophotometric assay, respectively. The results revealed a strong correlation between DH and radical scavenging activity of the hydrolysates, where among these, protein hydrolysates produced by papain after 38 h hydrolysis exhibited the highest DH (91 ± 0.1%) and DPPH• radical scavenging activity (73.5 ± 0.25%) compared to the other hydrolysates. In addition, fractionation of the most effective (potent) hydrolysate by reverse phase high performance liquid chromatography indicated a direct association between hydrophobicity and radical scavenging activity of the hydrolysates. Isoelectric focusing tests also revealed that protein hydrolysates with basic and neutral isoelectric point (pI) have the highest radical scavenging activity, although few fractions in the acidic range also exhibited good antioxidant potential.     

Angiotensin I-Converting Enzyme (ACE) Inhibitory Activity and ACE Inhibitory Peptides of Salmon (Salmo salar) Protein Hydrolysates Obtained by Human and Porcine Gastrointestinal Enzymes

The objectives of the present study were two-fold: first, to detect whether salmon protein fractions possess angiotensin I-converting enzyme (ACE) inhibitory properties and whether salmon proteins can release ACE inhibitory peptides during a sequential in vitro hydrolysis (with commercial porcine enzymes) and ex vivo digestion (with human gastrointestinal enzymes). Secondly, to evaluate the ACE inhibitory activity of generated hydrolysates. A two-step ex vivo and in vitro model digestion was performed to simulate the human digestion process. Salmon proteins were degraded more efficiently by porcine enzymes than by human gastrointestinal juices and sarcoplasmic proteins were digested/hydrolyzed more easily than myofibrillar proteins. The ex vivo digested myofibrillar and sarcoplasmic duodenal samples showed IC₅₀ values (concentration required to decrease the ACE activity by 50%) of 1.06 and 2.16 mg/mL, respectively. The in vitro hydrolyzed myofibrillar and sarcoplasmic samples showed IC₅₀ values of 0.91 and 1.04 mg/mL, respectively. Based on the results of in silico studies, it was possible to identify 9 peptides of the ex vivo hydrolysates and 7 peptides of the in vitro hydrolysates of salmon proteins of 11 selected peptides. In both types of salmon hydrolysates, ACE-inhibitory peptides IW, IY, TVY and VW were identified. In the in vitro salmon protein hydrolysates an ACE-inhibitory peptides VPW and VY were also detected, while ACE-inhibitory peptides ALPHA, IVY and IWHHT were identified in the hydrolysates generated with ex vivo digestion. In our studies, we documented ACE inhibitory in vitro effects of salmon protein hydrolysates obtained by human and as well as porcine gastrointestinal enzymes.     

Optimization of antioxidant hydrolysate production from flying squid muscle protein using response surface methodology

The squid muscle protein, extracted from by-products of flying squid (Ommastrephes bartrami) was hydrolyzed by five proteases (pepsin, trypsin, papain, alcalase and flavourzyme). DPPH radical scavenging power was used to evaluate antioxidative activity of hydrolysates. The hydrolysate obtained by papain exhibited the most excellent potential of antioxidative activity. Furthermore, response surface methodology (RSM) was employed to optimize hydrolysis conditions, including enzyme to substrate (E/S) ratio, reaction temperature, and hydrolysis time. The optimum conditions obtained were as follows: E/S ratio of 1.74%, temperature of 51 °C and time of 46 min, under which, DPPH radical scavenging activity of 74.25% was obtained. Moreover, it was found that the optimum hydrolysate of 8 mg/mL displayed relatively stronger inhibitory effect on lipid peroxidation compared with α-Tocopherol of 0.1 mg/mL.     

An In-vitro Investigation of Selected Biological Activities of Hydrolysed Flaxseed (Linum usitatissimum L.) Proteins

A study was conducted to determine bioactivities of flaxseed (Linum usitatissimum L.; variety: Valour) proteins and their hydrolysates. Isolated flaxseed proteins were treated with Flavourzyme^® at different levels of enzyme to substrate ratio (E/S) and hydrolysis time. The unhydrolysed proteins and hydrolysates were studied for angiotensin I-converting enzyme inhibiting (ACEI) activity, hydroxyl radical (OH·) scavenging activity and bile acid binding ability. Flavourzyme catalysed hydrolysis generated hydrolysates with a 11.94–70.62% degree of hydrolysis (DH). The hydrolysates (0.67 mg/ml) had strong ACEI activity (71.59–88.29%). The maximum ACEI activity containing hydrolysate exhibited an IC₅₀ of 0.07 mg/ml (E/S: 1.5; Time: 12 h; DH: 11.94%). The OH· scavenging activity of the hydrolysates (0.5 mg/ml) was 12.48–22.08% with an IC₅₀ of 1.56 mg/ml in the sample possessing maximum activity (E/S: 47.5; Time 0.7 h; DH: 24.63%). Both these activities were greater in hydrolysates with lower DH and higher peptide chain length (PCL) than those with higher DH and lower PCL. Hydrolysed flaxseed proteins (0.67 mg/ml) had no bile acid binding ability. The unhydrolysed proteins had no ACEI or OH· scavenging activity but demonstrated bile acid binding ability.     

In Vitro Acetylcholinesterase-Inhibitory Properties of Enzymatic Hemp Seed Protein Hydrolysates

The aim of this work was to characterize the structural and functional properties of hemp seed protein‐derived acetylcholinesterase (AChE)‐inhibitory enzymatic hydrolysates. Hemp seed protein isolate hydrolysis was performed using six different proteases (pepsin, papain, thermoase, flavourzyme, alcalase and pepsin + pancreatin) at different concentrations (1–4 %). The degree of hydrolysis was directly related to the amount of protease used but had no relationship with AChE‐inhibitory activity. Amino acid composition results showed that the hemp seed protein hydrolysates (HPHs) had high levels of negatively charged amino acids (39.62–40.18 %) as well as arginine. The 1 % pepsin HPH was the most active AChE inhibitor with ~6 µg/mL IC₅₀ value when compared to 8–11.6 µg/mL for the other HPHs. Mass spectrometry analysis showed that most of the peptides in all the hydrolysates were less than 1000 Da in size. However, the pepsin HPHs contained larger‐sized peptides (244–1009 Da) than the papain HPHs (246–758 Da), which in turn was larger than the alcalase HPH (246–607 Da). The higher AChE‐inhibitory effects of the pepsin HPHs may be due to increased synergistic effects from a wider peptide size range when compared to the papain and alcalase HPHs that had narrower ranges. The narrow peptide size range in the alcalase HPH confirms the higher efficiency of this protease in releasing small‐sized peptides from food proteins.     

Enhancing ACE-inhibition of food protein hydrolysates by selective adsorption using porous carbon materials

Bioactive peptides from food proteins such as natural ACE (angiotensin-converting enzyme)-inhibitors have attracted particular attention for their potential to prevent hypertension. ACE-inhibiting peptides were enriched from food protein hydrolysates prepared from α-lactalbumin and lysozyme by selective adsorption on microporous activated carbons. For the eluate, it was shown by liquid chromatography that the strongest inhibitor isoleucyl-tryptophan was enriched by a factor of 11.2 compared to the initial α-lactalbumin hydrolysate. Natural inhibitors derived from lysozyme hydrolysates (e.g., alanyl-tryptophan) were successfully enriched as well. Identification of the enriched peptide fraction by mass spectroscopy revealed the hydrophobic character of the enriched peptides. The molecular weight distribution of the enriched peptide fraction can be controlled by the pore size distribution of the chosen adsorbent, which was proven by size exclusion chromatography of enriched peptide fractions derived from three different model carbons differing in their pore size. The selective enrichment of natural ACE-inhibitors from the α-lactalbumin hydrolysate lead to a 6 times stronger in vitro ACE-inhibition demonstrating the high potential as ingredients for hypotensive functional foods with reduced side effects.     

Enzymatic modification of proteins of commercial sesame meals (Sesamum indicum, L.)

Sesame (Sesamum indicum, L.) is one of the most important oilseed crops in Venezuela. However, the low solubility of the flour made of commercial meals does not allow its use in the preparation of fluid foods. To solve this situation, the alternative of solubilizing the sesame proteins by an enzymatic method, using commercial proteases, was studied. Hydrolysis was carried out with two types of bacterial proteases: neutrasa 0.5L, and alcalase 0.6L. Basically, the process consisted of milling and sieving the sesame cake (60 mesh), concentrating the proteins by solubilizing them at a pH of 9.5, and then precipitating at a pH of 4.5. Proteins were hydrolyzed by an enzymatic method, and the hydrolysates freeze-dried and spray-dried. Optimal conditions of hydrolysis using neutrase 0.5L at a pH of 7 were: 6% substrate concentration, 3% enzyme:substrate ratio, temperature 50 degrees +/- 1 degree C, and hydrolysis degree of 8%. When alcalase 0.6L was used at a pH of 8, optimal conditions were: 8% substrate concentration, 2.3% enzyme:substrate ratio, temperature 58 degrees +/- 1 degree C, and hydrolysis degree of 10%. The enzyme affinity (Km) was best at temperatures near the optimal temperature for the hydrolysates. Dried hydrolysates had protein values which ranged between 66.3% and 66.9% and a nitrogen solubility in water, of approximately 85%. Hydrolysis yields referred to the concentrate dried mass were 42% for the atomized hydrolysate, and 56% for the freeze-dried one. In conclusion, the enzymatic hydrolysis process improved the nitrogen solubility in water of the sesame proteins.     

Physicochemical Properties and ACE-I Inhibitory Activity of Protein Hydrolysates from a Non-Genetically Modified Soy Cultivar

Arkansas‐grown non‐genetically modified soybean cultivar, R08‐4004, was selected to prepare a protein isolate, which was treated with Alcalase for limited enzymatic hydrolysis. The objective was to optimize the Alcalase hydrolysis condition to produce soy protein hydrolysate (SPH) with high protein yield, low bitterness, and clarity for beverage applications. The degree of hydrolysis ranged between 14 and 52 % during the study at varying incubation times using two different concentrations of Alcalase enzyme. Recovery of soluble protein, between 21 and 53 %, was achieved with a decrease in turbidity. There was an increase in surface hydrophobicity (S₀) which is correlated with bitterness of SPH treated with 1.0 AU (3.2 µL/g) of Alcalase 2.4 L. The sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analysis showed a distinct hydrolysis pattern in which 7S globulin and the two acidic sub‐units of 11S globulin were hydrolyzed extensively in comparison to the two basic sub‐units of 11S globulin. Limited enzymatic hydrolysis produced low molecular weight peptides <17 kDa. Among these SPHs, the one derived after 120 min incubation had the highest soluble protein yield (43 %), low S₀ value (35.4), low turbidity (0.88), and highest angiotensin‐I converting enzyme (ACE‐I) inhibition activity (66.6 %). This hydrolysate has potential use as protein rich nutraceutical for developing many non‐genetically modified food product applications.     

Molecular Weight Analysis of Blue Shark (Prionace glauca) Collagen Hydrolysates by GPC-LS; Effect of High Molecular Weight Hydrolysates on Fibroblast Cultures: mRNA Collagen Type I Expression and Synthesis

High molecular weight (Mw) collagen hydrolysates have been demonstrated to produce a higher synthesis of collagen type I mRNA. Mw determination is a key factor maximizing the effect of collagen hydrolysates on collagen type I synthesis by fibroblasts. This work aimed to achieve a high average Mw in Blue Shark Collagen Hydrolysate, studying different hydrolysis parameters by GPC-LS analysis and testing its effect on mRNA Type I collagen expression. Analysis revealed differences in blue shark collagen hydrolysates Mw depending on hydrolysis conditions. Papain leads to obtaining a significantly higher Mw hydrolysate than Alcalase at different times of hydrolysis and at different enzyme/substrate ratios. Besides, the time of the hydrolysis factor is more determinant than the enzyme/substrate ratio factor for obtaining a higher or lower hydrolysate Mw when using Papain as the enzyme. Contrary, Alcalase hydrolysates resulted in similar Mw with no significant differences between different conditions of hydrolysis assayed. Blue shark collagen hydrolysate showing the highest Mw showed neither cytotoxic nor proliferation effect on fibroblast cell culture. Besides, it exhibited an increasing effect on both mRNA expression and pro-collagen I production.     

Molecular Targets of Antihypertensive Peptides: Understanding the Mechanisms of Action Based on the Pathophysiology of Hypertension

There is growing interest in using functional foods or nutraceuticals for the prevention and treatment of hypertension or high blood pressure. Although numerous preventive and therapeutic pharmacological interventions are available on the market, unfortunately, many patients still suffer from poorly controlled hypertension. Furthermore, most pharmacological drugs, such as inhibitors of angiotensin-I converting enzyme (ACE), are often associated with significant adverse effects. Many bioactive food compounds have been characterized over the past decades that may contribute to the management of hypertension; for example, bioactive peptides derived from various food proteins with antihypertensive properties have gained a great deal of attention. Some of these peptides have exhibited potent in vivo antihypertensive activity in both animal models and human clinical trials. This review provides an overview about the complex pathophysiology of hypertension and demonstrates the potential roles of food derived bioactive peptides as viable interventions targeting specific pathways involved in this disease process. This review offers a comprehensive guide for understanding and utilizing the molecular mechanisms of antihypertensive actions of food protein derived peptides.     

In Vitro Proliferation and Anti-Apoptosis of the Papain-Generated Casein and Soy Protein Hydrolysates towards Osteoblastic Cells (hFOB1.19)

Casein and soy protein were digested by papain to three degrees of hydrolysis (DH) 7.3%–13.3%, to obtain respective six casein and soy protein hydrolysates, aiming to clarify their in vitro proliferation and anti-apoptosis towards a human osteoblastic cell line (hFOB1.19 cells). Six casein and soy protein hydrolysates at five levels (0.01–0.2 mg/mL) mostly showed proliferation as positive 17β-estradiol did, because they conferred the osteoblasts with cell viability of 100%–114% and 104%–123%, respectively. The hydrolysates of higher DH values had stronger proliferation. Casein and soy protein hydrolysates of the highest DH values altered cell cycle progression, and enhanced cell proportion of S-phase from 50.5% to 56.5% and 60.5%. The two also antagonized etoposide- and NaF-induced osteoblast apoptosis. In apoptotic prevention, apoptotic cells were decreased from 31.6% to 22.6% and 15.6% (etoposide treatment), or from 19.5% to 17.7% and 12.4% (NaF treatment), respectively. In apoptotic reversal, soy protein hydrolysate decreased apoptotic cells from 13.3% to 11.7% (etoposide treatment), or from 14.5% to 11.0% (NaF treatment), but casein hydrolysate showed no reversal effect. It is concluded that the hydrolysates of two kinds had estradiol-like action on the osteoblasts, and soy protein hydrolysates had stronger proliferation and anti-apoptosis on the osteoblasts than casein hydrolysates.     

In vitro antioxidant activity of enzymatic hydrolysates prepared from abalone (Haliotis discus hannai Ino) viscera

Pacific abalone (Haliotis discus hannai Ino) viscera, which are normally discarded as byproducts, were hydrolyzed with five commercially available proteases, including alkali protease, papain, neutral protease, pepsin, and trypsin. The hydrolysates obtained were fractionated using ultrafiltration membrane bioreactor system. The resulting hydrolysate fractions were investigated for their antioxidant activities, including the scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, the scavenging effect on hydroxyl radical, and the reducing power. Results showed that the hydrolysate fractions were effective antioxidants, and the antioxidant activity of the hydrolysates was related to the enzyme type employed. As byproducts, abalone viscera can be used as a potential source of antioxidant peptides.     

Production of fermentable sugars from corn fiber using soaking in aqueous ammonia (SAA) pretreatment and fermentation to succinic acid using <Emphasis Type="Italic">Escherichia coli</Emphasis> AFP184

Conversion of corn fiber (CF), a by-product from the corn-to-ethanol conversion process, into fermentable sugar and succinic acid was investigated using soaking in aqueous ammonia (SAA) pretreatment followed by biological conversions, including enzymatic hydrolysis and fermentation using genetically engineered E. coli (AFP184). The SAA pretreatment (using a 15% w/w NH₄OH solution at a solid-to-liquid ratio of 1: 10 at 60 °C for 24 h) removed 20-38% of lignin and significantly improved the digestibility of the treated solid (85-99% of glucan digestibility). Following the enzymatic hydrolysis, the sugar-rich hydrolysate was subjected to dilute sulfuric acid treatment (1 wt% sulfuric acid and 120 °C for 1 h), which hydrolyzed the oligosaccharides in the hydrolysate into fermentable monomeric sugars. The mixed sugar hydrolysates containing hexose and pentose obtained from the two-step hydrolysis and SAA pretreatment were fermented to succinic acid using a genetically engineered microorganism, Escherichia coli AFP184, for evaluating the fermentability. Engineered E. coli AFP184 effectively converted soluble sugars in the hydrolysate to succinic acid (20.7 g/L), and the production rate and yield were further enhanced with additional nutrients; the highest concentration of succinic acid was 26.3 g/L for 48 h of fermentation.     

Optimization of the Preparation of Fish Protein Anti-Obesity Hydrolysates Using Response Surface Methodology

The enzymatic condition for producing the anti-obesity hydrolysates from fish water-soluble protein was optimized with the aid of response surface methodology, which also derived a statistical model for experimental validation. Compared with neutral protease, papain and protamex, the porcine pancreas lipase inhibitory rate of hydrolysates from fish water-soluble protein was higher with alkaline protease. Results showed that the model terms were significant, the terms of lack of fit were not significant, and the optimal conditions for the hydrolysis by alkaline protease were initial pH 11, temperature 39 °C, enzyme dosage 122 U/mL and 10 h of hydrolysis time. Under these conditions, the porcine pancreas lipase and the α-amylase inhibitory rate could reach 53.04% ± 1.32% and 20.03 ± 0.89%, while predicted value were 54.63% ± 1.75%, 21.22% ± 0.70%, respectively. In addition, Lineweaver-Burk plots showed noncompetitive inhibition. The K_i value calculated was 84.13 mg/mL. These results demonstrated that fish water-soluble protein could be used for obtaining anti-obesity hydrolysates.     

酶法水解和筛选蛋黄蛋白质中的药物前驱型降血压肽

为了筛选鸡蛋蛋黄蛋白质的酶解产物中的药物前驱型降血压肽,将鸡蛋蛋黄蛋白质经超临界CO2-乙醇萃取脱脂和NaOH溶液脱磷处理,用12种蛋白酶在各自适宜的条件下进行酶解,采用HPLC分析各酶解产物对血管紧张素酶(ACE)的抑制活性(IC50),并对IC50较小的6种水解产物进行保温实验,筛选药物前驱型降血压肽。结果显示,12种酶解产物对ACE的IC50值在0.69 mg.mL-1~4.06 mg.mL-1;保温实验显示仅有酶L的酶解产物IC50值明显减小,即由1.19 mg.mL-1降至0.59 mg.mL-1,其他5种酶解产物的IC50值则保持不变或升高,表明酶L的酶解产物中含药物前驱型降血压肽。     

Antioxidant and ACE Inhibitory Bioactive Peptides Purified from Egg Yolk Proteins

Protein by-products from the extraction of lecithin from egg yolk can be converted into value-added products, such as bioactive hydrolysates and peptides that have potential health enhancing antioxidant, and antihypertensive properties. In this study, the antioxidant and angiotensin converting enzyme (ACE) inhibitory activities of peptides isolated and purified from egg yolk protein were investigated. Defatted egg yolk was hydrolyzed using pepsin and pancreatin and sequentially fractionated by ultrafiltration, followed by gel filtration to produce egg yolk gel filtration fractions (EYGF). Of these, two fractions, EYGF-23 and EYGF-33, effectively inhibited the peroxides and thiobarbituric acid reactive substance (TBARS) in an oxidizing linoleic acid model system. The antioxidant mechanism involved superoxide anion and hydroxyl radicals scavenging and ferrous chelation. The presence of hydrophobic amino acids such as tyrosine (Y) and tryptophan (W), in sequences identified by LC-MS as WYGPD (EYGF-23) and KLSDW (EYGF-33), contributed to the antioxidant activity and were not significantly different from the synthetic BHA antioxidant. A third fraction (EYGF-56) was also purified from egg yolk protein by gel filtration and exhibited high ACE inhibitory activity (69%) and IC₅₀ value (3.35 mg/mL). The SDNRNQGY peptide (10 mg/mL) had ACE inhibitory activity, which was not significantly different from that of the positive control captopril (0.5 mg/mL). In addition, YPSPV in (EYGF-33) (10 mg/mL) had higher ACE inhibitory activity compared with captopril. These findings indicated a substantial potential for producing valuable peptides with antioxidant and ACE inhibitory activity from egg yolk.