Extraction of antioxidant and ACE inhibitory peptides from Thai traditional fermented shrimp pastes

Decoding volatile-microbial-physicochemical interplay of sensory preference in commercial shrimp paste based on flavoromics and high-throughput sequencing

Despite the long-standing tradition of shrimp paste in China, the aroma profiles driving consumer preferences remain poorly characterized. This study applied flavoromics and high-throughput sequencing to analyze nine commercial shrimp pastes, aiming to identify critical odorants influencing sensory acceptance and investigate their correlation with physicochemical properties and microbial communities. Nine distinct aroma attributes were identified as significant determinants of consumer preferences. Comprehensive volatile profiling using GC-IMS and GC-MS detected 44 and 40 volatiles, respectively, with 30 identified as aroma-active compounds (odor-active value ≥ 1). According to partial least squares regression analysis, fourteen key AACs significantly contributed to aroma attributes. Desirable AACs including 2,3-butanedione, isoamyl acetate, benzaldehyde, 2-heptanone, dimethyl trisulfide, 2,6-dimethyl pyrazine, 2,5-dimethyl pyrazine, and trimethyl pyrazine were associated with aroma attributes, such as sweet, meaty, cooked-garlic-like, sesame oil-like, and soy sauce-like aromas. Conversely, six AACs, including 3-methyl butanoic acid, naphthalene, trimethylamine, indole, 1-penten-3-ol, and Z-3-hexen-1-ol, contributed to off-odors characterized as pungent, earthy, rotten, and fishy. Significant variations were observed in physicochemical parameters and microbial composition, with dominant genera including Tetragenococcus, Corynebacterium_1, Vagococcus, Acinetobacter, Alkalibacterium, and Psychrobacter showing strong correlations with aroma formation. Metabolic pathway analysis revealed that microbial enzymatic activities-particularly decarboxylation, deamination, lysis, and lipid oxidation-critically shape the volatile profile through the degradation of amino acids and polyunsaturated fatty acids. This work systematically deciphers the molecular basis of shrimp paste flavor, providing actionable insights for optimizing fermentation processes to enhance sensory quality and consumer acceptance.

Bioactive Peptides from Fermented Foods: Production Approaches, Sources, and Potential Health Benefits

Microbial fermentation is a well-known strategy for enhancing the nutraceutical attributes of foods. Among the fermentation outcomes, bioactive peptides (BAPs), short chains of amino acids resulting from proteolytic activity, are emerging as promising components thanks to their bioactivities. Indeed, BAPs offer numerous health benefits, including antimicrobial, antioxidant, antihypertensive, and anti-inflammatory properties. This review focuses on the production of bioactive peptides during the fermentation process, emphasizing how different microbial strains and fermentation conditions influence the quantity and quality of these peptides. Furthermore, it examines the health benefits of BAPs from fermented foods, highlighting their potential in disease prevention and overall health promotion. Additionally, this review addresses the challenges and future directions in this field. This comprehensive overview underscores the promise of fermented foods as sustainable and potent sources of bioactive peptides, with significant implications for developing functional foods and nutraceuticals.

Impact of backslopping in TERASI manufacture, as an improving method to reduce shrimp allergenicity

The backslopping method was applied to the manufacture of Terasi (fermented shrimp paste) as countermeasures against the technical issue depending on the raw material, and its contribution to reduction of the potential allergenicity of Terasi was examined. Three kinds of starters, the low allergenic Indonesian commercial Terasi (CT), Akiami (Acetes japonicus) Terasi produced in laboratory scale (AT) and heated AT (HAT) were added to the manufacturing process of the Isazaami (Neomysis awatchensis) Terasi which contained tropomyosin (TM) with high IgE-binding ability. Addition of the starter effectively promoting the degradation of the shrimp protein and the reduction of the IgE-binding ability of TM. Interestingly, Terasi added as a starter would have acted primarily as a nutrient source to promote microbial fermentation rather than as a source of fermenting microorganisms and endogenous proteases. The backslopping method is one of the improving methods for reduction of potential allergenicity of Terasi product.

In-situ and real-time monitoring of two-stage enzymatic preparation of ACE inhibitory peptides from Cordyceps militaris medium residues by ultrasonic-assisted pretreatment

A protocol for the preparation of angiotensin-Ⅰ-converting enzyme (ACE) inhibitory peptides from Cordyceps militaris medium residues (CMMR) was established by two-stage enzymatic hydrolysis (amylase and protease). In a combination (mono-, dual-, and tri-frequency) of five different frequencies (20, 28, 35, 40 and 50 kHz), ultrasound-assisted pretreatment increased ACE inhibition rate in hydrolysate by 63.30 % under the mode of 20/28 kHz. Afterwards, near-infrared (NIR) spectrometer combined with spectral preprocessing methods and multivariate analysis like partial least square (PLS), synergy interval-PLS (Si-PLS), random frog-PLS (RF-PLS) and competitive adaptive reweighted sampling (CARS-PLS) was used to monitor the ACE inhibitory activity. The performance of models was evaluated by the correlation coefficient (R_p) and root mean square error (RMSEP). CARS-PLS models achieved optimal results for both amylase and protease hydrolysis with R_p = 0.9693, RMSEP = 0.01 for the former and R_p = 0.9454, RMSEP = 0.03 for the latter. NIR spectrometer combined with CARS-PLS models may be employed for in-situ and real-time monitoring of the preparation of ACE inhibitory peptides under ultrasonic-assisted pretreatment.

Bacillus subtilis K-C3 as Potential Starter to Improve Nutritional Components and Quality of Shrimp Paste and Corresponding Changes during Storage at Two Alternative Temperatures

This study aimed to evaluate Bacillus subtilis K-C3 as a potential starter to improve shrimp paste quality, particularly in terms of nutritional profiles. The quality/characteristic changes of shrimp paste with and without inoculation during storage for 18 months when stored at low (4 °C) and room (28 °C) temperature were also investigated. The results found that this B. strain increased essential amino acids (EAAs) and polyunsaturated fatty acids (PUFAs), as well as antioxidant properties including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, ferric reducing antioxidant power (FRAP) and metal chelating activity in the experimental shrimp paste compared to traditional shrimp paste (p < 0.05). The faster development of some characteristics of inoculated samples were also noted, as indicated by the higher total viable count (TVC), formal and amino nitrogen content, pH, and browning index, as well as biogenic amines, indicating different quality which may be further responsible for different product acceptability. The changes in quality/characteristics of shrimp paste were observed throughout the 18 months of storage. Shrimp paste stored at room temperature accelerated those changes faster than samples stored at low temperature (p < 0.05); however, the quality of them still meets the product’s standard even storage for 18 months. Meanwhile, shrimp paste stored at a low temperature had an amount of yeast and mold over the limitation (>3.00 log CFU/g), indicating food spoilage. Thus, storage at room temperature can extend this product’s shelf-life better than storage at low temperature. Overall, inoculation with B. subtilis K-C3, in conjunction with storage at room temperature, resulted in quality improvement and maintenance in shrimp paste, particularly in the aspects of nutritional profiles and safety concern, as the shrimp paste should have a shelf-life of at least 18 months.

Antioxidant peptides: Overview of production, properties, and applications in food systems

In recent years, several studies have reported the beneficial effects of antioxidant peptides in delaying oxidation reactions. Thus, a growing number of food proteins have been investigated as suitable sources for obtaining these antioxidant peptides. In this study, some of the most critical developments in the discovery of peptidic antioxidants are discussed. Initially, the primary methods to release, purify, and identify these antioxidant peptides from various food-derived sources are reviewed. Then, computer-based screening methods of the available peptides are summarized, and methods to interpret their structure-activity relationship are illustrated. Finally, approaches to the large-scale production of these bioactive peptides are described. In addition, the applications of these antioxidants in food systems are discussed, and gaps, future challenges, and opportunities in this field are highlighted. In conclusion, various food items can be considered promising sources to obtain these novel antioxidant peptides, which present various opportunities for food applications in addition to health promotion. The lack of in-depth data on the link between the structure and activity of these antioxidants, which is critical for the prediction of possible bioactive amino acid sequences and their potency in food systems and in vivo conditions (rather than in vitro systems), requires further attention. Consequently, future collaborative research activities between the industry and academia are required to realize the commercialization objectives of these novel antioxidant peptides.

Extraction and Characterization of Protein Concentrates from Limpets (Patella vulgata) and Peptide Release Following Gastrointestinal Digestion

This study investigated the characterization of proteins from the Irish limpet (Patella vulgata) and assessed the in vitro biological activities of hydrolysates obtained following gastrointestinal digestion (INFOGEST) of a limpet protein concentrate (LPC). The physicochemical properties and the digestibility of the LPC were investigated, along with the angiotensin-converting enzyme (ACE) inhibition and antioxidant activities of the LPC-digested samples. All the digested samples examined outperformed the LPC in terms of activity. Peptides were identified using LC-MS/MS after digestion. A total of 38 and 19 peptides were identified in LPC-G and LPC-GI, respectively, using a database search and a de novo approach. Most of the identified peptides had hydrophobic amino acids, which may contribute to their antioxidant and ACE inhibitory activities. The findings of this study showed that LPC has high nutritional quality with good digestibility and could serve as a potential source of antioxidative and ACE inhibitory peptides following gastrointestinal digestion.

In vitro angiotensin-converting enzyme and dipeptidyl peptidase-IV inhibitory, and antioxidant activity of blue mussel (Mytilus edulis) byssus collagen hydrolysates

Large quantities of mussel byssus are generated annually as a co-product of the mussel-processing industry. This fibrous material is a rich source of collagen, which when extracted has potential uses as an alternative source of collagen for food applications. However, due the complex structure of the material, the extraction of the collagenous components using food-friendly strategies has proved challenging to date. An enzyme-aided method, using a proline endoproteinase, was employed for the extraction of collagen from mussel byssus yielding 138.82 ± 2.25 mg collagen/g dry weight. Hydrolysates of the collagen extract were generated using five food-grade enzyme preparations with Corolase® PP giving the highest extent of hydrolysis. Reversed-phase and gel permeation high-performance liquid chromatography of the extracted collagen and its enzymatic hydrolysates showed significant hydrolysis of collagen. The hydrolysates generated with Corolase® PP showed the highest in vitro bioactivities: angiotensin-converting enzyme (ACE) IC50 = 0.79 ± 0.17 mg/ml, dipeptidyl peptidase-IV (DPP-IV) IC50 = 0.66 ± 0.17 mg/ml and oxygen radical absorbance capacity (ORAC) activity = 311.23 ± 13.41 µmol trolox equivalents (TE)/g. The results presented herein indicate that in addition to acting as an alternative source of collagen for food applications, mussel byssus collagen-derived hydrolysates have potential applications as functional food ingredients for the management of metabolic diseases such as type II diabetes and hypertension.

Regulation of microbial metabolism on the formation of characteristic flavor and quality formation in the traditional fish sauce during fermentation: a review

Fish sauce is a special flavored condiment formed by traditional fermentation of low-value fish in coastal areas, which are consumed and produced in many parts of the world, especially in Southeast Asia. In the process of fish sauce fermentation, the diversity of microbial flora and the complex metabolic reactions of microorganisms, especially lipid oxidation, carbohydrate fermentation and protein degradation, are accompanied by the formation of flavor substances. However, the precise reaction of microorganisms during the fersmentation process is difficult to accurately control in modern industrial production, which leads to the loss of traditional characteristic flavors in fermented fish sauces. This paper reviews the manufacturing processes, core microorganisms, metabolic characteristics and flavor formation mechanisms of fermented fish sauces at home and abroad. Various methods have been utilized to analyze and characterize the composition and function of microorganisms. Additionally, the potential safety issues of fermented fish sauces and their health benefits are also reviewed. Furthermore, some future directions and prospects of fermented fish sauces are also reviewed in this paper. By comprehensive understanding of this review, it is expected to address the challenges in the modern production of fish sauce thereby expanding its application in food or diet.

Preparation, Identification, Molecular Docking Study and Protective Function on HUVECs of Novel ACE Inhibitory Peptides from Protein Hydrolysate of Skipjack Tuna Muscle

To prepare bioactive peptides with high angiotensin-I-converting enzyme (ACE)-inhibitory (ACEi) activity, Alcalase was selected from five kinds of protease for hydrolyzing Skipjack tuna (Katsuwonus pelamis) muscle, and its best hydrolysis conditions were optimized using single factor and response surface experiments. Then, the high ACEi protein hydrolysate (TMPH) of skipjack tuna muscle was prepared using Alcalase under the optimum conditions of enzyme dose 2.3%, enzymolysis temperature 56.2 °C, and pH 9.4, and its ACEi activity reached 72.71% at 1.0 mg/mL. Subsequently, six novel ACEi peptides were prepared from TMPH using ultrafiltration and chromatography methods and were identified as Ser-Pro (SP), Val-Asp-Arg-Tyr-Phe (VDRYF), Val-His-Gly-Val-Val (VHGVV), Tyr-Glu (YE), Phe-Glu-Met (FEM), and Phe-Trp-Arg-Val (FWRV), with molecular weights of 202.3, 698.9, 509.7, 310.4, 425.6, and 606.8 Da, respectively. SP and VDRYF displayed noticeable ACEi activity, with IC₅₀ values of 0.06 ± 0.01 and 0.28 ± 0.03 mg/mL, respectively. Molecular docking analysis illustrated that the high ACEi activity of SP and VDRYF was attributed to effective interaction with the active sites/pockets of ACE by hydrogen bonding, electrostatic force, and hydrophobic interaction. Furthermore, SP and VDRYF could significantly up-regulate nitric oxide (NO) production and down-regulate endothelin-1 (ET-1) secretion in HUVECs after 24 h treatment, but also abolish the negative effect of 0.5 μM norepinephrine (NE) on the generation of NO and ET-1. Therefore, ACEi peptides derived from skipjack tuna (K. pelamis) muscle, especially SP and VDRYF, are beneficial components for functional food against hypertension and cardiovascular diseases.

Fermented fish products in South and Southeast Asian cuisine: indigenous technology processes, nutrient composition, and cultural significance

The cleaner production of biomass into value-added products via microbial processes adds uniqueness in terms of food quality. The microbe-mediated traditional process for transforming biomass into food is a sustainable practice in Asian food industries. The 18 fermented fish products derived through this process as well as the associated micro-flora and nutritional composition have been focused. This review aims to update the process of green conversion biomass into value-added food products for a more sustainable future. Fish products are classified based on the substrate and source of the enzymes used in fermentation, which includes the three types of technology processing discussed. According to the findings, these fermented fish contain a plethora of beneficial microbiota, making them a valuable source of probiotics that may confer nutritional and health benefits.Bacillus(12 products),Lactobacillus(12 products),Micrococcus(9 products), andStaphylococcus(9 products) were the most common bacterial genera found in 18 fermented fish products. Consuming fermented fish products is beneficial to human health due to their high levels of carbohydrate, protein, fat, and lactic acid. However, biogenic amines, which are produced by certain bacteria as a by-product of their catabolic activity, are a significant potential hazard in traditionally fermented fish.

Enzyme-Assisted Release of Antioxidant Peptides from Porphyra dioica Conchocelis

The conchocelis life cycle stage of P. dioica represents an unexplored source of bioactive compounds. The aim of this study was to generate and characterise, for the first time, hydrolysates of conchocelis using a specific combination of proteases (Prolyve^® and Flavourzyme^®). Hydrolysate molecular mass distribution and free amino acid contents were assessed, and the antioxidant activity was determined using a range of in vitro assays. The protein content and the total amino acid profiles of conchocelis were also studied. Conchocelis contained ~25% of protein (dry weight basis) and had a complete profile of essential amino acids. Direct sequential enzymatic treatment modified the profile of the generated compounds, increasing the amount of low molecular weight peptides (<1 kDa). There was a significant improvement in the antioxidant activity of the hydrolysates compared with the control (up to 2.5-fold), indicating their potential as a novel source of antioxidant ingredients.

Activity and bioavailability of food protein-derived angiotensin-I-converting enzyme-inhibitory peptides

Angiotensin-I-converting enzyme (ACE) inhibitory peptides are able to inhibit the activity of ACE, which is the key enzymatic factor mediating systemic hypertension. ACE-inhibitory peptides can be obtained from edible proteins and have the function of antihypertension. The amino acid sequences and the secondary structures of ACE-inhibitory peptides determine the inhibitory activities and stability. The resistance of ACE-inhibitory peptides to digestive enzymes and peptidase affect their antihypertensive bioactivity in vivo. In this paper, the mechanism of ACE-inhibition, sources of the inhibitory peptides, structure-activity relationships, stability during digestion, absorption and transportation of ACE-inhibitory peptides, and consumption of ACE-inhibitory peptides are reviewed, which provide guidance to the development of new functional foods and production of antihypertensive nutraceuticals and pharmaceuticals.

Fermented fish products in South and Southeast Asian cuisine: indigenous technology processes, nutrient composition, and cultural significance

The cleaner production of biomass into value-added products via microbial processes adds uniqueness in terms of food quality. The microbe-mediated traditional process for transforming biomass into food is a sustainable practice in Asian food industries. The 18 fermented fish products derived through this process as well as the associated micro-flora and nutritional composition have been focused. This review aims to update the process of green conversion biomass into value-added food products for a more sustainable future. Fish products are classified based on the substrate and source of the enzymes used in fermentation, which includes the three types of technology processing discussed. According to the findings, these fermented fish contain a plethora of beneficial microbiota, making them a valuable source of probiotics that may confer nutritional and health benefits. Bacillus (12 products), Lactobacillus (12 products), Micrococcus (9 products), and Staphylococcus (9 products) were the most common bacterial genera found in 18 fermented fish products. Consuming fermented fish products is beneficial to human health due to their high levels of carbohydrate, protein, fat, and lactic acid. However, biogenic amines, which are produced by certain bacteria as a by-product of their catabolic activity, are a significant potential hazard in traditionally fermented fish.

Recent Advances in Marine-Based Nutraceuticals and Their Health Benefits

The oceans have been the Earth's most valuable source of food. They have now also become a valuable and versatile source of bioactive compounds. The significance of marine organisms as a natural source of new substances that may contribute to the food sector and the overall health of humans are expanding. This review is an update on the recent studies of functional seafood compounds (chitin and chitosan, pigments from algae, fish lipids and omega-3 fatty acids, essential amino acids and bioactive proteins/peptides, polysaccharides, phenolic compounds, and minerals) focusing on their potential use as nutraceuticals and health benefits.

Bioactive peptides from food fermentation: A comprehensive review of their sources, bioactivities, applications, and future development

Bioactive peptides (BPs) are specific protein fragments that exert various beneficial effects on human bodies and ultimately influence health, depending on their structural properties and amino acid composition and sequences. By offering promising solutions to solve diverse health issues, the production, characterization, and applications of food-derived BPs have drawn great interest in the current literature and are of particular interest to the food and pharmaceutical industries. The microbial fermentation of protein from various sources is indubitably a novel way to produce BPs with numerous beneficial health effects. Apart from its lower cost as compared to enzymes, the BPs produced from microbial fermentation can be purified without further hydrolysis. Despite these features, current literature shows dearth of information on the BPs produced from food via microbial fermentation. Hence, there is a strong necessity to explore the BPs obtained from food fermentation for the development of commercial nutraceuticals and functional foods. As such, this review focuses on the production of BPs from different food sources, including the extensively studied milk and milk products, with emphasis on microbial fermentation. The structure-activity (antihypertensive, antioxidant, antimicrobial, opiate-like, anti-inflammatory, anticancer/antiproliferative, antithrombotic, hypolipidemic, hypocholesterolemic, and mineral binding) relationship, potential applications, future development, and challenges of BPs obtained from food fermentation are also discussed.

Virgibacillus halodenitrificans ST-1 for fermentation of shrimp paste and hydrolysates of its protease

The nutrition and flavor of shrimp paste came from hydrolyzation by enzymes that were produced by microorganisms. The salt-tolerant strain Virgibacillus halodenitrificans ST-1 isolated from shrimp paste was studied and used in the fermentation of shrimp paste. The strain and the protease produced by ST-1 were investigated. The optimum pH of the protease was 8.0, and the reaction temperature was 30°C. The protease showed high activity in the range of pH (5.0-11.0) and NaCl concentration (1%-15%). Divalent cations such as Ba2+, Ca2+, Mg2+, Mn2+, and Si2+ could enhance the protease activity. Residual activity of protease was more than 90% when it was incubated with PMSF and H2O2. Also, the enzyme retained more than 90% of initial activity after it was incubated with organic solvents. Variety of natural proteins could be substrates of the protease. By analyzing the release rate of free amino acids, it was predicted that the cleavage sites of the protease were mainly Glu, Asp, Gly, Leu, and Lys. Moreover, the hydrolysates of the protease had antioxidant activity, especially for DPPH and superoxide anion radical scavenging. The strain ST-1 and the protease both were excellent candidates for food industries.

Influence of Hydrolysis on the Bioactive Properties and Stability of Chickpea-Protein-Based O/W Emulsions

This study evaluated the effect of enzymatic hydrolysis on the emulsion microstructure and bioactive properties of oil-in-water emulsions generated using chickpea protein concentrate (CP) and its 10 and 210 min Alcalase CP hydrolysates (CPH₁₀ and CPH₂₁₀, respectively) at three pH values (2.5, 5.0, and 7.5). Chromatographic profiles demonstrated CP protein breakdown following hydrolysis. Increasing the degree of hydrolysis resulted in increased emulsion droplet size and decreased viscoelastic moduli. The antioxidant capacities of the emulsions generated with CPH₁₀ and CPH₂₁₀ increased significantly compared to those generated with CP and were pH-dependent. Both angiotensin-converting enzyme and dipeptidyl peptidase-IV inhibitory activities were significantly increased in emulsions stabilized with CPH₂₁₀; however, these results were also pH-dependent. In vitro gastrointestinal digestion of the emulsions resulted in a significant increase in all bioactivities. These results demonstrate the potential for enzymatic hydrolysis to beneficially modulate the emulsifying and bioactive properties of CP proteins.

Advances on Food-Derived Peptidic Antioxidants-A Review

The oxidation process is considered to be the main reason behind human aging, human degenerative diseases and food quality degradation. Food-derived peptidic antioxidants (PAs) have wide sources and great activity, and have broad application prospects in removing excess reactive oxygen species in the body, anti-aging and preventing and treating diseases related to oxidative stress. On the other hand, PAs are expected to inhibit the lipid peroxidation of foods and increase the stability of the food system in the food industry. However, the production pathways and action mechanism of food-derived PAs are diverse, which makes it is difficult to evaluate the performance of PAs which is why the commercial application of PAs is still in its infancy. This article focuses on reviewing the preparation, purification, and characterization methods of food-derived PAs, and expounds the latest progress in performance evaluation and potential applications, in order to provide an effective reference for subsequent related research of PAs.

Enzymatic Modification of Porphyra dioica-Derived Proteins to Improve their Antioxidant Potential

Enzymatic hydrolysis has been employed to modify protein functional properties and discover new sources of antioxidants. In this study, the effect of different enzymatic treatments on antioxidant activity of Porphyra dioica (blades and protein isolate (PI)) was investigated. Protein nitrogen content of P. dioica blades and PI were 23 and 50% (dry weight), respectively. Blades and PI were hydrolyzed with Prolyve® and Prolyve® plus Flavourzyme®. Peptide profiles and molecular mass distribution of the hydrolysates were investigated. The hydrolysis promoted generation of peptides and low molecular mass components <1 kDa. Antioxidant activity was assessed using ferric reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH·) scavenging, 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS·+) inhibition, and reactive oxygen species scavenging ability, i.e., oxygen radical absorbance capacity (ORAC) and hypochlorous acid (HOCl) scavenging assays. In general, enzymatic hydrolysis of P. dioica blades and PI enhanced the in vitro antioxidant activity. Direct hydrolysis of blades improved ORAC values up to 5-fold (from 610 to 3054 μmol Trolox eq./g freeze dried sample (FDS). The simultaneous release of phenolic compounds suggested a potential synergistic activity (ORAC and ABTS·+ assays). Such hydrolysates may be of value as functional food ingredients.

Effect of in vitro simulated gastrointestinal digestion on the antioxidant activity of the red seaweed Porphyra dioica

Porphyra sp. is one of the most cultivated and commercially valuable species, recognized for its high protein content (up to 47% dry weight) and complete amino acids profile. Based on these characteristics, P. dioica produced in an integrated multitrophic aquaculture system was selected for this study. The aim was to evaluate the effect of in vitro simulated gastrointestinal digestion (SGID) on the antioxidant activity of the hydrolysates generated from dried blades and from the protein isolate (PI) extracted from them. The alkali extraction and isoelectric precipitation (pH 4.5) of P. dioica protein prior SGID allowed isolating/enriching protein, while direct SGID of blades allowed assessing the potential influence of other constituents of the sample on the bioactive properties. Overall, SGID promoted the release of smaller bioactive peptides and their in vitro antioxidant activity, which was assessed by different methods (DPPH and ABTS⁺ scavenging capacity, ORAC and FRAP), was improved compared to the intact samples. Blades submitted to direct SGID presented significantly higher ORAC values compared to PI (2010 ± 136 vs 542 ± 21 µmol TE/g FDS, respectively). For the remaining assays, PI presented more potent antioxidant activity, especially FRAP (131 ± 2 vs 16 ± 1 µmol TE/g FDS) and ABTS⁺ (1244 ± 157 vs 230 ± 15 µmol TE/g FDS). The results indicated that gastrointestinal digestion improved the antioxidant activity of P. dioica-derived hydrolysates, as they presented effective activity against different oxidative mechanisms, thus suggesting health-protecting effects.

Nitrogen-Doped Hollow Copolymer Tube via Template-Free Asynchronous Polymerization with Highly Selective Separation of Hydrophilic Dipeptide for Enhancing Inhibitory Activity of Angiotensin Converting Enzyme

A N-doped hollow copolymer tube (NHCT) was fabricated via template-free one-pot asynchronous polymerization strategy. Discrepancies of monomer polymerization speed and their hydrophilic-hydrophobic interaction resulted in the assembly of a hollow tube having inner diameter and double wall thickness of ∼230 and 40 nm, respectively. The formation and growth mechanism of NHCT analyzed via advanced characterization revealed that the unique growth processes tuned a demarcating surface layer between inner (hydrophilic) and outer (hydrophobic) layers. The screening and recognition ability of NHCT were determined for two specific dipeptides (WW and RR) possessing great discrepancies in hydrophilicity and angiotensin converting enzyme inhibitory (ACE-I) activity. NHCT realized high adsorption capacity (1.57 mmol/g) and selectivity (∼1274) for hydrophilic dipeptide RR (low ACE-I activity) from the mixture of RR/WW. As a result, ACE-I activity for residual solution were enhanced about 4.1 times as compared to original solution from natural silkworm pupae protein hydrolysate. Awarding to these results and its facile and discerning ability, NHCT can be envisioned to be of great value for the separation of small functional peptides from a natural edible source.

Changes in ACE inhibitory and antioxidant activities in alcalase treated idli batter and idli after fermentation

Idli is a cereal-legume fermented food consumed widely in India. Fermentation and addition of external enzymes have been suggested as methods for release of bioactive peptides from parent proteins. The present study was aimed at exploring the changes in angiotensin-I converting enzyme (ACE) inhibitory and antioxidant activity of 14 h fermented idli batter treated with alcalase in varied amounts (100-700 U/g batter) kept at 30 ± 2 °C. Various batter parameters along with sensory attributes of cooked idli were assessed. The viscosity (12170-7795 cP) and rise in volume (29-20 mL) of batter decreased with addition of alcalase in the batter when compared with control batter (14130 cP, 31 mL). The free amino nitrogen content and radical scavenging activity of alcalase treated batter exhibited an increase by 2-5 and 2-7 fold, respectively while ACE inhibitory activity showed a decrease in IC₅₀ value (lowest being 52.53 ± 1.12 mg/mL of batter containing 600 U alcalase/g batter) when compared with the control fermented set. The hardness and bulk density values of control cooked idli was 0.59 kg and 0.53 g/cm³, respectively while alcalase treated idlis showed a range of 0.71-1.68 kg and 0.53-0.69 g/cm³. The overall acceptance of idli prepared from alcalase treated batters till 600 U/g batter was judged as 'good' by semi-trained panellists. Moreover, the ACE inhibitory and radical scavenging activity of cooked idli prepared from 600 U alcalase/g batter showed enhancement over the control idli. Thus, alcalase treated idli shows potential to be used as a functional food.

Marine Organisms as Potential Sources of Bioactive Peptides that Inhibit the Activity of Angiotensin I-Converting Enzyme: A Review

Angiotensin I-converting enzyme (ACE) is a paramount therapeutic target to treat hypertension. ACE inhibitory peptides derived from food protein sources are regarded as safer alternatives to synthetic antihypertensive drugs for treating hypertension. Recently, marine organisms have started being pursued as sources of potential ACE inhibitory peptides. Marine organisms such as fish, shellfish, seaweed, microalgae, molluscs, crustaceans, and cephalopods are rich sources of bioactive compounds because of their high-value metabolites with specific activities and promising health benefits. This review aims to summarize the studies on peptides from different marine organisms and focus on the potential ability of these peptides to inhibit ACE activity.

Purification of Angiotensin-I-Converting Enzyme Inhibitory Peptides Derived from Camellia oleifera Abel Seed Meal Hydrolysate

China is a large country that produces Camellia oleifera Abel seed meal (COASM), a by-product of tea-seed oil, which is only used as an organic fertilizer, resulting in a serious waste of high-quality resources. The preparation of the ACE inhibitory peptide from COASM and the study of its functional properties are of practical importance in improving the comprehensive utilization of COASM. Our manuscript presents an optimized preparation of ACE inhibitory peptides with alkaline protease and enzyme kinetics parameters. Ultrafiltration, gel chromatography, and RP-HPLC purification were conducted for ACE inhibitory peptides, and peptide molecular weight distribution and amino acid composition were analyzed in the enzymolysis liquid. The following were the conditions of the optimized enzymatic hydrolysis to obtain ACE inhibitory peptides from COASM: 15 times of hydrolysis in distilled water for 3.5 h at 50°C, pH = 8.5, substrate concentration of 17 mg/g, and addition of 6% (w/w) alkaline protease. Under this condition, the peptides produced exhibited an ACE inhibition rate of 79.24%, and the reaction kinetics parameters are as follows: Km = 0.152 mg/mL and Vmax = 0.130 mg/mL·min. The majority of ACE inhibitory peptides from COASM have molecular weight below 1 kDa, and a high ACE inhibitory rate was achieved after dextran gel chromatography separation and purification (whose IC50 was 0.678 mg/mL). The hydrophobic amino acid content in this fraction reached 51.21%.

Identification and characterization of antioxidant peptides from hydrolysate of blue-spotted stingray and their stability against thermal, pH and simulated gastrointestinal digestion treatments

This study was conducted to identify and characterize antioxidant peptides from the alcalase hydrolysate of the blue-spotted stingray. Purification steps guided by ABTS cation radical (ABTS+) scavenging assay and de novo peptide sequencing produced two peptides, WAFAPA (661.3224 Da) and MYPGLA (650.3098 Da). WAFAPA (EC50 = 12.6 µM) had stronger antioxidant activity than glutathione (EC50 = 13.7 µM) and MYPGLA (EC50 = 19.8 µM). Synergism between WAFAPA and MYPGLA was detected. WAFAPA and MYPGLA surpassed carnosine in their ability to suppress H2O2-induced lipid oxidation. The peptides protected plasmid DNA and proteins from Fenton's reagent-induced oxidative damage. Thermal (25-100 °C) and pH 3-11 treatments did not alter antioxidant activity of the peptides. MYPGLA maintained its antioxidant activity after simulated gastrointestinal digestion, whereas WAFAPA showed a partial loss. The two peptides may have potential applications as functional food ingredients or nutraceuticals, whether used singly or in combination.

Characterisation of the bioactive properties and microstructure of chickpea protein-based oil in water emulsions

Legumes, such as chickpea, represent a good source of high quality proteins for which there is an increasing global consumer demand. A chickpea protein concentrate (CP) was generated by isoelectric precipitation. Protein determination, electrophoretic and gel permeation chromatographic analysis revealed that the order of CP solubility was pH 7.5 > 2.5 > 5.0. Sunflower oil in water (O/W) emulsions were generated with the CP at pH 2.5, 5.0 and 7.5. Microstructural evaluation of the emulsions using laser light-scattering particle size analysis, optical microscopy and rheological analysis showed that smaller droplet size (3.1 ± 0.2 and 1.1 ± 0.1 μm) and the highest elastic moduli (876.0 ± 3.2 and 563.5 ± 6.5 Pa) were obtained in those emulsions generated with CP at pH 2.5 and 7.5. The ferric reducing (FRAP) and oxygen radical absorbance capacity (ORAC) values of the CP emulsions ranged from 194.5 ± 19.2 to 242.4 ± 8.4 μmol Trolox Eq·g^-1 CP for FRAP at pH 2.5 and 5.0, respectively, and from 313.2 ± 2.6 to 369.0 ± 1.6 μmol Trolox eq·g^-1 CP for ORAC at pH 5.0 and 2.5, respectively. The enzyme inhibitory activity of the emulsions was generally low irrespective of the pH value (c.a. 3 and 30% inhibition for dipeptidyl peptidase IV (DPP-IV) and angiotensin converting enzyme (ACE) activity, respectively). Simulated gastrointestinal digestion (SGID) of the emulsions significantly decreased their FRAP whereas it increased their ORAC values as well as their ACE and DPP-IV inhibitory activities irrespective of the pH value of the CP. These results demonstrate the potential application of reduced fat CP-stabilized emulsions for the provision of antioxidant and enzyme inhibitory activities.

Characterisation of the in vitro bioactive properties of alkaline and enzyme extracted brewers' spent grain protein hydrolysates

Brewer's spent grain (BSG) is a co-product of the brewing industry that has been shown to contain a range of bioactive peptides encrypted within its protein sequences. Two methods were evaluated herein to generate bioactive peptides; (i) an alkaline extracted BSG protein rich fraction (BSG-PI) was hydrolysed using different combinations of proteolytic enzymes and (ii) BSG was pre-treated with carbohydrases followed by direct hydrolysis using proteolytic enzymes (BSG-DH). BSG-DH with Alcalase/Flavourzyme resulted in significantly higher (p < .05) protein yield when compared to BSG-PI (63.09 ± 0.27 and 58.90 ± 1.45%, respectively). The antioxidant activities (ORAC, FRAP and ABTS) of the BSG-PI and -DH hydrolysates differed depending on the assay and proteolytic enzyme combination preparations used for hydrolysis. Inhibition of DPP-IV by the BSG-PI hydrolysates ranged from 87.01 ± 0.15 to 89.61 ± 0.12% while inhibition by the BSG-DH hydrolysates ranged from 35.71 ± 0.72 to 85.06 ± 0.17%. A significant reduction in the release of interleukin-6 in lipopolysaccharide-stimulated RAW 264.7 cells was observed following treatment with BSG-PI hydrolysates generated with Prolyve/Protease P (58.30 ± 13.76%) and Corolase PP/Flavourzyme (48.02 ± 10.82%) when compared to untreated LPS stimulated control cells (100%). BSG-DH hydrolysates were subjected to in vitro simulated gastrointestinal digestion (SGID) which resulted in a reduction in antioxidant activity, an increase in DPP-IV inhibition and no change in the immunomodulatory activity. Ultrafiltration of selected BSG-DH hydrolysates (through 30 and 10 kDa membranes) gave some permeates with enhanced bioactivities. The results demonstrate that direct enzymatic hydrolysis of BSG is a feasible approach for the generation of bioactive peptides without the prior use of an alkali protein extraction step.

Novel Natural Angiotensin Converting Enzyme (ACE)-Inhibitory Peptides Derived from Sea Cucumber-Modified Hydrolysates by Adding Exogenous Proline and a Study of Their Structure⁻Activity Relationship

Natural angiotensin converting enzyme (ACE)-inhibitory peptides, which are derived from marine products, are useful as antihypertensive drugs. Nevertheless, the activities of these natural peptides are relatively low, which limits their applications. The aim of this study was to prepare efficient ACE-inhibitory peptides from sea cucumber-modified hydrolysates by adding exogenous proline according to a facile plastein reaction. When 40% proline (w/w, proline/free amino groups) was added, the modified hydrolysates exhibited higher ACE-inhibitory activity than the original hydrolysates. Among the modified hydrolysates, two novel efficient ACE-inhibitory peptides, which are namely PNVA and PNLG, were purified and identified by a sequential approach combining a sephadex G-15 gel column, reverse-phase high-performance liquid chromatography (RP-HPLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS), before we conducted confirmatory studies with synthetic peptides. The ACE-inhibitory activity assay showed that PNVA and PNLG exhibited lower IC₅₀ values of 8.18 ± 0.24 and 13.16 ± 0.39 μM than their corresponding truncated analogs (NVA and NLG), respectively. Molecular docking showed that PNVA and PNLG formed a larger number of hydrogen bonds with ACE than NVA and NLG, while the proline at the N-terminal of peptides can affect the orientation of the binding site of ACE. The method developed in this study may potentially be applied to prepare efficient ACE-inhibitory peptides, which may play a key role in hypertension management.

Identification and Antithrombotic Activity of Peptides from Blue Mussel (Mytilus edulis) Protein

The blue mussel (Mytilus edulis) reportedly contains many bioactive components of nutritional value. Water-, salt- and acid-soluble M. edulis protein fractions were obtained and the proteins were trypsinized. The resultant peptides were analyzed by ultra-performance liquid chromatography quadrupole time of flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS). 387 unique peptides were identified that matched 81 precursor proteins. Molecular mass distributions of the proteins and peptides were analyzed by sodium dodecyl sulfate-polyacryl amide gel electrophoresis (SDS-PAGE). The differences between the three protein samples were studied by Venn diagram of peptide and protein compositions. Toxicity, allergic and antithrombotic activity of peptides was predicted using database website and molecular docking respectively. The antithrombotic activity of enzymatic hydrolysate from water-, salt- and acid-soluble M. edulis protein were 40.17%, 85.74%, 82.00% at 5 mg/mL, respectively. Active mechanism of antithrombotic peptide (ELEDSLDSER) was also research about amino acid binding sites and interaction, simultaneously.

Exploration of the molecular interactions between angiotensin-I-converting enzyme (ACE) and the inhibitory peptides derived from hazelnut (Corylus heterophylla Fisch.)

The mechanism of action of food-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides has not been completely elucidated. In the present study, ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography, and liquid chromatography-electrospray ionization-tandem mass (LC-ESI-MS/MS) were employed for purifying and identifying the ACE inhibitory peptides from hazelnut. To understand the mode of action of these peptides, ACE inhibition kinetics, in vitro and in vivo bioavailability assays, active site analysis, and interaction between the inhibitory peptides and ACE were investigated. The results identified novel ACE inhibitory peptides Ala-Val-Lys-Val-Leu (AVKVL), Tyr-Leu-Val-Arg (YLVR), and Thr-Leu-Val-Gly-Arg (TLVGR) with IC₅₀ values of 73.06, 15.42, and 249.3 μM, respectively. All peptides inhibited the ACE activity via a non-competitive mode. The binding free energies of AVKVL, YLVR, and TLVGR for ACE were -3.46, -6.48, and -7.37 kcal/mol, respectively. The strong inhibition of ACE by YLVR may be attributed to the formation of cation-pi interactions.