Purification and characterisation of antioxidant and nitric oxide inhibitory peptides from Tilapia (Oreochromis niloticus) protein hydrolysate

Nitric oxide (NO)‐inhibitory and antioxidative activities of tilapia hydrolysates were prepared using ultrasound pretreatment at 70 W for 30 and 45 min, respectively, followed by Flavourzyme hydrolysis for 1 h. Both hydrolysates were fractionated using size exclusion chromatography on Sephadex G‐25 column and purified by RP‐HPLC. The amino acid sequence of the most potent and purified fractions was determined using LC/MS/MS. The antioxidant peptide (KAFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK, MW: 6334.49 KDa) and NO‐inhibitory peptide (AFAVIDQDKSGFIEEDELKLFLQNFSAGARAGDSDGDGKIGVDEFAALVK, MW: 6309.49 Da) produced no cytotoxicity in RAW264.7 macrophage cell lines at the concentration of 100 mg mL^?1. The purified peptides at the concentration 100 μg mL^?1 possessed antioxidative and NO‐inhibitory activities 83.0 ± 1.1% and 40.9 ± 0.2%, respectively, which were about 100 times those of their counterpart crude hydrolysates.     

Antioxidant and nitric oxide inhibitory activities of tilapia (Oreochromis niloticus) protein hydrolysate: effect of ultrasonic pretreatment and ultrasonic‐assisted enzymatic hydrolysis

Ultrasound was incorporated to processing of fish protein hydrolysate to facilitate homogenate pretreatment and enzymatic hydrolysis of tilapia (Oreochromis niloticus) muscle protein. Their effects on Flavourzyme hydrolysis and biological activities of the tilapia hydrolysate were examined. The ultrasound‐assisted hydrolysis caused reduction in degree of hydrolysis ranging from 23% to 35% relative to that of the conventional process. The 70 W ultrasound‐assisted hydrolysis process increased DPPH radical‐scavenging activity and reducing power of tilapia hydrolysate prepared from the non‐pretreatment homogenate by 33% and 45%, respectively. All hydrolysates have no cytotoxicity on RAW264.7 cell lines at the maximum concentration of 20 mg protein mL^?1. The 70 W ultrasound pretreatment at 30 and 45 min combined with conventional hydrolysis is the suitable condition for producing tilapia hydrolysate with nitric oxide inhibitory and antioxidative activities on RAW264.7 cell lines, respectively. As a result, ultrasound could be applied to enzymatic protein hydrolysis either as pretreatment or during the hydrolysis.     

Characterisation of processing wastes of Atlantic Salmon (Salmo salar) and Yellowtail Kingfish (Seriola lalandi) harvested in Australia

Atlantic Salmon (AS) and Yellowtail Kingfish (YTK) are two major commercial fish species in Australia. During food processing, waste material of 40–50% of the whole AS and YTK is generated, including the head, skin, frame, belly flap and viscera. This material is usually discarded even though it is rich in protein and fat. The aim of this study was to characterise the composition of these wastes for their potential applications. The contents of protein and fat in these wastes are 10–20% and 20–30%, respectively. Profiles of amino acids, fatty acids and minerals showed they are good sources of essential amino acids (20–30% of total amino acids), omega‐3 fatty acids (about 20% of total fatty acids) and various elements. For example, AS viscera is high in zinc (740 mg kg^?1). Molecular weight distribution of the protein was mainly between 25 and 250 kDa. The potential commercial applications of these wastes are discussed on the basis of these analyses.     

Enzymatic hydrolysis of hard‐to‐cook bean (Phaseolus vulgaris L.) protein concentrates and its effects on biological and functional properties

Inadequate postharvest handling and storage under high temperature and relative humidity conditions produce the hard‐to‐cook (HTC) defect in beans. However, these can be raw material to produce hydrolysates with functional activities. Angiotensin I‐converting enzyme (ACE) inhibitory and antioxidant capacities were determined for extensively hydrolysed proteins of HTC bean produced with sequential systems Alcalase‐Flavourzyme (AF) and pepsin–pancreatin (Pep‐Pan) at 90 min ACE inhibition expressed as IC₅₀ values were 4.5 and 6.5 mg protein per mL with AF and Pep‐Pan, respectively. Antioxidant activity as Trolox equivalent antioxidant capacity (TEAC) was 8.1 mm  mg^?1 sample with AF and 6.4 mm  mg^?1 sample with Pep‐Pan. The peptides released from the protein during hydrolysis were responsible for the observed ACE inhibition and antioxidant activities. Nitrogen solubility, emulsifying capacity, emulsion stability, foaming capacity and foam stability were measured for limited hydrolysis produced with Flavourzyme and pancreatin at 15 min. The hydrolysates exhibited better functional properties than the protein concentrate.     

Effect of limited enzymatic hydrolysis on physico‐chemical properties of soybean protein isolate‐maltodextrin conjugates

The effect of limited hydrolysis was investigated on the physico‐chemical properties of soy protein isolate–maltodextrin (SPI‐Md) conjugate. The hydrolysates at a degree of hydrolysis (DH) of 1.8% showed much higher surface hydrophobicity (H₀; 71.39 ± 3.60) than that of the SPI control (42.09 ± 2.17) and SPI‐Md conjugates (53.46 ± 2.74). Intrinsic fluorescence analysis demonstrated the unfolding of protein molecule and exposure of hydrophobic groups of SPI‐Md conjugate hydrolysates. As evidenced by far‐UV circular dichroism (CD) spectroscopy, the limited hydrolysis increased the unordered secondary structures of SPI‐Md conjugates. The denaturation temperature (T_d) of SPI‐Md conjugate was significantly increased by subsequent limited hydrolysis from 102.53 ± 0.60 °C to 108.11 ± 0.61 °C at DH 1.8%. In particular, the emulsifying activity index (EAI) was improved notably after limited hydrolysis of DH 1.8% (147.76 ± 4.39 m² g^?1) compared with that of native SPI (88.90 ± 1.44 m² g^?1) and SPI‐Md conjugate (108.97 ± 1.45 m² g^?1).     

Biochemical properties and antioxidant activity of myofibrillar protein hydrolysates obtained from patin (Pangasius sutchi)

Antioxidant activities of myofibrillar protein hydrolysates (MPH) prepared from patin (Pangasius sutchi) using papain and Alcalase^® 2.4 L with different degrees of hydrolysis (DH) were investigated. With a DH of 65.83%, the hydrolysate prepared with papain exhibited the maximum of 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical‐scavenging activity (71.14%) with a reducing power of 0.310. At a concentration of 1 mg mL^?1, the papain‐MPH exhibited a Trolox equivalent antioxidant capacity (TEAC) of 70.50 ± 1.22 μmol g^?1 protein. With a DH of 83.6%, the Alcalase‐MPH had the highest metal‐chelating activity. Low molecular weight peptides showed higher antioxidant activities than high molecular weight peptides. Both papain‐MPH and Alcalase‐MPH contained high amounts of the essential amino acids (48.71% and 48.10%, respectively) with glutamic acid, aspartic acid and lysine as the dominant amino acids. These results suggest that the protein hydrolysates derived from patin may be used as an antioxidative ingredient in both functional food and nutraceutical applications.     

Two‐stage processing of salmon backbones to obtain high‐quality oil and proteins

Traditional processing technologies for fish by‐products containing significant amounts of oils usually either give high amounts of oil or maximised solubilisation of proteins. Due to lower yields and insufficient quality, the proteins or the oil is considered as secondary products. The proposed concept combines a gentle thermal separation of oil followed by enzymatic hydrolysis of the remaining protein‐rich fraction. The first stage, thermal treatment (40 °C) of fresh salmon backbones, separated up to 85% of the oil from the raw material and gave high‐quality oil (PV = 0.2 ± 0.0 meq kg^?1, 0.16 ± 0.05% free fatty acids). Separation of a significant part of the oil gave reduced mass flow into the enzymatic stage, which then requires less enzymes and reduced energy consumption. Among the tested enzymes: Trypsin, Corolase PP and Mixture of Papain and Bromelain gave the highest yield of fish protein hydrolysates (FPH), while use of Protamex and Corolase PP resulted in FPH with the best sensory properties leading to the lowest bitterness.     

Influence of degree of hydrolysis on functional properties and angiotensin I‐converting enzyme‐inhibitory activity of protein hydrolysates from cuttlefish (Sepia officinalis) by‐products

BACKGROUND: In Tunisia the cuttlefish‐processing industry generates large amounts of solid wastes. These wastes, which may represent 35% of the original material and constitute an important source of proteins, are discarded without any attempt at recovery. This paper describes some functional properties and the angiotensin I‐converting enzyme (ACE)‐inhibitory activity of protein hydrolysates prepared by hydrolysis of cuttlefish (Sepia officinalis) by‐products with crude enzyme extract from Bacillus licheniformis NH1. RESULTS: Cuttlefish by‐product protein hydrolysates (CPHs) with different degrees of hydrolysis (DH 5, 10 and 13.5%) were prepared. All CPHs contained 750–790 g kg^?1 proteins. Solubility, emulsifying capacity and water‐holding capacity increased while fat absorption and foaming capacity decreased with increasing DH. All hydrolysates showed greater fat absorption than the water‐soluble fraction from undigested cuttlefish by‐product proteins and casein. CPHs were also analysed for their ACE‐inhibitory activity. CPH3 (DH 13.5%) displayed the highest ACE inhibition (79%), with an IC₅₀ value of 1 mg mL^?1. CONCLUSION: Hydrolysis of cuttlefish by‐product proteins with alkaline proteases from B. licheniformis resulted in a product with excellent solubility over a wide pH range and high ACE‐inhibitory activity. This study suggests that CPHs could be utilised to develop functional foods for prevention of hypertension. Copyright © 2010 Society of Chemical Industry     

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

Soy proteins are less soluble at acidic pH value, which impedes their utilisation in acidic beverages. Soy protein isolate (SPI) was hydrolysed using varying Alcalase concentrations (0.0001–2.0 U g^?1 protein) at different pHs (3.0–4.0). Degree of hydrolysis (DH) of soy protein hydrolysates (SPH) at pH 3.0, 3.5 and 4.0 were 5.0–10.7%, 2.3–6.1% and 0–5.4%, respectively, while solubilities ranged from 70.7 to 74.9%, 18.8 to 51.2% and 7.1 to 40.4%, respectively. The highest solubility (74.9%) was observed at pH 3.0 with 1.5 U Alcalase per g protein (DH = 9.2%). Emulsifying activities of SPHs at pH 3.0 and 4.0 ranged from 0.49 to 0.63 AU and 0.19 to 0.24 AU, respectively, while the emulsifying stabilities were 12.2–14.7 min and 18.7–56.0 min, respectively. The foaming capacity at pH 3.0 and 4.0 was 44.9–46.3 mL and 31.2–41.3 mL, respectively, whereas the foaming stability was 25.5–35.2 min and 12.8–15.1 min, respectively. However, hydrolysates had an insignificant effect on ACE‐I inhibitory and DPPH scavenging activities in comparison with SPI.     

Extraction and characterisation of Riceberry bran protein hydrolysate using enzymatic hydrolysis

Riceberry bran protein hydrolysate (RBPH) was prepared from bran of purple‐pigmented Riceberry rice using enzymatic hydrolysis. The effect of enzyme type (Alcalase, Flavourzyme and Neutrase) and hydrolysis time (2, 4 and 6 h) on protein content, protein yield, total phenolic content (TPC), antioxidant activities (ABTS and FRAP) and molecular weight patterns of RBPH was investigated. The enzyme type significantly (P < 0.05) affected the properties of RBPH whereas the hydrolysis time had no significant effect (P ≥ 0.05) on those properties. Flavourzyme was the most effective to increase protein yield, TPC and antioxidant activities compared to Alcalase and Neutrase. The optimal hydrolysis condition was 4 h using Flavourzyme which yielded 74.9% extracted protein. This hydrolysate contained peptides ranging from 16 to 64 kDa. The high antioxidant activity was related to negative charge peptides as shown by anion exchange chromatography. With high protein content and antioxidant properties, RBPH using Flavourzyme could be practically utilised in functional foods.     

Antioxidant activities and functional properties of soy protein isolate hydrolysates obtained using microbial proteases

Soy protein isolate (SPI) hydrolysates were prepared using microbial proteases to produce peptides with antioxidant activity. The process parameters (substrate and enzyme concentrations), hydrolysis time, functional properties and the effects of ultrafiltration were further investigated. The results showed that the soy protein isolate exhibited a 7.0‐fold increase in antioxidant activity after hydrolysis. The hydrolysis parameters, defined by the experimental design, were a substrate concentration of 90 mg mL^?1 and the addition of 70.0 U of protease per mL of reaction. The maximum antioxidant activities were observed between 120 and 180 min of hydrolysis, where the degree of hydrolysis was approximately 20.0%. The hydrolysis increased solubility of the soy protein isolate; however, the hydrolysates exhibited a tendency to decrease in the interfacial activities and the heat stability. The SPI hydrolysates fractions obtained by ultrafiltration showed that the enzymatic hydrolysis resulted in samples with homogenous size and strong antioxidant activity.     

Characterisation of protein‐rich isolates and antioxidative phenolic extracts from pale and black brewers' spent grain

Protein‐enriched isolates and co‐product fractions were obtained from sheared, pale and black brewers' spent grain (BSG) using sequential aqueous and alkaline (110 mm NaOH) extraction, followed by isoelectric precipitation at pH 3.8. A recovery of 59% of the original pale BSG protein and 15% of the black BSG protein was obtained for the final isolates. Gel permeation HPLC (GP‐HPLC) revealed that 59% of the extracted pale BSG protein and only 6% of black BSG protein had a molecular mass >10 kDa. Glutamine/glutamate and proline were the most abundant amino acids present in both isolates. Analysis of four co‐product fractions obtained during fractionation from both pale and black BSG revealed the presence of phenolics, with higher concentrations in the black BSG extracts. These fractions possessed antioxidant and free radical scavenging activity when tested using the ferric reducing ability of plasma (0.16 ± 0.01 to 4.33 ± 0.11 mg Trolox equivalents g^?1 BSG dry weight) and diphenylpicrylhydrazyl (12.85 ± 1.16% to 59.50 ± 3.47% DPPH?_sc) assays, respectively. The protein‐enriched isolates and the phenolic‐rich extracts may find use as value‐added ingredients for incorporation into conventional and functional foods.     

Enzymatic hydrolysis of by‐products from the fish‐filleting industry; chemical characterisation and nutritional evaluation

Fish frames without heads from Atlantic cod and Atlantic salmon were proteolysed with the industrial enzymes neutrase®, alcalase® and pepsin for 1, 15, 30, 45, 60, 90 and 120 min. After 120 min of hydrolysis, salmon treated with alcalase and cod treated with pepsin yielded significantly (p < 0.05) higher protein recoveries (67.6 and 64% respectively) as compared to salmon treated with neutrase or pepsin and cod treated with neutrase or alcalase (53–62%). To minimise bitterness in the fish hydrolysates, kojizyme™ was added after 120 min of pre‐hydrolysis with alcalase, and the hydrolysis was run for additional times of 120, 240, 360, 480, 600 and 720 min. Protein recovery did not change significantly during the hydrolysis with kojizyme, but the degree of hydrolysis increased significantly (p < 0.01) in both the cod and salmon hydrolysates. A hydrolysate from cod treated with alcalase (150 min) followed by treatment with kojizyme (510 min) was produced. The final hydrolysate was freeze‐dried to a fish protein hydrolysate (FPH) and chemically characterised. The nutritional value of the FPH was established in an experiment with rats. Inclusion of 10% FPH‐N showed significantly (p < 0.05) higher nutritional value as compared to rats fed higher inclusion levels of FPH. © 2000 Society of Chemical Industry     

Enzymatic hydrolysis of heated whey: iron-binding ability of peptides and antigenic protein fractions

This study evaluated the influence of various enzymes on the hydrolysis of whey protein concentrate (WPC) to reduce its antigenic fractions and to quantify the peptides having iron-binding ability in its hydrolysates. Heated (for 10 min at 100°C) WPC (2% protein solution) was incubated with 2% each of Alcalase, Flavourzyme, papain, and trypsin for 30, 60, 90, 120, 150, 180, and 240 min at 50°C. The highest hydrolysis of WPC was observed after 240 min of incubation with Alcalase (12.4%), followed by Flavourzyme (12.0%), trypsin (10.4%), and papain (8.53%). The nonprotein nitrogen contents of WPC hydrolysate followed the hydrolytic pattern of whey. The major antigenic fractions (β-lactoglobulin) in WPC were degraded within 60 min of its incubation with Alcalase, Flavourzyme, or papain. Chromatograms of enzymatic hydrolysates of heated WPC also indicated complete degradation of β-lactoglobulin, α-lactalbumin, and BSA. The highest iron solubility was noticed in hydrolysates derived with Alcalase (95%), followed by those produced with trypsin (90%), papain (87%), and Flavourzyme (81%). Eluted fraction 1 (F-1) and fraction 2 (F-2) were the respective peaks for the 0.25 and 0.5 M NaCl chromatographic step gradient for analysis of hydrolysates. Iron-binding ability was noticeably higher in F-1 than in F-2 of all hydrolysates of WPC. The highest iron contents in F-1 were observed in WPC hydrolysates derived with Alcalase (0.2 mg/kg), followed by hydrolysates derived with Flavourzyme (0.14 mg/kg), trypsin (0.14 mg/kg), and papain (0.08 mg/kg). Iron concentrations in the F-2 fraction of all enzymatic hydrolysates of WPC were low and ranged from 0.03 to 0.05 mg/kg. Fraction 1 may describe a new class of iron chelates based on the reaction of FeSO₄·7H₂O with a mixture of peptides obtained by the enzymatic hydrolysis of WPC. The chromatogram of Alcalase F-1 indicated numerous small peaks of shorter wavelengths, which probably indicated a variety of new peptides with greater ability to bind with iron. Alcalase F-1 had higher Ala (18.38%), Lys (17.97%), and Phe (16.58%) concentrations, whereas the presence of Pro, Gly, and Tyr was not detected. Alcalase was more effective than other enzymes at producing a hydrolysate for the separation of iron-binding peptides derived from WPC.     

Effects of microwave and ultrasound pretreatments on enzymolysis of milk protein concentrate with different enzymes

Milk protein concentrate was pretreated either by microwave irradiation or by ultrasound before initiation of 3‐h enzymatic hydrolysis. The duration of pretreatment ranged from 1 to 8 min at a power level of 800 W, with the control not being subjected to any pretreatment, and five enzymes (Alcalase, Trypsin, Neutrase, Alkaline Protease and Flavourzyme) were employed. The effects of microwave and ultrasound pretreatments on the kinetics and degree of hydrolysis, protein solubility, bitterness and angiotensin‐converting enzyme inhibitory activity were evaluated. Pretreatments increased the degree of hydrolysis and stabilised the solubility of the hydrolysates but could not significantly reduce bitterness of the hydrolysates The angiotensin‐converting enzyme inhibitory activity of the hydrolysates were improved with 5‐min ultrasound‐pretreated Neutrase hydrolysates giving IC₅₀ value of 0.23 mg mL^?1. Kinetic parameters showed improved catalytic efficiencies. Pretreatments of milk protein concentrates with either microwave or ultrasound significantly improve the bioactivity and functional characteristics of the resulting hydrolysates.     

Use of food-grade proteases to recover umami protein–peptide mixtures from rice middlings

The effects of enzymatic hydrolysis induced by food-grade exo- plus endo-proteases (i.e. Umamizyme and Flavourzyme) on the sensory characteristics and functional properties of rice middlings were investigated. Enzymatic hydrolysis was confirmed by sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE), by monitoring the rate of hydrolysis with the Coefficient of Protein Degradation (CPD). The presence of medium-low size polypeptides at the end point of 24 h was detected, resulting from 24.84 ± 1.28 % and 67.04 ± 0.55 % hydrolysis for Flavourzyme and Umamyzyme, respectively. Sensory and functional properties, including emulsifying and foaming properties, were evaluated on hydrolysates obtained after 24 h incubation. The sensory analysis described the umami taste as the most intense attribute for all the products and good emulsifying and foaming properties were observed, mainly in Umamizyme hydrolysates. Then the hydrolysis procedure here described could be convenient to provide ingredients characterized by a good taste profile and by functional properties useful for industrial food processing, storage and consumption.     

Antioxidant function of tea dregs protein hydrolysates in liposome–meat system and its possible action mechanism

Tea dregs possess abundant proteins, and the objective of this study was to investigate the antioxidant activity of tea dregs protein hydrolysate with limited hydrolysis by protamex and its possible action mechanism. Tea dregs protein was hydrolysed by alcalase, protamex or neutrase. The hydrolysis condition was optimised, and the hydrolysate was characterised for 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) radical‐scavenging activity, hydroxyl radical‐scavenging activity and antioxidant activity in linoleic acid (LA) system and in chicken products. Tea dregs protein hydrolysate (TDPH) was formulated (0.1%, 0.5%, 1.0%, w/w) into chicken products to determine in situ antioxidant efficacy. Thiobarbituric acid‐reactive substances (TBARS) and peroxide value (POV) formed in chicken products during storage (4 °C, 0–7 days) were analysed. Results showed that the optimum hydrolysis condition was at 50 °C, pH 7.0 for 20 min, and the concentration of tea dregs protein was 1.5%; ratio of protamex to substrate was 6000 U g^?1. The radical‐scavenging ratio of TDPH to 1,1‐diphenyl‐2‐picryl hydrazyl (DPPH) was 90.30% at the concentration of 0.1 mg mL^?1 and that to hydroxyl radical was 65.18% at the concentration of 1.0 mg mL^?1. Moreover, it also showed strong antioxidant activity both in linoleic acid (LA) system and in chicken products. The molecular weight distribution of tea dregs hydrolysates was determined by nanofiltration tubular membrane, and the protein hydrolysates with molecular weight above 8000 Da had more effective antioxidant activity. The radical‐scavenging activities to DPPH and hydroxyl radical were 85.72% at 0.1 mg mL^?1 and 71.52% at 1.0 mg mL^?1, respectively. These findings suggest that the enzymatic hydrolysate of tea dregs protein probably possesses the specific peptides/amino acids which could stabilise or terminate the radicals through donating hydrogen. In addition, the hydrolysate could form a physical barrier around the fat droplets.     

Antioxidant and biochemical properties of protein hydrolysates prepared from Silver carp (Hypophthalmichthys molitrix)

The antioxidant and biochemical properties of enzymatically hydrolyzed silver carp (Hypophthalmichthys molitrix) protein were studied. The molecular weight of the main peaks of the hydrolysates by both Alcalase and Flavourzyme was lower than 5000 Da. The hydrolysates treated by Alcalase for ?1.5 h (hydrolysis time) showed that the relative proportion of <1000 Da fraction was more than 60%. For the biochemical properties, hydrolysis by both enzymes increased protein solubility to above 75% over a wide pH range; and when the hydrolysis time was prolonged (>3 h), the colour of the hydrolysates turned yellowish. The protein hydrolysates exhibited significant hydroxyl radical-scavenging activity and inhibited linoleic acid peroxidation. For Alcalase treatment, the hydroxyl radical-scavenging activity and the inhibition of linoleic acid peroxidation of hydrolysates appeared to reach a maximum level for 1.5, 2.0 h of hydrolysis, respectively; and their antioxidant activity was close to that of α-tocopherol in a linoleic acid emulsion system, and carnosine in the 2-deoxyribose oxidation system. The hydrolysate with lower molecular weight distribution possessed stronger Fe²⁺ chelation ability at a sample concentration of 5.0 mg/mL. The results suggested that the antioxidant activity of silver carp protein hydrolysates were related to its degree of hydrolysis (DH), hydrolysis time and molecular weight.     

ACE-inhibitory activity of tilapia protein hydrolysates

Fish processing wastes can be used for preparing bioactive peptides with various functionalities. Our objective was to evaluate the in vitro angiotensin converting enzyme (ACE) inhibitory activity of tilapia protein hydrolysates and its corresponding fractionates. Tilapia protein was alkali-solubilised at pH 11.0 and recovered at pH 5.5 to obtain a stable substrate. This substrate was hydrolysed using two enzymes, Cryotin-F or Flavourzyme, to 7.5% and 25% degree of hydrolysis (DH). The hydrolysates were ultra-filtered into three fractions: >30 kDa fraction, 10–30 kDa fraction, and <10 kDa fractions. Both hydrolysates and fractionates were tested for ACE inhibition. Results showed that both Cryotin and Flavourzyme hydrolysates with 25% DH gave maximum ACE inhibitory activity. Low MW peptides showed higher ACE inhibition than high MW peptides. The inhibitory activity of fractionates was lower than that of the corresponding hydrolysates, possibly due to separation and removal of synergistic peptides by ultrafiltration. Amongst fractionates, all the 7.5% DH Cryotin fractions and 25% DH Flavourzyme fractions exhibited optimum % ACE inhibition. The results of this research could be used for optimising enzyme parameters to obtain peptides from tilapia with optimum in vitro ACE inhibitory activity.     

A new nanofibrillated and hydrophobic grafted dietary fibre derived from bamboo leaves: enhanced physicochemical properties and real adsorption capacity of oil

Dietary fibre (DF) has been used for enhancing health benefits for centuries. In this study, an innovative nanofibrillated cellulose (NFC) was obtained by the combined application of high‐density steam flash‐explosion and enzymatic hydrolysis of bamboo leaves. The NFC prepared in this study was characterised by long, well‐defined and distinct NFC fibres, exhibiting excellent functional properties (water retention capacity: 20 g water g^?1, swelling capacity: 97 mL g^?1, oil‐holding capacity: 13 g oil g^?1, and higher adsorption of bile acids and cholesterol). Octenyl succinic anhydride (OSA) was further successfully grafted onto the NFC to improve its hydrophobicity. Thus, the oil‐holding capacity of the NFC reached 18.5 g oil g^?1 and the adsorption of bile acids and cholesterol increased twofold. A gastrointestinal digestion experiment further showed that the nanofibrillated and hydrophobic grafted dietary fibre represented a high‐quality dietary supplement providing enhanced health benefits, highlighted by the strong ability to absorb oil. These results indicate that the OSA‐NFC has a great potential for use as a functional ingredient in food products.