Neuroprotective Effect of ß-secretase Inhibitory Peptide from Pacific Hake (Merluccius productus) Fish Protein Hydrolysate.

BACKGROUND: Various methodologies have been employed for the therapeutic interpolation of the progressive brain disorder Alzheimer's disease. Thus, ß-secretase inhibition is significant to prevent disease progression in the early stages. OBJECTIVE: This study seeks to purify and characterize a novel ß-secretase inhibitory peptide from Pacific hake enzymatic hydrolysate. METHODS: A potent ß-secretase inhibitory peptide was isolated by sequential purifications using Sephadex G-25 column chromatography and octadecylsilane (ODS) C18 reversed-phase HPLC. A total of seven peptides were synthesized using the isolated peptide sequences. SH-SY5Y cells stably transfected with the human ''Swedish'' amyloid precursor protein (APP) mutation APP695 (SH-SY5YAPP695swe) were used as an in-vitro model system to investigate the effect of Leu-Asn peptide on APP processing. RESULTS: The ß-secretase inhibitory activity (IC50) of the purified peptide (Ser-Leu-Ala-Phe-Val-Asp- Asp-Val-Leu-Asn) from fish protein hydrolysate was 18.65 µM and dipeptide Leu-Asn was the most potent ß-secretase inhibitor (IC50 value = 8.82 µM). When comparing all the seven peptides, the inhibition pattern of Leu-Asn dipeptide was found to be competitive by Lineweaver-Burk plot and Dixon plot (Ki value = 4.24 µM). The 24 h treatment with Leu-Asn peptide in SH-SY5Y cells resulted in reducing the ß-amyloid (Aß) production in a dose-dependent manner. CONCLUSION: Therefore, the results of this study suggest that ß-secretase inhibitory peptides derived from marine organisms could be potential candidates to develop nutraceuticals or pharmaceuticals as antidementia agents.

Transepithelial transport across Caco-2 cell monolayers of angiotensin converting enzyme (ACE) inhibitory peptides derived from simulated in vitro gastrointestinal digestion of cooked chicken muscles.

Korat-chicken breast and thigh were subjected to heating at 70, 100 or 121 °C for 30 min and simulated in vitro gastrointestinal digestion. At 70 or 100 °C heating, digests of breast possessed higher ACE inhibitory activity than those of thigh. The highest ACE inhibitory activity was found in the digest of breast cooked at 70 °C (B/H-70), whereas breast heated at 121 °C (B/H-121) exhibited the lowest. The 1-kDa permeate of the B/H-70 digest revealed higher permeability through colorectal adenocarcinoma monolayers and ACE inhibitory activity than did B/H-121. Among nine transported peptides, APP derived from myosin showed the highest ACE inhibition, with a non-competitive characteristic (Ki 0.93 µM). Molecular docking showed that APP interacts with ACE via hydrogen bonds, electrostatic and van der Waals interactions. In conclusion, mild thermal treatment of chicken breast resulted in a higher amount of transported peptides, exerting higher ACE inhibitory activity, which could lead to potential health benefits.

Production and assessment of Pacific hake (Merluccius productus) hydrolysates as cryoprotectants for frozen fish mince.

The aim of this study was to investigate application of fish protein hydrolysates (FPHs) as cryoprotectants for cod fish mince subjected to freeze-thaw abuse. Response surface methodology revealed little difference in cryoprotectant ability between FPHs produced from Pacific hake muscle within the range of conditions studied, namely Flavourzyme® enzyme/substrate ratio (E/S 1-4%), time (1-6h) and pH (5-7). When added at 4% or higher concentrations, FPH minimized expressible moisture and cook loss, while maximizing salt extractable protein from freeze-thaw abused fish mince, providing similar or better cryoprotection compared to an 8% sucrose-sorbitol blend, and a stabilizing effect of FPH on myosin was observed by differential scanning calorimetry. Sensory evaluation showed that addition of 8% FPH in fish ball products increased the perception of fishiness, saltiness, bitterness and firmness while decreasing moistness. FPH could be a viable alternative to the sugar-based cryoprotectants currently used for frozen fish products.

Optimization of vitamins A and D3 loading in re-assembled casein micelles and effect of loading on stability of vitamin D3 during storage.

The objectives of this study were to apply response surface methodology to optimize fat-soluble vitamin loading in re-assembled casein micelles, and to evaluate vitamin D stability of dry formulations during ambient or accelerated storage and in fortified fluid skim milk stored under refrigeration. Optimal loading of vitamin A (1.46-1.48mg/100mgcasein) was found at 9.7mM phosphate, 5.5mM citrate and 30.0mM calcium, while optimal loading of vitamin D (1.38-1.46mg/100mg casein) was found at 4.9mM phosphate, 4.0mM citrate and 26.1mM calcium. In general, more vitamin D was retained in vitamin D-re-assembled casein micelles than control powders during storage, while vitamin D loss was not different for vitamin D-re-assembled casein micelles and control fortified milks after 21days of refrigerated storage with light exposure. In conclusion, re-assembled casein micelles with high loading efficiency show promise for improving vitamin D stability during dry storage.

Investigation into the bioavailability of milk protein-derived peptides with dipeptidyl-peptidase IV inhibitory activity using Caco-2 cell monolayers.

In recent years, peptides derived from a variety of dietary proteins have been reported to exhibit inhibitory activity against the dipeptidyl-peptidase IV (DPP-IV) enzyme, a target in the management of type 2 diabetes. While much attention has been given to the production and identification of peptides with DPP-IV inhibitory activity from food proteins, particularly dairy proteins, little is known on the bioavailability of these molecules. In this study, the stability and transport of five previously identified milk-derived peptides (LKPTPEGDL, LPYPY, IPIQY, IPI and WR) and a whey protein isolate (WPI) digest with DPP-IV-inhibitory activity were investigated using Caco-2 cell monolayers as a model system for human intestinal absorption. Even though a small percentage (ranging from 0.05% for LPYPY to 0.47% for WR) of the bioactive peptides added to the apical side was able to cross the monolayer intact, all five peptides investigated were susceptible to peptidase action during the transport study. Conversely, only minor changes to the WPI digest composition were observed. Determination of the DPP-IV inhibitory activity of the peptides and amino acids identified in the apical and basolateral solutions showed that most degradation products were less effective at inhibiting DPP-IV than the peptide they originated from. Findings from this research suggest that the susceptibility of food-derived DPP-IV inhibitory peptides to degradation by intestinal brush border membrane enzymes may alter their biological activity in vivo. Further research should be conducted to enhance the bioavailability of DPP-IV inhibitory peptides.

Household Consumption of Thiamin-Fortified Fish Sauce Increases Erythrocyte Thiamin Concentrations among Rural Cambodian Women and Their Children Younger Than 5 Years of Age: A Randomized Controlled Efficacy Trial.

OBJECTIVES: To assess whether ad libitum consumption of thiamin-fortified fish sauce over 6 months yields higher erythrocyte thiamin diphosphate concentrations (eTDP) among women of childbearing age and their children aged 12-59 months compared with control sauce containing no thiamin. STUDY DESIGN: In this double-blind, randomized controlled efficacy trial, 276 nonpregnant, nonlactating women (18-45 years of age) and their families in Prey Veng, Cambodia, were randomized to receive 1 of 3 fish sauce formulations: low thiamin concentration (low, 2 g/L), high thiamin concentration (high, 8 g/L), or a control (no thiamin) fish sauce. Baseline (t = 0) and endline (t = 6 months) eTDP were measured with the use of high-performance liquid chromatography with a fluorescence detector. RESULTS: Fish sauce consumption did not differ between treatment groups (P = .19). In intent-to-treat analysis, women's baseline-adjusted endline eTDP (mean; 95% CI) was higher among women in the low (259; 245-274 nmol/L) and high (257; 237-276 nmol/L) groups compared with control (184; 169-198 nmol/L; P < .001); low and high groups did not differ (P = .83). Similarly, children's baseline-adjusted eTDP was higher in the low (259; 246-271 nmol/L) and high (257; 243-270 nmol/L) groups compared with control (213; 202-224 nmol/L; P < .001). CONCLUSION: Fortified fish sauce appears to be an efficacious means of improving biochemical thiamin status in nonpregnant, nonlactating women and their children (1-5 years of age) living in rural Cambodia. TRIAL REGISTRATION: ClinicalTrials.gov: NCT02221063.

Perinatal Consumption of Thiamine-Fortified Fish Sauce in Rural Cambodia: A Randomized Clinical Trial.

IMPORTANCE: Infantile beriberi, a potentially fatal disease caused by thiamine deficiency, remains a public health concern in Cambodia and regions where thiamine-poor white rice is a staple food. Low maternal thiamine intake reduces breast milk thiamine concentrations, placing breastfed infants at risk of beriberi. OBJECTIVE: To determine if consumption of thiamine-fortified fish sauce yields higher erythrocyte thiamine diphosphate concentrations (eTDP) among lactating women and newborn infants and higher breast milk thiamine concentrations compared with a control sauce. DESIGN, SETTING, AND PARTICIPANTS: In this double-blind randomized clinical trial, 90 pregnant women were recruited in the Prey Veng province, Cambodia. The study took place between October 2014 and April 2015. INTERVENTIONS: Women were randomized to 1 of 3 groups (n = 30) for ad libitum fish sauce consumption for 6 months: control (no thiamine), low-concentration (2 g/L), or high-concentration (8 g/L) fish sauce. MAIN OUTCOMES AND MEASURES: Maternal eTDP was assessed at baseline (October 2014) and endline (April 2015). Secondary outcomes, breast milk thiamine concentration and infant eTDP, were measured at endline. RESULTS: Women's mean (SD) age and gestational stage were 26 (5) years and 23 (7) weeks, respectively. April 2015 eTDP was measured among 28 women (93%), 29 women (97%), and 23 women (77%) in the control, low-concentration, and high-concentration groups, respectively. In modified intent-to-treat analysis, mean baseline-adjusted endline eTDP was higher among women in the low-concentration (282nM; 95% CI, 235nM to 310nM) and high-concentration (254nM; 95% CI, 225nM to 284nM) groups compared with the control group (193nM; 95% CI, 164nM to 222M; P < .05); low-concentration and high-concentration groups did not differ (P = .19). Breast milk total thiamine concentrations were 14.4 µg/dL for the control group (95% CI, 12.3 µg/dL to 16.5 µg/dL) (to convert to nanomoles per liter, multiply by 29.6); 20.7 µg/dL for the low-concentration group (95% CI, 18.6 µg/dL to 22.7 µg/dL ); and 17.7 µg/dL for the high-concentration group (95% CI, 15.6 µg/dL to 19.9 µg/dL). Mean (SD) infant age at endline was 16 (8) weeks for the control group, 17 (7) weeks for the low-concentration group, and 14 (8) for the high-concentration group. Infant eTDP was higher among those in the high-concentration group (257nM; 95% CI, 222nM to 291nM; P < .05) compared with the low-concentration (212nM; 95% CI, 181nM to 244nM) and control (187nM; 95% CI, 155nM to 218nM) groups. CONCLUSIONS AND RELEVANCE: Compared with women in the control group, women who consumed thiamine-fortified fish sauce through pregnancy and early lactation had higher eTDP and breast milk thiamine concentrations and their infants had higher eTDP, which was more pronounced in the high group. Thiamine-fortified fish sauce has the potential to prevent infantile beriberi in this population. TRIAL REGISTRATION: Clinicaltrials.gov Identifier: NCT02221063.

Identification and characterization of alpha-I-proteinase inhibitor from common carp sarcoplasmic proteins.

Purification of proteinase inhibitor from common carp (Cyprinus carpio) sarcoplasmic proteins resulted in 2.8% yield with purification fold of 111. Two inhibitors, namely inhibitor I and II, exhibited molecular mass of 47 and 52 kDa, respectively, based on non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both inhibitors I and II were identified to be alpha-1-proteinase inhibitor (α1-PI) based on LC-MS/MS. They were glycoproteins and molecular mass after peptide-N-glycosidase F treatment was 38 and 45 kDa, respectively. The N-glycosylation sites of both inhibitors were determined to be at N214 and N226. The inhibitors specifically inhibited trypsin. The common carp α1-PI showed high thermal stability with denaturation temperatures of 65.43 and 73.31 °C, which were slightly less than those of ovomucoid. High stability toward NaCl was also evident up to 3M. The common carp α1-PI effectively reduced autolytic degradation of bigeye snapper surimi at the concentration as low as 0.025%.

Effect of high intensity ultrasound on transglutaminase-catalyzed soy protein isolate cold set gel.

The effects of high intensity ultrasound (HIU, 105-110 W/cm(2) for 5 or 40 min) pre-treatment of soy protein isolate (SPI) on the physicochemical properties of ensuing transglutaminase-catalyzed soy protein isolate cold set gel (TSCG) were investigated in this study. The gel strength of TSCG increased remarkably from 34.5 to 207.1 g for TSCG produced from SPI with 40 min HIU pre-treatment. Moreover, gel yield and water holding capacity also increased after HIU pre-treatments. Scanning electron microscopy showed that HIU of SPI resulted in a more uniform and denser microstructure of TSCG. The content of free sulfhydryl (SH) groups was higher in HIU TSCG than non-HIU TSG, even though greater decrease of the SH groups present in HIU treated SPI was observed when the TSCG was formed, suggesting the involvement of disulfide bonds in gel formation. Protein solubility of TSCG in both denaturing and non-denaturing solvents was higher after HIU pretreatment, and changes in hydrophobic amino acid residues as well as in polypeptide backbone conformation and secondary structure of TSCG were demonstrated by Raman spectroscopy. These results suggest that increased inter-molecular ε-(γ-glutamyl) lysine isopeptide bonds, disulfide bonds and hydrophobic interactions might have contributed to the HIU TSCG gel network. In conclusion, HIU changed physicochemical and structural properties of SPI, producing better substrates for TGase. The resulting TSCG network structure was formed with greater involvement of covalent and non-covalent interactions between SPI molecules and aggregates than in the TSCG from non-HIU SPI.

Determination of Sudan I in paprika powder by molecularly imprinted polymers-thin layer chromatography-surface enhanced Raman spectroscopic biosensor.

Sudan I is a carcinogenic and mutagenic azo-compound that has been utilized as a common adulterant in spice and spice blends to impart a desirable red color to foods. A novel biosensor combining molecularly imprinted polymers (MIPs), thin layer chromatography (TLC) and surface enhanced Raman spectroscopy (SERS) could determine Sudan I levels in paprika powder to 1 ppm (or 2 ng/spot). Sudan I spiked paprika extracts (spiking levels: 0, 1, 5, 10, 40, 70 and 100 ppm) were prepared. Sudan I imprinted polymers were synthesized by employing the interaction between Sudan I (template) and methacrylic acid (functional monomer), followed by washing to remove Sudan I leaving the Sudan I-binding sites exposed. MIPs were used as a stationary phase for TLC and could selectively retain Sudan I at the original spot with little interference. A gold colloid SERS substrate could enhance Raman intensity for Sudan I in this MIP-TLC system. Principal component analysis plot and partial least squares regression (R(2)=0.978) models were constructed and a linear regression model (R(2)=0.983) correlated spiking levels (5, 10, 40, 70 and 100 ppm) with the peak intensities (721 cm(-1)) of Sudan I SERS spectra. Both separation (30-40s) and detection (1s or 0.1s) were extremely fast by using both commercial bench-top and custom made portable Raman spectrometers. This biosensor can be applied as a rapid, low-cost and reliable tool for screening Sudan I adulteration in foods.

Comparison of the susceptibility of porcine and human dipeptidyl-peptidase IV to inhibition by protein-derived peptides.

The enzyme dipeptidyl-peptidase IV (DPP-IV) is recognized to be a promising target for the management of type 2 diabetes. Over the last decade, numerous synthetic molecules and more recently, peptides from dietary proteins, have been reported to be able to inhibit DPP-IV activity. Most studies that have investigated the in vitro effect of these inhibitors have used porcine or human DPP-IV. Although structurally alike, it is unclear whether these two species display similar inhibition patterns. Therefore, the objective of this study was to compare the effects of protein-derived peptides on the activity of porcine and recombinant human DPP-IV. The two species showed different inhibition susceptibility to 43 of the 62 peptide sequences investigated. While 37 protein-derived peptides were more effective at inhibiting the porcine DPP-IV, only six caused a stronger inhibition of the activity of the human enzyme. Although the peptides WR, IPIQY and WCKDDQNPHS were found to be among the most potent inhibitors of both species, the inhibitory effect was greater on the porcine enzyme than on human DPP-IV (αKi or Ki=11.5, 13.4, 13.3 µM and 31.4, 28.2, 75.0 µM for porcine and human DPP-IV, respectively). Investigation into the mode of action of the most effective inhibitory peptides revealed that both species were inhibited in a similar manner by short fragments (≤5 amino acid residues), but that some of the longer peptides acted differently on the enzymes. This study shows that porcine DPP-IV is generally inhibited with greater potency by protein-derived peptides than is the human enzyme.

Poor thiamin and riboflavin status is common among women of childbearing age in rural and urban Cambodia.

BACKGROUND: Thiamin deficiency in infancy is the underlying cause of beriberi, which can be fatal without rapid treatment. Reports of thiamin deficiency are common in Cambodia; however, population representative data are unavailable. Because B-complex vitamin deficiencies commonly occur in combination, riboflavin was also investigated. OBJECTIVE: We determined the biomarker status of thiamin and riboflavin in women of childbearing age in rural and urban Cambodia. METHODS: We measured thiamin (erythrocyte thiamin diphosphate; TDP) and riboflavin (erythrocyte glutathione reductase activity coefficient; EGRac) status in a representative sample of Cambodian women (aged 20-45 y) in urban Phnom Penh (n = 146) and rural Prey Veng (n = 156), Cambodia, and, for comparison purposes, in a convenience sample of women in urban Vancouver, British Columbia, Canada (n = 49). RESULTS: Thiamin insufficiency (TDP ≤ 90 nmol/L) was common among both urban (39%) and rural (59%) Cambodian women (P < 0.001), whereas <20% of Vancouver women were thiamin insufficient (P < 0.001). The prevalence of suboptimal and deficient riboflavin status (EGRac ≥ 1.3) was 89%, 92%, and 70% among women in Phnom Penh, Prey Veng, and Vancouver, respectively (P < 0.001). CONCLUSIONS: Suboptimal status of both thiamin and riboflavin were common in Cambodian women, with substantially higher rates among women living in rural Prey Veng than in urban Phnom Penh. Strategies may be needed to improve the thiamin and riboflavin status of women in Cambodia. The unexpected finding of high riboflavin inadequacy status in Vancouver women warrants further investigation.

Detection of melamine in milk using molecularly imprinted polymers-surface enhanced Raman spectroscopy.

A novel biosensor combining molecularly imprinted polymers and surface-enhanced Raman spectroscopy (MIPs-SERS) determines melamine in whole milk. MIPs were synthesized by bulk polymerization of melamine (template), methacrylic acid (functional monomer), ethylene glycol dimethacrylate (cross-linking agent) and 2,2'-azobisisobutyronitrile (initiator). Static and kinetic adsorption tests validated the use of MIPs to efficiently separate and enrich melamine from whole milk. Silver dendrite nanostructure served as SERS-active substrate for signal collection. Principal component analysis and hierarchical cluster analysis segregated Raman signatures of whole milk samples with different melamine concentrations. Regression models showed a good linear relationship (R(2)=0.93) between the height of melamine SERS band (at 703cm(-1)) and melamine concentration in the range from 0.005mmolL(-1) to 0.05mmolL(-1). The limit of detection and limit of quantification were 0.012mmolL(-1) and 0.039mmolL(-1), confirming the high sensitivity of this biosensor to accurately determine melamine in whole milk. Simple sample pretreatment reduced full analysis time to determine melamine in whole milk to less than 20min.

Detection and quantification of chloramphenicol in milk and honey using molecularly imprinted polymers: Canadian penny-based SERS nano-biosensor.

We integrated molecularly imprinted polymers with surface-enhanced Raman spectroscopy (MIPs-SERS) to develop an innovative nano-biosensor for the determination of chloramphenicol (CAP) in milk and honey products. Template molecule (CAP), functional monomer (acrylamide), cross-linking agent (ethylene glycol dimethacrylate), initiator (2,2'-azobis(isobutyronitrile)), and porogen (methanol) were employed to form MIPs via "dummy" precipitation polymerization. Static and kinetic studies validated the specific selectivity of MIPs toward CAP over nonimprinted polymers (imprinting factor >4). Canadian penny-based silver nano-structure was synthesized as SERS-active substrate for determination of CAP in food matrices. Collected spectra were processed by principal component analysis to differentiate various concentrations of CAP in foods. Partial least squares regression models showed good prediction values (R > 0.9) of actual spiked contents (0, 0.1, 0.5, 1, 5 ppm) of CAP in milk and honey. This developed nano-biosensor is low cost, requires little sample pretreatment, and can provide reliable detection of trace level of chemical hazards in food systems within a total of 15 min.

Peptide array on cellulose support--a screening tool to identify peptides with dipeptidyl-peptidase IV inhibitory activity within the sequence of α-lactalbumin.

The inhibition of the enzyme dipeptidyl-peptidase IV (DPP-IV) is an effective pharmacotherapeutic approach for the management of type 2 diabetes. Recent findings have suggested that dietary proteins, including bovine α-lactalbumin, could be precursors of peptides able to inhibit DPP-IV. However, information on the location of active peptide sequences within the proteins is far from being comprehensive. Moreover, the traditional approach to identify bioactive peptides from foods can be tedious and long. Therefore, the objective of this study was to use peptide arrays to screen α-lactalbumin-derived peptides for their interaction with DPP-IV. Deca-peptides spanning the entire α-lactalbumin sequence, with a frame shift of 1 amino acid between successive sequences, were synthesized on cellulose membranes using "SPOT" technology, and their binding to and inhibition of DPP-IV was studied. Among the 114 α-lactalbumin-derived decamers investigated, the peptides 60WCKDDQNPHS69 (αK(i) = 76 µM), 105LAHKALCSEK114 (K(i) = 217 µM) and 110LCSEKLDQWL119 (K(i) = 217 µM) were among the strongest DPP-IV inhibitors. While the SPOT- and traditionally-synthesized peptides showed consistent trends in DPP-IV inhibitory activity, the cellulose-bound peptides' binding behavior was not correlated to their ability to inhibit the enzyme. This research showed, for the first time, that peptide arrays are useful screening tools to identify DPP-IV inhibitory peptides from dietary proteins.

Marine actinobacteria: an important source of bioactive natural products.

Marine environment is largely an untapped source for deriving actinobacteria, having potential to produce novel, bioactive natural products. Actinobacteria are the prolific producers of pharmaceutically active secondary metabolites, accounting for about 70% of the naturally derived compounds that are currently in clinical use. Among the various actinobacterial genera, Actinomadura, Actinoplanes, Amycolatopsis, Marinispora, Micromonospora, Nocardiopsis, Saccharopolyspora, Salinispora, Streptomyces and Verrucosispora are the major potential producers of commercially important bioactive natural products. In this respect, Streptomyces ranks first with a large number of bioactive natural products. Marine actinobacteria are unique enhancing quite different biological properties including antimicrobial, anticancer, antiviral, insecticidal and enzyme inhibitory activities. They have attracted global in the last ten years for their ability to produce pharmaceutically active compounds. In this review, we have focused attention on the bioactive natural products isolated from marine actinobacteria, possessing unique chemical structures that may form the basis for synthesis of novel drugs that could be used to combat resistant pathogenic microorganisms.

Identification by GeLC-MS/MS of trypsin inhibitor in sarcoplasmic proteins of three tropical fish and characterization of their inhibitory properties.

UNLABELLED: Sarcoplasmic proteins from 3 fish species were fractionated by 50% to 70% ammonium sulfate precipitation. Lyophilized fractionated sarcoplasmic proteins of threadfin bream (TB-SP), bigeye snapper (BS-SP), and yellow croaker (YC-SP) showed 80% to 92% trypsin inhibitory activity. Trypsin inhibitory activity staining gel electrophoresis revealed bands at 32, 33, 37, 45, 48, and 50 kDa for the 3 species, and a band at 95 kDa was observed for TB-SP and YC-SP. Alpha-1-antitrypsin with molecular mass of 45 to 50 kDa was identified in YC-SP by gel-based liquid chromatography-tandem mass spectrometry (GeLC-MS/MS). Other major protein bands appeared on trypsin activity staining included phosphorylase, glyceraldehyde-3-phosphate dehydrogenase, and creatine kinase with molecular mass of 95 and 35 to 40 kDa, respectively. But, these 3 proteins did not show true trypsin inhibitory activity. Trypsin inhibitory activity of fractionated sarcoplasmic proteins showed good stability, with >80% activity retained at 60 °C and up to 0.6 M NaCl. TB-SP showed the highest inhibitory activity against autolysis of washed threadfin bream mince at 65 °C. Addition of 0.5% or 1% TB-SP improved textural properties of threadfin bream surimi gels preincubated at 37 or 65 °C followed by heating at 90 °C. Therefore, TB-SP could be a promising protein ingredient for enhancing surimi gel texture. PRACTICAL APPLICATION: Threadfin bream, bigeye snapper, and yellow croaker are the main species used as raw material for tropical surimi production. Sarcoplasmic proteins from 3 species contain trypsin inhibitor(s) that can minimize proteolytic activity and improve gel texture of proteinase-laden fish muscle. Therefore, sarcoplasmic proteins that are byproducts from surimi processing of these species could be recovered, fractionated, and utilized as a functional protein ingredient.

Isolation and characterization of peptides with dipeptidyl peptidase-IV inhibitory activity from pepsin-treated bovine whey proteins.

Inhibition of the enzyme dipeptidyl peptidase (DPP)-IV is one of the strategies used for the treatment of type 2 diabetes. In the present study, pepsin-treated whey protein isolate (WPI) and α-lactalbumin displaying DPP-IV inhibitory activity were fractionated by successive chromatographic steps and the resulting active fractions analyzed for their constituent peptides by liquid chromatography-electrospray ionization-tandem mass spectrometry. Among the identified sequences, 24 peptides derived from α-lactalbumin and 11 from ß-lactoglobulin were synthesized and their effects on DPP-IV activity assessed. The most potent fragments, LKPTPEGDL and LKPTPEGDLEIL (IC50=45 and 57 µM, respectively), were found to inhibit DPP-IV in an un-competitive manner. Although several of the peptides tested showed some inhibitory activity, only two were as effective as the un-fractionated WPI hydrolysate and none were as potent as the un-fractionated α-lactalbumin hydrolysate. The peptides' structural features, including length and amino acid composition, were found to impact their inhibitory activity. This study provides new insights on the active components responsible for the DPP-IV inhibitory activity of pepsin-treated whey proteins.

Investigation of the putative associations between dairy consumption and incidence of type 1 and type 2 diabetes.

A growing body of evidence suggests a possible relationship between the consumption of dairy products and the incidence of diabetes. A positive correlation between the early introduction of dairy in infancy and the incidence of type 1 diabetes (T1D) in genetically predisposed infants has been suggested by studies on rodents and humans. However, the lines of evidence supporting this association, including epidemiological studies and the observation of antibodies to bovine serum albumin, ß-casein and bovine insulin in the serum of patients with T1D, are not without controversy. On the other hand, an inverse relationship between the consumption of dairy foods and the development of metabolic syndrome and/or type 2 diabetes (T2D) has been implied by epidemiological studies. Several dairy components, especially milk proteins, are believed to play a role in the beneficial effect of dairy consumption on glucose regulation by modulation of incretin hormones. Other dietary factors have also been associated with the incidence of T1D and T2D, indicating that dairy foods might be only one among many dietary agents possibly implicated in the development of diabetes. The present paper critically reviews the evidence and plausible mechanisms for the putative associations between dairy food consumption and incidence of T1D and T2D.

Application of taste sensing system for characterisation of enzymatic hydrolysates from shrimp processing by-products.

The objective of this study was to investigate the potential of an instrumental taste-sensing system to distinguish between shrimp processing by-products hydrolysates produced using different proteases and hydrolysis conditions, and the possible association of taste sensor outputs with human gustatory assessment, salt content, and bioactivity. Principal component analysis of taste sensor output data categorised samples according to the proteases used for hydrolysis. High umami sensor outputs were characteristic of bromelain- and Flavourzyme-produced hydrolysates, compared to low saltiness and high bitterness outputs of Alcalase-produced hydrolysates, and high saltiness and low umami outputs of Protamex-produced hydrolysates. Extensively hydrolysed samples showed higher sourness outputs. Saltiness sensor outputs were correlated with conductivity and sodium content, while umami sensor responses were related to gustatory sweetness, bitterness and umami, as well as angiotensin-I converting enzyme inhibitory activity. Further research should explore the dose dependence and sensitivity of each taste sensor to specific amino acids and peptides.