Emulsion and Surface-Active Properties of Fish Solubles Based on Direct Extraction and after Hydrolysis of Atlantic Cod and Atlantic Salmon Backbones

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Sensory Properties and Chemical Composition of Fish Solubles Obtained from Upcycling of Fish Filleting Side Streams

The whitefish processing industry igenerates large amounts of food-grade side streams consisting of trimmings, head-backbone-skin (HBS), and viscera. Several factory fishing vessels have fishmeal plants to utilize the residues after onboard processing of the fish, however, at present, the protein-rich solubles is discarded. . In this study, fish solubles based on side streams from cod, saithe, haddock, and golden redfish were produced based on cooking, mechanical dewatering, centrifugation, and membrane filtration. All products had high flavor intensity, and only minor differences between fish species on sensory attributes were observed, suggesting a potential application as broth and flavor enhancer.Sensory Properties and Chemical Composition of Fish Solubles Obtained from Upcycling of Fish Filleting Side StreamspublishedVersio

Effects of Bioactive Peptides from Atlantic Salmon Processing By-Products on Oxyntopeptic and Enteroendocrine Cells of the Gastric Mucosa of European Seabass and Gilthead Seabream

The present study was designed to evaluate the effects of dietary levels of bioactive peptides (BPs) derived from salmon processing by-products on the presence and distribution of peptic cells (oxyntopeptic cells, OPs) and enteric endocrine cells (EECs) that contain GHR, NPY and SOM in the gastric mucosa of European seabass and gilthead seabream. In this study, 27 seabass and 27 seabreams were divided into three experimental groups: a control group (CTR) fed a control diet and two groups fed different levels of BP to replace fishmeal: 5% BP (BP5%) and 10% BP (BP10%). The stomach of each fish was sampled and processed for immunohistochemistry. Some SOM, NPY and GHR-IR cells exhibited alternating “open type” and “closed type” EECs morphologies. The BP10% group (16.8 ± 7.5) showed an increase in the number of NPY-IR cells compared to CTR (CTR 8.5 ± 4.8) and BP5% (BP10% vs. CTR p ≤ 0.01; BP10% vs. BP5% p ≤ 0.05) in the seabream gastric mucosa. In addition, in seabream gastric tissue, SOM-IR cells in the BP 10% diet (16.8 ± 3.5) were different from those in CTR (12.5 ± 5) (CTR vs. BP 10% p ≤ 0.05) and BP 5% (12.9 ± 2.5) (BP 5% vs. BP 10% p ≤ 0.01). EEC SOM-IR cells increased at 10% BP (5.3 ± 0.7) compared to 5% BP (4.4 ± 0.8) (5% BP vs. 10% BP p ≤ 0.05) in seabass. The results obtained may provide a good basis for a better understanding of the potential of salmon BPs as feed ingredients for seabass and seabream.publishedVersio

Fish protein hydrolysates based on Atlantic salmon by-products. Enzyme cost-efficiency and characterization of sensory, surface-active and nutritional properties

The world fisheries and fish farming industries generate large amounts of by-products after the primary processing of fish to edible products. In Norway alone, this accounted for almost 900,000 tons in 2014. Based on present industrial practice, most of the by- products are either discarded or used in the manufacture of low-value commodity products such as fish silage, fishmeal and oil. By-product material from the primary filleting process, such as heads and backbones, contain high-quality food grade proteins with a great potential for value creation. The production of water-soluble protein hydrolysates using exogenous proteases may give an increased valorization of the by- products for human consumption and offers a mild and efficient processing approach without prejudicing the nutritional value. Proteases act by cleaving proteins into smaller peptides and free amino acids that are more water-soluble and have altered sensory and surface-active properties compared to the intact protein. A major drawback in the production of commercial fish protein hydrolysates (FPHs) is the formation of bitter and unpalatable tastes due to exposure of hydrophobic amino acids and moieties during the hydrolysis process. Moreover, the cost of enzymes and high processing expenses may be a hindrance in a profitable production of FPHs for human consumption. This has led to a demand for new and improved knowledge of cost-efficiency of enzymes and the process conditions that influences the formation and reduction of bitter taste. Reduction of the bitter taste is of utmost importance in the production of FPHs, but also knowledge of the surface-active and nutritional properties of a hydrolysate may be important for its potential inclusion in food products. The main objective of this study has been to produce FPHs based on Atlantic salmon (Salmo salar) head and backbone products with low bitter taste, good surface-active properties and high nutritional value. The hydrolytic and cost efficiency of five commercial endopeptidases (Alcalase 2.4L, Corolase 7089, Neutrase 0.8L, Promod 671L and Protex 7L) have been evaluated and compared in the hydrolysis of the salmon substrate, based on the pH-STAT method. The sensory properties of the hydrolysates were assessed based on generic descriptive analysis by a trained sensory panel. The hydrolysate surface-active properties were evaluated based on critical micelle concentration (CMC) using 1H NMR. Nutritional properties have been evaluated based on calculations of protein efficiency ratio (PER), amino acid score (AAS), digestible indispensable AAS (DIAAS) and protein digestibility corrected (PDCAAS) using FAO recommendations of indispensable amino acids for small children (six months to three years). In Paper I, substrate specific numbers for nitrogen factor (fN = 5.23 g protein/g nitrogen) and total number of peptide bonds (htot = 9.3 meqv/g protein) were developed to enable more accurate calculations of hydrolysis parameters, such as protein recovery (PR) and degree of hydrolysis (DH). Based on the experimental pH-STAT data, response surface regression models were established to evaluate the combined effects of hydrolysis time and enzyme activity-to-substrate ratio (U/S) on DH and yield of solubilized proteins. The models were combined with activity-specific enzyme cost to estimate the cost efficiency of the individual enzymes, important in upscale and industrial applications. The study demonstrated that all enzymes were equally efficient in hydrolyzing the substrate at low U/S, however, Alcalase 2.4L, Protex 7L and Promod 671L gave higher final DH at high enzyme addition, compared to Corolase 7089 and Neutrase 0.8L. All enzymes were equally efficient in solubilizing the substrate. This may be explained by the enzymes preferentially cleaving peptides already solubilized at high enzyme dose, rather than dissolving new proteins. A linear correlation of DH determined by the pH- STAT and OPA methods was established, which permits the use of the regression models in upscaling of processes where pH-STAT is not applicable. The studies in Paper II confirmed that both molecular weight distribution and enzyme specificity were important for the formation of bitter taste and surface-active properties of the hydrolysates. High intensity of bitter, astringent and pungent attributes was associated with a high DH (≥25%) and peptides with molecular weight 500 Da and the hydrolytic specificity of the used exopeptidase. Acidic ACs gave largest reduction of bitter taste when added at 1% on protein basis (p = 0.09). The reduction of bitter taste could not be explained by the adsorption of peptides and amino acids from the hydrolysates. Chemical analyses revealed a decrease in salt-free ash and an increase in crude protein on dry matter content in the hydrolysates after treatment with AC. This suggested that ACs adsorb non-protein constituents. The nutritional properties of the raw material and resulting hydrolysates revealed low levels of tryptophan, leucine, isoleucine and valine to meet dietary requirements of children under three years of age. Treatment with exopeptidase and AC did not influence the hydrolysates nutritional properties

Enzymatisk hydrolyse av kollagenproteiner i fiskebein – hvordan skape verdier av problemavfall

Det er stor interesse for anvendelse av kollagenproteiner innenfor kosmetisk industri, i kosttilskudd, til produksjon av gelatin (tekniske formål), og til bruk i legemiddel/medisinsk industri. Kollagen i intakt form består av en trippelhelikskjede av lange peptider som er lite fordøyelig (60%). Det er mulig å øke ernæringsmessig kvalitet av kollagen ved å denaturere peptidkjedene (varmebehandling) eller ved å bryte ned proteinkjedene til mindre peptider (enzymbehandling). Målet med dette prosjektet var å vurdere egnethet av to ulike enzymer for produksjon av hydrolysert kollagen fra fiskebein. Dette prosjektet brukte fiskebein fra sild, framstilt i en prosess som inkluderte demineralisering (ved syrehydrolyse), avfetting og vasking, før enzymatisk hydrolyse av kollagenprotein. I laboratorieforsøk (200 g kollagenpulver), ble det testet to ulike enzymer (Promod 144P, Promod 192P) ved to pH nivå (pH=3; pH=5). Basert på N-utbytte, aminosyresammensetting og molekylvektfordeling av peptider, viste forsøket at hydrolyse med Promod144P (pH=5) var mest effektiv for å oppnå høy hydrolysegrad av kollagenproteiner i bein (> 60% N-utbytte). Hydrolyse ved pH=3 ga lavere utbytte for begge enzymer (≈50 %). Bestemmelse av hydrolysegrad ved OPA metoden ga unøyaktige svar og ble vurdert som ikke egnet for bestemmelse av hydrolysegrad for kollagen. Det ble oppskalert til produksjon av 2 kg porsjoner av kollagenprotein basert på Promod144P, pH=5. Beregnet N-utbytte for kollagenprotein var høyt, og indikerte at 75– 80 % av intakt kollagenprotein ble brutt ned til vannløselige proteiner. Spraytørket sluttprodukt inneholdt 80,1 % protein (N x 6,25), og kan ansees som et proteinkonsentrat. Aminosyresammensettingen var karakteristisk for beinkollagen med høyt innhold av Gly (17,1 %), Glut (7,5%), Pro (7,5%), Ala (5,9%), Arg (5,9%) og Asp (4,8%), mens nivået av Hyp var lavt (0,1%), mest sannsynlig av analytiske grunner. Intakt kollagenprotein er lite fordøyelig, og det har vært ønskelig å teste effekter av hydrolyseprosessen på fordøyelighet av kollagenproteiner. Det ble testet 3 kollagen-ingredienser basert på A) Ubehandlet kollagen fra sildebein (restprotein i bein etter syrehydrolyse); B) Varmebehandlet kollagen fra sildebein (120 °C/60min i autoklav); og C) Enzymbehandlet kollagen fra sildebein (Promod 144P, pH=5). Resultatene viste at enzymatisk behandling effektivt brøt ned store peptider i intakt kollagen til mindre peptider og frie aminosyrer (< 10.000 Da). Effekter på fordøyelighet av protein lot seg ikke gjennomføre fordi forsøksdyrene (mink) fikk diare. Mulige årsaker til dette må undersøkes. Hovedkonklusjonen er at prosessen for enzymbehandling av sildebein kan gjennomføres med høyt N utbytte, og at det er mulig å produsere et proteinkonsentrat fra fiskebeinråstoffet som gjenstår etter demineralisering med en sterk syre. Det er behov for å evaluere effekter av ulike enzymer med hensyn til utbytte og kostnadseffektivitet, samt for å kartlegge bioaktivitet av peptider i proteinkonsentratet. Prosjektaktiviteten vil bli videreført i RFFVest prosjekt 256952 (2016–2018), «Verdiskaping av næringsstoffer i laksebein»

A Systematic Approach to the Comparison of Cost Efficiency of Endopeptidases for the Hydrolysis of Atlantic Salmon (Salmo salar) By-Products

The hydrolytic and cost efficiencies of five endopeptidases (Alcalase 2.4L, Corolase 7089, Neutrase 0.8L, Promod 671L and Protex 7L) to hydrolyze Atlantic salmon by-products were compared at standardized activity levels based on a casein assay. The substrate was characterized prior to the hydrolytic experiments (pH=6.5, t=50 °C) to obtain substrate-specifi c constants for nitrogen to protein mass (in g) ratio, i.e. conversion factor fN=5.23 and total amount of peptide bonds htot=9.3 mmol per g of protein. At low enzyme activity to substrate ratio, all enzymes were equally effi cient in hydrolyzing the substrate. At highest enzyme activity to substrate ratio, Protex 7L, Alcalase 2.4L and Promod 671L gave higher degree of hydrolysis (DH=14.2–14.6 %) than Corolase 7089 (13.2 %) and Neutrase 0.8L (11.6 %) after 120 min of hydrolysis. No differences were observed in protein recovery (yield of solubilized protein) relative to DH. Determination of DH was followed by the pH-STAT and o-phthaldialdehyde methods. Based on pH-STAT data, response surface regression models were established based on the combined eff ects of hydrolysis time and enzyme activity to substrate ratio on DH and protein recovery. The modelling approach was combined with enzyme cost to identify the most cost-efficient enzyme (Protex 7L)

Sensory and Chemical Properties of Protein Hydrolysates Based on Mackerel (Scomber scombrus) and Salmon (Salmo salar) Side Stream Materials

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Sustavni pristup ispitivanju ekonomske isplativosti hidrolize nusprodukata obrade atlantskog lososa (Salmo salar) pomoću endopeptidaza

The hydrolytic and cost efficiencies of five endopeptidases (Alcalase 2.4L, Corolase 7089, Neutrase 0.8L, Promod 671L and Protex 7L) to hydrolyze Atlantic salmon by-products were compared at standardized activity levels based on a casein assay. The substrate was characterized prior to the hydrolytic experiments (pH=6.5, t=50 °C) to obtain substrate-specifi c constants for nitrogen to protein mass (in g) ratio, i.e. conversion factor fN=5.23 and total amount of peptide bonds htot=9.3 mmol per g of protein. At low enzyme activity to substrate ratio, all enzymes were equally effi cient in hydrolyzing the substrate. At highest enzyme activity to substrate ratio, Protex 7L, Alcalase 2.4L and Promod 671L gave higher degree of hydrolysis (DH=14.2–14.6 %) than Corolase 7089 (13.2 %) and Neutrase 0.8L (11.6 %) after 120 min of hydrolysis. No differences were observed in protein recovery (yield of solubilized protein) relative to DH. Determination of DH was followed by the pH-STAT and o-phthaldialdehyde methods. Based on pH-STAT data, response surface regression models were established based on the combined eff ects of hydrolysis time and enzyme activity to substrate ratio on DH and protein recovery. The modelling approach was combined with enzyme cost to identify the most cost-efficient enzyme (Protex 7L).U radu je pomoću standardnih metoda u podlozi s kazeinom ispitana i uspoređena hidrolitička aktivnost i ekonomska isplativost primjene pet komercijalnih endopeptidaza (Alcalase 2.4L, Corolase 7089, Neutrase 0.8L, Promod 671L i Protex 7L) u hidrolizi nusprodukata obrade atlantskog lososa. Nakon karakterizacije supstrata provedena je hidroliza pri pH=6,5 i t=50 °C, te su izračunate specifične konstante koje ovise o masenom omjeru dušika i proteina: konverzijski faktor fN=5.23 i ukupna količina peptidnih veza htot=9.3 mmol/g. Svi su enzimi bili jednako učinkoviti u hidrolizi pri malom omjeru enzimske aktivnosti i koncentracije supstrata. Pri najvećem omjeru enzimske aktivnosti i koncentracije supstrata dobivene su veće vrijednosti stupnja hidrolize (DH=14,2-14,6 %) nakon 120 min obrade pomoću endopeptidaza Protex 7L, Alcalase 2.4L i Promod 671L, nego pomoću endopeptidaza Corolase 7089 (13.2 %) i Neutrase 0.8L (11.6 %). Nije opaženo da iskorištenje proteina ovisi o stupnju hidrolize. Nakon toga je izmjerena aktivnost enzima pomoću pH stata, te je određen udjel reaktivnih amino skupina o-ftaldialdehid (OPA) metodom. Na osnovi podataka dobivenih pomoću pH stata izrađeni su regresijski modeli odzivnih površina. Dobiveni su modeli upotrijebljeni za ispitivanje utjecaja vremena hidrolize i omjera enzimske aktivnosti i koncentracije supstrata na stupanj hidrolize i iskorištenje proteina. Modeliranjem i analizom troškova proizvodnje enzima utvrđeno je da je Protex 7L najisplativija endopeptidaza za hidrolizu nusprodukata obrade atlantskog lososa

Reduction in flavor-intense components in fish protein hydrolysates by membrane filtration

Enzymatic protein hydrolysates based on side stream materials from the fish-filleting industry are increasingly explored as food ingredients. However, intense sensory properties, and high salt contents, are often a limiting factor. Most of the sensory attributes, such as fish flavor and salty taste, can be ascribed to low-molecular-weight, water-soluble components, whereas bitterness is associated with small hydrophobic peptides. In this study, protein hydrolysates based on head and backbone residuals from Atlantic salmon (Salmo salar) and Atlantic cod (Gadus morhua) were produced using two different enzymes. The effects of micro- and nanofiltration on the chemical composition, protein recovery, and sensory properties of the final products were investigated. The choice of raw material and enzyme had negligible effects, whereas nanofiltration caused a considerable reduction in metabolites, ash, and the intensity of several sensory attributes. The intensity of bitterness increased after nanofiltration, indicating that small peptides associated with bitter taste were retained by the membrane. Total protein yield after microfiltration was 24%–29%, whereas 19%–24% were recovered in the nanofiltration retentate.publishedVersio

Sensory and Chemical Properties of Protein Hydrolysates Based on Mackerel (Scomber scombrus) and Salmon (Salmo salar) Side Stream Materials

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