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Fish protein hydrolysates based on Atlantic salmon by-products. Enzyme cost-efficiency and characterization of sensory, surface-active and nutritional properties
Full text linkThe 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
Full text linkDet 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»
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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