1,720,968 research outputs found
Physico-biochemical properties of extruded Cape Horse mackerel (Trachurus capensis).
Get PDFCape horse mackerel (Trachurus capensis) is an underutilized pelagic fish from Namibia. In this study, the physico-chemical characteristics, nutritional composition and functionality (thermal and rheological) properties of horse mackerel and local cereals found in Namibia were investigated. This knowledge of the physico-chemical composition and functionality of these ingredients and their behaviour in mixed food model systems was applied to optimize the extrusion process, used to make snack foods. Proximate, biochemical, amino acid and fatty acid analyses, and differential scanning calorimetry (DSC), rheology and Raman spectroscopy studies were conducted on horse mackerel mince, cassava, maize, pearl millet flour, mixtures of these ingredients, an extruded horse mackerel snack and a commercial shrimp cracker. Differences in the protein bands identified by Raman spectroscopy provided detailed information on the protein structure of the raw materials, protein denaturation and gel formation of the extruded snacks. Products of similar textural properties were developed despite the varying composition of mixtures. A mixture comprising 20% horse mackerel, 20% maize flour, 30% pearl millet flour and 30% cassava flour showed the optimum starch and protein interactions as evidenced by thermal and rheological properties; this formulation was used to develop the horse mackerel extruded snack. Extrusion provided an efficient method for combining essential protein and lipids from fish and starchy cereal mixtures into a balanced and nutritious snack food. The horse mackerel extruded snack product had a higher protein quality compared to the commercial shrimp cracker. The raw material quality used in the development of an extruded horse mackerel snack significantly influenced its final quality and total cost. Poor quality fish used in the processing of the extruded horse mackerel snack resulted in an increase in failure costs and consequently the total quality cost. Failure costs decreased from 80% to 40% of Total Quality Costs when good raw material was used
Elucidation of bioactive properties of salmon skin proteins.
Get PDFBioactive peptides are peptides that are able to exert beneficial health effects apart from providing the nutritional aspect. In this study, bioactive peptides were produced and purified from alcalase hydrolysed Salmon skin gelatin. A gel filtration fraction, GF28, was identified as the most potent fraction. A further aim of this study was to investigate the bioactive properties including antioxidant, ACE inhibition, and anti-proliferative activities of the peptide. GF28 exhibited ACE inhibition activity of 46.5 %. Further studies elucidated GF28 acts as a competitive inhibitor of ACE. GF28 also exhibited comparable antioxidant activity to the positive control trolox (67.1 % and 67.3 % respectively). The antioxidant mechanism of GF28 mainly involved transition metal ion chelating activity and less reducing power activity. Apart from that, GF28 had poor radical scavenging activity in both hydrophobic and hydrophilic environments. GF28 also showed cytotoxic effects in hepatocellular carcinoma, HepG2 cells (IC50=0.154 mg/mL). In addition, GF28 also affected the endogenous antioxidant defence system in HepG2 cells by decreasing SOD, total glutathione and GPx activity. Catalase activity in GF28 treated HepG2 cells also increased. Anti-proliferative effects of GF28 were also observed in Caco-2 cells (IC50=0.16 mg/mL). In 0.15 mg/mL GF28 treated Caco-2 cells, intracellular and mitochondrial ROS (15.3 % and 7.8 % respectively) were significantly lower than untreated cells (32.9 % and 25.2 % respectively). Caco-2 cells treated with GF28 showed cell cycle arrest in the G1 phase as well as apoptosis. The extrinsic and intrinsic apoptosis pathway was activated with GF28. Caspase-8, caspase-3/7 and PARP were activated in the extrinsic pathway whereas caspase-9 and LaminA/C were activated in the intrinsic pathway
Elucidation of bioactive properties of salmon skin proteins.
No full textBioactive peptides are peptides that are able to exert beneficial health effects apart from providing the nutritional aspect. In this study, bioactive peptides were produced and purified from alcalase hydrolysed Salmon skin gelatin. A gel filtration fraction, GF28, was identified as the most potent fraction. A further aim of this study was to investigate the bioactive properties including antioxidant, ACE inhibition, and anti-proliferative activities of the peptide. GF28 exhibited ACE inhibition activity of 46.5 %. Further studies elucidated GF28 acts as a competitive inhibitor of ACE. GF28 also exhibited comparable antioxidant activity to the positive control trolox (67.1 % and 67.3 % respectively). The antioxidant mechanism of GF28 mainly involved transition metal ion chelating activity and less reducing power activity. Apart from that, GF28 had poor radical scavenging activity in both hydrophobic and hydrophilic environments. GF28 also showed cytotoxic effects in hepatocellular carcinoma, HepG2 cells (IC50=0.154 mg/mL). In addition, GF28 also affected the endogenous antioxidant defence system in HepG2 cells by decreasing SOD, total glutathione and GPx activity. Catalase activity in GF28 treated HepG2 cells also increased. Anti-proliferative effects of GF28 were also observed in Caco-2 cells (IC50=0.16 mg/mL). In 0.15 mg/mL GF28 treated Caco-2 cells, intracellular and mitochondrial ROS (15.3 % and 7.8 % respectively) were significantly lower than untreated cells (32.9 % and 25.2 % respectively). Caco-2 cells treated with GF28 showed cell cycle arrest in the G1 phase as well as apoptosis. The extrinsic and intrinsic apoptosis pathway was activated with GF28. Caspase-8, caspase-3/7 and PARP were activated in the extrinsic pathway whereas caspase-9 and LaminA/C were activated in the intrinsic pathway
The investigation of the physical-chemical and functional properties of fish gelatin from warm-water fish (tilapia).
Get PDFFish skin, a by-product of filleting could be upgraded to value-added products for human consumption, thereby preventing waste and pollution. The aims were to prepare gelatin from skin of Nile or black tilapia (Oreochromis nilotica); characterize its physical-chemical, rheological and thermal properties and those of fish gelatin-whey protein mixtures; prepare hydrolysates and assess their foaming properties in the presence and absence of whey protein and green tea.
Gelatin extracted successfully from tilapia skins, gave a 19-26% yield and comprised high protein (90.2 + 0.68 %) and low fat (0.62 + 0.03 %), moisture (5.2 + 0.62 %) and ash content (0.08 + 0.05 %). Amino acid profile included mainly glycine (33.94%), alanine (26.1%) and glutamic acid, proline, arginine, aspartic acid and imino acids. The Bloom strength of 6.67% (w/v) tilapia gelatin in distilled water was higher (301 + 11.6 g) than commercial tilapia (207 + 5.6 g), bovine (~ 225 g), and porcine (~ 300 g) gelatins.
The rheological properties of 3,5 and 10% (w/v) tilapia gelatin indicated G’ (elastic modulus) values 1,135 and 720 Pa, respectively, and gelling points of 16.2°C, 5% 17.2°C and 19.8°C respectively whereas melting temperatures were 14.9°C, 14.9°C and 15.0°C respectively. The gels were highly stable over a frequency range of 0-100 rad/sec.
DSC results indicated high melting temperatures (Tm) 22oC, compared to bovine (26.2°C) and porcine (30.7°C) gelatin. Cold water fish gelatin did not gel. However, bovine and porcine gelatins had lower enthalpy change (∆H) values 0.58 J/g and 0.45 J/g respectively, compared with tilapia gelatin (2.51 J/g), probably due to protein denaturation of collagen.
In tilapia gelatin-whey protein mixed gels, whey proteins were dominant. Gelling temperatures of 10% WPI with 5% gelatin (88.9°C) or 10% gelatin (87.4°C) mixtures were higher than for WPI (80.3°C) or gelatin at 3% (16.2°C), 5% (17.2°C) and 10% (19.8°C). Whey protein (10%) was unstable but formed a good stable gel network with gelatin at 5 % (597 Pa) and 10% (26974 Pa). Whey (10 %) and gelatin (10%) also gave a strong gel by large deformation analysis. Tm and ∆H for 10% whey protein and 5 or 10% gelatin/ mixtures were higher (67.2°C, 68.8°C and 68.2°C respectively) than for gelatin or whey protein alone. The ∆H values of gelatins increased when combined with the WPI. Three % gelatin (0.03 J/g), 10% WPI + 3% gelatin (0.44 J/g), 5 % gelatin (0.18 J/g), 10% WPI + 5% gelatin (0.56), 10% gelatin (1.3 J/g) and 10% WPI + 10% gelatin (0.59). Phase contrast microscopy of gelatin showed a fine uniform and homogeneous network with small particles whereas the whey protein structure had larger aggregates. The gelatin-whey mixtures formed a compatible network.
Gelatin produced the highest volume of foam FE (933%), followed by gelatin + whey protein (853%), gelatin hydrolysate + whey protein (767%); these were not significantly different (p>0.05). This was followed by a mixture of gelatin + whey protein + green tea (575%) that was significantly lower (p< 0.05). Foaming stability of mixtures of gelatin + whey protein + green tea was significantly higher at 47%, than gelatin + whey protein (34%) and gelatin + green tea (25%) (p<0.05). Tilapia gelatin was significantly higher than that of whey protein alone (p<0.05) but the combination of whey protein with gelatin resulted in a significant increase (P<0.05) compared to WP or TG alone. Whey protein at FS of 8% was not as stable as the gelatin (18%) or green tea (21%). Gelatin hydrolysate prepared with alcalase had poor FE and FS which improved with added green tea and whey protein due to protein-polyphenol interactions. Tilapia skin gelatin displayed very good nutritional and rheological properties and can be used as an alternative to mammalian gelatins if food products
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
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