1,721,002 research outputs found
Is coffee silverskin actually a suitable source of either food supplements or additives? UPLC-PDA-ESI-TOF/MS metabolic profiling of aqueous extracts: natural antioxidants vs phytotoxins
No full textIn the last decades coffee has been widely recognized as an important source of antioxidants and radical scavengers, with increasing evidence supporting its health-promoting potential. Many of these benefits are ascribed to chlorogenic acids (CGAs) contained in coffee beans. A growing interest in the valorization of coffee wastes like spent coffee grounds and by-products like Silverskin (SS) is justified by their richness in polyphenols. As a consequence of the increasing consumption of Green Coffee (GC) as antioxidant-rich dietary supplement, concern has been expressed about its use as food additive or supplement. In fact, atractyligenin and its derivatives, compounds structurally related to the phytotoxin atractyloside, have been recently extracted from raw coffee and their phytotoxic activity has been evaluated. A deeper knowledge about the presence of such compounds also in SS, is supported by the recent interest in the use of SS as a source of food additives or dietary supplements. In this contribution, the UPLC-PDA-ESI-TOF/MS metabolic profiles of SS aqueous extracts of different coffee varieties have been determined and compared to that of GC. Atractyligenin, carboxyatractyligenin and five glucosyde derivatives were identified. In contrast to GC, where only atractyligenin glucopyranosyl derivatives were detected, in all SS also the aglycones were identified and their content was higher in Arabica than in Robusta. Compared to GC, GPCA reaches higher concentration in Arabica and comparable concentration in Robusta SS. Interestingly, the content of CGA in aqueous extracts of SS is reversed compared to atractyligenin derivatives. Moreover, an atractyligenin derivative not previously detected in GC, has been detected in GC. Concluding, the use of SS as food or dietary supplements needs careful evaluation and further and adequate controls on SS raw material are necessary in order to assess its suitability as functional ingredient for food or nutraceutical products
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
Trimethoprim Removal from Aqueous Solutions via Volcanic Ash-Soil Adsorption: Process Modeling and Optimization
No full textAntibiotic contamination of water sources is a significant environmental and public health concern. This contamination is classified among the most dangerous types of pollution currently because of their harmful effects. Therefore, it is essential to identify effective and environmentally friendly ways to deal with those dangerous compounds. Within this context, this work looked into whether soils made from volcanic ash could be used as cost-effective adsorbents to remove the antibiotic trimethoprim (TRM) from aqueous solutions. To examine the impacts of the main operating parameters on TRM removal, which are the initial antibiotic concentration (C), contact time (t), stirring speed (S), and solid-to-liquid ratio (R), a Central Composite Design (CCD) based on the Response Surface Methodology (RSM) was employed. Full quadratic polynomial models were used to correlate the experimental data, allowing for the estimation of each factor’s influence. With a predicted removal efficiency of 77.59%, the removal process optimization yielded the following set of optimal conditions: C = 4.5 mg/L, t = 45.5 min, S = 747 rpm, and R = 0.04 g/mL. Experiments conducted under predicted ideal conditions supported both the result and the previously developed model’s capacity for prediction. Additionally, the adsorption mechanism was also proposed based on the characterization of the adsorbent before and after the treatment. The study’s findings provide the possibility of using soils formed from volcanic ash as a cost-effective adsorbent material for the removal of TRM and likely other similar pollutants from contaminated waters
Recovery of natural antioxidants from spent coffee grounds
No full textSpent coffee grounds (SCG) were extracted with an environmentally friendly procedure and analyzed to evaluate the recovery of relevant natural antioxidants for use as nutritional supplements, foods, or cosmetic additives. SCG were characterized in terms of their total phenolic content by the Folin-Ciocalteu procedure and antioxidant activity by the DPPH scavenging assay. Flavonoid content was also determined by a colorimetric assay. The total phenolic content was strongly correlated with the DPPH scavenging activity, suggesting that phenolic compounds are mainly responsible for the antioxidant activity of SCG. An UHPLC-PDA-TOF-MS system was used to separate, identify, and quantify phenolic and nonphenolic compounds in the SCG extracts. Important amounts of chlorogenic acids (CGA) and related compounds as well as caffeine (CAF) evidenced the high potential of SCG, a waste material that is widely available in the world, as a source of natural phenolic antioxidants. © 2013 American Chemical Society
Green synthesis of gold nanoparticles using Kiwifruit juice
Full text linkThe use of kiwifruit juice as a source of metal-reducing and stabilizing agents for the production of gold nanoparticles (AuNPs) was investigated. The reaction was carried out in batch by mixing appropriate amounts of kiwifruit juice and gold(III) chloride solution. The formation of AuNPs was monitored by measuring the intensity of the surface plasmon resonance (SPR) band of gold. The effects of temperature (20-60 °C), pH (8-12) and gold-to-polyphenol ratio (GPR) were investigated. Characterisation of AuNPs by XRD, DLS and zeta-potential measurements showed that they were highly crystalline, with an average hydrodynamic diameter of about 50 nm and a zeta-potential ranging between -29.2 and -21.7 mV. Under the best reaction conditions (60 °C, pH 9, GPR = 5 mol Au3+/mol GAE), AuNPs with an average size of about 30 nm were produced. The results obtained suggest that kiwifruit juice is a suitable medium for the production of small-sized and stable AuNPs
Green extraction of value-added compounds form microalgae. A short review on natural deep eutectic solvents (NaDES) and related pre-treatments
No full textSustainability and renewability are demanding the most important challenges that need to be achieved. Therefore, microalgae and Natural deep eutectic solvents (NaDEs) are two classes that deserve particular attention that can allow to meet the sustainability. Microalgae, as raw materials, can produce a variety of value-added compounds, which have numerous applications in pharmaceutical, nutraceutical and cosmetics sector. While, NaDES have peculiar characteristics that allow the recovery of various value-added compounds from microalgae biomass in sustainable manner. Microalgal compounds can be extracted using organic acids, alcohols or sugars by employing the NaDES process. These solvents act as are non-toxic, non-volatile and renewable during NaDES process. Considering the properties shown by microalgae and NaDES separately, a combined microalgae-NaDES extraction is extremely promising for future industrial applications. However, this technology requires proper pre-treatment of microalgal biomass to attain the complete recovery of valuable compounds. In conclusion, this review summarize the potential application of NaDES for extraction of intracellular compounds from microalgal biomass and their related pre-treatments to improve the extraction efficiency
UHPLC-PDA-ESI-TOF/MS metabolic profiling of aqueous extracts of Arabica and Robusta Coffee Silverskin: not only natural antioxidants.
No full textCoffee wastes and by-products from coffee industry are a source of contamination and a serious environmental problem, being mainly unutilized, discharged to the environment or burned. This promoted the interest of researchers in the characterization of wastes and by-products as coffee silverskin (CS, the tegument covering the coffee beans) to evaluate the possibility of reusing them.
The high content of caffeine (CAF) and chlorogenic acids (CGAs) in CS and a significant antioxidant activity make them attractive for the recovery of natural antioxidants to be used as food supplements, dietary additives or cosmetic ingredients. The presence of phytotoxins and miycotoxins in green and roasted coffee beans, in CS and in dietary supplements containing green coffee (GC) extracts has recently been reported suggesting that a deeper knowledge of the metabolic profile of CS is required in order to evaluate advantages and risks associated with its consumption.
In the present study, a comprehensive UHPLC-PDA-ESI-TOF/MS metabolic profiling of aqueous extracts of Arabica (CS-A) and Robusta (CS-R) CS was carried out. CS-A and CS-R were also characterized in terms of total polyphenols, flavonoids and antioxidant activity. The results were compared to those of Arabica GC aqueous extracts.
Caffeic acid (CA) derivatives were found as the main CGAs in GC and CS, and the content of both CAF and CGAs followed the order GC >> CS, with CS-R > CS-A. Furokauranes as mozambioside and mascaroside, not previously reported in CS, were found and their levels in CS-A were much higher than in CS-R. The aglycone of mozambioside, not previously reported in coffee, was also evidenced. Atractyligenin and differently glycosilated derivatives were detected in GC and CS, the estimated content being CS-A >> CS-R
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
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