In this work, the efficient extraction of pectin from sugar beet by-products (pressed, ensiled and dried pulp), by using an acid method or a commercial cellulose, is accomplished. The extraction ...method had an impact on the pectin monomeric composition, mainly in xylose, arabinose, and galacturonic acid content, as determined by GC-FID. FTIR and SEC analyses allowed the determination of similar degrees of methoxylation and molecular weights, respectively, in the extracted pectins. The acid extraction of pectin in the ensiled by-product led to the highest yield (19%) with a galacturonic acid content of 46%, whereas the application of the enzymatic extraction method resulted in a lower yield (13%) but higher galacturonic acid content (72%). Moreover, the stability in aqueous solution as well as the emulsifying activity index was higher for pectin extracted by the acid method, whereas the viscosity was higher in pectin extracted by the enzymatic method. To the best of our knowledge, this is the first study analyzing the physicochemical properties and exploring the potential reuse of ensiled and dried by-products from sugar beet industry for the extraction of pectin to be further used in the food and pharmaceutical areas.
•A Dynamic Simulator was used for digestion and fermentation of citrus pectin.•Pectin molecular weight showed minor changes after gastric and intestinal digestion.•High increase of Bifidobacterium, ...Bacteroides and Faecalobacterium prausnitzii.•High gains of short chain fatty acids during pectin fermentation in the colon stages.
The behaviour of citrus pectin during digestion and its potential prebiotic properties were examined using a Dynamic Gastrointestinal Simulator (simgi®) model for the human gut, which simulates processes in the stomach, small intestine, ascending, transverse and descending colon. A remarkable non-digestibility of pectin in the upper gastrointestinal tract was observed by HPLC-ELSD analysis, where ∼88% of citrus pectin remained intact during its transit through the stomach and small intestine. Fermentation of pectin stimulated the growth of beneficial bacteria such as Bifidobacterium spp, Bacteroides spp and Faecalobacterium prausnitzii. High increases of short-chain fatty acids (SCFA) were observed, especially in acetate and butyrate concentration due to direct fermentation of pectin or by cross-feeding interaction between bacteria. This is the first study on the digestibility and fermentation of pectin carried out in a complex dynamic gastrointestinal simulator, being of special relevance the results obtained for F. prausnitzii.
Display omitted
•Artichoke and sunflower by-products are renewable sources of fermentable pectins.•Pectic compounds from sunflower and artichoke by-products have prebiotic potential.•Positive ...correlation of combined arabinose/galactose content and prebiotic properties.•Decrease of molecular weight had a positive effect on artichoke pectin fermentability.
The suitability of artichoke and sunflower by-products as renewable sources of pectic compounds with prebiotic potential was evaluated by studying their ability to modulate the human faecal microbiota in vitro. Bacterial populations and short-chain fatty acid (SCFA) production were measured. Reduction of the molecular weight of artichoke pectin resulted in greater stimulation of the growth of Bifidobacterium, Lactobacillus and Bacteroides/Prevotella, whilst this effect was observed only in Bacteroides/Prevotella for sunflower samples. In contrast, the degree of methoxylation did not have any impact on fermentability properties or SCFA production, regardless of the origin of pectic compounds. Although further in vivo studies should be conducted, either pectin or enzymatically-modified pectin from sunflower and artichoke by-products might be considered as prebiotic candidates for human consumption showing similar ability to promote the in vitro growth of beneficial gut bacteria as compared to well-recognized prebiotics such as inulin or fructo-oligosaccharides.
•Pectin depolymerisation increases with time and intensity of US in aqueous media.•US treatment with nitric/citric acids leads to an improved pectin depolymerisation.•US treatment gives rise to ...high-methoxylated pectin (degree esterification of >50%)•Hardly any impact of US was observed in enzymatic pectin depolymerisation.•US under certain conditions can be an alternative to current depolymerisation methods.
Pectin-derived oligosaccharides are emerging as a new generation of functional ingredients with new or improved technological and/or bioactive properties as compared to pectin. This work addresses the impact of power ultrasound (US) on the structure of citrus and apple pectin under different experimental conditions of power, amplitude and pectin concentration in aqueous and acid media, as well as in the presence of a pectinase. Results indicated that depolymerisation of both pectin increased with time and intensity of US in aqueous media and their polydispersity decreased. In general, a higher depolymerisation was observed in pectin treated by US in the presence of nitric and citric acids than in water, and hardly any difference was detected between both types of acids. Most of the assays gave rise to high-methoxylated pectin with a degree of esterification above 50%, pointing out their suitability for potential gelling agents. Finally, US did not have any impact in assisted enzymatic hydrolysis on the degree and/or rate of depolymerisation at low and medium levels of pectin concentration (0.5 and 2%), whereas a higher diversity of pectin fragments was found at 5% which could be indicative of a more controlled depolymerisation. These findings highlight the importance of the selection of appropriate US processing conditions to diversify the applications of modified pectin, as well as the potential of US as a prospective alternative to currently used depolymerisation techniques.
We present a novel approach to real-time dense visual simultaneous localisation and mapping. Our system is capable of capturing comprehensive dense globally consistent surfel-based maps of room scale ...environments and beyond explored using an RGB-D camera in an incremental online fashion, without pose graph optimization or any post-processing steps. This is accomplished by using dense frame-to-model camera tracking and windowed surfel-based fusion coupled with frequent model refinement through non-rigid surface deformations. Our approach applies local model-to-model surface loop closure optimizations as often as possible to stay close to the mode of the map distribution, while utilizing global loop closure to recover from arbitrary drift and maintain global consistency. In the spirit of improving map quality as well as tracking accuracy and robustness, we furthermore explore a novel approach to real-time discrete light source detection. This technique is capable of detecting numerous light sources in indoor environments in real-time as a user handheld camera explores the scene. Absolutely no prior information about the scene or number of light sources is required. By making a small set of simple assumptions about the appearance properties of the scene our method can incrementally estimate both the quantity and location of multiple light sources in the environment in an online fashion. Our results demonstrate that our technique functions well in many different environments and lighting configurations. We show that this enables (a) more realistic augmented reality rendering; (b) a richer understanding of the scene beyond pure geometry and; (c) more accurate and robust photometric tracking.
In-the-field PID related experiences Martínez-Moreno, F.; Figueiredo, G.; Lorenzo, E.
Solar energy materials & solar cells/Solar energy materials and solar cells,
January 2018, 2018-01-00, 20180101, Letnik:
174
Journal Article
Recenzirano
Odprti dostop
Potential induced degradation could considerably decrease the performance of photovoltaic systems which operate at high DC voltages. Nonetheless, methodologies for dealing with it in field are not ...clearly yet defined. This work explains the kinetics of this phenomenon in the field and presents an assessment of its occurrence, detection and prediction in real PV installations. Measurements of the instantaneous operating voltages of the photovoltaic module as a verification routine and predictive maintenance is proposed here as a reasonable and most accurate way of analyzing the actual power losses of the photovoltaic system related to this kind of degradation, as well as detecting and predicting it. Potential induced degradation prevention and recovery have also been carried out by the application of reverse voltage during the night, showing the validity of this technique. A literature review for the PID dynamics of different kinds of photovoltaic cell technologies and development of PID test methodologies and standards is also presented.
Display omitted
•Two experiences related to PID in real commercial PV plants are presented.•PV modules operating voltage are useful for detecting and predicting PID in-the-field.•Monitoring of PV modules operating voltage allows continuous PID surveillance.•A new method for predicting occurrence of PID at the location concerned is proposed.
Liquid metal foam owes its stability to the presence of solid particles. To elucidate the conditions under which such particles stabilise foams, 15 different aluminium-alloy based metal matrix ...composites were melted, after which air was injected with the objective to create bubbles and eventually metal foam. Foam formation was monitored in-situ by X-ray radioscopy. All systems were classified foamable, partially foamable and unfoamable. Foamable composites form a preferred range in the stability diagram displaying particle fractions vs. particle size, thus experimentally confirming earlier claims. All investigated composites fall into the same range even though their alloy and particle types vary.
Display omitted
The stress shielding and the poor osseointegration in titanium implants are still problems to be resolved. In this context, this work proposes a balanced solution. Titanium samples were fabricated, ...with a porosity of 100–200μm of pore size employing space-holder technique (50vol% NH4HCO3, 800MPa at 1250°C during 2h under high vacuum conditions), obtaining a good equilibrium between stiffness and mechanical resistance. The porous titanium substrates were coated with hydroxyapatite, obtained by sol-gel technique: immersion, dried at 80°C and heat treatment at 450°C during 5h under vacuum conditions. Phases, surface morphology and interfacial microstructure of the transverse section were analyzed by Micro-Computed Tomography, SEM and confocal laser, as well as the infiltration capability of the coating into the metallic substrate pores. The FTIR and XRD showed the crystallinity of the phases and the chemical composition homogeneity of the coating. The size and interconnected pores obtained allow the infiltration of hydroxyapatite (HA), possible bone ingrowth and osseointegration. The scratch resistance of the coating corroborated a good adherence to the porous metallic substrate. The coated titanium samples have a biomechanical and biofunctional equilibrium, as well as a potential use in biomedical applications (partial substitution of bone tissue).
•Porous Ti substrates were coated with hydroxyapatite by the sol-gel technique.•A HA porous thin films onto the porous titanium substrates was obtained.•The HA - porous Ti showed good mechanical interlocking and chemical bonding.•The HA coatings can prevent the corrosion of Ti substrate and make it bioactive.•The proposed HA coating on porous Ti allows a biofunctional and mechanical balance.
PDF
