Browsing by Author "Alves, Rita C."
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- Angolan cymbopogon citratus used for therapeutic benefits: nutritional composition and influence of solvents in phytochemicals content and antioxidant activity of leaf extractsPublication . Soares, Marta O.; Alves, Rita C.; Pires, Pedro C.; Oliveira, M. Beatriz P. P.; Vinha, Ana F.Folk medicine is a relevant and effective part of indigenous healthcare systems which are, in practice, totally dependent on traditional healers. An outstanding coincidence between indigenous medicinal plant uses and scientifically proved pharmacological properties of several phytochemicals has been observed along the years. This work focused on the leaves of a medicinal plant traditionally used for therapeutic benefits (Angolan Cymbopogon citratus), in order to evaluate their nutritional value. The bioactive phytochemical composition and antioxidant activity of leaf extracts prepared with different solvents (water, methanol and ethanol) were also evaluated. The plant leaves contained ~60% of carbohydrates, protein (~20%), fat (~5%), ash (~4%) and moisture (~9%). The phytochemicals screening revealed the presence of tannins, flavonoids, and terpenoids in all extracts. Methanolic extracts also contained alkaloids and steroids. Several methods were used to evaluate total antioxidant capacity of the different extracts (DPPH; NO; and H2O2 scavenging assays, reducing power, and FRAP). Ethanolic extracts presented a significantly higher antioxidant activity (p < 0.05) except for FRAP, in which the best results were achieved by the aqueous extracts. Methanolic extracts showed the lowest radical scavenging activities for both DPPH; and NO; radicals.
- Detection of Arah1 (a major peanut allergen) in food using an electrochemical gold nanoparticle-coated screen-printed immunosensorPublication . Alves, Rita C.; Pimentel, Filipa B.; Nouws, Henri P.A.; Marques, Raquel C.B.; González-García, María Begoña; Oliveira, M. Beatriz P.P.; Delerue-Matos, CristinaA gold nanoparticle-coated screen-printed carbon electrode was used as the transducer in the development of an electrochemical immunosensor for Ara h 1 (a major peanut allergen) detection in food samples. Gold nanoparticles (average diameter=32 nm) were electrochemically generated on the surface of screen-printed carbon electrodes. Two monoclonal antibodies were used in a sandwich-type immunoassay and the antibody–antigen interaction was electrochemically detected through stripping analysis of enzymatically (using alkaline phosphatase) deposited silver. The total time of the optimized immunoassay was 3 h 50 min. The developed immunosensor allowed the quantification of Ara h 1 between 12.6 and 2000 ng/ml, with a limit of detection of 3.8 ng/ml, and provided precise (RSD <8.7%) and accurate (recovery >96.6%) results. The immunosensor was successfully applied to the analysis of complex food matrices (cookies and chocolate), being able to detect Ara h 1 in samples containing 0.1% of peanut.
- Detection of the peanut allergen Ara h 6 in foodstuffs using a voltammetric biosensing approachPublication . Alves, Rita C.; Pimentel, Filipa B.; Nouws, Henri P. A.; Correr, Wagner; González-García, María Begoña; Oliveira, M. Beatriz P. P.; Delerue-Matos, CristinaA voltammetric biosensor for Ara h 6 (a peanut allergen) detection in food samples was developed. Gold nanoparticle-modified screen-printed carbon electrodes were used to develop a sandwich-type immunoassay using two-monoclonal antibodies. The antibody-antigen interaction was detected through the electrochemical detection of enzymatically deposited silver. The immunosensor presented a linear range between 1 and 100 ng/ml, as well as high precision (inter-day RSD ≤9.8 %) and accuracy (recoveries ≥96.7 %). The detection and quantification limits were 0.27 and 0.88 ng/ml, respectively. It was possible to detect small levels of Ara h 6 in complex food matrices.
- Effect of peel and seed removal on the nutritional value and antioxidant activity of tomato (Lycopersicon esculentum L.) fruitsPublication . Vinha, Ana F.; Alves, Rita C.; Barreira, Sérgio V. P.; Castro, Ana; Costa, Anabela S. G.; Oliveira, M. Beatriz P. P.The effect of peel and seed removal, two commonly practiced procedures either at home or by the processing industry, on the physicochemical properties, bioactive compounds contents and antioxidant capacity of tomato fruits of four typical Portuguese cultivars (cereja, chucha, rama and redondo) were appraised. Both procedures caused significant nutritional and antioxidant activity losses in fruits of every cultivar. In general, peeling was more detrimental, since it caused a higher decrease in lycopene, bcarotene, ascorbic acid and phenolics contents (averages of 71%, 50%, 14%, and 32%, respectively) and significantly lowered the antioxidant capacity of the fruits (8% and 10%, using DPPH. and b-carotene linoleate model assays, correspondingly). Although seeds removal favored the increase of both color and sweetness, some bioactive compounds (11% of carotenoids and 24% of phenolics) as well as antioxidant capacity (5%) were loss. The studied cultivars were differently influenced by these procedures. The fruits most affected by peeling were those from redondo cultivar (-66% lycopene, -44% b-carotene, -26% ascorbic acid and -38% phenolics). Seeds removal, in turn, was more injurious for cereja tomatoes (-10% lycopene, -38% b-carotene, -25% ascorbic acid and -63% phenolics). Comparatively with the remaining ones, the rama fruits were less affected by the trimming procedures.
- How functional foods endure throughout the shelf storage? Effects of packing materials and formulation on the quality parameters and bioactivity of smoothiesPublication . Nunes, M. Antónia; Costa, Anabela S. G.; Barreira, João C. M.; Vinha, Ana F.; Alves, Rita C.; Rocha, Ada; Oliveira, M. Beatriz P. P.Smoothies are blended beverages that could contain fruit pulp, fruit juice, vegetables, yoghurt, milk, or honey. These beverages are typical examples of the food industry reply to the increase awareness of consumers for healthier foods with simple ingredients and clean labels. As emerging products, different profiling studies are needed to ensure their claimed properties. Accordingly, different physicochemical parameters, bioactive compounds, as well as the antioxidant activity, were assessed in commercial smoothies along different shelf storage periods. ANOVA, HCA and LDA statistical tools were used to allow a suitable comprehension of the obtained results. Some significant differences were found at initial time, which might be associated to smoothies’ composition. On the other hand, the physicochemical and chromatic parameters were stable during the shelf storage, while the content in bioactive compounds and the antioxidant activity indicators were significantly affected (independently of the applied thermal treatment). Nevertheless, none of the assayed formulations or packing types showed to be more susceptible to undergone specifically relevant changes during shelf storage. Overall, the results advice in favor of an earlier consumption of these products (far from the expiring date) in order to obtain the desired health effects.
- Impact of boiling on phytochemicals and antioxidant activity of green vegetables consumed in the Mediterranean dietPublication . Vinha, Ana F.; Alves, Rita C.; Barreira, Sérgio V. P.; Costa, Anabela S. G.; Oliveira, M. Beatriz P. P.The effect of boiling (10 minutes) on eleven green vegetables frequently consumed in the Mediterranean diet was evaluated. For that, some physicochemical parameters and the contents of vitamin C, phenolics and carotenoids, as well as the antioxidant activity, were determined in raw and boiled samples. The raw vegetables analysed in this study were good sources of vitamin C, carotenoids and phenolic compounds, with contents ranging from 10.6 to 255.1 mg/100 g, 0.03 to 3.29 mg/100 g and 202.9 to 1010.7 mg/100 g, respectively. Boiling promoted losses in different extensions considering both the different bioactive compounds and the distinct vegetables analysed. Contrary to phenolics (more resistant), vitamin C was the most affected compound. Boiling also originated significant losses in the antioxidant activity of the vegetables. Considering all the parameters analysed, the vegetables most affected by boiling were broccoli and lettuce. The least affected ones were collard and tronchuda cabbage.
- Improving bioactive compounds extractability of Amorphophallus paeoniifolius (Dennst.) NicolsonPublication . Costa, Anabela S. G.; Barreira, João C. M.; Ruas, Adilson; Vinha, Ana F.; Pimentel, Filipa B.; Alves, Rita C.; Ferreira, Isabel C. F. R.; Oliveira, M. Beatriz P. P.Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is an underground, unbranched deciduous plant that produces a large tubercle (rhizome) with recognized health effects. In this study, the influence of solvent nature (water, water/etanol (1:1) and absolute ethanol) and processing type (fresh, lyophilized and boiled) on the antioxidant activity and bioactive compounds extractability of elephant foot yam was evaluated. Extracts were compared for their contents in total phenolics, flavonoids and tannins. Moreover, their antioxidant capacity was assessed by the ferric reducing antioxidant power (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPHradical dot) scavenging capacity assays. Phenolics (154 mg GAE/L) and tannins (109 mg GAE/L) were maximized in lyophilized samples extracted with the hydroalcoholic solvent, which attained also the highest FRAP value (711 mg FSE/L). In turn, flavonoids reached the highest yields in lyophilized samples (95 mg ECE/L) extracted with pure ethanol, as well as the highest DPPHradical dot scavenging activity. These findings might have practical applications to define the best processing methodology regarding the enhancement of elephant foot yam, either for prompt consumption, as well as to develop food supplements or pharmaceutical related products.
- Improving the extraction of Ara h 6 (a peanut allergen) from a chocolate-based matrix for immunosensing detection: Influence of time, temperature and additivesPublication . Alves, Rita C.; Pimentel, Filipa B; Nouws, Henri P.A.; Silva, Túlio H B; Oliveira, M Beatriz P P; Delerue-Matos, CristinaThe extraction of Ara h 6 (a peanut allergen) from a complex chocolate-based food matrix was optimized by testing different temperatures, extraction times, and the influence of additives (NaCl and skimmed milk powder) in a total of 36 different conditions. Analyses were carried out using an electrochemical immunosensor. Three conditions were selected since they allowed the extraction of the highest levels of Ara h 6. These extractions were performed using 2g of sample and 20ml of Tris-HNO3 (pH=8) containing: a) 0.1M NaCl and 2g of skimmed milk powder at 21°C for 60min; b) 1M NaCl and 1g of skimmed milk powder at 21°C for 60min; and c) 2g of skimmed milk powder at 60°C for 60min. Recoveries were similar or higher than 94.7%. This work highlights the importance to adjust extraction procedures regarding the target analyte and food matrix components.
- Improving the extraction of Ara h 6 (a peanut allergen) from a chocolatebased matrix for immunosensing detection: Influence of time, temperature and additivesPublication . Alves, Rita C.; Pimentel, Filipa B.; Nouws, Henri P.A.; Silva, Túlio H.B.; Oliveira, M. Beatriz P.P.; Delerue-Matos, CristinaThe extraction of Ara h 6 (a peanut allergen) from a complex chocolate-based food matrix was optimized by testing different temperatures, extraction times, and the influence of additives (NaCl and skimmed milk powder) in a total of 36 different conditions. Analyses were carried out using an electrochemical immunosensor. Three conditions were selected since they allowed the extraction of the highest levels of Ara h 6. These extractions were performed using 2 g of sample and 20 ml of Tris-HNO3 (pH = 8) containing: a) 0.1 M NaCl and 2 g of skimmed milk powder at 21 C for 60 min; b) 1 M NaCl and 1 g of skimmed milk powder at 21 C for 60 min; and c) 2 g of skimmed milk powder at 60 C for 60 min. Recoveries were similar or higher than 94.7%. This work highlights the importance to adjust extraction procedures regarding the target analyte and food matrix components.
- Lipid content and fatty acid profile of Senegalese sole (Solea senegalensis Kaup, 1858) juveniles as affected by feed containing different amounts of plant protein sourcesPublication . Fernandes, Telmo J. R.; Alves, Rita C.; Souza, Tiago; Silva, J. M. G.; Castro-Cunha, M.; Valente, Luísa M.P.; Oliveira, M. Beatriz P. P.A growth trial with Senegalese Sole (Solea senegalensis Kaup, 1858) juveniles fed with diets containing increasing replacement levels of fishmeal by mixtures of plant protein sources was conducted over 12 weeks. Total fat contents of muscle, liver, viscera, skin, fins and head tissues were determined, as well as fatty acid profiles of muscle and liver (GC-FID analysis). Liver was the preferential local for fat deposition (5.5–10.8% of fat) followed by fins (3.4–6.7% fat). Increasing levels of plant protein in the diets seems to be related to increased levels of total lipids in the liver. Sole muscle is lean (2.4–4.0% fat), with total lipids being similar among treatments. Liver fatty acid profile varied significantly among treatments. Plant protein diets induced increased levels of C16:1 and C18:2 n -6 and a decrease in ARA and EPA levels. Muscle fatty acid profile also evidenced increasing levels of C18:2 n 6, while ARA and DHA remained similar among treatments. Substitution of fishmeal by plant protein is hence possible without major differences on the lipid content and fatty acid profile of the main edible portion of the fish – the muscle.
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