Loading...
12 results
Search Results
Now showing 1 - 10 of 12
- Physicochemical and bioactive caracterisation of edible and waste parts of “piel de sapo” melonPublication . Miller, Fátima Alves; Fundo, Joana Freitas; Garcia, Ester; Santos, João Rodrigo; Silva, Cristina Luisa Miranda; Brandão, Teresa Ribeiro SilvaSeveral scientific studies point fruits as rich sources of antioxidants but mainly focus on their edible part. However, fruits wastes are abundant sources of bioactive compounds and nutrients, which are considered to be health beneficial. The main purpose was to characterise juice, pulp, peel and seeds of Piel de Sapo melon, in terms of several physicochemical characteristics (soluble solids content, titratable acidity, pH, potassium, colour and water activity), some bioactive compounds (total phenolics, vitamin C, chlorophylls and total carotenoids) and total antioxidant activity. Juice, pulp, peel and seeds represent 47, 19, 27 and 5% of melon total weight, respectively. Peel and seeds stood out by their higher concentration of total phenolics compounds and antioxidant activity when compared to edible parts. The highest potassium concentration was found in seeds. Chlorophylls were only detected in peel, while carotenoids were not detected in any part of the melon analysed. Juice and pulp contributed to 69% of vitamin C amount of the whole fruit. However, its concentration in peel was equivalent to the ones observed in juice and pulp. These results pointed out the importance of fruit wastes valorisation and the development of strategies for their re-utilisation.
- In-line monitoring of the coffee roasting process with near infrared spectroscopy: Measurement of sucrose and colourPublication . Santos, João Rodrigo; Viegas, Olga; Páscoa, Ricardo N. M. J.; Ferreira, Isabel M. P. L. V. O.; Rangel, António O. S. S.; Lopes, João AlmeidaIn this work, a real-time and in-situ analytical tool based on near infrared spectroscopy is proposed to predict two of the most relevant coffee parameters during the roasting process, sucrose and colour. The methodology was developed taking in consideration different coffee varieties (Arabica and Robusta), coffee origins (Brazil, East-Timor, India and Uganda) and roasting process procedures (slow and fast). All near infrared spectroscopy-based calibrations were developed resorting to partial least squares regression. The results proved the suitability of this methodology as demonstrated by rangeerror- ratio and coefficient of determination higher than 10 and 0.85 respectively, for all modelled parameters. The relationship between sucrose and colour development during the roasting process is further discussed, in light of designing in real-time coffee products with similar visual appearance and distinct organoleptic profile.
- Exploiting near infrared spectroscopy as an analytical tool for on-line monitoring of acidity during coffee roastingPublication . Santos, J. R.; Lopo, M.; Rangel, António O. S. S.; Lopes, J. A.This work focused on the monitoring during the roasting process of one of the main characteristics of coffee's organoleptic profile: acidity. Batches of Arabica and Robusta coffee varieties from different origins were roasted following different process conditions. Simultaneously, real-time on-line monitoring of the coffee roasting process was performed with near infrared spectroscopy (NIRS) using a diffuse reflectance probe. Spectral data were analysed with chemometric tools and acidity profiles were estimated directly from NIR spectra, revealing an encouraging agreement with values obtained with the reference analytical methodology. NIRS proved to be a reliable non-invasive technique for real-time monitoring of coffee roasting processes and may be used as an end-roasting signalizing tool. Furthermore, the approach presented also revealed good perspectives for the exploration of NIRS in the monitoring of other relevant compounds during coffee roasting.
- Determinação de trigonelina em café por cromatografia líquida de baixa pressão e detecção electroquímicaPublication . Santos, João Rodrigo; Rangel, António O. S. S.
- A total analytical system featuring a novel solid–liquid extraction chamber for solid sample flow analysisPublication . Galvis-Sánchez, Andrea C.; Santos, João Rodrigo; Rangel, António O. S. S.In this work, a total flow analysis system based on a novel solid–liquid extraction chamber is presented. This strategy enables all the main experimental procedures for the analysis of a solid sample to be performed automatically: enrichment of the liquid extract, sample treatment, filtration of the liquid extract from the solid sample, directing the extract towards detection, and finally cleansing of the chamber for the following solid sample to be analyzed. The chamber designed to be incorporated in the flow manifold presents two main features: it accommodates stirring bars for enhancing the extraction process, and it presents replaceable solid sample containers (a spare part of the solid–liquid extraction chamber) to easily replace the solid sample and therefore enhance sample analysis throughput. The chamber performance was assessed using two different solid samples, an ion exchanger resin and vegetable samples, focussing on proton and nitrate on extraction, respectively. The main figures of merit achieved were relative standard deviation (RSD) and relative error values below 7 % for all determinations. The determination rate for vegetable samples was ca. 12 samples h−1. The proposed strategy may be exploited to perform automatically the analysis of solid samples as it embodies a simple automatic strategy of a very important but time consuming and laborious analytical operation.
- Standard addition flow method for potentiometric measurements at low concentration levels: application to the determination of fluoride in food samplesPublication . Galvis-Sánchez, Andrea C.; Santos, João Rodrigo; Rangel, António O. S. S.A standard addition method was implemented by using a flow manifold able to perform automatically multiple standard additions and in-line sample treatment. This analytical strategy was based on the in-line mixing of sample and standard addition solutions, using a merging zone approach. The flow system aimed to exploit the standard addition method to quantify the target analyte particularly in cases where the analyte concentration in the matrix is below the lower limit of linear response of the detector. The feasibility of the proposed flow configuration was assessed through the potentiometric determination of fluoride in sea salts of different origins and different types of coffee in fusions. The limit of quantification of the proposed manifold was 5x 10 6 mol L -1, 10-fold lower than the lower limit of linear response of the potentiometric detector used. A determination rate of 8 samples h -1 was achieved considering an experimental procedure based on three standard additions per sample. The main advantage of the proposed strategy is the simple approach to perform multiple standard additions, which can be implemented with other ion selective electrodes, especially in cases when the primary ion is below the lower limit of linear response of the detector.
- Development of a chromatographic low pressure flow injection system:Application to the analysis of methylxanthines in coffeePublication . Santos, João Rodrigo; Rangel, António O.S.S.In this work, the coupling of a commercial monolithic column to a traditional low pressure FIA system is proposed for the analysis of theobromine, theophylline and caffeine in coffee brewed samples using UV detection. The parameters mobile phase composition, flow rate and loop volume were evaluated and discussed considering the various chromatographic parameters in order to enable resolution of the methylxanthines studied within the coffee brewed sample matrix. The analyses of methylxanthines in coffee brewed samples by the proposed methodology were in good agreement with those obtained by the reference procedure based on HPLC. Relative errors were below 6% for all samples analyzed. Detection limits in the selected experimental conditions were within 10−6M range for theobromine and theophylline, and 10−5M for caffeine. The determination rate of the three methylxanthines for coffee brewed samples was ca of 10 h−1. The main advantage of the proposed flow system was the possibility to perform chromatographic separations in low pressure flow systems. This substantial improvement was achieved due to the compatibility of monolithic columns within the flow injection system surpassing in this way one of the main handicaps of traditional flow analysis systems. Additional features of the strategy presented were low cost, efficiency, high versatility and low reagent consumption comparing to HPLC methodologies usually followed in the case study herein presented.
- Physicochemical characteristics, bioactive compounds and antioxidant activity in juice, pulp, peel and seeds of Cantaloupe MelonPublication . Fundo, Joana F.; Miller, Fátima A.; Garcia, Ester; Santos, João Rodrigo; Silva, Cristina L. M.; Brandão, Teresa R. S.Although it is known that fruit products are rich sources of natural bioactive compounds, information on the nutritional value of their waste parts is scarce. The objective was to characterize the edible (juice and pulp) and waste (peel and seeds) parts of Cantaloupe melon (Cucumis melon L. var. reticulatus) in terms of some physicochemical characteristics, bioactive compounds and total antioxidant activity. Juice, pulp, peel and seeds represent 42, 23, 25 and 7% of total weight, respectively. Juice and pulp presented identical profiles in terms of physicochemical characteristics, bioactive compounds and antioxidant activity. They contributed to the majority of the overall content of carotenoids (80%) and vitamin C (84%) in Cantaloupe. Peel and seeds had the highest concentrations of potassium, being seeds the richest portion (7.08 ± 0.16 mg/g). Seeds had also the significantly highest total phenolics concentration (229.13 ± 20.92 μg/g), antioxidant activity (653.67 ± 169.20 μg/g), and soluble solids content (11.79 ± 0.90 °Brix). Peel stood out by the presence of chlorophylls. Since waste parts of Cantaloupe melon represent around 32% of total weight, their valorization is a challenge and strategies to improve ways of re-using them should be developed.
- Authenticity control of roasted coffee brands using near-infrared spectroscopyPublication . Sarraguça, Mafalda Cruz; Santos, João Rodrigo; Rangel, António O. S. S.; Lopes, João AlmeidaIn this work, a methodology based on near-infrared spectroscopy (NIRS) was exploited in order to discriminate between commercial coffee brands. The main advantages of this approach compared to other strategies (e.g., wet chemistry methods) are its lower cost, less labor, and lower time per analysis. Two commercial brands were discriminated among several others present in the Portuguese market. The chemometric method used to estimate discriminant models was partial least squares discriminant analysis (PLSDA). Results show that it is possible to discriminate coffee brands using this strategy with a correct classification of 100 %. The spectral region, more favorable to discrimination of roasted coffee brands, can be related with differences in the concentrations of compounds, such as, chlorogenic acid and sucrose, and also due to differences on lipid fraction. This methodology is adequate for field implementation, namely, adopting handheld NIRS instruments.
- Development of a chromatographic low pressure flow injection system using amperometric detection: Application to the analysis of niacin in coffeePublication . Santos, João Rodrigo; Rangel, António O. S. S.In this work, an analytical flow system able to perform low pressure chromatography with amperometric detection is presented. As case study, the determination of niacin (vitamin B3) in coffee brewed samples was selected. The manifold comprised a 1.0 cm length monolithic column coated with didecyldimethylammonium bromide, a laboratory-made boron doped diamond electrode, and featured in-line ionic strength adjustment of the mobile phase. The figures of merit concerning the selected case study namely, detection limit, 7.90 10 7 M, determination rate, ca. 10 samples h 1, mobile phase and ISA solution consumption, ca. 2.6 mL per analysis, and CV, below 5% for retention time and peak height, showed the competitiveness of this analytical strategy comparing to the described HPLC methods for niacin determination. The strategy displays a simple configuration, low cost, fast and easy assembling, foreseeing its use to general purpose applications.