Percorrer por autor "Fernandes, Andreia"
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- Analysis of single-cultivar extra virgin olive oil using cyclic voltammetryPublication . Fernandes, Andreia; Dias, L.G.; Pereira, J.A.; Veloso, Ana C.A.; Peres, António M.Extra virgin olive oils (EVOO) quality evaluation is a complex task. The development of fast, simple and low-cost electrochemical methods to assess the quality of high-valued EVOOs, namely of "single-cultivar" EVOOs, which are very appreciated by consumers, is still a challenge task. Few works can be found in the literature regarding the application of sensor devices for classifying "single-cultivar" EVOOs according to the olive cultivar, in order to guarantee their authenticity. Cimato et al. [1] used the signals recorded with an electronic nose to separate among clusters of 12 different single-cultivar EVOOs. Apetrei et al. [2] showed that combining the electrochemical signal data obtained from electronic eye, nose and tongue allowed a good predictive classification capacity according to the olive variety of three single-cultivar EVOOs, with different degree of bitterness. In this work an approach based on cyclic voltammetry (CV) is proposed to analyze 4 different single-cultivar EVOOs (1 Portuguese (pt) and 3 Spanish (es) cultivars): Cobran~osa (C-pt), Manzanilla (M-es), Frantoto (F-es) and Redondilha (R-es). For each EVOO sample, 3 extractions were performed using a solution of ethanol/water (EtCH/H 20 1:4; v:v). The CV technique has been evaluated using an Ag/AgCI double-junction reference electrode (M90-02, Orion) and two pairs of counter/working electrodes: (i) platinum (M241Pt, Radiometer) and silver (M295Ag, Radiometer) electrodes or (ii) two platinum (M241Pt and M21, Radiometer) electrodes. The resultant currents of the potentiostat-galvanostat device (PG580, Uniscan) have been acquired between -1.5 to +0.8 V (Pt/Ag) or -2 to +2V (Pt/Pt), at a potential scan rate of 100 mV /s (UiEChem v.1.34 software, Unisann Instruments Ltd) and considered for data analysis. The preliminary results, allow expecting that, the differences of shape and pOSition of the peaks from the CV, observed from one extract to another, can be used to differentiate between single-cultivar EVOOs, according to cultivar and/or geographical origin.
- Assessing the prebiotic potential of xylooligosaccharides produced by one-step fermentation using agro-residuePublication . Cordeiro, Ana; Fernandes, Andreia; Sousa, Joana; Cardoso, Beatriz; Alves, Joana; Silvério, Sara; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaA prebiotic is defined as a substrate that is selectively utilized by host microrganisms, conferring a health benefit
- Assessing the prebiotic potential of xylooligosaccharides produced by one-step fermentation using agro-residuesPublication . Cordeiro, Ana; Fernandes, Andreia; Sousa, Joana; Cardoso, Beatriz; Alves, Joana; Silvério, Sara; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaThe prebiotic effect is a fundamental concept in the fields of nutrition and gut health, referring to the beneficial effects of specific non-digestible dietary components on the gut microbiota, including xylooligosaccharides (XOS). These compounds function as food sources for beneficial gut bacteria, fostering their growth and activity. In this work, in vitro studies were performed to evaluate the prebiotic potential of XOS produced from olive stones (OS) and coffee silver skin (CSS) via a one step fermentation using a recombinant Bacillus subtilis 3610 harbouring the xylanase gene xyn2 from Trichoderma reesei. This potential was compared with a commercially available prebiotic oligofructose (Orafti®, BENEO, Germany). A mixture of human faeces from four healthy donors aged between 24 and 28 years old was used as inoculum. The pH variation and the production of short-chain fatty acids (SCFAs), gases, and ammonia were analysed during the 48 hours fermentations. The prebiotic supplementation resulted in a reduction of the pH value over time, with oligofructose presenting the most significant pH drop at 48 hours (ΔpH=3.65). The addition of prebiotics also significantly increased the production of beneficial SCFAs, with oligofrutose exhibiting a notable increase in the production of lactic and acetic acid production after 48 hours (28.0±0.1 and 28±1 mM, respectively), while OS-XOS and CSS-XOS demonstrated a more prominent rise towards the production of acetic acid (14.8±0.4 and 20.4±0.1 mM, respectively), butyric acid (2.5±0.3 and 3.29±0.04 mM, respectively), and valeric acid (75±1 and 110±14 mM, respectively) at 48 hours. Remarkably, the gas analysis revealed that the addition of OS/CSS-XOS fully suppressed the production of CH4 and increased the CO2 generation after 48 hours (2.6±0.7 and 5.20±0.05 mmol.L-1medium, respectively). These findings strongly suggest that the XOS produced from OS and CSS holds potential prebiotic properties for human health.
- Olive oil by-products as potential alternative substrates for xylooligosaccharides productionPublication . Cordeiro, Ana; Fernandes, Andreia; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaOlive pomace (OP) and olive stones (OS) are industrial by-products from the olive oil production. These residues have a high percentage of cellulose, hemicellulose, and lignin, which makes them a good source of fermentable sugars and xylan, as well as a potential alternative substrate for xylooligosaccharides (XOS) production. In this work, OP and OS were chemically characterized and used for the first time as a xylan source to produce XOS through direct fermentation by Bacillus subtilis 3610 containing the xylanase gene xyn2 from Trichoderma reesei. OS presented the highest potential for XOS production. The fermentation process was further optimized for this residue in terms of residue concentration (5, 10, 20, 40 and 60 g L-1), pH (5.0, 6.0, 7.0 and 8.0), and temperature (30, 37, 45 and 50°C). The highest total sugars yield (27 ± 2 mg g-1) was achieved after 12 h, using 20 g L-1 of OS at pH 7.0 and 45°C.
- Single-cultivar extra virgin olive oil classification using a potentiometric electronic tonguePublication . Dias, L.G.; Fernandes, Andreia; Veloso, Ana C.A.; Machado, Adélio A.M.; Pereira, J.A.; Peres, António M.Label authentication of monovarietal extra virgin olive oils is of great importance. A novel approach based on a potentiometric electronic tongue is proposed to classify oils obtained from single olive cultivars (Portuguese cvs. Cobrançosa, Madural, Verdeal Transmontana; Spanish cvs. Arbequina, Hojiblanca, Picual). A meta-heuristic simulated annealing algorithm was applied to select the most informative sets of sensors to establish predictive linear discriminant models. Olive oils were correctly classified according to olive cultivar (sensitivities greater than 97%) and each Spanish olive oil was satisfactorily discriminated from the Portuguese ones with the exception of cv. Arbequina (sensitivities from 61% to 98%). Also, the discriminant ability was related to the polar compounds contents of olive oils and so, indirectly, with organoleptic properties like bitterness, astringency or pungency. Therefore the proposed E-tongue can be foreseen as a useful auxiliary tool for trained sensory panels for the classification of monovarietal extra virgin olive oils.
- Valorisation of olive oil by-products into pectic- and glucuronoxylo-oligosaccharides via one-step fermentationPublication . Cordeiro, Ana; Fernandes, Andreia; Ferreira, Andreia S.; Coelho, Elisabete; Coimbra, Manuel A.; Silvério, Sara C.; Cadavez, Vasco; Peres, António M.; Rodrigues, Lígia R.; Amorim, CláudiaOlive pomace (OLP) and stones (OLS) are key by-products of olive oil production, rich in lignocellulose and pectin, making them viable substrates for prebiotic oligosaccharide (OS) production. This study evaluated the chemical composition of OLP and OLS powders (OLPp and OLSp) and their potential for OS production through one-step fermentation using recombinant Bacillus subtilis 3610. Both substrates had comparable xylan and pectin levels, but OLSp showed greater potential, achieving a maximum total sugar yield of 60 +/- 3 mg.g- 1 after 12 h under optimal conditions (20 g.L- 1 OLSp, pH 7.0, 45 degrees C). The resulting OS mixture from OLSp was predominantly composed of pectic oligosaccharides (72.1 %mol) and glucurono-xylooligosaccharides (11.6 %mol). This innovative process, competitive with commercial enzymes, highlights the potential of by-product valorisation for producing value-added food compounds. The findings provide insights into low-cost bioprocesses and underscore the importance of sustainable approaches in the industry of functional food ingredients.