Percorrer por autor "Guilherme, Rosa"
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- Controlo de infestantes em Horticultura em modo de produção biológico.Publication . Guilherme, Rosa; Baptista, Paula; Reboredo, Fernando; Pereira, J.A.Na produção de hortícolas em modo de produção biológico (MPB), o controlo das plantas infestantes é de grande dificuldade, limitando a produção devido à competição que exercem pela água e nutrientes. Neste sistema de produção a minimização dos prejuízos causados pelas infestantes, é conseguida normalmente pelo recurso a métodos culturais, físicos e mecânicos, onde é impedida a germinação, limitado o seu desenvolvimento, ou eliminação das infestantes através do arranque/corte/queima, colocação de barreiras ou mobilização do solo, este o mais usual. Neste sentido, no presente trabalho pretendem avaliar-se três técnicas para o controlo de infestantes, nomeadamente a monda térmica, a monda mecânica e a cobertura com tela, em comparação com a testemunha onde não se realizará qualquer intervenção. Para tal, num campo certificado em MPB na região do Baixo Mondego, será instalado um ensaio com as diferentes modalidades em estudo, em cultivo de três espécies hortícolas: couve crespa (Brassica oleraceae L.), alho francês (Allium porrum L.), ambas de cultivo habitual no outono-inverno e pimento (Capsicum annum L.) com um ciclo cultural característico de primaveraverão. O sistema de rega a utilizar é de gota a gota e todas as intervenções necessárias para o desenvolvimento das culturas como por exemplo as fertilizações e tratamentos fitossanitários, respeitam as normas de MPB. A avaliação das diferentes técnicas ocorrerá ao nível: I) do controlo de plantas infestantes; II) da biodiversidade e propriedades físicas e químicas do solo; III) e da produtividade, composição química e nutricional das três espécies cultivadas. Neste trabalho apresenta-se o desenho experimental, as metodologias que serão usadas para avaliação de cada um dos parâmetros e as principais metas que se pretendem alcançar.
- Phenolics and antioxidant activity of green and red sweet peppers from organic and conventional agriculture: A comparative studyPublication . Guilherme, Rosa; Aires, Alfredo; Rodrigues, Nuno; Peres, António M.; Pereira, J.A.Today, consumers are very concerned regarding food quality, nutritional composition and positive health effects of consumed foods. In this context, the preference and consumption of organic products has been increasing worldwide. In the present work, sweet peppers in two maturation stages (i.e., green and red peppers) from organic and conventional production systems were evaluated in regards to phenolic composition and antioxidant activity. Nine phenolic compounds were identified and quantified by a high-performance liquid chromatography-diode-array detector (HPLC-DAD), namely resveratrol, meta-coumaric acid, ortho-coumaric acid, clorogenic acid, caffeic acid, myricetin, rutin, luteolin-7-O-glucoside and quercitin-3-O-rhamnoside. In contrast to the production system, the maturation stage showed a pronounced significant effect on the phenolic composition of the studied sweet peppers; in general, green peppers possessed higher contents than red ones. Meta-coumaric acid, ortho-coumaric acid and quercitin-3-O-rhamnoside were more abundant in green conventional peppers and chlorogenic acid, caffeic acid and rutin were found in higher levels in red organic peppers. Regarding the antioxidant activity, green conventional peppers showed the highest DPPH, ABTS•+ and total reducing capacities, while red conventional peppers had higher TEAC values. Finally, principal component analysis showed that the phenolic composition together with the antioxidant capacities could be used to differentiate the production system and the maturation stage of sweet peppers. This finding confirmed that both factors influenced the peppers’ phenolic composition and antioxidant capacity, allowing their possible use as maturation–production biomarkers.
- Sweet peppers discrimination according to agronomic production mode and maturation stage using a chemical-sensory approach and an electronic tonguePublication . Guilherme, Rosa; Rodrigues, Nuno; Marx, Ítala; Dias, L.G.; Veloso, Ana C.A.; Ramos, Ana Cristina; Peres, António M.; Pereira, J.A.The demand for organic foods has increased worldwide, in particular due to the association with healthier, more nutritious and tasty products, being a clear trend on sweet peppers’ consumption. Thus, this study aimed to evaluate the effects of agronomic production mode (conventional and organic) and maturation stage (associated to green, turning and red colours) on the chemical-sensory attributes of peppers grown in open field. It was found that organic peppers had a better visual/tactile aspect (greater firmness and more intense colours) but lower chemical quality (lower titratable acidity and total soluble solids). On the other hand, red peppers (higher maturation stage) had lower visual-tactile quality but higher chemical quality. From sensory analysis, conventional peppers had better overall aspect, colour intensity-homogeneity and brightness. Then again, the maturation stage of peppers mostly influenced the sensory visual attributes, being turning colour peppers the less appreciated, although organic red peppers were less succulent and had a lower global quality. Even so, the chemical-sensory parameters could be used to discriminate peppers taking into account the agronomic production mode and the maturation stage/colour (79 ± 12% of correct classifications for the repeated K-fold cross-validation procedure). However, a trained sensory panel is required, which can be a major drawback considering their scarcity. This limitation was successfully overcome by using a potentiometric electronic tongue, which allowed discriminating the peppers with a higher predictive sensitivity (85 ± 9%), showing that this device could be used as an accurate taste sensor for the qualitative analysis of sweet peppers.