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- Volatile-olfactory profiles of cv. Arbequina olive oils extracted without/with olive leaves addition and their discrimination using an electronic nosePublication . Marx, Ítala; Rodrigues, Nuno; Veloso, Ana C.A.; Casal, Susana; Pereira, J.A.; Peres, António M.Oils from cv. Arbequina were industrially extracted together with olive leaves of cv. Arbequina or Santulhana (1%, w/w), and their olfactory and volatile profiles were compared to those extracted without leaves addition (control). -e leaves incorporation resulted in green fruity oils with fresh herbs and cabbage olfactory notes, while control oils showed a ripe fruity sensation with banana, apple, and dry hay grass notes. In all oils, total volatile contents varied from 57.5 to 65.5 mg/kg (internal standard equivalents), being aldehydes followed by esters, hydrocarbons, and alcohols the most abundant classes. No differences in the number of volatiles were observed. -e incorporation of cv. Arbequina or Santulhana leaves significantly reduced the total content of alcohols and esters (minus 37–56% and 10–13%, respectively). Contrary, cv. Arbequina leaves did not influence the total content of aldehydes or hydrocarbons, while cv. Santulhana leaves promoted a significant increase (plus 49 and 10%, respectively). -us, a leaf-cultivar dependency was observed, tentatively attributed to enzymatic differences related to the lipoxygenase pathway. Olfactory or volatile profiles allowed the successful unsupervised differentiation of the three types of studied cv. Arbequina oils. Finally, a lab-made electronic nose was applied to allow the nondestructive discrimination of cv. Arbequina oils extracted with or without the incorporation of olive leaves (100% and 99 ± 5% of correct classifications for leave-one-out and repeated K-fold crossvalidation variants), being a practical tool for ensuring the label correctness if future commercialization is envisaged. Moreover, this finding also strengthened that olive oils extracted with or without olive leaves incorporation possessed quite different olfactory patterns, which also depended on the cultivar of the olive leaves.
- Ancient olive trees as a source of olive oils rich in phenolic compoundsPublication . Rodrigues, Nuno; Casal, Susana; Pinho, Teresa; Peres, António M.; Bento, Albino; Baptista, Paula; Pereira, J.A.Olive oil phenolic compounds are receiving increased attention due to its influence on sensory characteristics and to scientific evidences of positive health effects. In this work, 28 ancient olive trees were selected and, during four consecutive seasons (2014–2017), oils were extracted and their phenolic fraction characterized. Hydroxytyrosol and tyrosol secoiridoids were the predominant groups, with contents between 32 and 496 mg of tyrosol equivalents/kg. Based on principal component analysis it could be concluded that the individual phenolic contents enabled the unsupervised grouping of olive oils by crop year. Furthermore, linear discriminant analysis allowed achieving sensitivities greater than 90%. It was shown that some specimens consistently allowed obtaining oils with high phenolic contents (≥500 mg tyrosol equivalents/kg). The identification of centenarian specimens for breeding based on their potential to produce oils with high levels of healthy compounds is of utmost interest, contributing to preserve the genetic heritage.
- Efeito da aplicação de diferentes dotações de rega, num olival jovem de alta densidade, na composição em ácidos gordos e tocoferóis dos azeitesPublication . Rodrigues, Nuno; Casal, Susana; Ribeiro, A.C.; Peres, Fátima; Almeida, Arlindo; Manzke, Gabriel; Bento, Albino; Pereira, J.A.Na região de Trás-os-Montes o olival, é na sua grande maioria, olival tradicional extensivo conduzido em condições de sequeiro. Contudo, nos últimos anos têm sido plantados alguns olivais de alta densidade com rega. Neste sentido, com o presente trabalho pretendeu-se avaliar a aplicação de três dotações de rega, nomeadamente 25, 75 e 100% de evapotranspiração, ao nível da composição em ácidos gordos e tocoferóis de azeites elementares de três cultivares, Arbequina, Cobrançosa e Negrinha de Freixo. O ensaio decorreu num olival jovem instalado na região de Mirandela e para cada dotação de rega e cultivar em estudo, foram seleccionados três grupos de três árvores onde foram colhidas as azeitonas e extraído o azeite. Nos azeites obtidos foi avaliada a composição em ácidos gordos por cromatografia gasosa com detetor de ionização em chama e o teor em tocoferóis, por cromatografia líquida de alta eficiência com detetor de fluorescência. Os resultados indicam uma composição relativa diferenciada, quer em ácidos gordos quer em tocoferóis, entre os azeites das três cultivares em estudo. O efeito da dotação de rega foi diferente entre cultivares, sendo na cv. Negrinha de Freixo onde mais se fez sentir, com um aumento de C16:0, C16:1, C18:2cc, e somatório de ácidos gordos saturados e ácidos gordos polinsaturados, e uma diminuição do ácido oleico (C18:1) e da soma dos ácidos gordos monoinsaturados. Na Cv. Arbequina apenas foram registados aumentos dos teores em C16:0, C16:1 e soma de ácidos gordos saturados, enquanto na Cv. Cobrançosa não foi observado qualquer efeito. No que respeita ao teor em tocoferóis, nas Cvs Cobrançosa e Arbequina as diferentes dotações de rega não influíram na sua composição, tendo os seus azeites valores na ordem dos 480 e dos 370 mg/kg de azeite enquanto na Cv. Negrinha de Freixo houve um incremento do teor destes compostos passando de 220 mg/kg, na menor dotação de rega, para 269mg/kg, na rega máxima.
- Effect of olive trees density on the quality and composition of olive oil from cv. ArbequinaPublication . Rodrigues, Nuno; Casal, Susana; Peres, António M.; Baptista, Paula; Bento, Albino; Martín, Hugo; Asensio-S.-Manzanera, M. Carmen; Pereira, J.A.The number of plants per hectare is a key factor for olive tree productivity. Nevertheless, information about the effect of tree density on olive oil quality and composition is scarce. Thus, the effect of planting densities of cv. Arbequina trees on olive oil quality and composition was studied along the first four years of production. Two types of planting tree arrangements were evaluated, namely olive trees planted at different distances within a row (2.0 m; 1.5 m; 1.25 m; and 1.0 m, fixing the space between rows equal to 4.0 m) or at different distances between rows (4.0 m; 3.5 m; and 3.0 m, fixing the space within the same row at 1.5 m), which led to planting densities from 1250 to 2500 trees ha−1. The results indicated that the quality parameters, composition, antioxidant activity and oxidative stability were significantly affected by the densities of plants and the crop year (Pvalue < 0.0001, for one-way ANOVA). An increase of plants in the row and between rows showed a tendency for a slight increase of free acidity, and a reduction of the peroxide value and of the extinction specific coefficients. Fatty acid composition was also affected, with a tendency for the decrease of C16:0, C18:0, SFA and PUFA, and an increase of C18:1, C18:2 and MUFA. The antioxidant activity and the oxidative stability also showed a reduction trend. For all parameters evaluated, the crop year had a marked influence. The year of production had significant statistical effects on the evaluated parameters, which could be related to agro-climatic factors.
- Fatty acid composition from olive oils of portuguese centenarian trees is highly dependent on olive cultivar and crop yearPublication . Rodrigues, Nuno; Casal, Susana; Pinho, Teresa; Cruz, Rebeca; Peres, António M.; Baptista, Paula; Pereira, J.A.The high proportions of monounsaturated fatty acids (MUFA) represent one of the most important technological and nutritional features of olive oils. The present study details the fatty acid (FA) composition of autochthonous cultivars (Lentisca, Madural, Redondal, Rebolã, Verdeal, and Verdeal Transmontana) produced from centenarian trees during five crop years (2013–2017). Olive cultivar highly influenced the FA composition, namely, oleic acid (70.3% for Madural to 80.7% for Redondal) and palmitic acid (10.4% for Lentisca to 13.5% for Verdeal). Similarly, crop year significantly influenced the individual FA contents. Principal component analysis of FA data enabled the unsupervised classification by cultivar and, within each cultivar, by crop year. Furthermore, the levels of nine individual FAs, together with the polyunsaturated fatty acid contents, selected using the simulated annealing algorithm, allowed for their correct classification, on the basis of linear discriminant analysis, according to the olive cultivar, with an overall sensitivity of 92%, for leave-one-out cross-validation procedure. Globally, the cultivar effect superimposed that of crop year, showing that some cultivars, such as Redondal and Verdeal Transmontana, have consistently high and homogeneous proportions of MUFA, indicating that they are worth exploring in terms of future selection of cultivars that are able to produce olive oils with increased nutritional value and that are less prone to oxidation.
- Classification of olive oils according to sensory defects using a potentiometric electronic tonguePublication . Silva, Lucas M.; Dias, L.G.; Rodrigues, Nuno; Veloso, Ana C.A.; Rebello, Ligia P.G.; Pereira, J.A.; Peres, António M.Olive oil is a highly appreciated food product being very prone to frauds. Olive oils may be graded as extra-virgin, virgin or lampante. This classification is attributed according to legal requirements, including chemical parameters and sensorial analysis. Among the organoleptic sensations, the capability of perceiving the presence or absence of sensory defects plays a key role for olive oils grade classification. This task is time-consuming and quite expensive, requiring the use of an official taste panel, which can only evaluate a low number of samples per day. In this work, an electronic tongue is proposed to discriminate olive oils according to the defect predominantly perceived (winey-vinegary, wet-wood, rancid and fusty/muddy sediment), by a trained sensory panel. Sub-sets of potentiometric signal profiles obtained from the lipid sensor membranes of the taste electrochemical device were selected using a simulated annealing meta-heuristic algorithm, allowing establishing classification linear discriminant model, which showed a predictive success classification rate of 81% for leave-one-out or cross-validation procedure. The satisfactory predictive performance achieved pointed out the practical potential of using this artificial taste sensor as a complementary methodology for olive oil sensory analysis.
- Evaluation of the effect of extracted time conditions on the phenolic content of olive pastes from cv. Arbequina and discrimination using a lab-made potentiometic electronic tonguePublication . Marx, Ítala; Rodrigues, Nuno; Veloso, Ana C.A.; Pereira, J.A.; Peres, António M.The present study investigated the effect of malaxation times (Mt: 0, 15, 30, 45 and 60 min), during the industrial extraction of cv. Arbequina oils at 25 ºC on total phenolic content and bitterness index of olive pastes. Additionally, the possibility of applying a lab-made potentiometric electronic tongue (E-tongue), comprising 40 lipid/polymer sensor membranes with cross sensitivity, to discriminate the olive pastes according to the Mt, was evaluated. The results pointed out that the olive pastes’ total phenolic contents significantly decreased (P-value < 0.001, one-way ANOVA) with the increase of the Mt (from 2.21±0.02 to 1.99±0.03 g GAE/kg olive paste), being observed a linear decreasing trend (R-Pearson = -0.910). Similarly, the bitterness index also decreased with the Mt (23.4±0.3 to 21.9±0.4 oleuropein/kg olive paste). These findings may be tentatively attributed to the migration of the phenolic compounds from the olive pastes to the extracted oil and water phases, during the malaxation process. Finally, the E-tongue signals, acquired during the analysis of the olive pastes’ methanolic extracts (methanol:water, 80:20 v/v), together with a linear discriminant analysis (LDA), coupled with a simulated annealing (SA) algorithm, allowed to establish a successful classification model. The E-tongue-LDA-SA model, based on 11 selected non-redundant sensors, allowed to correctly discriminate all the studied olive pastes according to the Mt (sensitivities of 100% for training and leave-one-out cross-validation). The satisfactory performance of E-tongue could be tentatively explained by the known capability of lipid/polymeric sensor membranes to interact with phenolic compounds, through electrostatic interactions and/or hydrogen bonds, which total content depended on the Mt.
- 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.
- Alterações químicas do azeite das Cvs Negrinha de Freixo e Santulhana com a maturação do frutoPublication . Rodrigues, Nuno; Laira, Matheus; Cruz, Rebeca; Pinho, Teresa; Casal, Susana; Pereira, J.A.Diferentes trabalhos têm demonstrado que o grau de maturação das azeitonas influi na composição do azeite extraído, com alterações ao nível da sua composição química e sensorial. No entanto, não existe qualquer informação para as cultivares Negrinha de Freixo e Santulhana produzidas em Trás-os-Montes, sendo a primeira maioritária no concelho de Freixo de Espada à Cinta e a segunda largamente difundida nos concelhos de Bragança e Macedo de Cavaleiros. Assim, no presente trabalho foram colhidos frutos das duas cultivares em quatro índices de maturação distintos (l, 2, 3 e 4)nos quais se extraiu o azeite numa linha de extraçâo laboratorial. Os azeites obtidos foram caraterizados no que respeita aos parâmetros de qualidade (acidez, índice de peróxidos, coeficientes de extinção específica no ultravioleta e avaliação sensorial), resistência à oxidação pelo método de Rancimat, perfil em ácidos gordos e teor em tocoferóis. Os resultados obtidos indicam que todos os azeites poderiam ser classificados na categoria de Azeite Virgem Extra, uma vez que não apresentaram qualquer defeito sensorial, a média do frutado foi superior a zero e os restantes parâmetros se encontravam dentro dos limites estabelecidos pelo Regulamento (CEE) no 2568/91 e alterações posteriores para essa categoria. Ao nível da composição em ácidos gordos, as cultivares avaliadas são diferentes entre si, mas dentro da cultivar não se registou qualquer influência do índice de maturação na sua composição. No que respeita ao teor em tocoferóis, o seu perfil é semelhante tendo sido identificados o a-tocoferol, p-tocoferol e v-tocofèrol, com teor de tocoferóis totais a variar entrel65,08 e 178,96 mg/Kg de azeite, para a Cv. Negrinha de Freixo, e entre 279,64 e 219,15 mg/Kg de azeite para a cv Santulhana. Na Cv. Negrinha de Freixo o índice de maturação dos frutos apenas exerceu alguma influência ao nível do teor em y-tocoferol, com ligeiros aumentos ao longo da maturação. Por sua vez na Cv. Santulhana, registou-se uma diminuição no teor destes compostos, na ordem dos 20%. com a maturação do fruto. Os resultados vêm comprovar que nestas cultivares a maturação dos frutos influi na composição do azeite obtido em modos semelhantes aos registados em outras cultivares produzidas na mesma região mas cada cultivar apresenta características específicas.
- Characterization of commercial Tunisian monovarietal olive oils produced from autochthonous olive cultivarsPublication . Slim, Souihli; Rodrigues, Nuno; Veloso, Ana C.A.; Dias, L.G.; Cruz, Rebeca; Casal, Susana; Oueslati, Souheib; Pereira, J.A.; Peres, António M.Tunisian commercial monovarietal olive oils, produced from two predominant autochthonous olive cultivars (cvs Chétoui and Oueslati) and another less investigated olive cultivar (cv Sahli) were studied. Chemical and sensory data have shown that most olive oils should be classified as lampante olive oil, pointing out the need of improving producing and/or storage conditions. Sahli olive oils showed the lowest total phenols content (157±48 mg/kg), oxidative stability (6.5±2.1 h), DPPH scavenging activity (68%±14) and monounsaturated fatty acids content (63.1%±3.1). These olive oils had the highest saturated and polyunsaturated fatty acids contents (19.9%±2.4 and 16.9%±1.4) as well as total tocopherols levels (222±49 mg/kg). Finally, the information of 12 selected parameters (total phenols, oxidative stability, nine fatty acids and γ-tocopherol), allowed establishing a linear discriminant model that correctly classified olive oils according to the olive cultivar with predictive rates of 90%±8. Heptadecenoic, behenic and eicosenoic acids were the three fatty acids identified as the most relevant chemical markers of Sahli olive oils.