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- Aromatização e fortificação de azeites virgens - Análise da situação no mercado portuguêsPublication . Lamas, Sandra; Pereira, J.A.; Rodrigues, NunoA aromatização e fortificação de azeites virgens é uma tendência em crescimento. Sendo que, os azeites aromatizados e fortificados podem apresentar algumas vantagens. No caso dos azeites aromatizados, podem contribuir para o enriquecimento das caraterísticas sensoriais, aumento do tempo de vida útil, incorporação de compostos com atividades biológicas, como por exemplo antioxidantes que contribuem para o aumento da resistência à oxidação. Como desvantagens da aromatização de azeites aponta-se o fato da adição de aromatizantes poder contribuir para mascarar defeitos sensoriais, e desta forma constituir uma fraude para o consumidor. Em termos sensoriais, o excesso de aromatizante pode tornar desagradável o sabor do azeite. Por sua vez a fortificação terá a vantagem de incorporar um determinado composto ou extrato com propriedades específicas, contribuindo desta forma para o enriquecimento biológico do azeite, mas também pode aumentar a turbidez e ter um aspeto menos agradável e sensorialmente menos apelativo para o consumidor. Assim, este trabalho teve como objetivo avaliar a situação acerca dos azeites aromatizados comercializados no mercado nacional. Desse modo, realizou-se um levantamento das empresas que comercializam azeites aromatizados, obtendo 64 empresas, distribuídas por todo o território nacional, que no seu conjunto comercializam 226 referências diferentes de azeites aromatizados. A grande maioria das empresas comercializa entre três e quatro referências de azeites aromatizados. Do total das referências analisadas 154 são azeites aromatizados com um único agente, dos quais 46 % correspondem à aromatização com plantas aromáticas, maioritariamente alecrim e orégãos. Em azeites com combinações de dois ou mais agentes aromatizantes as plantas aromáticas, maioritariamente loureiro e especiarias, sobretudo pimentas, representam 68 %. Nos azeites analisados, a capacidade líquida das embalagens que predomina foi de 250 mL, enquanto que a técnica de aromatização mais utilizada pelas empresas com 71,7 % é a aromatização por contato permanente entre o azeite e o agente aromatizante. O número de azeites fortificados foi muito baixo. Desse modo, o mercado nacional de azeites aromatizados disponibiliza uma vasta gama de opções, desde vários agentes aromatizantes, diferentes capacidades líquidas, vários métodos de aromatização e diferentes embalagens.
- Application of the FTIR technique as a non‐invasive tool to discriminate Portuguese olive oils with protected designation of originPublication . Lamas, Sandra; Ruano, Daniela Filipa Magalhães; Dias, Francisco; Barreiro, M.F.; Pereira, J.A.; Peres, António M.; Rodrigues, NunoThree Portuguese olive oils with PDO (‘Azeite do Alentejo Interior’, ‘Azeites da Beira Interior’ and ‘Azeite de Trás-os-Montes’) were studied considering their physicochemical quality, antioxidant capacity, oxidative stability, total phenols content, gustatory sensory sensations and Fourier transform infrared (FTIR) spectra. All oils fulfilled the legal thresholds of EVOOs and the PDO's specifications. Olive oils from ‘Azeite da Beira Interior’ and ‘Azeite de Trás-os-Montes’ showed greater total phenols contents and antioxidant capacities, while ‘Azeites da Beira Interior′ presented higher oxidative stabilities. Linear discriminant models were developed using FTIR spectra (transmittance and the 1st and 2nd derivatives), allowing the correct identification of the oils’ PDO (100 % sensitivity and specificity, repeated K-fold-CV). This study also revealed that multiple linear regression models, based on FTIR transmittance data, could predict the sweet, bitter, and pungent intensities of the PDO oils (R2≥0.979±0.016; RMSE≤0.26±0.05, repeated K-fold-CV). This demonstrates the potential of using FTIR as a non-destructive technique for authenticating oils with PDO.
- An electronic tongue as a tool for discriminating canned tuna with different coating oilsPublication . Lamas, Sandra; Peres, António M.; Pereira, J.A.; Rodrigues, NunoCanned fish is a food highly appreciated in Europe, with a great tradition in European and Mediterranean cuisines. In recent years there has been a growing demand for canned fish (e.g., sardines, tuna), either because of its usefulness and ease of use, but above all due to the health benefits related with this type of food. There has also been a growing trend in the market for providing differentiated products, traditionally called gourmet, with the emergence of new recipes, seasonings, and topping liquids. Canned foods are usually commercialized with different coating liquids, including natural preserves (water), with vegetable oils or olive oils with different commercial grades. This latter strategy is quite popular as a way of valuing and differentiating this type of canned food. However, the interaction between the fish and the coating liquid during storage, together with the technological processing of the canned food turns the authenticity assessment a hard analytical task, which is of major relevance considering the high price and the premium market envisaged for commercialization. Thus, this work aimed to evaluate the use of a potentiometric electronic tongue to discriminate canned tuna with different coating oils, namely, olive oil (extra virgin or virgin olive oil), refined olive oil and sunflower oil. Fifteen tuna samples were acquired, including five canned cans from different commercial brands for each studied oil. The samples were drained for 2 min, the tuna was removed from each can, extracted with a methanol-water solution (80:20, v/v) and then analysed with the electronic tongue (E-tongue). In total, for each sample, 40 potentiometric signal profiles were recorded by the 40 lipid sensor membranes comprised in the lab-made E-tongue (Figure 1)1. The results clearly showed that the acquired E-tongue profiles together with chemometrics (linear discriminant analysis coupled with the simulated annealing variable selection algorithm, LDA-SA), allowed correctly classifying 100% (Figure 2) of the original grouped data (training). The LDA-SA-E-tongue model was based on the potentiometric signals recorded by 7 of the 40 sensors, leading to a satisfactory predictive performance (internal validation), namely 93% and 86% for leave-one-out cross-validation and repeated K-fold cross-validation (4 folds and 10 random split repeats) procedures. In conclusion, the E-tongue could be foreseen as a practical and accurate tool for guaranteeing the label correctness of tuna canned cans according to the coating oil used, namely allowing a clear recognition of the type of vegetable oil used, i.e., sunflower or olive oil.
- Utilização do nariz eletrónico como ferramenta para discriminação de azeites aromatizadosPublication . Lamas, Sandra; Peres, António M.; Pereira, J.A.; Rodrigues, NunoA aromatização de azeites, pela adição de especiarias, plantas aromáticas ou frutos, é uma prática comum com vista à melhoria das características e propriedades sensoriais, indo ao encontro das espectativas de alguns consumidores. Contudo, esta prática pode promover fraudes, mascarando defeitos organoléticos ou até a utilização de misturas com azeites de categorias comerciais inferiores. Assim, o desenvolvimento de técnicas instrumentais não invasivas, como o nariz eletrónico, afigura-se da maior importância. Esta ferramenta tem sido utilizada para detetar adulterações, avaliar níveis de oxidação, classificar azeites de acordo com a classificação comercial e diferenciar azeites monovarietais. Assim, o objetivo deste trabalho foi utilizar o nariz eletrónico como ferramenta rápida para deteção e discriminação de azeites aromatizados. Para tal, de um lote de azeite, foram constituídos sub lotes que foram aromatizados por contato, durante 15 dias no escuro e à temperatura ambiente, com canela em pó, alho em pó e alecrim seco na proporção de 1,5 % (m/v). Para cada tipo de azeite foram feitas cinco repetições sendo o azeite original, não aromatizado utilizado como controlo. Os azeites obtidos foram filtrados e analisados com um nariz eletrónico, com 9 sensores MOS (metal oxide semiconductors), construído pela equipa de investigação. Aproximadamente 0,5 mL de azeite foram colocados num vial (unidade de amostragem, 28 ºC), sendo posteriormente a fase gasosa, representativa da composição volátil do azeite, transferida por vácuo, e colocada em contacto com sensores do nariz eletrónico (35 ºC), sendo posteriormente registados os sinais gerados (resistência elétrica, em Ohms). Os resultados mostraram que o nariz eletrónico, foi capaz de discriminar corretamente 100% dos azeites analisados. A capacidade de previsão do nariz eletrónico foi ainda confirmada, por validação cruzada, utilizando o procedimento leave-one-out, permitindo classificar corretamente 94 % das amostras, sendo dois azeites aromatizados com canela mal classificados como sendo aromatizados com alecrim. Os resultados obtidos mostram que o nariz eletrónico pode ser uma ferramenta prática e não-invasiva para o controlo e discriminação de azeites aromatizados.
- The effect of essential oils on the post-harvest quality of sweet cherry, Prunus avium L. cv. SummitPublication . Silva, Kevin; Lamas, Sandra; Ferreiro, Nuno Manuel; Ramalhosa, Elsa; Pereira, J.A.; Rodrigues, NunoSweet cherry (Prunus avium L.) is a very well appreciated and consumed fruit, not only for its sweetness, smell, and fruity taste, but also for its visual attractiveness and recognized nutritional value. Sweet cherries are rich in sugars, phenolics, anthocyanins and melatonin. Its consumption prevents the appearance of vascular diseases, cancer, diabetes and inflammatory diseases. In 2019, the national production was 19130 ton. The production is concentrated in two producing regions, one in the interior centre of the country, Fundão region, and the other in the north interior land, in the regions of Lamego-Resende and Alfandega da Fé. Sweet cherry is a non-climacteric fruit with a reduced post-harvest period that requires low temperature around 0.5 °C and relative humidity around 90%. The fruits are generally consumed in fresh as raw fruit. Nevertheless, the modern style of life looks for practical ways to present the fruits, generally in individual packages. Furthermore, in some cases, in the local market, there are no availability of cold storage, being the fruits preserved at room temperature, causing high percentages of decay in few days. Essential oils are recognized as possessing antioxidant and antimicrobial activities and could be used as food preservative among other applications in food industry. In this context, with this work we intended to study the effect of two essential oils, from sweet orange (Citrus sinensis cv. Late) and lavender (Lavanda angustifolia Mill.), on the post-harvest quality of sweet cherry, P. avium Cv. Summit. Plastic individual packages with 100 g of fruits were prepared, and in the top of the recipient, a filter paper of 1 cm2 of diameter was put. In each paper filter, 10 microliters of essential oil were added, being the control treated with distilled water. The packages were stored at room temperature. On each day, during seven consecutive days, the following parameters were evaluated for each treatment: colour, rupture force, elasticity, loss of weight, total soluble solids (TSS), titratable acidity, pH, and sensory evaluation. For each treatment and each day, three independent assays were made. In general, the results indicated that the treatments caused different effects on the cherries. The colour of the cherries changed along storage, acquiring brownish colour after 7 days. This effect was mainly observed in the fruits of the control and those submitted to the lavender essential oil. It was also with this essential oil, that the highest loss on the texture, measured by the rupture force, was observed. When comparing the rupture force measured after 7 days with the beginning, a decrease of 39, 53 and 36% were determined for the control (without essential oil), lavender and orange essential oils, respectively. Similar trend was observed for elasticity, suggesting a softening effect by the lavender essential oil. Almost all situations, the loss of weight increased after 4 days. Concerning the TSS, the values oscillated along the storage time, without a definite trend, ranging the means between 11.3 and 13.4 ºBrix. The titratable acidity was not affected by the treatments and the storage time, varying between 0.4 and 0.6 g malic acid/100 g fresh weight. Similar trend was observed for the pH (3.5 to 4.1). Concerning the sensory evaluation, the essential oils were detected by the panellists as a strange odour; however, the orange essential oil was more acceptable than the lavender. Furthermore, after 7 days, the damage intensity was higher in the control and lavender essential oil. In conclusion, the present work indicated that after four days at room temperature, the quality of the cherries was quite affected; however, the orange essential oil seems to delay these effects.
- A utilização de espectroscopia no infravermelho por transformada de Fourier (FTIR) na caracterização de azeites da cv. Galega vulgar provenientes de diferentes regiõesPublication . Lamas, Sandra; Peres, António M.; Barreiro, M.F.; Pereira, J.A.; Rodrigues, NunoA ‘Galega vulgar’, é uma cultivar de oliveira autóctone portuguesa, com uma distribuição de norte a sul do território nacional, fazendo parte integrante de cinco das seis Denominações de Origem Protegida (DOP) para azeite. A região geográfica de origem, onde a oliveira cresceu e se desenvolveu pode ter influência na composição físico-química e caraterísticas dos azeites. A espectroscopia no infravermelho por transformada de Fourier (FTIR) é uma técnica com utilização crescente pela facilidade de uso, rapidez e qualidade de resultados podendo ser usada como uma alternativa não-invasiva a outras técnicas na avaliação da composição e qualidade dos azeites. O FTIR permite estabelecer um espectro representativo da composição química de uma dada amostra. Neste sentido, e considerando que a região de origem influi na composição dos azeites da cv. ‘Galega vulga’, procedeu-se à análise de azeites elementares desta cultivar provenientes de sete origens geográficas diferentes (Alijó, Castelo Branco, Covilhã, Elvas, Mirandela, Penamacor e Vila Velha de Rodão) num total de 36 amostras. Procedeu-se à análise dos azeites utilizando a região de espectro FTIR caraterística para esta matriz, entre 4000 a 600 cm-1, tendo as amostras sido analisadas em duplicado. Os azeites analisados possuem espectros típicos, com bandas de absorção nas regiões entre 3080 a 2750 cm-1 e 1850 a 600 cm-1. Os resultados mostram que as diferenças de transmitância observadas em 7 números de onda (1468, 1215, 1132, 1095, 1028, 918 e 642 cm-1) permite estabelecer um modelo de análise discriminante linear, capaz de prever corretamente a origem geográfica dos 36 azeites estudados. Esta capacidade de discriminação deverá estar relacionada com as diferenças na composição dos azeites nomeadamente ao nível da composição em triglicerídeos. O estudo permite, assim, confirmar a possibilidade e o potencial de aplicar a técnica FTIR como uma ferramenta promissora, rápida e não destrutiva para identificar a origem geográfica de azeites da cv. Galega vulgar.
- Aplicação de óleos essenciais na conservação de cerejas cv. SummitPublication . Lamas, Sandra; Ferreiro, Nuno Manuel; Silva, Kevin; Ramalhosa, Elsa; Pereira, J.A.; Rodrigues, NunoA cereja (Prunus avium L.) é um fruto com teores elevados em açúcares, compostos fenólicos, antocianina, etc. Em Portugal, a produção está maioritariamente concentrada nas regiões do Fundão, Resende e Alfandega da Fé. Contudo, o fruto é muito perecível, e necessita de ser conservado a baixas temperaturas. A utilização de óleos essenciais (OE), pela sua reconhecida ação antimicrobiana, tem sido proposta como agentes capazes de aumentar o período de pós-colheita de frutos. Nesse sentido, este trabalho teve como objetivo estudar o efeito da aplicação de 2 OE, de laranja (Citrus sinesis cv. Late) e de lavanda (Lavanda angustifolia Mill), em pós-colheita de cereja Cv. Summit. Para tal, foram colocadas 100g de cerejas em caixas de plástico individuais, nas quais na parte superior se colocou um papel de filtro de 1 cm2 humedecido com 10 μl de OE. As cerejas foram armazenadas sob refrigeração (5 ºC) e a cada 5 dias, durante 30 dias, foi avaliada a qualidade dos frutos (acidez, pH, brix, textura, cor, força de rutura do pedúnculo, número de frutos impróprios para consumo e perdas de massa). Para cada observação, foram avaliadas 3 amostras independentes. Os resultados obtidos demonstraram uma degradação dos parâmetros ao longo do ensaio, verificando, que o tratamento com OE de laranja reduziu, em T30 dias, o número de frutos impróprios para consumo (8,3 % ± 7,2), quando comparado com o controlo (36,6% ± 9,5) e o tratamento com OE de lavanda (37,7 % ± 7,4). Os restantes parâmetros avaliados não apresentaram diferenças significativas entre tratamentos.
- Flavoured and fortified olive oils - Pros and consPublication . Lamas, Sandra; Rodrigues, Nuno; Peres, António M.; Pereira, J.A.Flavouring and fortifying virgin olive oils is an increasing commercial trend, aiming to meet new consumers’ preferences and provide new differentiated products. These practices usually positively impact the oils’ sensory profile and chemical composition, increasing their natural richness on bioactive compounds. However, some negative effects have also been reported. Scope and approach: This review provides a summary of common flavouring/fortification techniques as well as of the usual natural agents used. Co-extraction, contact and essential oils incorporation techniques are addressed. Usually, flavouring/fortification enhances desirable sensory sensations, and shelf-life, and promotes the incorporation of bioactive compounds like antioxidants. Also, the excess of flavouring may promote the appearance of unpleasant sensory sensations and, in some cases, results in pro-oxidant activity. Fortification, in turn, involves the incorporation of extracts rich in bioactive compounds, contributing to the nutritional and healthy enrichment of the olive oil. However, fortification may also increase the oil’s turbidity and/or promote the appearance of unpleasant sensory sensations, resulting in a less appealing oil, hindering the consumers’ purchasing. Key findings and conclusions: Although traditional in the Mediterranean, olive oil flavouring or fortification may have positive/negative effects at chemical and sensory levels. This awareness is of paramount commercial importance and can be used as a decision-maker tool for olive oil producers. Thus, the advantages/disadvantages of the different methodologies are discussed, and some perspectives and possible future directions are proposed and briefly discussed.
- Advantages and disadvantages of flavouring olive oilsPublication . Lamas, Sandra; Rodrigues, Nuno; Peres, António M.; Pereira, J.A.Flavoured and fortified olive oils have been a growing trend, meeting consumer preferences and offering differentiated and innovative products. However, these preparations can positively or negatively affect the physicochemical and sensory characteristics. The most noticeable changes occur in sensory terms, which can lead to the appearance of desired sensations, depending on the flavouring agent used. On the other hand, it can mask the presence of any sensory defect present in the olive oil. For the physicochemical characteristics and stability, flavouring can influence the levels of antioxidants and increase the olive oils' shelf-life, increasing the incorporation of antioxidant compounds, promoting oxidative stability and reducing oxidation. However, some studies report that incorporating flavouring agents has pro-oxidant effects. Generally, three techniques are used for flavouring olive oils: i) through permanent or temporary contact with the flavouring agent, ii) by co-extraction, and iii) the the addition of essential oils1. From them, direct contactbetween the olive oil and the flavouring agent is the most usual and traditional technique. Currently, natural extracts rich in a certain compound, such as lycopene or lutein, in the olive oils are used to fortify olive oils2. These extracts are incorporated to enrich it in a certain compound or set of compounds, with nutritional and healthy properties but without sensory objectives. Nevertheless, fortification can cause turbidity in the olive oil and/or can promote the appearance of unpleasant sensory sensations. For the present work, a vast bibliographic review3 was done devoted to the flavouring of olive oils, pointing out the interest in this ancient Mediterranean practice, as well as the diversity of techniques, agents and effects of the flavouring process. Based on the available data, it can be stated that the use of flavouring by direct contact is the most studied technique, which could be attributed to the easily of implementation of this technique, not requiring any change in the usual oil extraction process. Furthermore, considering that flavouring is performed directly on the extracted oils, the desirable sensory properties of the flavouring agent can migrate to the olive oil. Even so, a considerable number of studies still report the production of flavoured olive oils by co-extraction or by adding essential oils. However, a lower but significant number of studies have focused on the enrichment of olive oil with specific bioactive compounds, mainly antioxidants, to enhance the nutritional and healthy properties of olive oils. Regarding the used flavouring agents and based on the compiled literature (Figure 1), different classes can be grouped, namely aromatic plants, which represent more than 42% of the references compiled in this work, followed by spices, with around 24% of the references, fruits, with 14%, and the other agents representing around 19%. Within the aromatic plants, oregano and rosemary were the most common agents (14 references), followed by thyme (12 references) and basil(9 references). The lemon dominates with eight references in fruit, followed by tomato (with 7) and orange (3 references). Regarding spices, three flavouring agents should be highlighted, namely garlic (11 references), pepper (7 references) and chilli (4 references). In the other flavouring agents, the olive leaves had been frequently used (11 references), which is justified as a by-product of olive growing. The huge use of aromatic plants could be related to different factors, such as the wide range of flavours and aromas, the great availability, low price and easiness of use. It is also possible to infer that different, sometimes contradictory, effects were obtained by different studies when using the same flavouring agent or the same flavouring technique. These differences may be due to or attributed to different factors, which must be considered when comparing similar studies, such as the conditions under which the flavouring is carried out (time, temperature), the amount of flavouring agent used and itsstate (dry, fresh, powdered), the chemical composition of the flavouring and its storage conditions before use. Hence, the world of flavoured olive oils still needs to be further studied, being clear the need to go through a path that would allow the standardization of this Mediterranean tradition, aiming to limit and/or overcome the intrinsic variabilities of the flavouring/fortification commercial strategies.
- Fourier transform infrared spectroscopy-chemometric approach as a non-destructive olive cultivar tool for discriminating Portuguese monovarietal olive oilsPublication . Lamas, Sandra; Rodrigues, Nuno; Fernandes, Isabel P.; Barreiro, M.F.; Pereira, J.A.; Peres, António M.Four Portuguese monovarietal olive oils (cvs. Cobrançosa, Madural, Santulhana and Verdeal Transmontana) were evaluated, totalizing 24 independent samples. Olive cultivar significantly influenced (P values lt 0.05, one-way ANOVA) the oils’ physicochemical and sensory attributes, fulfilling all oils the legal thresholds for extra-virgin classification. Oils from cv. Verdeal Transmontana had the highest oxidative stability (16.9 ± 1.0 h), whereas cvs. Cobrançosa and Santulhana oils have the highest total phenols content (204 ± 30 and 177 ± 33 mg GAE/kg, respectively). Concerning the sensory attributes, only cv. Santulhana oils fitted fruity greenly oils type, presenting, in general, significantly higher olfactory and gustatory intensities (P values lt 0.05, one-way ANOVA), with a higher number of perceived sensory attributes (e.g., herbaceous sensations), compared to the other monovarietal oils. Free acidity, peroxide value, extinction coefficients, total phenols and oxidative stability allowed the unsupervised differentiation (principal component analysis, PCA) of the four monovarietal oils, and in a less extent, the sensory data. Fourier transform infrared (FTIR) spectroscopy-chemometric procedure was developed based on raw or transformed forms of the recorded spectra. Raw, 1st and 2nd derivative spectra allowed the unsupervised (PCA) and supervised (linear discriminant analysis, LDA) identification of the olive cultivar of the studied oils. In fact, FTIR-LDA models, based on the raw transmittance or on their 1st or 2nd derivatives, recorded at 5, 4 or 3 selected wavenumbers, respectively, allowed to correctly classify all oils (sensitivities greater than 99 ± 7% for the repeated K-fold-CV internal validation). Therefore, FTIR spectroscopy could be used as a fast, reliable, environmentally friendly and non-destructive olive cultivar-classification tool for monovarietal oils.
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