Língua eletrónica: uma ferramenta prática na análise sensorial de azeitonas de mesa

Mestrado com dupla diplomação com a Universidade Tecnológica Federal do ParanáAs azeitonas de mesa são consumidas e apreciadas em todo o mundo e, embora a sua classificação comercial não seja legalmente exigida, o Conselho Oleícola Internacional sugere que seja regulamentada com base na avaliação sensorial por um painel de provadores. A implementação de tal requer o cumprimento de diretrizes estabelecidas pelo Conselho Oleícola Internacional, resultando numa tarefa complexa, demorada e cujas avaliações não estão isentas de subjetividade. Neste trabalho, pela primeira vez, uma língua eletrónica foi utilizada com o intuito de classificar azeitonas de mesa em categorias comerciais, estipuladas com base na presença e na mediana das intensidades do defeito organolético predominante percebido pelo painel de provadores. Modelos de discriminação lineares foram estabelecidos com base em subconjuntos de sinais potenciométricos de sensores da língua eletrónica, selecionados recorrendo ao algoritmo de arrefecimento simulado. Os desempenhos qualitativo de previsão dos modelos de classificação estabelecidos foram avaliados recorrendo à técnica de validação cruzada leave-one-out e à técnica de validação cruzada K-folds com repetição, que permite minimizar o risco de sobreajustamento, permitindo obter resultados mais realistas. O potencial desta abordagem qualitativa, baseada nos perfis eletroquímicos gerados pela língua eletrónica, foi satisfatoriamente demonstrado: (i) na classificação correta (sensibilidades ≥ 93%) de soluções padrão (ácido n-butírico, 2-mercaptoetanol e ácido ciclohexanocarboxílico) de acordo com o defeito sensorial que mimetizam (butírico, pútrido ou sapateira); (ii) na classificação correta (sensibilidades ≥ 93%) de amostras de referência de azeitonas e salmouras (presença de um defeito único intenso) de acordo com o tipo de defeito percebido (avinhado-avinagrado, butírico, mofo, pútrido ou sapateira), e selecionadas pelo painel de provadores; e, (iii) na classificação correta (sensibilidade ≥ 86%) de amostras de azeitonas de mesa com grande heterogeneidade, contendo um ou mais defeitos organoléticos percebidos pelo painel de provadores nas azeitona e/ou salmouras, de acordo com a sua categoria comercial (azeitona extra sem defeito, extra, 1ª escolha, 2ª escolha e azeitonas que não podem ser comercializadas como azeitonas de mesa). Por fim, a capacidade língua eletrónica em quantificar as medianas das intensidades dos atributos negativos detetados pelo painel nas azeitonas de mesa foi demonstrada recorrendo a modelos de regressão linear múltipla-algoritmo de arrefecimento simulado, com base em subconjuntos selecionados de sinais gerados pela língua eletrónica durante a análise potenciométrica das azeitonas e salmouras. O xii desempenho de previsão dos modelos quantitativos foi validado recorrendo às mesmas duas técnicas de validação cruzada. Os modelos estabelcidos para cada um dos 5 defeitos sensoriais presentes nas amostras de azeitona de mesa, permitiram quantificar satisfatoriamente as medianas das intensidades dos defeitos (R² ≥ 0,97). Assim, a qualidade satisfatória dos resultados qualitativos e quantitativos alcançados permite antever, pela primeira vez, uma possível aplicação prática das línguas eletrónicas como uma ferramenta de análise sensorial de defeitos em azeitonas de mesa, podendo ser usada como uma técnica rápida, económica e útil na avaliação organolética de atributos negativos, complementar à tradicional análise sensorial por um painel de provadores.Table olives are consumed and appreciated all around the world and although its commercial classification is not legally required, the International Olive Council suggests the implementation of specific regulation based on the organoleptic evaluation carried out by sesnory panel. The implementation of a trained sensory panel requires the compliance with the guidelines established by the International Olive Council, being a complex and time-consuming task, which evalautions are not without subjectivity. In this work, first, an electronic tongue was used to classify table olives according to commercial categories established based on the presence and median intensities of the predominantl organoleptic defects perceived by the taste panel. Linear discrimination models were established based on the most informative subsets of potentiometric signals recorded by the electronic tongue sensors and selected using the simulated annealing algorithm. The qualitative predictive performance of the established classfication models were evaluated using the leave-one-out cross-validation and the repeated K-folds cross-validation techniques, the latter the minimizes the risk of overfitting, allowing more realistic results. The potential of this qualitative approach based on electrochemical profiles generated by the electronic tongue, has been satisfactorily demonstrated by: (i) the correct classification (sensitivity ≥ 93%) of standard solutions (n-butyric acid, 2-mercaptoethanol and cyclohexanecarboxylic acid) according to the sensory defects that they mimicked (butyric, putrid or zapateria); (ii) the correct classification (sensitivity ≥ 93%) of reference samples of olives and brines solutions (possessing a single intense defect) according to the type of default perceived by the panel (winey-vinegary, butyric, musty, putrid or zapateria ) and selected by the taste panel; and (iii) the correct classification (sensitivity ≥ 86%) of table olives samples despite their great heterogeneity, which presented one or more organoleptics defects, identified by the sensory panel during the olive and/or brine solutions evaluation, according to their commercial category (extra olive without defects, extra, 1st choice, 2nd choice and olives that can not be sold as table olives). Finally, the electronic tongue ability to quantify the median intensities of the negative attributes perceived by the sensory panel in table olives was demonstrated using multiple linear regression models based on subsets of potentiometric signals generated by the electronic tongue during the table olives and brine solutions analysis, and selected using the simulated annealing algorithm. The predictive performances of the quantitative models xiv was evalauted using the same two cross-validation techniques. The established model, for each of the five sensory defects perceived in the table olives samples allowed to satisfactorily quantify the medians of defects intensities (R² ≥ 0.97). Thus, based on the satisfactory quality and quantitative results achieved allows to foresee, for the first time a possible practical application of electronic tongues as a sensory tool for table olives’ defects assessment, being a fast, economic and useful technique for the organoleptic evaluation of negative attributes, complementary to the traditional sensory evaluation carried out by trained sensory panels.Este trabalho foi em parte financiado pelo Projeto POCI-01-0145-FEDER-006984 - Laboratório Associado LSRE-LCM - financiado pelo Fundo Europeu de Desenvolvimento Regional (FEDER), através do COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI) e por fundos nacionais através da Fundação para a Ciência e a Tecnologia

Improvement of olive oil flavor and bioactive composition by optimizing industrial extraction using taste sensor devices

Olive oil is appreciated by consumers due to sensory and health properties [1]. Indeed, it is well known that virgin olive oil (VOO) is a potential antioxidant [2] showing anti-inflammatory, cardioprotective, anticancer, antidiabetic and neuroprotective effects [2]. Specifically, an important expansion of the nutraceutical market has been observed with olive products due to the health benefits associated with their polyphenols [3]. The increasing levels of competition of the worldwide olive oil market and the need of satisfying the consumers incessant search for healthy foods, led to the appearance of differentiated high-value olive oils. The possibility of producing enriched olive oils with related health claims [4], either by optimizing production key variables or by using flavoring techniques is a challenge and an opportunity to segment the broad trade category of olive oils. The present work aims evaluate the feasibility of producing enriched “ready-to-sell” olive oils with enhanced flavor and high contents of bioactive natural compounds. Furthermore, profiting from the fast progress in material sciences, software innovations and electronic systems integration, novel electrochemical taste sensors (electronic tongue and nose) will be designed as in-situ cost effective alternative devices to standard analytical techniques. The expected outputs may contribute to the sustained economic growth of the olive oil national industry.info:eu-repo/semantics/publishedVersio

Evaluation of the effect of extracted time conditions on the phenolic content of olive pastes from cv. Arbequina and discrimination using a lab-made potentiometric electronic tongue

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 °C on total phenolic content 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 gallic acid equivalents/kg olive paste), there being observed a linear decreasing trend (R-Pearson = −0.910). 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 us to establish a successful classification model. The E-tongue-LDA-SA model, based on 11 selected non-redundant sensors, allowed us 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 the 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.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), to CEB (UIDB/04469/2020), to REQUIMTE-LAQV (UIDB/50006/2020) and to BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte. Ítala Marx acknowledges the Ph.D. research grant (SFRH/BD/137283/2018) provided by FCT. Nuno Rodrigues thanks the National funding by FCT-Foundation for Science and Technology, P.I., through the institutional scientific employment program contract.info:eu-repo/semantics/publishedVersio

Application of an electronic tongue as a single-run tool for olive oils’ total phenols and oxidative stability estimation

Olive oil quality can be enhanced during olive oil extraction, particularly by promoting the extraction of phenolic compounds extraction leading to the increase of the oxidative stability (OS). However, both total phenols content (TPC) and OS measurements (Folin-Ciocalteau spectrophotometric method and Rancimat, respectively) are time-consuming and expensive tasks, of difficult implementation in production lines. Thus, the present work studied the feasibility of using a potentiometric lab-made electronic tongue (E-tongue, Figure 1A), comprising non-specific lipid polymeric sensor membranes, coupled with multiple linear regression (MLR) models to predict TPC and an estimative of the OS of cv. Cobrançosa oils extracted at different malaxation temperatures (22 to 34 °C). For the potentiometric analysis, the oils’ polar phenol fraction was extracted with n-hexane and an aqueous methanolic solution (MeOH/H2O 80:20 v/v). The E-tongue-MLR models, based on sub-sets of 11 non-redundant sensors selected using the simulated annealing algorithm, allowed predicting (repeated K-folds-CV) the TPC (175<TPC<240 mg GAE/kg; RMSE=2.0±0.8 mg GAE/kg; R2=0.99±0.01) and, indirectly, to estimate the OS (11.5<OS<14.5 h; RMSE=0.08±0.07 h; R2=0.99±0.01), which values are directly related with the TPC. The satisfactory quantitative performance can be visualized in Figure 1B. In conclusion, the results showed that the E-tongue could be applied for quantifying TCP and predicting OS, both abovementioned shelf-life related parameters.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), CEB (UIDB/04469/2020) and REQUIMTE-LAQV (UID/QUI/50006/2019)). I.M.G. Marx would also like to acknowledge FCT/MCTES for the Ph.D. grant number SFRH/BD/137283/2018. It is also acknowledge the national funding by FCT through the individual scientific employment program-contract with N. Rodriguesinfo:eu-repo/semantics/publishedVersio

Effect of malaxation temperature on olive oil chemical and sensory profiles and their evaluation using an electronic tongue

Olive oil is highly appreciated due to its nutritional and organoleptic characteristics. Olive oils rich in bioactive compounds can be obtained by optimizing the time and temperature of the malaxation process. In this sense, this study aimed investigating the effect of the malaxation temperature (22 to 34°C) on the olive oil's physicochemical and sensory quality and, in more detail, on the phenolic profile. So, virgin olive oils were produced (November 2018), using olives from cv. Cobrancosa. Furthermore, the possibility of using an electronic tongue, i.e., a multisensor potentiometric device, comprising non-specific lipid polymeric with cross-sensitivity sensor membranes, to monitor the malaxation temperature influence on the olive oil's quality and phenolic composition, was evaluated. For that, multivariate statistical tools were developed for discriminating the olive oils according to the malaxation conditions as well as to predict some key quality parameters, including the extinction coefficients (K232, K268 and |ΔK|), free acidity, oxidative stability, peroxide value, bitterness index, total phenols, phenolic composition and gustatory-retronasal positive attributes. The study aims to determine the best malaxation temperature as well as to assess the versatility of the electronic tongue as a single-run, fast and cost-effective analytical device for olive oils quality evaluation.This work was financially supported by Associate Laboratory LSRE-LCM - UID/EQU/50020/2019, strategic funding UID/BIO/04469/2019 -CEB and BioTecNorte operation (NORTE-01-0145-FEDER-000004), strategic project PEst-OE/AGR/UI0690/2014 -CIMO and by UID/QUI/50006/2019 funded by FCT/MCTES (PIDDAC) through national funds. I.M.G. Marx would also like to acknowledge FCT/MCTES for the Ph.D. grant number SFRH/BD/137283/2018.info:eu-repo/semantics/publishedVersio

A potentiometric electronic tongue as a discrimination tool of water-food indicator/contamination bacteria

Microorganism assessment plays a key role in food quality and safety control but conventional techniques are costly and/or time consuming. Alternatively, electronic tongues (E-tongues) can fulfill this critical task. Thus, a potentiometric lab-made E-tongue (40 lipid sensor membranes) was used to differentiate four common food contamination bacteria, including two Gram positive (Enterococcus faecalis, Staphylococcus aureus) and two Gram negative (Escherichia coli, Pseudomonas aeruginosa). Principal component analysis and a linear discriminant analysis-simulated annealing algorithm (LDA-SA) showed that the potentiometric signal profiles acquired during the analysis of aqueous solutions containing known amounts of each studied bacteria allowed a satisfactory differentiation of the four bacterial strains. An E-tongue-LDA-SA model (12 non-redundant sensors) correctly classified 98 ± 5% of the samples (repeated K-fold-CV), the satisfactory performance of which can be attributed to the capability of the lipid membranes to establish electrostatic interactions/hydrogen bonds with hydroxyl, amine and/or carbonyl groups, which are comprised in the bacteria outer membranes. Furthermore, multiple linear regression models, based on selected subsets of E-tongue sensors (1215 sensors), also allowed quantifying the bacteria contents in aqueous solutions (0.993 ± 0.011 R2 0.998 ± 0.005, for repeated K-fold-CV). In conclusion, the E-tongue could be of great value as a preliminary food quality and safety diagnosis tool.Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020) and to CEB (UIDB/04469/2020), as well as to the BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte. Ítala M.G. Marx also acknowledges the Ph.D. research grant (SFRH/BD/137283/2018) provided by FCT.info:eu-repo/semantics/publishedVersio

Monitoring physicochemical and sensory attributes during debittering of stoned green olives

Associate Laboratory LSRE-LCM -UID/EQU/50020/2019 -funded by national funds through FCT/MCTES (PIDDAC) and by Project UID/BIO/04469/2013–CEB, and strategic project PEst- OE/AGR/UI0690/2014–CIMO all funded by European Regional Development Fund (ERDF) through COMPETE2020 –Programa Operacional Competitividade e Internacionalização (POCI) –and by national funds through FCT–Fundação para a Ciência e a Tecnologia. Ítala M.G. Marx acknowledges Fundação para a Ciência e a Tecnologia (FCT) through FCT PhD reference: (SFRH/BD/137283/2018)info:eu-repo/semantics/publishedVersio

Impact of thermal sterilization on the physicochemical-sensory characteristics of Californian-style black olives and its assessment using an electronic tongue

The effect of thermal sterilization processes on the physicochemical parameters and sensory characteristics of Californian-style black olives, from Hojiblanca and Manzanilla Cacereña brine solutions, were evaluated. Two-way ANOVA showed that Hojiblanca olives had a lower phenols content and defect intensity and that increasing the sterilization period resulted in a decrease in total phenols and an increase of the cooked defect. The impact of thermal sterilization was further evaluated using a potentiometric electronic tongue, which was capable of discriminating the different sterilization treatments (repeated K-fold cross-validation sensitivity: 89.0?±?15.0% to 97.0?±?6.0%). Moreover, multiple regressions allowed the prediction of phenols (R2???0.95?±?0.03) and the intensity of the defect (R2???0.95?±?0.04). These results point out the feasibility of the electronic tongue as an analytical tool for monitoring the effects of thermal sterilization treatments. Furthermore, the satisfactory results obtained for the brine solutions may foresee a practical non-destructive method for indirect quality assessment of table olives.Consejería de Educación y Empleo of the Junta de Extremadura to work with a scholarship at the Polytechnic Institute of Bragança for 4 months (Resolución de 18 de julio de 2019, DOE de 25 de julio de 2019, no 143) (Expedient number A28). Nuno Rodrigues thanks to National funding by FCT- Foundation for Science and Technology, P.I., through the institutional scientific employment program-contract. The authors are also grateful to the Foundation for Science and Technology (FCT, Portugal) and FEDER, under Programme PT2020, for the financial support of CIMO (UID/AGR/00690/2019) and of CEB (UID/BIO/04469/2019) and to BioTecNorte operation (NORTE-01-0145-FEDER-000004)info:eu-repo/semantics/publishedVersio

Effect of malaxation temperature on the physicochemical and sensory quality of cv. Cobrançosa olive oil and its evaluation using an electronic tongue

Olive oil is consumed worldwide due to its appreciated sensory attributes and health benefits, which are related with its fatty acid profile and richness in phenolic compounds that support a health claim concerning olive oil protective effects on blood lipids. However, to ensure that oils possess a rich phenolic content, the extraction conditions can be optimised. Therefore, the effects of malaxation temperature (22, 28 and 34 ºC) on the physicochemical and sensory characteristics of cv. Cobrançosa olive oils were evaluated. The oils extracted at 22 ºC had an overall better physicochemical quality (higher total phenols content, greater oxidative stability, lower free acidity and oxidation markers) and more intense positive sensory sensations (higher bitterness and pungency). Additionally, this study showed that a potentiometric electronic tongue could be used to discriminate oils taking into account the effect of malaxation temperature on the overall physicochemical and sensory scores (all samples correctly classified for leave-one-out cross-validation) with a predictive classification similar to that achieved by trained panellists. This finding strengthens the hypothesis that this device could be used as a complementary/alternative taste tool for assessing the impact of the extraction conditions on the oils physicochemical and sensory characteristics.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), to CEB (UIDB/04469/2020), to REQUIMTE-LAQV (UIDB/50006/2020) units and to BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte 2020 - Programa Operacional Regional do Norte. ´Itala M.G. Marx also acknowledges the PhD research grant (SFRH/BD/137283/2018) provided by FCT. Nuno Rodrigues thanks to National funding by FCT- Foundation for Science and Technology, P.I., through the institutional scientific employment program-contract.info:eu-repo/semantics/publishedVersio

Volatile-olfactory profiles of cv. Arbequina olive oils extracted without/with olive leaves addition and their discrimination using an electronic nose

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). The 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 65.5mg/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. The incorporation of cv. Arbequina or Santulhana leaves significantly reduced the total content of alcohols and esters (minus 3756% and 1013%, 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). Thus, 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 cross-validation 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.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020), CEB (UIDB/04469/2020), REQUIMTE-LAQV (UIDB/ 50006/2020) units, and the Associate Laboratories for Green Chemistry-LAQV (UIDB/50006/2020) and SusTEC (LA/P/0007/2020), as well as to BioTecNorte operation (NORTE01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020—Programa Operacional Regional do Norte. ´Itala M.G. Marx also acknowledges the PhD research grant (SFRH/BD/137283/2018) provided by FCT. Nuno Rodrigues likes to thank national funding by FCT—Foundation for Science and Technology, P.I., through the institutional scientific employment program contract.info:eu-repo/semantics/publishedVersio