The effect of drought on energy and water vapour exchange above a mediterranean C3/C4 grassland in Southern Portugal

We studied the seasonal and interannual variation in surface energy fluxes – net radiation (Rn), soil heat (G), sensible heat (H) and latent heat (lE) fluxes – and water vapour exchange above a Mediterranean C3/C4 grassland in Portugal, during two hydrological years, i.e., the period from 1 October to 30 September of the next year, of contrasting rainfall. The first year, 2004–2005, was dry, with total precipitation 45% below the long-term mean (669 mm), whereas the following, 2005–2006, was normal, with total precipitation only 12% above the long-term mean. Soil water availability and plant canopy growth were the most important factors in determining the seasonal and interannual variation in energy partitioning. During autumn, winter and early spring the ratio lE/Rn dominated over H/Rn, in the two years of the study, whereas on an annual basis, the major portion of Rn was consumed in H and lE in the dry and normal years, respectively. The total annual evapotranspiration (E) and its daily maximum were 316 mmand 2.8 mmper day, respectively, for the dry year, and 481mmand 4.5 mmper day for the normal year. After the senescence of the C3 species, the warm-season perennial C4 grass, Cynodon dactylon L., played a preponderant role in maintaining substantial E rates contributing to soil water depletion. In this study, we assessed the effects of the most relevant biophysical factors on surface conductance (gs) and E.We found that the Priestley–Taylor coefficient and gs were substantially reduced when the average volumetric soil moisture content in the top 15 cm of the soil profile dropped below 14%. With abundant soil moisture and leaf area index (LAI) greater than 1, the evaporative fractions (lE/Rn) were linearly related to LAI (R2 = 0.73). The decoupling coefficient (V) ranged from a maximum of about 0.7, under non-limiting soil moisture conditions, to a minimumof about 0.1, under soil moisture deficit. This suggests that E was strongly controlled by the vapour pressure deficit of the air and gs during the periods with limiting soil moisture

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

Olive oils qualitative evaluation using a potentiometric electronic tongue: a review of practical applications

Olive oil is a food product highly prone to fraud, including mislabeling of olive oil commercial category, geographical or olive cultivar origin. Several analytical techniques have been reported to assess olive oil quality, authenticity as well as to detect possible adulterations, namely gas-, liquid- and mass-spectrometry chromatography, DNA and spectroscopy based methods. However, in general, these techniques require expensive pre-sample treatments, are time-consuming and need cost equipments and high skilled technicians. So, fast and more cost-effective methods are still needed and their development a challenge. Among these, electrochemical sensors have been proposed within this field of research, including both voltammetric and potentiometric electronic noses and electronic tongues, individually or as a fused methodology. In this study it is intended to review some of the most recent applications described in the literature including those of the research team regarding the application of a potentiometric electronic tongue, containing cross-sensitive lipidic membranes, to discriminate single-cultivar extra-virgin olive oils by cultivar or sensory intensity, showing its range of applicability and the possibility of using this artificial taste sensor as a complementary/alternative methodology for olive oil sensory analysis.info:eu-repo/semantics/publishedVersio

An electronic nose as a non-destructive analytical tool to identify the geographical origin of portuguese olive oils from two adjacent regions

The geographical traceability of extra virgin olive oils (EVOO) is of paramount importance for oil chain actors and consumers. Oils produced in two adjacent Portuguese regions, Côa (36 oils) and Douro (31 oils), were evaluated and fulfilled the European legal thresholds for EVOO categorization. Compared to the Douro region, oils from Côa had higher total phenol contents (505 versus 279 mg GAE/kg) and greater oxidative stabilities (17.5 versus 10.6 h). The majority of Côa oils were fruity-green, bitter, and pungent oils. Conversely, Douro oils exhibited a more intense fruity-ripe and sweet sensation. Accordingly, different volatiles were detected, belonging to eight chemical families, from which aldehydes were the most abundant. Additionally, all oils were evaluated using a lab-made electronic nose, with metal oxide semiconductor sensors. The electrical fingerprints, together with principal component analysis, enabled the unsupervised recognition of the oils’ geographical origin, and their successful supervised linear discrimination (sensitivity of 98.5% and specificity of 98.4%; internal validation). The E-nose also quantified the contents of the two main volatile chemical classes (alcohols and aldehydes) and of the total volatiles content, for the studied olive oils split by geographical origin, using multivariate linear regression models (0.981 < R2 < 0.998 and 0.40 < RMSE < 2.79 mg/kg oil; internal validation). The E-nose-MOS was shown to be a fast, green, non-invasive and cost-effective tool for authenticating the geographical origin of the studied olive oils and to estimate the contents of the most abundant chemical classes of volatiles.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES (PIDDAC) to CIMO (UIDB/00690/2020 and UIDP/00690/2020), to CEB (UIDB/04469/2020) and to the Associate Laboratory SusTEC (LA/P/0007/2020). The authors are also grateful to the “Project OLIVECOA—Centenarian olive trees of Côa Valley region: rediscovering the past to valorize the future” (ref. COA/BRB/0035/2019), financed by FCT (Portugal). 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

The use of electronic nose as alternative non-destructive technique to discriminate flavored and unflavored olive oils

Cv. Arbequina extra virgin olive oils (EVOO) were flavored with cinnamon, garlic, and rosemary and characterized. Although flavoring significantly affected the physicochemical quality parameters, all oils fulfilled the legal thresholds for EVOO classification. Flavoring increased (20 to 40%) the total phenolic contents, whereas oxidative stability was dependent on the flavoring agent (a slight increase for rosemary and a decrease for cinnamon and garlic). Flavoring also had a significant impact on the sensory profiles. Unflavored oils, cinnamon, and garlic flavored oils had a fruity-ripe sensation while rosemary flavored oils were fruity-green oils. Fruit-related sensations, perceived in unflavored oils, disappeared with flavoring. Flavoring decreased the sweetness, enhanced the bitterness, and did not influence the pungency of the oils. According to the EU regulations, flavored oils cannot be commercialized as EVOO. Thus, to guarantee the legal labelling requirement and to meet the expectations of the market-specific consumers for differentiated olive oils, a lab-made electronic nose was applied. The device successfully discriminated unflavored from flavored oils and identified the type of flavoring agent (90 ± 10% of correct classifications for the repeated K-fold cross-validation method). Thus, the electronic nose could be used as a practical non-destructive preliminary classification tool for recognizing olive oils’ flavoring practice.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) and to CEB (UIDB/04469/2020) units and to the Associate Laboratory SusTEC (LA/P/0007/2020), as well as 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. Nuno Rodrigues thanks to National funding by FCT—Foundation for Science and Technology, P.I., through the institutional scientific employment program-contractinfo:eu-repo/semantics/publishedVersio

On the assessment of time-shift variations from backscattered ultrasound for large temperature changes in biological phantoms

This work reports the assessment of time-shifts (TS) from backscattered ultrasound (BSU) signals when large temperature variations (up to 15 degrees C) were induced in a gel-based phantom. The results showed that during cooling temperature is linear with TS at a rate of approximately 74 ns/degrees C. However during a complete heating/cooling cycle, the relation is highly non-linear. This can be explained by the fact that during cooling the temperature distribution is more uniform. Another problem to report is that TS is very sensitive to external movements