53 research outputs found
Detection of adulterations in food products containing milk and/or milk proteins
A critical review of the most relevant analytical methodologies for quality and authenticity control of dairy products and foods containing milk proteins is presented. Chromatographic, electrophoretic and immunological methods are used for: detection of cow's milk in ewe and goat milks, detection of whey added to milk, detection of caseins and/or whey proteins in non-lactic foods and study compounds resulting from milk proteins degradation. Techniques based on polimerase chain reaction are also suitable for detection of cow's milk on cheeses of ewe and goat milks
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
Evaluation of cheese authenticity and proteolysis by HPLC and urea-polyacrylamide gel electrophoresis
Chromatographic and electrophoretic methods have been established as useful tools in characterising cheese ripening and in the detection of milk adulteration. The purpose of this work was to evaluate casein proteolysis of cheeses made from bovine, ovine or mixtures of bovine and ovine milks, as well as ovine cheese authenticity, for 30 days of ripening by HPLC and urea–polyacrylamide gel electrophoresis. Complementary information was obtained by both techniques when applied to the study of casein proteolysis during 30 days of ripening of ovine milk cheeses, ovine milk cheeses with 10% and 20% of bovine milk and bovine milk cheeses, manufactured according to the traditional Terrincho technology. For ovine cheeses, a-casein was the fraction that showed the higher degradation during cheese ripening. A similar behaviour was observed for ovine milk cheese with 10% of bovine milk. The profile for ovine milk cheese with 20% of bovine milk was more similar to that obtained for bovine cheese. Concerning bovine milk cheeses, electrophoresis was the most sensitive technique for the evaluation of proteolysis in these cheeses. Ten and 20% of bovine milk could be detected in ovine milk cheeses by urea–polyacrylamide gel electrophoresis and HPLC, respectively, even after 30 days of ripening.Project Agro No. 26, Medida 8, Acção 8.
Pomegranate peels and seeds as a source of phenolic compounds: effect of cultivar, by-product, and extraction solvent
The nutraceutical properties of Punica granatum L. are not restricted to the edible portion of the fruit but also to the peels and
seeds, flowers, leaves, and tree bark. The recovery and valorization of the peel and seeds (ca. 50% of the whole fruit), besides
the positive environmental impact, can be viewed as a source of natural bioactive compounds. Thus, the bioactive properties of
extracts of pomegranate peel and seeds from Acco and Wonderful known cultivars, as well as of the novel Big Full cultivar,
were evaluated. The dried and ground pomegranate by-products were submitted to a conventional solid/liquid extraction with
ethanol/water mixtures (0%, 25%, 50%, and 75% of EtOH, v/v). The obtained extracts were characterized in terms of total
phenolic compounds (TPC), total flavonoids (TF), and antioxidant activity (AA), determined by the DPPH radical scavenging
activity and expressed as IC50 (half maximum inhibitory concentration). With the exception of the Acco cultivar, the
extraction yield (EY) was higher for peels, whose extracts showed higher TPC, TF, and IC50 (lower AA). The extracts obtained
from the by-products of the Big Full cultivar had a statistically higher overall bioactive potential (TPC: 0.36 mg GAE/mg
extract; TF: 0.031 mg CATE/mg extract; IC50: 0.51 mg/mL) compared to the other two studied cultivars. Furthermore, the EY
was enhanced by solvents richer in ethanol (50-75%), allowing obtaining extracts richer in TPC and TF with higher AA.
Finally, it was shown that EY combined with bioactive data allowed a satisfactory principal component unsupervised
differentiation of the pomegranate extracts according to the type of by-product used.This work was supported by the Foundation for Science and
Technology (FCT, Portugal) through national funds to the
research units CEB (UIDB/04469/2020), CERNAS (UIDB/00681/2020), and CIMO (UIDB/00690/2020) as well as to
the Associate Laboratory SusTEC (LA/P/0007/2020). The
European Regional Development Fund, under the Norte2020
Program funded BioTecNorte operation (NORTE-01-0145-
FEDER-000004) and funded MobFood operation (LISBOA-
01-0247-FEDER-024524). Lara Campos acknowledges the
research grants (CEB-BI-14-2019) and (FCT-IPC-i2A-CERNAS/
Escola de Verão/BI-01-08), and Luana Seixas acknowledges
the research grant (FCT-IPC-i2A-CERNAS/Escola de
Verão/BII-01-07), all provided by FCT.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
Monitoring fructooligossacharides production using Aspergillus aculeatus by HPLC ELSD
Fructooligosaccharides (FOS) are present in plants and fruits at low concentrations, thus their extraction
from natural sources may not be economically viable for a large scale industrial application. Therefore,
FOS production by fermentation using fungi can be an alternative. In this work, FOS were produced using
Aspergillus aculeatus at different sucrose initial concentrations (88 to 265 g/L) and at temperatures from
22 to 32ºC. FOS production was monitored by HPLC-ELSD, allowing to confirm that the initial sucrose
concentration significantly influenced biomass growth (a maximum value of 16 ± 2 g was achieved)
although it did not significantly affect the maximum FOS yield (amount of FOS produced per initial
sucrose) obtained, which varied from 51 to 59 g/g) obtained, which varied from 51 to 59 g/g. Finally, the
preliminary results enabled verifying that depending on the fermentation conditions, slightly different FOS
production profiles were obtained (Figure 1), revealing differences in the individual FOS concentrations
(i.e., 1-kestose, nystose and fructofuranosylnystose), which could be of interest since it has been
reported that the beneficial health effects of FOS may depend on the relative FOS composition.This work was also financially supported by Project POCI-01–0145-FEDER-006984–Associate Laboratory LSRE-LCM,
UID/AGR/00690/2013 –CIMO and UID/BIO/04469/2013 funded by FEDER - Fundo Europeu de Desenvolvimento
Regional through COMPETE2020-Programa Operacional Competitividade e Internacionalização (POCI) – and by
national funds through FCT - Fundação para a Ciência e a Tecnologia, Portugal.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
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