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Classification of olive oils according to sensory defects using a potentiometric electronic tongue

Publication . Silva, Lucas M.; Dias, L.G.; Rodrigues, Nuno; Veloso, Ana C.A.; Rebello, Ligia P.G.; Pereira, J.A.; Peres, António M.

Olive oils may be graded according to their overall physicochemical composition and sensorial attributes as: -extra-virgin olive oils (EVOOs); -virgin olive oils (VOOs); - lampante olive oils (LOOs). Olive oils are quite prone to frauds thus there are legal protection EU Commission regulations: - EU Commission Regulation, 1991; - EU Commission Regulation, 2011. Maximum levels are established for: - Chemical and physicochemical parameters (e.g., free acidity, peroxide value, UV extinction coefficients and alkyl esters content)i -Sensory attributes (presence/absence of organoleptic defects, fruity sensation and positive attribute).

2017Conference object

Open access

Monitoring fructooligossacharides production using Aspergillus aculeatus by HPLC-ELSD

Publication . Lama, Aelina; Silvério, Sara; Veloso, Ana C.A.; Rodrigues, Lígia R.; Dias, Teresa; Peres, António M.

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.

2017Conference object

Open access

Sensory classification of table olives using an electronic tongue: analysis of aqueous pastes and brines

Publication . Marx, Ítala; Rodrigues, Nuno; Dias, L.G.; Veloso, Ana C.A.; Pereira, J.A.; Drunkler, Deisy A.; Peres, António M.

Table olives are highly appreciated and consumed worldwide. Different aspects are used for trade category classification being the sensory assessment of negative defects present in the olives and brines one of the most important. The trade category quality classification must follow the International Olive Council directives, requiring the organoleptic assessment of defects by a trained sensory panel. However, the training process is a hard, complex and sometimes subjective task, being the low number of samples that can be evaluated per day a major drawback considering the real needs of the olive industry. In this context, the development of electronic tongues as taste sensors for defects' sensory evaluation is of utmost relevance. So, an electronic tongue was used for table olives classification according to the presence and intensity of negative defects. Linear discrimination models were established based on sub-sets of sensor signals selected by a simulated annealing algorithm. The predictive potential of the novel approach was first demonstrated for standard solutions of chemical compounds that mimic butyric, putrid and zapateria defects (≥93% for cross-validation procedures). Then its applicability was verified; using reference table olives/brine solutions samples identified with a single intense negative attribute, namely butyric, musty, putrid, zapateria or winey-vinegary defects (≥93% cross-validation procedures). Finally, the E-tongue coupled with the same chemometric approach was applied to classify table olive samples according to the trade commercial categories (extra, 1(st) choice, 2(nd) choice and unsuitable for consumption) and an additional quality category (extra free of defects), established based on sensory analysis data. Despite the heterogeneity of the samples studied and number of different sensory defects perceived, the predictive linear discriminant model established showed sensitivities greater than 86%. So, the overall performance achieved showed that the electrochemical device could be used as a taste sensor for table olives organoleptic trade successful classification, allowing a preliminary quality assessment, which could facilitate, in the future, the complex task of sensory panelists.

2017Journal article

Open access

Electrochemical taste sensor for unmasking extra-virgin olive oils adulterated with rancid or winey-vinegary olive oils

Publication . Veloso, Ana C.A.; Harzalli, Ussama; Rodrigues, Nuno; Dias, L.G.; Oueslati, Souheib; Pereira, J.A.; Peres, António M.

Olive oils may be commercially classified, in a decrease order of quality and economic value, as extra-virgin (EVOO), virgin (VOO) or lampante (LOO) olive oils, being quite prone to frauds. Thus legal protection regulations have been approved by the European Union Commission [1,2], being required the fulfilment of several physicochemical and sensory thresholds [3,4]. Unfortunately, the mixture of expensive olive oils with low quality oils aiming fraudulent economic revenue is still a common practice difficult to detect. In this work, a potentiometric electronic tongue (E-tongue) was used to detect adulteration of an EVOO with different added levels (2.5%, 5%, 10%, 20% and 40%; v/v) of an LOO with an intense sensory defect (rancid or wineyvinegary). Previously, similar electrochemical devices, also comprising lipid polymeric sensor membranes, showed to be able to give qualitative and/or quantitative responses towards basic taste sensations (acid, bitter, salty, sweet, and umami), positive sensory attributes (bitter, fruity, green and pungency) or defects (e.g., butyric, musty, putrid, winey-vinegary and zapateria) [5-8]. The E-tongue coupled with linear discriminant technique (based on the signal profiles of 19 or 20 E-tongue sensors, chosen using a simulated annealing meta-heuristic variable selection algorithm, for rancid and wineyvinegary adulterations, respectively) allowed to semi-quantitatively distinguish olive oils with different adulteration levels (repeated K-fold crossvalidation predictive correct classifications of 84±10% and 94±8% for rancid and winey-vinegary adulterations, respectively). The preliminary results showed the practical potential of the E-tongue as a taste device for the successful detection of EVOOs adulterated with LOO containing organoleptic defects.

2017Conference object

Open access

Honey evaluation using electronic tongues: An overview

Publication . Veloso, Ana C.A.; Sousa, Mara E.B.C.; Estevinho, Leticia M.; Dias, L.G.; Peres, António M.

Honey-rich composition in biologically active compounds makes honey a food products highly appreciated due to the nutritional and healthy properties. Food-manufacturing is very prone to different types of adulterations and fraudulent labelling making it urgent to establish accurate, fast and cost-effective analytical techniques for honey assessment. In addition to the classical techniques (e.g., physicochemical analysis, microscopy, chromatography, immunoassay, DNA metabarcoding, spectroscopy), electrochemical based-sensor devices have arisen as reliable and green techniques for food analysis including honey evaluation, allowing in-situ and on-line assessment, being a user-friendly procedure not requiring high technical expertise. In this work, the use of electronic tongues, also known as taste sensor devices, for honey authenticity and assessment is reviewed. Also, the versatility of electronic tongues to qualitative (e.g., botanical and/or geographical origin assessment as well as detection of adulteration) and quantitative (e.g., assessment of adulterants levels, determination of ﬂavonoids levels or antibiotics and insecticides residues, ﬂavonoids) honey analysis is shown. The review is mainly focused on the research outputs reported during the last decade aiming to demonstrate the potentialities of potentiometric and voltammetric multi-sensor devices, pointing out their main advantages and present and future challenges for becoming a practical quality analytical tool at industrial and commercial levels.

2018Journal article

Open access