Application of an electronic tongue as a single-run tool for olive oils’ physicochemical and sensory simultaneous assessment

Abstract

A B S T R A C TOlive oil is highly appreciated due to its nutritional and organoleptic characteristics. However, a huge compositional variation is observed between olive oils, requiring the use of diverse analytical techniques for its classification including titration, spectrophotometry and chromatography, as well as sensory analysis. Chemical analysis is usually time-consuming, expensive and require skilled technicians, while the sensorial ones are dependent upon individual subjective evaluations, even if performed by trained panellists. This work evaluated and demonstrated the feasibility of using a potentiometric electronic tongue, comprising non-specific lipid polymeric and cross-sensitive sensor membranes, coupled with chemometric tools based on different sub-sets of sensors (from 11 to 14 sensors), to predict key quality parameters of olive oils based on single-run assays. The multivariate linear models established for 23 centenarian olive trees from different cultivars allowed predicting peroxide value, oxidative stability, total phenols and tocopherols contents, CIELAB scale parameters (L*, a* and b* values), as well as 11 gustatory-retronasal positive attributes (green, sweet, bitter, pungent, tomato and tomato leaves, apple, banana, cabbage, fresh herbs and dry fruits) with satisfactory accuracy (0.90 ± 0.07 ≤ R 2 ≤ 0.98 ± 0.02 for the repeated K-fold-CV procedure, which ensured that 25% of the data was used for internalvalidation purposes). The electronic tongue device had an accuracy statistically similar to that achieved with standard analytical techniques, pointing out the versatility of the device for the fast and simultaneous chemical and sensory analysis of olive oil. titrations, spectrophotometry and chromatography, as well as the availability of official sensory panels. Still, these methodologies are, in most cases, time-consuming and/or expensive, requiring sample pretreatments, expensive equipment and skilled technicians [7], which turns them unaffordable for most traditional worldwide olive oil producers.Therefore, several research groups have been trying to overcome some of these economic and technical limitations, by developing fast, accurate, cost-effective and user-friendly sensor-based analytical devices, namely the so-called electronic tongues (E-tongues) [8] or electronic noses (E-noses) [9]. In fact, the use of electrochemical devices (e.g., potentiometric and voltammetric ones) has been widely reported for food analysis and, more specifically for olive oils evaluation. For

Unmasking Sensory Defects of Olive Oils Flavored with Basil and Oregano Using an Electronic Tongue‐Chemometric Tool

“…The values of the free acidity (FA), extinction coefficients at 232 and 270 nm (K 232 and K 270 ), and peroxide value (PV) of the samples withdrawn from each of the 80 olive oil bottles, unflavored (20 bottles), or flavored (60 bottles) by incorporating different concentrations of oregano or basil dehydrated/dried leaves were determined according to the EC regulation (Commission Delegated Regulation [EU] 2015[EU] /1830[EU] , 2015. The oils OS was also assessed using the Rancimat method (Rodrigues et al, 2019). The oils sensory analysis was performed by the abovementioned panel, following the EC regulation (Commission Delegated Regulation [EU] 2015[EU] /1830[EU] , 2015, being specifically asked the assessment of the olfactory and gustatory-retronasal fruity positive attribute and of possible organoleptic defects, using an intensity scale ranging from 0 (absence of attribute) to 10 (maximum attribute intensity).…”

“…A lab-made potentiometric multisensor E-tongue, comprising two cylindrical arrays, was used (Rodrigues et al, 2019). Each array contained 20 lipid polymeric crosssensitive sensor membranes (40 sensors in total), with a composition (lipid additive, 3%; plasticizer, 32%; and, polyvinyl chloride, 65%) similar to that reported for the screen-printed E-tongues developed by the research team (Rodrigues et al, 2019;Veloso et al, 2016), although with greater diameter and thickness (greater contact surface), which allowed achieving more repeatable signal profiles and to minimize signal drifts (intraday coefficient of variation lower than 5%) (Rodrigues et al, 2019). The sensor membranes were connected to a multiplexer Agilent Data Acquisition Switch Unit (model 34970A) controlled by the Agilent BenchLink Data Logger software installed on a PC.…”

“…Officially, olive oils sensory profile must be established by a trained taste panel (Commission Delegated Regulation [EU] 2015/1830, which poses several drawbacks, namely due to the scarcity of official panels, lack of reference standards, and a low number of analyses per day (Sinelli et al, 2010). Alternatively, potentiometric and voltammetric electronic tongues (E-tongues) have been successfully used to evaluate positive sensory attributes (e.g., bitter, green, and/or fruity sensations) and organoleptic defects (e.g., rancid, winey-vinegary, musty, fusty, zapateria, butyric, and putrid sensations) of olive oils and table olives as well as to unmask the deliberated addition of rancid or winey-vinegary olive oil to EVOO (Harzalli et al, 2018;Rodrigues et al, 2019;Veloso et al, 2016Veloso et al, , 2018. This work aims, for the first time, to evaluate the possibility of using a potentiometric E-tongue, comprising lipid-polymeric sensor membranes, in combination with chemometric tools to discriminate EVOO or LOO, flavored or not, with basil or oregano.…”

An electronic tongue as a classifier tool for assessing perfume olfactory family and storage time-period

“…A new lab-made potentiometric E-tongue multisensor device, comprising two cylindrical arrays, similar to that previous described [31], was re-designed and built ( Fig. 1) specifically for the perfume analysis, aiming to minimize the total perfume volume required for each assay.…”

“…Indeed, for high-value samples the required volume for each assay may be an economic concern and so, the new system was miniaturized aiming to reduce the amount of perfume used in each experimental assay. The arrays comprised the same 40 lipid polymeric cross-sensitive sensor membranes (20 sensors for each array), with the composition (lipid additive, 3%; plasticizer, 32%; and, polyvinyl chloride, 65%) [31]. The sensor membranes were linked to a multiplexer Agilent Data Acquisition Switch Unit (model 34970A), which was controlled by an Agilent BenchLink Data Logger software.…”