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

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Does water addition during the industrial milling phase affect the chemical-sensory quality of olive oils? The case of cv. Arbequina oils

Publication . Marx, Ítala; Casal, Susana; Rodrigues, Nuno; Cruz, Rebeca; Veloso, Ana C.A.; Pereira, J.A.; Peres, António M.

At olive oil industrial extraction, water addition is a practice overcoming the formation of thick pastes. The effect of water addition (0 to 6.2%, kgadded water/kgolives), during the industrial milling of cv. Arbequina olives, on the oils’ chemical-sensory quality, was evaluated. Despite the extra virgin olive oil classification, compared with the water incorporation (1.2–6.2%), extraction without water addition resulted into oils that showed less primary oxidation (lower peroxide values and K232), greater total phenolic content (+12–22%) and higher oxidative stability (+22–31%). No water addition increased the oils secoiridoids content (+5–13%), mainly oleacein (+27–79%). Oils extracted without water addition had a more intense ripe fruity sensation (≥ +11%) but lower fruit intensities (at least - 4%). Thus, the quality and stability of the cv. Arbequina oils can be favoured if extracted without adding water during the olives industrial milling.

2022Journal article

Open access

Monitoring physicochemical and sensory attributes during debittering of stoned green olives

Publication . Marx, Ítala; Rodrigues, Nuno; Veloso, Ana C.A.; Pereira, J.A.; Casal, Susana; Peres, António M.

Stoned green olives are traditional table olives produced in the Northeast of Portugal. They are highly appreciated due to their organoleptic characteristics and levels of complex phenols endowed with strong antioxidant activity, having a significant agro-economic relevance. During the natural debittering process, stoned olives are immersed in water, which is changed (each 1-2 days), leading to a reduction of the initial bitterness and increase of sweetness, turning these green olive edible [1]. Monitoring total phenols contents, the bitterness index as well as the basic sensorial attributes through this washing stage is very important. In this work, the debittering process of 110 samples of stoned green olives (cvs. Cobrançosa and Negrinha de Freixo), was monitoring during 20 days. After each debittering-washing time-period (water changed each 2-days) bitter, pungent and sweet intensities sensations were assessed by trained panelists. Furthermore, the bitterness index and total phenols contents were also evaluated spectrophotometrically. Figure 1 shows the trends observed for the sensory attributes and chemical parameters along the debittering-washing process. From the boxplots (Figure 1), it is clear that bitterness index and total phenols contents significantly decreased with the time, which could be directly related to the observed decrease of the bitter taste intensity (for both olive cultivars) while the decrease of the pungent sensation could be related with the decrease of the total phenols contents, mainly influenced by the increase of the sweet sensation. Furthermore, as can be inferred, the initial bitterness and pungency intensities of cv. Cobrançosa olives were higher than those from cv. Negrinha de Freixo. Nevertheless, after 16-20 days of debittering-washing steps, the bitter and pungent intensities perceived by the trained panelists, for both olive cultivars, were of the same order of magnitude, showing that the debittering procedure adopted was successful and technologically consistent.

2019Conference object

Open access

Impact of fresh olive leaves addition during the extraction of Arbequina virgin olive oils on the phenolic and volatile profiles

Publication . Marx, Ítala; Casal, Susana; Rodrigues, Nuno; Cruz, Rebeca; Peres, Fátima; Veloso, Ana C.A.; Pereira, J.A.; Peres, António M.

Leaves incorporation during the extraction of olive oils can enhance their chemical-sensory quality. Thus, leaves from cvs. Arbequina or Santulhana were added (1%, w/w) during the extraction of Arbequina oils using an Abencor system, being discussed the impacts on the phenolics and volatiles formation enzymatic pathways. Leaves addition contributed to a significant decrease (P-value < 0.05) of the contents of secoiridoids (- 11%), C6- aldehydes (- 16%), and ester compounds (–22%). This could be tentatively related to a reduction of the enzymatic activity of secoiridoids biosynthesis and lipoxygenase pathways, promoted by the leaves’ addition. Moreover, in the presence of leaves, the oils’ total contents of phenolics and volatiles were significantly reduced (- 7 and - 17%, respectively). Contrary, the incorporation of leaves significantly increased (P-value < 0.05) the contents of C6-alcohols (+37%) and the intensities of the green fruity (+25%) and apple (+30%) sensations.

2022Journal article

Open access

Application of a lab-made electronic nose for extra virgin olive oils commercial classification according to the perceived fruitiness intensity

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

An electronic nose, comprising nine metal oxide sensors, has been built aiming to classify olive oils according to the fruity intensity commercial grade (ripely fruity or light, medium and intense greenly fruity), following the European regulated complementary terminology. The lab-made sensor device was capable to differentiate standard aqueous solutions (acetic acid, cis-3-hexenyl, cis-3-hexen-1-ol, hexanal, 1-hexenol and nonanal) that mimicked positive sensations (e.g., fatty, floral, fruit, grass, green and green leaves attributes) and negative attributes (e.g., sour and vinegary defects), as well as to semi-quantitatively classify them according to the concentration ranges (0.05–2.25 mg/kg). For that, unsupervised (principal component analysis) and supervised (linear discriminant analysis: sensitivity of 92% for leave-one-out cross validation) classification multivariate models were established based on nine or six gas sensors, respectively. It was also showed that the built E-nose allowed differentiating/discriminating (sensitivity of 81% for leave-one-out cross validation) extra virgin olive oils according to the perceived intensity of fruitiness as ripely fruity, light, medium or intense greenly fruity. In conclusion, the gas sensor device could be used as a practical preliminary non-destructive tool for guaranteeing the correctness of olive oil fruitiness intensity labelling.

2021Journal article

Open access

Sensory analysis using electronic tongues

Publication . Marx, Ítala; Veloso, Ana C.A.; Casal, Susana; Pereira, J.A.; Peres, António M.

Electronic tongues include any electrochemical nonspecific multisensor device with global selectivity, aiming mimicking the human tongue taste capability. Electronic tongues have been widely and successfully applied as taste sensors in food and pharmaceutical areas showing huge potential as a complementary analytical tool for routine sensory analysis. In comparison with trained human panelists, the electronic tongue shows several advantages namely no detection fatigue, the possibility of analyzing toxic substances and performing objective analysis, while minimizing the risk of human subjectivity. This chapter aims to compile and discuss the main research advances reported in the last decade regarding the electronic tongues’ applications as taste sensors, being focused on the operating principles and types of devices. Thus, the main advantages and limitations of these fast, accurate, bioinspired potentiometric, voltammetric, and/or amperometric green sensor-based tools will be addressed, aiming to make an overview of the recent and future challenges toward industrial and commercial applications.

2021Book part

Restricted access