Unraveling the role of the enzymatic paths on olive oil phenolics and volatiles

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Volatile changes in cv. Verdeal Transmontana olive oil: From the drupe to the table, including storage

Publication . Malheiro, Ricardo; Casal, Susana; Rodrigues, Nuno; Renard, Catherine M.G.C.; Pereira, J.A.

This study focused on the volatile changes in cv. Verdeal Transmontana throughout the entire olive oil processing chain, from the drupe to olive oil storage up to 12 months, while correlating it with quality parameters and sensory quality. During crushing and malaxation, the volatiles formed were mainly “green-leaf volatiles” (GLVs), namely (E)-2-hexenal, hexanal, and 1-hexanol. Centrifugation and clarification steps increased the total volatile amounts to 130 mg kg−1. However, clarification also increased nonanal and (E)-2-decenal contents, two markers of oxidation, with a noticeable loss of phenolic compounds and oxidative stability. During storage, the total volatile amounts reduced drastically (94% at 12 months after extraction), together with the positive sensory attributes fruity, green, bitter, and pungent. Despite being classified as extra-virgin after one year of storage, peroxides and conjugated dienes were significantly higher while there was a reduction in antioxidant capacity as well as in phenolic compounds (less 50%) and oxidative stability (57%). The present work allowed concluding that the extraction process modulates the volatile composition of olive oil, with a concentration of volatiles at the clarification step. During storage, volatiles are lost, mainly eight months after extraction, leading to the loss of important sensory attributes.

2018Journal article

Open access

Improvement of sensorial and volatile profiles of olive oil by addition of olive leaves

Publication . Malheiro, Ricardo; Rodrigues, Nuno; Bissaro, Camila Andressa; Leimann, Fernanda Vitória; Casal, Susana; Ramalhosa, Elsa; Pereira, J.A.

The changes caused by the addition of olive leaves (0, 5, and 10%) during the extraction of olive oil and malaxation time (20, 30, and 30 min) in the volatile profile and sensory attributes of olive oil from cv. Cobrançosa were studied. To investigate such transformations, a central composite designs from the Response Surface Methodology (RSM) was used, retrieving 13 runs combining leaf percentages and malaxation times. Each run was extracted in triplicate (39 olive oils overall). Sensory attributes were improved to leaves addition, mainly green and fruitiness attributes in olfactory and gustatory-olfactory sensations, but high malaxation times ( > 30 min) reduced pungent and bitter notes. Leaves addition increased the amounts of total volatiles, particularly the GLV's (green leaves volatiles) (E)-2-hexenal, (Z)-3-hexenal, and (Z)-3-hexenyl acetate, directly correlated with the improved sensory attributes. RSM models a showed positive linear effect with leaves addition, but a negative effect with malaxation time. These results suggest the use of olive leaves as effective odorants for the olive mill industry, while enabling the reduction of malaxation times and by-product amounts. Practical applications: The results obtained clearly open new lines of research to use olive leaves, a sub-product of olive oil extraction, in a valuable way. Olive leaves can be used as natural sources of odorants for olive oils. Furthermore, their use during the extraction of olive oils from overmature olives may also lead to an improvement of the volatile fraction and provide enhanced sensory properties to the consumers, thus conferring an added value to these oils. Another important practical application is the extraction process. In our work, we advise to optimize both the percentage of leaves and the malaxation time as much as possible, as they facilitate both sensory and volatile fractions of the extracted olive oils. Sensory attributes are improved to leaves addition, mainly green and fruitiness attributes in olfactory 17 and gustatory-olfactory sensations, but high malaxation times ( > 30 min) reduced pungent and bitter 18 notes. Leaves addition increase the amounts of total volatiles, particularly the GLV's (green leaves 19 volatiles) (E)-2-hexenal, (Z)-3-hexenal, and (Z)-3-hexenyl acetate, directly cor related with the improved 20 sensory attributes. RSM models a show positive linear effect with leaves addition, but a negative effect 21 with malaxation time. These results suggest the use of olive leaves as effective odorants for the olive mill 22 industry, while enabling the reduction of malaxation times and by-product amounts.

2017Journal article

Open access