Mechanical damage and thermal effect induced by ultrasonic treatment in olive leaf tissue. Impact on polyphenols recovery

• Published in: Ultrasonics sonochemistry Vol. 82; p. 105895
• Main Authors: Abi-Khattar, Anna-Maria, Boussetta, Nadia, Rajha, Hiba N., Abdel-Massih, Roula M., Louka, Nicolas, Maroun, Richard G., Vorobiev, Eugene, Debs, Espérance
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-01-2022; Elsevier
• Subjects: Chemical Sciences; Diffusivity disintegration index; Electrical conductivity; Mechanical damage; Olea; Olive leaves; Phenols; Plant Leaves; Polyphenols; Short Communication; Ultrasonics; Ultrasound-assisted extraction; Mechanical damage; Diffusivity disintegration index; Electrical conductivity; Ultrasound-assisted extraction; Olive leaves; Olive leaves, Ultrasound-assisted extraction, Diffusivity disintegration index, Electrical conductivity, Mechanical damage
• ISSN: 1350-4177; 1873-2828
• DOI: 10.1016/j.ultsonch.2021.105895

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•Ultrasound impact results from a synergy between mechanical damage and thermal effect.•Ultrasound fosters extraction of phenolic compounds by cavitation phenomenon.•Ultrasound required three times less treatment duration than water bath.•Increasing ultrasound power improved mass transfer coefficient by 15 times.•Electrical conductivity of extracts correlates positively with treatment temperature.
The influence of ultrasound treatment (US) on cellular damage of olive leaf tissue was studied. Mechanical damage and thermal effect of US were characterized. The level of tissue damage was defined by the diffusivity disintegration index ZD based on the diffusivity of solutes extracted from olive leaves differently treated. The Arrhenius form using the temperature dependences of the thermal treatment time within the temperature interval 20–90 °C was observed for the thermal process. The corresponding activation energy ΔUT was estimated as 57 kJ/mol. The temperature dependences of electrical conductivity were measured for extracts of intact and maximally treated olive leaves. Then the diffusivity disintegration index ZD and total phenolic compounds recovery for three studied US powers were calculated (100, 200, and 400 W). The results evidenced that the mechanically stimulated damage in olive leaf tissue can occur even at a low US power of 100 W if treatment time is long enough (t = 3.5 h). The US treatment noticeably accelerated the diffusion process mechanically in addition to its thermal effect. Trials in aqueous solution revealed the dependence of polyphenols extraction on damage level with respect to the US power applied.