Application of microwaves and megasound to olive paste in an industrial olive oil extraction plant: impact on virgin olive oil quality and composition

Abstract

Traditional olive oil processing includes batch olive paste kneading for 30-60 min. Microwave (MW) treatment of the olive paste has recently shown to continuously provide faster conditioning, while megasound (MS) treatment has been shown to enhance oil extractability. The present work examined the virgin olive oil standard parameters, sensory descriptors, and phenolic and headspace composition upon treatment of oils obtained using novel process enhancement interventions and their combination in an industrial plant. Oils were obtained treating the paste with (a) malaxation for 30 min (control), (b) microwaves (6.0 kW at 2.45 GHz; 0.9 kJ/kg) (MW), (c) malaxation followed by a megasonic treatment (400 kHz + 600 kHz at 2 kW; 10 kJ/kg), (MS), and (d) microwave conditioning followed by a megasonic treatment (MW + MS). Standard parameters (free acidity, peroxide value, K₂₃₂, K₂₇₀, fatty acid ethyl esters) were within the international specifications. The Control and MW process provided similar phenolic composition but a post MS intervention significantly increased total phenolic content and decreased total C5 and C6 aldehydes in the MW treated paste. These results encourages further developments for a combined continuous microwave and megasonic conditioning technology to fasten the olive oil extraction, to enhance yields and total phenolic content.

Practical applications: Microwave and megasounds are two technologies easily implementable on industrial olive oil extraction plant. They permit to simplify the entire plant and could replace totally the malaxers section. This new technology allows having a uniform paste treatment in continuous mode, enhancing the olive oil quality.

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