Semi-industrial ultrasound-assisted virgin olive oil extraction: Impact on quality

This is the first effort to implement a continuous VOO ultrasound-assisted extraction system on a semi-industrial scale, studying its impact on product quality. Four sets of control/treated monovarietal VOOs were produced from Carolea and Ottobratica cultivars, at two maturation stages, in a low-scale mill plant (W-cap = 150 kg/h). Thirty minutes of traditional malaxation were set for control trials, whereas UAE tests underwent 15min of traditional malaxation and 15 min of sonication, performed in a continuous ultrasonic reactor placed between the malaxer and decanter. Basic VOO quality parameters, antioxidant content, and volatile profiles were studied. In the tested conditions, UAE treatment did not affect free acidity or peroxide values. A consistent and significant increase in the content of minor compounds, namely phenols (lignans, secoiridoids) and C-6 and C-5 volatile compounds, was generally observed when UAE was applied. However, UAE may have been responsible for a reduction in tocopherol content. UAE generally lead to higher extraction yields and higher intensities of positive sensory notes of fruity, bitter, and pungent. The results of semi-industrial trials support the application of UAE for VOO production, rendering its industrial implementation tangible. Practical applications: UAE allows enrichment of VOO in minor compounds with nutritional and sensory relevance, therefore, improving the quality and the commercial value of the VOO. It also appears to increase the extraction yield, thus, overcoming the need for employing extreme kneading conditions. Therefore, VOO-UAE seems to be a promising process that could represent a genuine innovation for the milling industry. The UAE-enrichment of VOOs in antioxidant content - in particular secoiridoids, which play a key role in VOO's health properties - assumes special relevance with the possibility to stake the labeled health claim, as in EU Reg. No. 432/2012. This is positive both for the consumer, who stands to gain added nutritional benefits, and for the oil miller, who could market a product with added value. Furthermore, the application of US to VOO production, as a non-thermal and continuous production method, provides an answer to the current trend toward healthy and nutritionally enriched products.