The application of an innovative ultrasounds (US) treatment, fully integrated in a low-scale plant for the production of virgin olive oils was studied. In particular, a prototyped US generator (500 W/L, effective ultrasonic power and 25 kHz, frequency), coupled with a tube-shaped transducer (2.25 L as internal capacity) and a screw-pump, was placed between the malaxator and the two-phases decanter. Two experimental trials were performed by processing separately 60 kg batches of destoned olives from different cultivars, collected in Italy during 2013. The effects of the US on the sensory and chemical quality parameters of the virgin olive oils were evaluated, by comparing the results of the two treated samples (U1, U2) with the respective ones, obtained extracting the oil using the same plant described above, but without the application of the US (C1, C2). The results showed that the application of such a treatment did not affect the basic quality parameters of the oils (free acidity, peroxide values, UV extinction coefficients), but increased the oil yield in respect with the control samples. On the other hand, a decrease of the oxidative stability (OSI test) of both the treated samples was registered, probably due to a reduction in the antioxidant fraction, mainly in terms of the dialdehydic form of ligstroside aglycone and -carotene, whereas the content in -tocopherol seems to be less susceptible. The application of the US treatment led also to a significant increase in the micro-dispersed water content, maybe due to the cavitation phenomena. This higher amount of water probably facilitates the transfer in the oil matrix of microorganisms/enzymes responsible for fermentation/degradation of sugars/protein material. This could explain the higher content of polar volatiles (ethanol, 3-methyl-1-butanol, ethyl acetate, acetic acid) markers of sensory defects, such as winey/fusty, in particular for U1, the richest in water. This study resumes the observations of some preliminary trials in order to verify if this innovative technology could be considered useful for an industrial scale application with a preservation of the product quality. Further tests have to be carry out to find convenient processing parameters.
Effects of ultrasounds treatment integrated in a low-scale plant on the quality of virgin olive oils: preliminary trials
VALLI, ENRICO;BENDINI, ALESSANDRA;DI LECCE, GIUSEPPE;GALLINA TOSCHI, TULLIA
2014
Abstract
The application of an innovative ultrasounds (US) treatment, fully integrated in a low-scale plant for the production of virgin olive oils was studied. In particular, a prototyped US generator (500 W/L, effective ultrasonic power and 25 kHz, frequency), coupled with a tube-shaped transducer (2.25 L as internal capacity) and a screw-pump, was placed between the malaxator and the two-phases decanter. Two experimental trials were performed by processing separately 60 kg batches of destoned olives from different cultivars, collected in Italy during 2013. The effects of the US on the sensory and chemical quality parameters of the virgin olive oils were evaluated, by comparing the results of the two treated samples (U1, U2) with the respective ones, obtained extracting the oil using the same plant described above, but without the application of the US (C1, C2). The results showed that the application of such a treatment did not affect the basic quality parameters of the oils (free acidity, peroxide values, UV extinction coefficients), but increased the oil yield in respect with the control samples. On the other hand, a decrease of the oxidative stability (OSI test) of both the treated samples was registered, probably due to a reduction in the antioxidant fraction, mainly in terms of the dialdehydic form of ligstroside aglycone and -carotene, whereas the content in -tocopherol seems to be less susceptible. The application of the US treatment led also to a significant increase in the micro-dispersed water content, maybe due to the cavitation phenomena. This higher amount of water probably facilitates the transfer in the oil matrix of microorganisms/enzymes responsible for fermentation/degradation of sugars/protein material. This could explain the higher content of polar volatiles (ethanol, 3-methyl-1-butanol, ethyl acetate, acetic acid) markers of sensory defects, such as winey/fusty, in particular for U1, the richest in water. This study resumes the observations of some preliminary trials in order to verify if this innovative technology could be considered useful for an industrial scale application with a preservation of the product quality. Further tests have to be carry out to find convenient processing parameters.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
