Red wine pilot-scale vinification assisted by pulsed electric fields: effect on sensory and physico-chemical quality of Syrah and Tempranillo varieties (Vitis vinifera L.)

Pulsed electric field (PEF) assisted vinification was tested in a pilot-scale winery for the extraction of must and production of red wines from Syrah and Tempranillo grape vine varieties. The grape mash obtained after destemming and crushing the grapes was subjected to pulsed electric fields with 2 kV/cm of electrical field intensity and specific energies of 2 kJ/kg and 2.8 kJ/kg for Syrah and Tempranillo, respectively. The long-term effects of the PEF assisted extraction on the physico-chemical parameters and sensory quality of the finished wines were investigated after 1.5 years of wine ageing. For sensory, discriminative triangle tests were carried out for each wine variety to assess any effect of PEF on colour and flavour. PEF did not affect most of the physico-chemical parameters analysed, such as density, alcoholic strength by volume, total acidity, total SO2, total dry extract, and tanning capacity. However, wines made with grapes treated with PEF have a higher pH value, turbidity, and electrical conductivity compared to control wines. The physico-chemical results showed that the permeabilisation of the grape skin caused by the PEF treatment led to an increase in total phenols, including flavonoid phenols and anthocyanins, in relation to wines made with grapes without PEF treatment. In agreement, the results of chromatic parameters showed that PEF increased the value of the a* parameter, corresponding to a more intense red colour, decreased the value of the L* parameter, corresponding to a darker wine, and increased the C* parameter, known as chroma, referring to the saturation of a colour. The sensory results showed that PEF promotes changes in colour and flavour (aroma and taste) of wines. The colour sensory results are in agreement with the analytical colour assessed by the chromatic characteristics and anthocyanin contents. Sensory characterisation of control and PEF wines, and panellists’ comments from triangle tests, favoured the wines vinified with PEF, which revealed a more intense red colour, fuller-bodied and rounder, and with greater intensity and persistence in the aftertaste aroma.