In all cases, an O/W emulsion with 20:80 (v/v) grapeseed oil and deionised water was prepared as control sample (code: C).
The study of the emulsion stability involved the following procedures:
(a)Surface tension measurements of the aqueous phase using a Sigma 70 tensiometer (KSV Instruments Ltd., Finland) at 25 °C. The Wilhelmy plate technique was applied in the Wilhelmy Constant Run programme mode. A platinum plate was partially immersed into the surface layer of an aqueous phase and the monitored surface tension decreased with time while the plate remained into position. The analysis ceased when the surface tension value was stabilized. Prior to each analysis, the surface tension of deionised water was measured as control.
(b)Interfacial tension measurements of the two-phase system using a K6 tensiometer (Krüss, Germany) at 25 °C. The Du Nouy ring method was employed. A platinum ring was used first to zero the indicator with grapeseed oil and then to measure the interfacial tension between grapeseed oil and each aqueous phase. Deionised water was used first as the aqueous phase for the reference measurement. Then followed the other aqueous phases which contained wine, measured from the most diluted one (5%, v/v wine) to the least diluted (100%, v/v wine). The interfacial tension of each system was measured at the point where the ring broke away from the interfacial layer of the two phases.
(c)Determination of the mean surface droplet diameter D[3,2] and droplet size distribution with the use of a Mastersizer 2000 with a HYDRO 2000MU unit (Malvern Instruments Ltd., UK). D[3,2] is the so called Sauter mean diameter and it is defined as the diameter of a sphere that has the same volume-to-surface area ratio as a particle or droplet of interest.
(d)Viscosity measurements with a LVTDV-II digital viscometer (Brookfield, USA) attached to a temperature controller (PolyScience, USA) and using 25/13R accessories at 1.32 min−1 and 25 °C. All measurements and macroscopic observations were performed at 0, 7, 15, 30, 45 and 60 days.