Fractionation of a red grape marc extract by colloidal gas aphrons

The objective of the current study was to investigate the application of colloidal gas aphrons (CGA) as a potential low-cost technology for the fractionation of phenolic extracts obtained from off-skins fermented red grape skins with high sugar content. The trials were aimed to investigate the possibility of using CGA generated from the non-ionic surfactant Tween20 to separate phenolic compounds from non-phenolic compounds (minerals and sugars) and to fractionate different fractions of phenolic compounds (total phenols, cinnamic acids and anthocyanins). Separation tests were carried out in a 0.7 L flotation column investigating the effect of both the volumetric ratio CGA/extract sample and the molar ratio CGA/extract sample on both the recovery yields and the separation factor (the ratio between the concentration of a compound in the recovered aphron phase and in the discharged liquid phase). Results revealed the possibility of reaching high recovery yield even though with a poor selective fractionation of the different compounds present in the extract, with glucose and cinnamic acids showing the highest affinity for the aphron phase.