Valorisation of vine-shoots: ultrasound-assisted extraction of proanthocyanidins

Vine-shoots are agricultural wastes of vineyards. About 1.4-2.0 tons of shoots can be obtained per hectare of vine per year. The world area under vines is about 7.5 million ha, and then an estimated total of 10.5-15 million tons of vine-shoots are produced each year. The studies conducted on the phenolic composition of vine-shoots generally focused on the stilbenes because of the interest in their health-promoting. However, to the best of our knowledge, there has been no work, thus far, on the proanthocyanidins (PAs) from vine-shoots. Proanthocyanidins exist as oligomers (OPCs), containing two to ten or more ‘catechin’ units, and polymers (PPCs). This study aims at performing optimisation of ultrasound-assisted extraction (UAE) of OPCs and PPCs from vine–shoots using response surface methodology