2.2. Chemicals
All solvents used for chromatographic purposes were HPLC
grade. HPLC water, acetonitrile and formic acid were from VWR
(Fontenay-sous-Bois, France). The HPLC grade anthocyanin standard
malvidin-3-O-glucoside was purchased from Extrasynthese
(Lyon, France), while phenolic standards gallic acid, caffeic acid
were from Alfa Aesar (Schitigheim, France). Catechin was purchased
from Sigma–Aldrich (Saint Quentin Fallavier, France).
2.3. Moisture content determination
Moisture content in grape berries and grape by-product, before
and after MHG extraction, was assessed by conventional Dean–
Stark distillation according to the American Oil Chemist’ Society
(AOCS) official methods (Zill-e-Huma, Abert-Vian, & Maingonnat,
2009). A moisture content of 80.9% was determined in the grape
fresh berries, vs. 43.8% and 37.0% in the grape by-product before
and after extraction, respectively