Fig. 4From: NMR-based metabolomics in wine quality control and authentication 13C CP–MAS NMR spectra of wine precipitates from 2012 to 2013 vintages and at different oak barrel aging times t: a Merlot 2012, t = 1 month; b Cabernet Sauvignon 2013, t = 1 month; c Merlot 2013, t = 4 months; and d Cabernet Sauvignon 2013, t = 4 months. A spinning frequency of 10 kHz was used for MAS, residual spinning side bands are marked with (*), and peaks from potassium bitartrate with (K). Reprinted from Ref. [32], Copyright (2016), with permission from ElsevierBack to article page