*3.5. Product Analysis*

Aliquots of the reaction mixture were subjected to HPLC analysis (Agilent 1200 series instrument, Agilent C-18 column, 15 cm length) in order to quantify the yield and conversion. The eluent was in all cases 60 vol.% aqueous acetonitrile solution. The conversions of GGGE and yields of the products (guaiacol, vanillin, vanillic acid) were determined from individual standard solutions with products identified by GC-MS analysis.
