Analytical methods
Glucose, DP4+ (high saccharides containing four or more glucose), lactic acid, and ethanol concentrations were determined by HPLC (Agilent 1200). The HPLC method is based on a normal chromatography procedure, using a Phenomenex Rezex Cal organic acid column (California, USA), the size of which is 300x7.8 mm, and a refractive index detector. Eluent was 5 mM H2SO4 flowing at 0.6 ml/min. The volume of injection for both standard solutions and sample extracts was 20 µl.