K amiar kits

Specific gravity was measured using a specific gravity meter (DA-300; Kyoto Instruments). All of the specific gravity measurements were converted to densities and then to degrees Plato, according to Brown and Hammond (2003) .
The volatile acidity and pH determinations were performed according to the Official European Union Methods (EC, 2000) . Ethanol content was measured according to the Association of Official Analytical Chemists (AOAC, 1990) . The contents of acetaldehyde, ethyl acetate, higher alcohols (n-propanol, isobutanol, amilic alcohol, isoamilic alcohol) were determined by direct injection into a gas-liquid chromatography system. The other volatile compounds were extracted using an ether-hexane (1:1) extraction technique, and evaluated using a capillary gas chromatography system (GC-2014; Shimadzu, Kyoto, Japan), as reported by Canonico et al. (2014) . The free amino nitrogen content was determined following a procedure described previously by Dukes and Butzke (1998) . The contents of glucose, sucrose, maltose, and ammonia were determinated using enzymatic kits (k-masug, k-amiar kits, respectively; Megazyme, Ireland), according to the manufacturer's instructions.