Formation of vitisin A during red wine fermentation and maturation

During alcoholic fermentation the formation of vitisin A occurred mainly in the period between 20% and 85% glucose utilisation, when the concentrations of the precursors, malvidin‐3‐glucoside and pyruvic acid were at a maximum. The maximum rate of vitisin A synthesis of 11 mg/Lh occurred when 57% of glucose had been utilised and 440 mg/L malvidin‐3‐glucoside, 114 mg/L pyruvic acid and 3.1 mg/L measured oxygen were present. During maturation, production of vitisin A appeared to be linked with the availability of a suitable oxidant. Synthesis of vitisin A continued for approximately 6 months of maturation in air‐tight bottles while the precursors were available. In wines that underwent malolactic fermentation, the malolactic bacteria consumed pyruvic acid and thereby limited the production of vitisin A. At the end of a 12 month maturation period, the concentration of vitisin A declined in wines made without any malolactic fermentation, even though malvidin‐3‐glucoside and pyruvic acid were still present. This indicated that there was a shortage of a suitable oxidant required to complete the reaction.