Volatile compounds in cider: Inoculation time and fermentation temperature effects

A cider fermentation at laboratory scale with controlled inoculation with selected yeasts and malolactic bacteria was performed. The composition of the major volatile compounds with low boiling points (< 145 degrees C) was determined by gas chromatography throughout the fermentation process, under the different operating conditions of inoculation time of the microorganisms (simultaneous or sequential) and fermentation temperature (15 degrees C or 22 degrees C). Temperature had a more important effect on the levels of certain volatile compounds when the simultaneous inoculation method was used. It was observed that when fermentation temperature increased to 22 degrees C, using the simultaneous method, the final concentrations of ethyl acetate and some of the higher alcohols decreased, while others maintained similar levels. In the sequential inoculation model, after completion of the alcoholic fermentation at 15 degrees C, an increase in the temperature of the malolactic fermentation (15 degrees C to 22 degrees C) showed no statistically significant differences in the profiles of the volatile compounds tested. Thus, malolactic fermentation could be conducted at 22 degrees C, favouring malic acid degradation, without losses in the major volatile compounds, in relation to the levels measured at the lower temperature. Considering the traditionally recognized preference for low alcoholic fermentation temperatures in cider making, the results allow for the optimisation of the operating conditions.