SECONDARY PRODUCTS FROM THE BREWING WORT FERMENTATION IN CONTINUOUS TUBULAR EQUIPMENT

The fermentation stage, the most prolonged step during brewing processing, receives special attention for new solutions aiming its optimization. In this context, continuous fermentation systems are reported as an alternative to process productivity improvement. The objective of this work was to evaluate the viability of a continuous tubular fermenter, operating by density gradient, comparing its secondary product concentration to the traditional’s batch fermentation. The continuous fermenter was made using a spiral silicone pipe, 15 m length and 0.0254 m internal diameter, fed by a peristaltic pump with a flow rate set at 0.85 mL/min. The batch process was conducted in 400 mL Schott flasks. For both processes, the wort was formulated from dehydrated malt extract (Liotecnica), diluted to 10.5 °Brix. Throughout the process, the fermentation secondary product concentration of diacetyl (mg/L), acetaldehyde (mg/L), ethyl acetate (mg/L) and isoamyl alcohol (mg/L), was determined by gas chromatography. The concentration of diacetyl (0.28 mg/L) obtained after 149 h of continuous fermentation was 72% lower than the obtained in the batch process (1 mg/L) at similar process times. The concentrations of acetaldehyde and isoamyl alcohol at the end of 149 h of the continuous process were 15 and 29 mg/L, respectively, values also below those found in the discontinuous process (Acetaldehyde -17 mg/L; isoamyl alcohol - 32 mg/L). Concerning to ethyl acetate, it presented higher values than its detection threshold (35 mg/L) in both processes. The results corroborate the hypothesis that this projected continuous fermenter can be equivalent to the conventional batch system, indicating a possible reduction in the beer maturation period by continuous fermentation.