Fed-batch fermentation with glucose syrup as an adjunct for high-ethanol beer brewing

Abstract

To produce a beer with a high ethanol content, preliminary research on fed-batch fermentation profiles with glucose syrup as an adjunct during the primary fermentation period was conducted. The ethanol concentration of the beer was elevated by feeding a glucose syrup into the fermentors at a later stage of primary fermentation. Fermentation trials were carried out using a typical lager strain, SC-9, with a pitching rate at 7.0 × 10 6 cells/mL. An all-malt wort (12.5°P) was employed and the primary fermentation temperature was 14°C. Glucose syrup was supplemented when the concentration of residual reducing sugars was decreased to~10 g/L. Results showed that the supplemented glucose was consumed rapidly and that the ethanol concentration in the final beer was raised to 67.9 g/L. Additional growth of yeast was observed after feeding accompanied by a low yield of ethanol (~0.46 g/g). Formation of diacetyl was enhanced by yeast growth and two additional peaks were obtained after feeding. The peak value of the diacetyl concentration was 1.90 mg/L. The fed-batch fermentation resulted in a beer with an overproduction of higher alcohols and esters, indicating that brewing under these experimental conditions led to an unbalanced flavour profile. Results of optimization demonstrated that the optimal conditions were found to be 15°P for initial wort extract, 10°C for fermentation temperature and 20 × 10 6 cells/mL for yeast pitching rate, leading to total higher alcohols of 173.8 mg/L, total esters of 22.8 mg/L and an acetaldehyde concentration of 40.5 mg/L. A 12 day maturation and fermentation temperature of 8°C was needed to reduce the acetaldehyde to 14.3 mg/L.

An HS-SPME-GC-MS Method for Profiling Volatile Compounds as Related to Technology Used in Cider Production

“…Therefore, the increased concentrations of these compounds are probably due to higher temperatures of fermentation, commonly used to reduce diacetyl, and to accelerate fermentation. These intensified processes may not be long enough for sufficient degradation of butane-2,3-diol [27], and thus these ciders contain high concentrations of butane-2,3-diol, but not as high as ciders fermented by wild or mixed cultures [28].…”