Fermentation Efficiency of High-Gravity Rye Mashes using Pressureless Starch Liberation Methods

The efficiency of ethanol production during simultaneous saccharification and fermentation (SSF) of gelatinised starch or in its native form, in high-gravity rye mashes (approx. 21% and approx. 25% dry matter) prepared by pressureless methods of starch release were compared. The obtained fermentation efficiency expressed in % of the theoretical yield was 72.98 +/- 1.46% for gelatinised starch and 84.27 +/- 1.68% for native starch in the mashes with 21% dry matter, while the use of mashes with 25% dry matter content resulted in 71.22 +/- 1.42% and 77.36 +/- 1.54% of the theoretical yield, respectively. However, the presence of residual dextrins (1.99 +/- 0.82 to 3.04 +/- 0.39 g/100 ml) in the fermented mashes suggests the need of further research on the improvement of the process.