Mf. Bajomo et Tw. Young, FERMENTATION OF WORTS MADE FROM 100-PERCENT RAW SORGHUM AND ENZYMES, Journal of the Institute of Brewing, 100(2), 1994, pp. 79-84
Worts made from raw sorghum and enzymes were successfully fermented ev
en though the level of FAN present (51 mg/1) is well below that essent
ial for fermentation of wort made from malted barley. Changes in typic
al fermentation parameters such as specific gravity, pH uptake of free
amino nitrogen (FAN) and ammonium ions mirrored the increase in yeast
cell concentration. Yeast viability remained high throughout the ferm
entation. Under identical fermentation conditions, malted barley worts
showed typical fermentation profiles. However, malted barley worts wi
th specific gravity maintained by the addition of D-glucose, but in wh
ich the FAN was diluted to a level similar to that found in a wort mad
e from sorghum and enzymes, fermented more slowly and failed to attenu
ate fully. Five consecutive fermentations, using yeast cropped from th
e preceding to pitch the current fermentation were conducted. The spec
ific gravity profiles were essentially the same in all five fermentati
ons. Final values of pH, yeast in suspension, yeast viability and FAN
were also indistinguishable. The yeast crop taken from fermentations o
f worts made from raw sorghum and enzymes represented a 5-fold increas
e over the initial pitching rate. When compared to commercial beers, t
he beers derived from fermentation of worts made from raw sorghum and
enzymes contained lower levels of ethyl acetate, and higher levels of
both 2- and 3-methyl butanol. In the beers derived from sorghum, isobu
tanol was always less than 20% of the total higher alcohol concentrati
on.