Oxygen deficiency in germinating barley

Ethanol can be found in the gaseous atmosphere at the beginning of industrial scale malting, indicating fermentative metabolism. While it is neither possible nor necessary to avoid the fermentative phase completely, a prolonged fermentative phase may increase malting losses and impair malt quality. This work was undertaken to study the effect of processing conditions on the oxygen deficiency in barley. Ethanol production was always detected at the beginning of malting, in all steeping conditions. During the steeping phase, germinating barley suffered from oxygen deficiency despite continuous aeration. Germinating barley also reacted to low external oxygen concentrations. The timing of the oxygen deficiency determined its effect on germination: the later oxygen deficiency occurred, the more it retarded germination. Aeration of the first steep water did not appear to relieve the oxygen deficiency in the barley grain, which is probably due to the impermeable seed coat. In industrial practice, aeration during the first wet steep may therefore serve more as remover of CO2 than as “oxygeniser” of barley.