Relationships Between the Duration of Steeping, Grain Microbes, Grain Maturity and the Response of De-Embryonated Grains to Gibberellic Acid

After steeping, with and without antimicrobial agents in the steep liquor, for 20 h or 60 h, barley grains were degermed. α-Amylase, produced in response to a fixed dose of gibberellic acid applied to the scutellar recess, was estimated at intervals during a subsequent incubation period. When samples with similar steeping periods were compared it was seen that enzyme production was greater in those that had been steeped in the presence of antimicrobial agents. This was particularly clear in samples that had been steeped for 60 h. Furthermore, grain which had been steeped for 60 h before de-embryonation produced more α-amylase, in response to gibberellic acid, than grain which had received a 20 h steep. Sub-samples of three lots of grain were warm-stored to overcome water sensitivity. When such grains were steeped, degermed and dosed with gibberellic acid they tended to produce more a-amylase than samples of control, cool-stored grain of the same original lots similarly treated and incubated. It is concluded that microbial activity on the surface layers of the grain, ‘maturity’ of the aleurone layer (enhanced by warm storage) and the duration of the steeping period all influence the responsiveness of barley aleurone layers to a dose of gibberellic acid.