Effect of Different Steeping Conditions on Endosperm Modification and Quality of Distilling Malt

摘要

This study showed that when barley was steeped in water for either 8 h or 16 h, hydration of endosperm materials was sub-optimal and modification of endosperm materials of barley malt was inadequate. The malt produced under these steeping regimes gave poor friability scores and produced a large number of whole grains. When barley was steeped for 24 h on a continuous basis, or when a regimented standard steeping method was used, the malt produced gave higher friability scores and a much lower number of whole grains. An important relationship was found between friability scores and whole grain results for the malt samples produced under these conditions. Optic barley, whose endosperm was more difficult to hydrate, gave a strong negative correlation between friability scores and number of whole grains at R~2 = 0.8689. Oxbridge, whose endosperm was more easily hydrated, gave a much stronger negative correlation between friability scores and number of whole grains at R~2 = 0.9769. Rapid visco-analysis (RVA) results also confirmed that steeping the barley samples for only 8 h or 16 h produced malt that modified poorly as the RVA peak viscosities were very high. RVA pasting results further confirmed that when barley was steeped for 24 h on a continuous basis, or when a standard regimented steeping method was used, good quality malt was produced and no differences were found in the RVA peak viscosities of the barley malt samples produced under the two different steeping conditions. The results of protein breakdown (proteolysis) during these experiments, measured in terms of total soluble nitrogen (TSN) production, or soluble nitrogen ratio (SNR) further confirmed that optimal proteolysis was achieved when barley was steeped for either 24 h on a continuous basis, or with a standard steep. Optimal results were also found for hot water ex-tractable materials such as hot water extract (HWE) and free amino nitrogen (FAN) when barley was steeped for 24 h or the standard steep. The 24 h continuous steep for barley produced quality malt comparable to that obtained when the standard regimented steep was used for steeping barley. For both Optic and Oxbridge barley, with a 24 h continuous steep, produced malt that gave significantly higher fermentabilities and PSY values,rnregardless of germination time, than those obtained using a standard regimented steep. Therefore steeping barley for 24 h on a continuous basis prior to malting will produce good quality malt for some barley samples/varieties. This will help to reduce water usage during steeping, will save steeping time thereby reducing malting time and will reduce the amount of water for effluent treatment. All of these factors result in an overall cost saving for the malting industry.