Effects of steeping condition and germination time on the alpha-amylase activity, phenolics content and malting loss of Nigerian local red and hybrid short Kaura sorghum malts

The effects of steeping condition (STC) and germination time (GMT) on the phenolics content (PC), alpha-amylase activity (DP) and malting loss (ML) of Nigerian local red (LRS) and hybrid (HSK) grain sorghum were investigated in 6-day micro-malting trials. Air-rested steeping (ARM) effected the highest increase in DP of both LRS (51.7%) and HSK (30.2%), which occurred on the fifth day of germination, while the lowest increase was from the low-temperature steeping treatment (LTM) in LRS (12.6%) and HSK (5.32%), based on the control (CSM). Reduction in PC was proportional to GMT. The greatest reduction, which occurred on the sixth day, in LRS (71.4%), was caused by formalin re-steeping of ARM germinates (FRM), while the least reduction was caused by ARM (28.3%) in HSK. Malting loss (ML) increased with GMT while ARM caused the greatest loss (46.2%) in the 6-day LRS malt. On average, ML of LTM was not significantly different from that of CSM in HSK, but it was in LRS (P ⩽ 0.05). Results of second-order ANOVA showed that the main factors—STC (A), GMT (B) and sorghum variety, SGV (C)—have significant influences (P ⩽ 0.025) on DP and ML, while SGV had none on PC. The interaction A × B affected DP (P ⩽ 0.10) and ML (P ⩽ 0.005); A × C exerted no statistically significant effects on any of the three quality attributes, while B × C influenced only DP (P ⩽ 0.05).