Hardness as a modification index for malting red and white sorghum (kaffir) grains

BACKGROUND This study investigated changes in the resistance to fracture of malting red and white sorghum grains using a hardness tester as another method for monitoring grain modification . RESULTS Grain hardness decreased progressively from 134.35 N and 137.29 N in malting red and white sorghums and levelled off after 120 h at 76.98 N and 69.14 N. In the red grain malts traditionally used for burukutu production, moisture content ( r  = −0.983), dhurrinase activity ( r  = −0.981), malting loss ( r  = −0.981), free amino nitrogen ( r  = −0.909) and cold wate r extract ( r  = −0.908) were better indicators of grain hardness than root length ( r  = −0.89). In the white sorghum malts, malting loss ( r  = −0.988), dhurrinase activity ( r  = −0.954) and diastatic activity ( r  = −0.936) were better indicators of grain modification than root length ( r  = −0.916). The soluble nitrogen ratio at the end of malting was lower in the red (0.049) compared with the white (0.0548) . CONCLUSION Grain hardness using a hand‐held tester is a simple, fast and good index of modification of malting red and white sorghum grains. Oven‐dried red and white sorghum malts could be considered to be well modified at hardness values/indices below 77 N/0.5730 and 72 N/0.5036, respectively. © 2013 Society of Chemical Industry