Determination of maize kernel hardness: comparison of different laboratory tests to predict dry-milling performance.

BACKGROUND: Numerous foods are produced from maize, and grain hardness has been described to have an impact on grain end-use value, and in particular for dry-milling performance. RESULTS: Thirty-three samples of commercial hybrids have been analysed for test weight (TW), thousand-kernel weight (TKW), hard : soft endosperm ratio (H/S), milling time (MT) and total milling energy (TME) through the Stenvert hardness test, coarse : fine material ratio (C/F), break force (HF) and break energy (HWF) through the puncture test, floating test (FLT), kernel dimensions and sphericity (S), protein (PC), starch (SC), lipid (LC), ash (AC) content and amylose : amylopectin ratio (AS/AP). Total grit yield (TGY) has been obtained through a micromilling procedure and used to compare the efficiency of the tests to predict the dry-milling performance. TW, H/S, MT, TME, C/F, FLT, S, PC, SC and AS/AP were significantly correlated with each other. TW has been confirmed to be a simple estimator of grain hardness. Among the hardness tests, C/F was shown to be the best descriptor of maizemilling ability, followed by FLT. A good correlation with TGY has also been observed with H/S, MT, TME and PC, while SC, S and AS/AP seem to play aminor role. The puncture test (HF and HWF) did not offer good indications on the impact of hardness on kernel grinding properties. CONCLUSION: This study can be considered as a contribution towards determining kernel properties which influence maize hardness measurement in relation to the end-use processing performance.