ALEURONE AND PERICARP FLUORESCENCE AS ESTIMATORS OF MILL STREAM REFINEMENT FOR VARIOUS CANADIAN WHEAT CLASSES

Mill streams from laboratory-scale and pilot-scale millings of seven C anadian wheat classes were used to extend previous evaluations of fluo rescence imaging as a flour refinement estimator. Flour streams and di verse mill streams derived from throughout the Grain Research Laborato ry (GRL) Pilot Mill during the milling of Canada Western Red Spring (C WRS) wheat were subjected to fluorescence measurement of pericarp and aleurone tissue. Both techniques showed clear differentiation among th e mill streams. Strong linear relationships of pericarp fluorescence t o ash content, grade colour and L (brightness) were found. Relationsh ips of aleurone fluorescence to the same refinement indices, although still statistically significant (P<0.05), were weaker because of the p reviously established tendency for break flours to exhibit lower aleur one fluorescence than reduction flours of comparable refinement. Exten ding the GRL Pilot Mill break system to broaden the refinement range w ithin CWRS break flours confirmed a strong linear relationship between break flour refinement and aleurone fluorescence. The robustness of f luorescence as a hour refinement indicator under different milling con ditions was examined for commercially grown wheats from seven Canadian wheat classes using three different mills. For every wheat class and every milling process both fluorescence techniques showed clear differ entiation among flour streams. Pericarp fluorescence was strongly rela ted to flour refinement for all wheat classes, aleurone fluorescence w as less strongly related because of anomalous low fluorescence of brea k flours. The relationships of pericarp fluorescence to the flour refi nement indices were heterogeneous among wheat classes. It is well esta blished that flour ash content and flour colour have limitations for e stimating the refinement of flours from wheats of diverse origin. Ther efore, the heterogeneity of pericarp flourescence relations among whea ts provides evidence that pericarp fluorescence is a more objective fl our refinement estimator. The regression equations of pericarp fluores cence to flour refinement indices when a single wheat was milled by di fferent mills were clustered closely, although heterogeneity was evide nt for several wheats. (C) 1996 Academic Press Limited