PATTERNS OF MODIFICATION IN MALTING BARLEY

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Abstract
The modified regions of the starch endosperms of malted grains were fragile and, in thin sections, the cell walls in these regions did not stain readily with Congo Red or Trypan Blue, although scanning electron microscopy demonstrated some cell-wall material remained. Initially the enzymes causing modification came from the scutellum, but later more came from the aleurone layer. Patterns of modification in different grains differed significantly, but usually resembled those recorded previously6 except that often modification had advanced further by the nucellar sheaf cells. In grains treated with gibberellic acid modification advanced faster, particularly beneath the aleurone layer, after two days germination. In tumbled or commercially abraded grains, malted with gibberellic acid, modification was even more rapid, but in more than 99% of the grains the same patterns of modification occurred. Two-way modification was a rare event. Rapid, general sub-aleurone modification occurred in grains cut at the apex and dosed with gibberellic acid. Decorticated grains modified exceptionally quickly and, when treated with gibberellic acid, massive subaleurone modification occurred. The cell walls of the tissues that resisted modification fluoresced strongly in ultra-violet light, in contrast to those of the starchy endosperm.