THE ROLE OF DEXTRINS IN THE STICKINESS OF BREAD CRUMB MADE FROM PREHARVEST SPROUTED WHEAT OR FLOUR CONTAINING EXOGENOUS ALPHA-AMYLASE

Dextrins were extracted in water from bread made from pre-harvest spro uted wheat or standard flour supplemented with exogenous alpha-amylase s. The dextrins were separated by gel permeation chromatography and th e dextrin content (% of crumb weight) determined for different degree of polymerisation (DP) size classes; DP 1-2, DP 3-10, DP 11-50, DP 51- 200 and DP > 200. There were significant correlations between the dext rin content in each size class and crumb stickiness (r = 0.84-0.91, 22 df). The most significant correlation (r = 0.96) was between total de xtrin content and crumb stickiness. Addition of dextrins of various DP ranges from various sources to standard flour produced bread with sti cky crumb. Again, the degree of stickiness was generally related to th e amount of total dextrin in the crumb and not to size distribution of dextrins. In this instance, extensive enzymic hydrolysis of starch wa s not necessary to produce sticky crumb; the dextrins caused crumb sti ckiness directly. Addition of dextrins to reconstituted gluten-starch flour produced bread with unexpectedly low dextrin levels and correspo ndingly low stickiness scores. It is concluded that, to produce sticky crumb, high levels of dextrin of any size are necessary in the crumb; a sticky mass is produced when dextrins dissolve in the excess 'free' water that is normally 'bound' to starch, gluten and other insoluble components of bread crumb. (C) 1996 Academic Press Limited