INFLUENCE OF THE STARCH GRANULE SURFACE ON THE RHEOLOGICAL BEHAVIOR OF WHEAT-FLOUR DOUGH

The influence of the properties of the starch granule surface on the r heological behaviour of wheat flour doughs was studied in dynamic osci llation measurements (frequency sweep and strain sweep) and in stress relaxation measurements. A flour with a high protein content (15%) was diluted with wheat starch to obtain a protein content of 10%. The gra nule surface of the substituted starch was modified in three different ways: by hear treatment, by adsorption of a wheat protein fraction an d by adsorption of lecithin to the granule surface. The effects of the se modified starches were compared with the results obtained for nonmo dified starch and protein or lecithin (in liposomes) added to the pour . Owing to the low concentration of the added protein and lecithin, no effect was observed when they were added to the bulk of flour. Howeve r, as a starch-surface modification the same components influenced the rheological parameters studied. Also the heat-treated starch had an e ffect on the rheological behaviour. The study established the importan ce of the properties of the starch-granule surface in wheat flour doug h.