STRUCTURAL-CHANGES IN INSOLUBLE CELL-WALLS IN WHOLEMEAL RYE DOUGHS

Structural changes in insoluble cell walls, and rheological changes oc curring during incubation of unyeasted wholemeal rye doughs were studi ed by fluorescence microscopy, image analysis and dynamic visco-elasti c measurements. Three samples were chosen to represent a range of spro uting resistance and type of rye. Ensi is an old Finnish rye variety w ith poor resistance to sprouting, Anna is typical of current Finnish b readmaking varieties, whilst Amando represents a new German hybrid var iety with good resistance to sprouting. Microstructural studies of gra in cross sections indicated that even before milling, great structural damage had occurred in the cell walls of Ensi, the sample with the lo west falling number (62). The blue fluorescence, present in intact cel l walls, was absent in the subaleurone layer and in the cells of ventr al endosperm. In the dough of Amando, the sample with the highest fall ing number (299), the area of fluorescing cell walls was greatest and it was lowest in that of Ensi with the lowest falling number,. Anna (f alling number 187) resembled Amando more than Ensi. The storage modulu s (G') decreased with increasing water content for all samples, with t he phase angle showing a corresponding increase. During incubation the area of cell walls decreased and the doughs became softer, as indicat ed by visco-elastic measurements. Changes in G' during incubation were largest in the Ensi dough at all studied water contents, whereas Aman do and Anna showed approximately the same change.