The effect of cell wall degrading enzymes on the microstructure of rye cell walls

The effect of cell wall hydrolyzing enzymes, endogenic and exogenic on the cell walls of rye kernel, and rye bread was studied by using fluorescence microscopy and image analysis. Endo-xylanase was able to degrade a small portion of the kernel cell walls. In addition to xylanase, arabinosidase was needed to hydrolyze the inner endosperm cell walls suggesting that the inner endosperm cell walls are more branched than the outer ones. Xylanase treat-ment of rye dough caused the endosperm cell walls to frag-ment, and when the dough was treated with 100 nkat xylanase/g flour, small cell wall fragments were observed in the breads. The effect of ferulic acid esterase on the microstructure of rye grains and breads was also studied. Relative to the native grains, weak germination induced minor local changes in the microstructure of cell walls and proteins in the kernels. Kernels of germinated and native grains were milled, and doughs were prepared from the flours. Microstructural examination of dough sections showed germination to cause two types of structural changes in the cell walls: 1) swelling and 2) fading of the blue fluorescence of cell walls. More extensive germination of rye grains at 15°C for 4 days resulted in the production of a-amylase, b-glucanase, endo-b-xylanase and a-arabinosidase. In all the grains the fluorescing cell wall area, measured by computer-assisted image analysis was less than 5% in germinated grains, whereas it was over 30% for non-germinated grains.