Effects of Purified Endo-β-xylanase and Endo-β-glucanase on the Structural and Baking Characteristics of Rye Doughs

The importance of arabinoxylans and b-glucans in rye baking was studied by depolymerizing these cell wall polysaccharides in situ with purified xylanase and β-glucanase. Two different rye cultivars, Danko (from Sweden) and Muskate (from Canada), were used. The most marked effect of the enzymes was the reduction in proofing time, with xylanase having the greater effect. Xylanase addition made the doughs soft and slack, as indicated by the viscoelastic measurements. Both xylanase and β-glucanase had a positive effect on the dough volume, but a negative effect on the oven rise. Addition of increasing levels of β-glucanase during baking degraded β-glucans extensively in the bread but did not influence the content or solubility of arabinoxylans. Microstructural studies showed xylanase addition to cause increased fragmentation of cell walls. Xylanase also increased the release of amylose from the starch granules. At high dosage of xylanase swelling of the starch granules and a release of proteins from aleurone cells were observed. Sugar analysis and NMR studies of soluble non-starch polysaccharides isolated from the bread revealed higher contents of soluble arabinose, xylose and glucose residues in the Danko bread without enzyme addition than in the corresponding Muskate.