The role of pentosans and starch in baking of wholemeal rye bread

In case of rye wholemeal with low enzymatic activity, high bread volume is obtained in cases, when pentosan fraction contains many water extractable polymers, and there is an optimum ratio of water extractable pentosans to starch, which should be in the range 1:16–1:20. This is also accompanied by starch properties such as high amylose content, good swelling capacity (big swelling factor) and consequently high solubility and pasting temperature. Moisture content of wholemeal rye bread is mainly controlled by the level of fiber, including soluble pentosans, compared to the amount of starch. Starch properties which seem to be important for establishing this value are amylose content, and the susceptibility to swelling and gelatinization. Hardness of wholemeal rye bread is influenced by the level of fiber, including soluble pentosans. Decline of bread texture is observed in the presence of extractable pentosans with high molecular weight. Use of starch with high amylose level, high swelling factor and low molecular weight is accompanied by increased crumb hardening.