Effect of soluble dietary fibre addition on rheological and breadmaking properties of wheat doughs

Abstract

The aim of this experimental work was to evaluate the effect of inulin addition on the rheological properties of common wheat doughs and bread quality. Three commercial fructan products of different number average degree of polymerisation (DPn) were used (DPn = 10 for inulin ST; DPn = 23 for inulin HP and HP-gel). Inulin contents from 2.5 to 7.5% on dry matter (wheat flour plus inulin) were used. Dough rheological properties were investigated using farinograph and dynamic rheological measurements. Upon addition of dietary fibre (DF), significant increase in mixing time and stability, and decrease in water absorption were recorded. Inulin ST exerted greater effect on water absorption than HP products. Inulin with high DP determined large changes in linear viscoelastic properties of dough. The storage modulus ( G′) gradually increased and tan δ decreased with increasing levels of inulin HP and HP-gel, which contribute to the overall dough elasticity and strength. The increase in solid-like behaviour with DF content prevented expansion of wheat dough during the fermentation stage. No significant differences were observed between sample HP and HP-gel. Enrichment with inulin ST led to lower changes in linear viscoelastic properties of dough at farinograph water absorption than inulin HP. Bread volume was significantly reduced and crumb hardness was enhanced by inulin HP level in the range 5–7.5%. When inulin ST was added to a flour suitable for breadmaking, a trend of increasing bread volume with the increase of DF content was found.