Influence of hydrocolloids on water absorption and rheology of wheat doughs

N.E. LINLAUD; M.C. PUPPO; C. FERRERO

Madrid

Congreso; 13 th ICC Cereal and Bread Congress; 2008

International Association for Cereal Science and Technology

Hydrocolloids are employed to improve bread quality and as preserving agents. Their main effects on the final product are the extension of shelf life, diminishing the dehydration of crumb during storage and the increase of the specific volume of bread. These effects depend on gum type and concentration. The objectives of the present work were: a) to determine the effect of hydrocolloids addition on water absorption of flour-hydrocolloid mixtures evaluated by different methods and b) to analyze their influence on dough rheology. Guar gum (GG), xanthan gum (XG), high methoxyl pectin (P), locust bean gum (LBG) and a 50:50 mixture of locust bean gum and xanthan gum (LBG+XG) were added at four levels (0.25, 0.5, 1.0, 1.5 g/100g flour) to commercial wheat flour. The influence of hydrocolloids on water absorption was tested by different techniques: farinograph water absorption (A), water imbibing capacity (WIC), sodium dodecyl-sulfate sedimentation test (SDS ST) and sucrose solvent retention capacity (SRCs). The microstructural characteristics of dough were evaluated by scanning electron microscopy (SEM). The rheological behavior was analyzed through the farinographic parameters (development time, dough stability and degree of softening) and texture profile analysis (TPA) parameters (hardness, adhesiveness, elasticity and cohesiveness). Farinograph water absorption increased with increasing gum levels, particularly in the case of XG. WIC values increased when XG or LBG + XG were added. In the case of LBG and P, no significant effect was observed. GG at 1.5 % significantly increased WIC value. Values of SDS ST were significantly increased by the addition of XG or LBG+XG, but this index decreased when P was added. In the SRCs test, an increase was observed when XG or LBG + XG were added while the effect was much less pronounced with the other types of gums. As shown by farinograph results, dough stability was increased in some cases (for example, with GG addition, at all levels) but for others, stability decreased (at the highest P level). When GG was added, TPA hardness did not change compared to control but it decreased when the other gums were used. Elasticity increased with higher levels of XG, GG or LBG+XG, but this effect was not observed with P or LBG. Cohesiveness decreased after gum addition. No major differences were observed in gluten network, as evaluated by SEM and compared to the control. Addition of hydrocolloids changed flour water absorption, particularly with XG. The different techniques employed in this work helped to determine the effects of gums on the hydration capacity of flour mixtures. Hydrocolloids addition also led to rheological changes in dough; trends were determined by the type and concentration of the gum employed.