Abstract:

Protein and starch are the abundant constituents in wheat flour and the major contributors for dough rheological properties. Most of the previous researches related to dough rhelolgical properties focused on the effect of protein and its components, but a very few on the effect of different protein and starch contents. It is well known that both protein and starch are important components to evaluate the quality of wheat flour, and closely related to dough rheological properties. In the present study, we used a strong gluten wheat cultivar Shannong 12 and a medium-strength wheat cultivar Shannong 11 to study the effect on dough rheological properties under different protein or starch percentage, in order to reveal the functions of protein and starch in dough and flour products, and therefore give advice on wheat breeding for quality. The fractionation and reconstitution method was adopted to make the flour samples have various protein and starch contents with a constant background composition. The results indicated that peak height (PH) and peak width (PW) of two kinds of dough were significantly increased (P<0.05) compared with those of control when protein content was increased from 100% to 120%, 140%, and 160%, the maximum resistances (MR) were increased from 40.7 to 49.8 g, 59.0 and 71.6 g in Shannong 12 and from 20.6 to 29.5 g, 32.1 and 36.0 g in Shannong 11, respectively. However, the extensibilities (EX) of these two doughs changed not obviously compared with those of control. PH and peak work input (PWI) of two kinds of dough were significantly decreased (P<0.05) with the increase of starch content. When the starch contents were increased from 81.11% (Shannong 12) and 83.85% (Shannong 11) to 85%, 90%, and 95%, the EX was decreased from 110.8 to 68.8 mm, 59.2 and 36.5 mm in Shannong 12 and from 81.6 to 75.8 mm, 59.1 and 50.3 mm in Shannong 11, respectively. However, the MR of these two doughs changed not too obviously compared with those of control.

Key words: Protein content, Starch content, Fractionation and reconstitution, Dough rheological property