Physicochemical, thermal and rheological properties of starches isolated from malting barley varieties.

The aim of this work was to characterize physicochemical, thermal and rheological properties of starches isolated from malting barley varieties. The analyzed starches contained 19.6-25.2 g of amylose, 42.47-70.67 mg of phosphorus, 0.50-1.26 g of protein and 0.10-0.61 g of fat per 100 g of starch dry mass. The clarity of the 1 % (w/w) starch pastes ranged from 5.4 to 9.8 %. Values of the characteristic gelatinization temperatures were in the ranges of 56.5-58.5 °C, 61.2-63.0 °C and 66.7-68.7 °C, respectively for TO, TP and TE, whereas values of gelatinization enthalpy were from 6.49 to 9.61 J/g. The barley starches showed various tendency to retrogradation, from 24.52 to 44.22 %, measured as R = ∆HR/∆HG value. The pasting curves showed differences in pasting characteristics of the barley starches, where values of peak (PV) and final (FV) viscosities were 133-230 mPa·s and 224-411 mPa·s, respectively. The barley starch pastes exhibited non-Newtonian, shear thinning flow behaviour and thixotropy phenomenon. After cooling the starch gels showed different viscoelastic properties, however, most of them behaved like weak gels (tan δ = G″/G' > 0.1). Significant linear correlations between the parameters of pasting characteristic and some rheological parameters were found.