Cereal Chem 63:436-441 | VIEW
Factors Affecting the Viscosity of Extrusion-Cooked Wheat Starch.
W. R. Mason and R. C. Hoseney. Copyright 1986 by the American Association of Cereal Chemists, Inc.
The factors responsible for the cold and hot paste viscosities of extrusion-cooked wheat starch were investigated. Hot paste viscosity was affected by die temperature and an interaction between screw speed and barrel temperature. Cold paste viscosity was affected by an interaction between moisture of the feed and throughput rate. The area of a peak on the descending amylograph heat cycle curve was measured. This "swell peak area" was highly correlated with cold paste viscosity. It was shown that the swell peak area corresponded to the quantity of starch that, although completely gelatinized, can undergo further swelling upon heati ng in water. Moreover, the swell peak area reflected the presence of insoluble starch, which absorbs water but excludes solubles, thus concentrating the soluble phase. Cold paste viscosity was shown to vary with the concentration of the soluble phase and the volume of insolubles that exclude solubles. The latter was measured with a dye-labeled soluble dextran. Water absorption index and water solubility index were negatively correlated with cold paste viscosity. Hot paste viscosity was found to be correlated with molecular degradation as measured with capillary viscometry.