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Effect of extrusion cooking of starch on molecular parameters of its molecules. T. Bruemmer (1), F.
MEUSER (2), B. van Lengerich (3), and C. Niemann (4). (1) Buehler, Uzwil, Switzerland; (2) Technical
University Berlin, Berlin, Germany; (3) General Mills, Minneapolis, USA; (4) Nestlé Research Center,
Lausanne, Switzerland.
The effect of mechanical and thermal energy input during extrusion
cooking of corn starches on the structure of its molecules was investigated. For this the specific mechanical
energy input (SME) and the temperature of the product (PT) exiting the extruder, which indicates the
thermal energy input, were used as process parameters. Extrusion cooking trials were carried out according
to a factorial design which included a computerized modeling based on fuzzy logic. The experimental
set-up enabled differentiation of the effects caused by each of both process parameters on the molecules. The
extrudates molecules were examined for mean molecular weight (Mw), molecular weight distribution,
polydispersity, short chain degradation products and distribution of their molecules. Up to PT 180°C the
SME exercised the strongest effect on molecular degradation, almost entirely of amylopectin. The
degradation resulted in molecular sizes well above that of the short chain molecules. Above 180°C the PT
had a pronouneal influence on the degradation of the molecules. In such extrudates short chain molecules
increased with the PT. It could be shown that the degradation resulting from SME was different from that of
PT above 180°C.
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