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High Amylose Corn Starch Gels – A Molecular Investigation of the Network Constituting Polymers

Ulbrich, Marco; Scholz, Fanni; Flöter, Eckhard

FG Lebensmittelverfahrenstechnik

The relationship between microstructural features and mechanical strength of aqueous starch gels is investigated. The gels are prepared by systematic variation of the factors starch type (high amylose [AM] corn starches [HACS] having about 50 and 70% w/w AM; HACS‐50/‐70), starch concentration (6 and 9% w/w) and storage time (1 and 14 days). The gel matrices are separated by means of a centrifugation method, and two phases are obtained account for the dissolved starch (liquid phase) and the network constituting starch (swollen phase). Subsequently, the latter starch fraction is partially digested using two amylases (AMY) and in combination with pullulanase (PUL) [α‐AMY, α‐AMY‐PUL, β‐AMY, β‐AMY‐PUL], too. The starch samples (dissolved and network constituting) and the degradation products (polysaccharides after partial enzymatic hydrolysis) are characterized molecularly by means of size exclusion chromatography (SEC)‐techniques, and amounts and molecular properties of specific fractions and molecule segments, respectively, are determined. A clear correlation between the specific involvement and contribution of the starch polymers (e.g., absolute amount, state, function) in the gel network and the mechanical gel strength is found. Particularly, the starch's AM content and the polymer concentration of the gel are evident as controlling factors in developing the gel's firmness.