FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Molecular structure and physico-chemical properties of pseudo cereal starches


Glucans of pseudo cereal starches with significant differences in their branching pattern – amaranth, quinoa and buckwheat – were investigated upon the correlation of their molecular characteristics with technological properties. Consistency of glucan conformation, in particular persistance against elevated temperature, acidic pH and mechanical stress was investigated with respect to consequences on molecular and supermolecular structures of starch/DMSO-solutions. For analytical purposes starch glucans were separated by semi-preparative size-exclusion chromatography (SEC) and obtained fractions were tested upon their iodine-complexing potential. Amaranth was found to be short chain branched (scb = amylopectin type); quinoa to be scb-type, but consisting of longer branches than amaranth; buckwheat was found to be a mixture of scb-glucans with approx. 24% of longchain branched (lcb = amylose-type) glucans. Molecular weight (degree of polymerization) for DMSO-dissolved starches was determined absolutely by means of aqueous SEC. Weight average molecular weights (Mw) were found close to 12·106 g/M for the investigated samples. Dimensions of starch glucan coils were estimated from SEC-data combined with universal calibration: values between 2-40 nm were found without significant differences for the three starches. However, in spite of these minor differences, the investigated starches differ significantly in their inter- and intramolecular interaction potential. Thus, obviously interaction potentials are strongly controlled by branching patterns, glucan-coil packing densities and by the ability to form supermolecular structures.