Molecular background of technological properties of selected starches

Selected starches, i.e. waxy maize, amaranth, quinoa, wheat, miller and buc kwheat starches, were investigated with respect to their technological prop erties such as gelatinization, stability to mechanical stress, resistance t o conditions and stability in continuous freeze/thaw cycles. Technological properties are correlated with molecular features such as branching charact eristics in terms of iodine-complexing potential, molar mass, occupied gluc an-coil volume, packing density of glucan coils and theological properties. Waxy maize and amaranth starches were found to be amylopectin-type short-ch ain branched (scb) glucans with weight average molar masses M-w = 17 x 10(6 ) g/mol and 12 x 10(6) g/mol, respectively. Waxy maize starch had a high ge latinization potential, high viscosity at 95 degrees C (340 mPas) low stabi lity at acidic conditions, average stability to shearing and good freeze/th aw stability. For amaranth starch a viscosity of 122 mPas at 95 degrees C, low resistance to acid, but high stability to applied shearing and even hig h freeze/thaw stability was determined. Investigated quinoa starch was clas sified as scb-type glucan, however, the branches are significantly longer t han those of waxy maize and amaranth. With a M-w = 11 x 10(6) g/mol and a v iscosity of 187 mPas at 95 degrees C, this sample is comparably resistant t o acidic conditions and to shearing, but instable in freeze/thaw experiment s. Wheat, millet and buckwheat starches contain significant percentages of amylose-type long-chain branched (Icb) glucans (22.1, 32.1 and 24.3 %, resp ectively) with M-w values of 5 x 10(6)g/mol, 12 x 10(6) g/mol and 15x10(6) g/mol, respectively. Wheat starch, with a viscosity of 107 mPas at 95 degre es C, shows low stability under acidic conditions, but high stability to sh earing. Wheat and millet starches, but not buckwheat starch, form weak gels in the course of subsequent freeze/thaw cycles. Millet starch, with a visc osity of 101 mPas at 95 degrees C was found to be moderately stable under a cidic conditions and to shearing. Buckwheat starch with a viscosity of 230 mPas at 95 degrees C shows no acid resistance and is instable upon shearing but performs very well in freeze/thaw experiments.