shape; concentrations of nonstarch components; amylose/amylopectin ratio;
molecular structure of amylopectin; type of molecular ordering in the
crystallites (type A or B; a third type, C, is also mentioned, but it probably is
a mixture of A and B); proportion crystalline; large scale structure of the
crystalline material, for instance the distancesaandb. Some cultivars make
no or very little amylose, especially ‘‘waxy’’ maize. The amylopectin in
potato starch contains phosphate groups, linked by esterification.
6.6.2 Gelatinization
Starch granules can be isolated from various plant materials, washed and
air-dried to obtain a powder. When the powder is put in cold water, the
granules take up a little water, but that is about all that happens. Native
FIGURE6.23 Schematic model of the crystal morphology in potato starch. At left,
the building blocks of double molecular helices are shown. At right, shape and
stacking of the large helices is depicted. The large helices are packed in a tetragonal
array, and neighboring helices partly interlock as they are shifted by half the
pitch with respect to each other. (Adapted from a figure by G. T. Oostergetel and
E. F. J. van Bruggen.Carbohydr. Polym.21 (1993) 7.)