Study of the structure and properties of native and hydrothermally processed wild-type, lam and r variant pea starches that affect amylolysis of these starches.

Starches from WT, lam, and r pea mutants differing in amylopectin/amylose contents (70, 90, and 28% amylopectin, respectively) were used in kinetic studies of pancreatic α-amylase action at 37 °C and for investigations of their supramolecular structure and physicochemical properties during heating. For WT and lam starches, amylase accessibility and catalytic efficiencies (CE) increased following hydrothermal processing up to 100 °C. Accessibility changed relatively less in r during heating with increasing K(m) between 60-90 °C.

Atomic force microscopy of pea starch: origins of image contrast.

Atomic force microscopy (AFM) has been used to image the internal structure of pea starch granules. Starch granules were encased in a nonpenetrating matrix of rapid-set Araldite. Images were obtained of the internal structure of starch exposed by cutting the face of the block and of starch in sections collected on water.

Atomic force microscopy of pea starch granules: granule architecture of wild-type parent, r and rb single mutants, and the rrb double mutant.

AFM studies have been made of the internal structure of pea starch granules. The data obtained provides support for the blocklet model of starch granule structure (Carbohydr. Polym.

Structural studies of starches with different water contents.

The proportion of double helices in starches from a series of pea [rb, rug4-b, rug3-a, and lam-c mutants, and the wild type (WT) parental line], potato and maize (normal and low amylose), and wheat (normal) lines, ranged from about 30-50% on a dry weight basis. In relatively dry starch powders, only about half of the double helices were in crystalline order, this proportion being higher for A-type than for B-type starches. Using starch from WT pea as an example, it was found that increasing water content results in an increase in total crystallinity.

The effect of water content on the ordered/disordered structures in starches.

(13)C cross-polarization magic angle spinning NMR has been used to study the ordered and disordered structures of starches with different water contents. The amorphous regions of starch have been shown to produce NMR patterns only if they are in a glassy state, the widths, positions, and areas of the peaks to some extent being dependent on the temperature and the water content of the starch. In the amorphous region, the peaks were all Gaussian in shape, while the peaks in the ordered regions had Lorentz profiles.