Nägeli amylodextrin and its relationship to starch granule structure. I. Preparation and properties of amylodextrins from various starch types



Nägeli-type amylodextrins were prepared from various starch types: native starch granules from potato, waxy maize, wrinkled pea, and high-amylose maize, and from a commercial amylose (“Superlose”). The granular starches and retrograded amylose were treated with 15% sulfuric acid at 22°–25° for 3 months, the undissolved residues were washed free of acid and air dried. X-ray diffraction patterns showed that amylodextrin from waxy maize starch (A-type) and potato starch (B-type) retain the same diffraction type as that of the parent starch. On conversion of a starch to an amylodextrin, the sharpness and intensity of the diffraction patterns are either retained (waxy maize starch), improved (slightly with potato, significantly with high-amylose maize, and very markedly with wrinkled pea) or developed (amylose). The results indicate that the crystalline regions of a native starch granule, retrograded amylose, or amylodextrin are exceedingly resistant to acidic hydrolysis at room temperature. In contrast to the parent starches, native amylodextrins stain little if at all with dilute iodine solution. The iodine stains of dissolved amylodextrins were red (waxy maize), red-purple (potato), or purple (amylose, high-amylose maize, and wrinkled pea).