An improved colorimetric procedure for determining apparent and total amylose in cereal and other starches

Publisher Summary This chapter reviews nonmutant starch granule composition and development, and focuses on genetic mutants and how they have been useful in understanding the complexity of polysaccharide biosynthesis and development. Plant species, which are important sources of commercial starch production are focused on, especially maize, because of the many known endosperm mutants of maize, which affect polysaccharide biosynthesis. The information gained applies to other species, and these effects are illustrated in the chapter. General trends in the genetics and physiology of starch development have been illustrated with examples. Starch is a common constituent of higher plants and a source of carbohydrates. Starch in chloroplasts is transitory and accumulates during the light period and is utilized during the dark. Storage starch accumulates in reserve organs during one phase of the plant's lifecycle and is utilized at another time. Starches from reserve organs of many plants are important in commerce. Although considerable effort has been directed at characterizing the enzymes involved in starch synthesis, the role of these enzymes and other factors in determining subtle variations in starch granule structure and starch fine structure remain largely unknown. Variations in granule structure can be associated with plant species, cultivars of a species, the environment in which a cultivar is grown, and genetic mutations.

Genetics and Physiology of Starch Development

It has been generally assumed that the [alpha]-(1->4)-linked and [alpha]-(1->6)-branched glucans of starch are generated by the coordinated action of elongation (starch synthases) and branching enzymes. We have identified a novel Chlamydomonas locus (STA7) that when defective leads to a wipeout of starch and its replacement by a small amount of glycogen-like material. Our efforts to understand the enzymological basis of this phenotype have led us to determine the selective disappearance of an 88-kD starch hydrolytic activity. We further demonstrate that this enzyme is a debranching enzyme. Cleavage of the [alpha]-(1->6) linkage in a branched precursor of amylopectin (preamylopectin) has provided us with the ground rules for understanding starch biosynthesis in plants. Therefore, we propose that amylopectin clusters are synthesized by a discontinuous mechanism involving a highly specific glucan trimming mechanism.

Preamylopectin Processing: A Mandatory Step for Starch Biosynthesis in Plants.

Ultrasound-treated starch: SEM and TEM imaging, and functional behaviour

When starch is heated in water, it absorbs water and swells. is is the process of gelatinization, a process that causes a tremendous change in the rheological properties of the starch suspension. e properties of starch gels are very sensitive to factors such as shearing, temperature, heating or cooling rate, and, of course, the source of the starch and the presence of other components. e gelatinization process depends on the presence of both crystalline and amorphous domains in the starch granule.

Starch: Physicochemical and Functional Aspects

The interaction of linear, amylose oligomers with iodine

Studies on starch degrading enzymes

Samples of synthetic amylopectins with long external chain-lengths have been prepared from degraded, waxy maize amylopectin and glucose-1-phosphate by the action of potato phosphorylase. Samples having external chain-lengths determined by enzymic assay of 23.4, 29.9, 46.5, and 109.5 glucose units (original sample = 13.7 glucose units) were prepared. The iodine-staining properties of these materials have been investigated, and a relation between λmax and average chain-length evaluated. A theoretical relation between chain-length and β-amylolysis limit has been proposed. The iodine-binding capacity of the samples has been studied in detail by potentiometric titration at 1.5 °C and 20 °C. Unambiguous conclusions regarding the observed iodine binding capacity and the length of external chain have been made for the first time. The properties of the synthetic products are discussed.

K.M. Khan

Papers

The interaction of linear, amylose oligomers with iodine

Studies on starch degrading enzymes

The Properties of Synthetic Amylopectin with Long External‐Chains

Studies on starch-degrading enzymes. 8. The action pattern of porcine, pancreatic alpha-amylase.

Studies on starch-degrading enzymes. XIV. The multiple forms of procine, pancreatic alpha-amylase.