Kiyoshi Shibanuma

Molecular structures of some wheat starches

Abstract Molecular structures of amyloses and amylopectins from three varieties of Japanese wheat, Chihoku, Horoshiri, and Norin-61, and two wheat classes, Australian standard white (ASW) and Western white (WW), were characterized. WW amylose was the largest (number-average degree of polymerization dp n , 1570) and Chihoku amylose was the smallest ( dp n 830). ASW and Chihoku amyloses had higher amounts of branched molecules (∼42% by mole) with lower average numbers of chains ( nc ∼ 13 ), than those of others (∼28% by mole, nc ∼ 19 ). The structural features of amylopectins by iodine affinity and chainlength distribution were also characterized by varieties and classes. The amylose contents of the starches were in the range of 21·7–27·4% for ASW and WW, respectively. A lower amylose content and a higher amount of the branched amylose molecule with a lower nc may produce better quality Japanese-type noodle.

Characterisation of hot-water-soluble components of starches

Abstract Starches of maize and wheat (cereals), potato (tuber), and sweet potato (rhizome) were extracted by 6 mM phosphate buffer (pH 6.2) above the gelatinisation temperatures, and fractionated into amylose (1-butanol precipitate) and amylopectin (supernatant solution). The amylose fraction was a mixture of linear and branched molecules and there were more branches in the amyloses from potato and sweet-potato amylose than in those from maize and wheat. The preponderant branches were short and probably clustered around the reducing terminal of the molecule. The amylose molecules in potato and sweet potato were larger than those in maize and wheat. The amylopectin fractions from potato and sweet potato showed some similarities in properties with their normal counterparts, whereas those of maize and wheat differed remarkably and contained considerable proportions of an unusual and novel fraction with dp 240 and 215, respectively, which may reflect the conditions of extraction and the botanical origin of the starch.

The fine structure of oyster glucogen

Abstract When oyster glycogen was hydrolysed in sequence with beta-amylase, isoamylase, and beta-amylase, fractionation of the products on Bio-Gel P2 revealed that the smallest and most abundant maltosyl-Ba chain fragment had d.p. 5, and carried 1 maltosyl residue. A considerable amount of maltotriose was produced from Ba chains by the debranching of maltosyl-Ba chain fragments. The Ba chains carried increased numbers of A chains with increase of the chain length. In the outermost layer of the molecule, there were abundant 1–2 intervening (1→4) linkages for an A chain bound to a Ba chain. High-performance anion-exchange chromatography with pulsed amperometric detection showed that the individual chains of the glycogen debranched with isoamylase were in the range from d.p. 2 to 30 and that the chain with d.p. 6 was the most abundant. The results are compatible with the random branching structure.