Annealing of maize starch

Abstract

A comparison was made between the annealing characteristics of commercial waxy, normal and amylomaize starches. The waxy and normal starches responded similarly to annealing where improved registration of amylopectin double helices is proposed, with perhaps optimisation of hydrogen bonding along the full length of individual helices. This is attributed to similar amylopectin crystalline structure of these starches. It is considered unlikely that the free amylose (FAM) forms any significant numbers of amylose–amylose or amylopectin–amylose double helices throughout its length, but may randomly form some double helical regions in the crystalline shells created essentially by the amylopectin. Single amylose helices are also considered unlikely. Probably lipid complexed amylose (LAM) is excluded from the amylopectin crystallites and is primarily located in amorphous shell regions (between crystalline shells) and consequently affects hydration (and glass transition, Tg) of these regions. In amylomaize starches, however, the larger amylopectin chain lengths, broad gelatinisation endotherm, leaching characteristics and double helix content (by NMR) indicates that FAM does here play a significant part in the crystalline regions of the starch. Annealing of amylomaize crystallites probably reflects enhanced registration (and possibly compartmentalisation) of amylopectin–amylopectin, amylopectin–amylose and amylose–amylose helices.