Changes of thermodynamic and structural properties of wrinkled peastarches (Z-301 and Paramazent varieties) during biosynthesis

摘要

Starches isolated at different stages of maturation (milky, waxy, complete maturation) of wrinkled peas were investigated by differential scanning calorimetry (DSC) and Xray diffraction (XRD). It was shown that the maturation of wrinkled peas is accompanied by changes in the structural and thermodynamic properties of starches. The melting process of milky starches could be approximated by means of a "two-state" model. The melting process of the waxy and completely maturated starches was described as the melting of a mixture of low and high temperature populations of double-helical type crystallites, denoted as B- and B*-types, as well as the melting of V-h-type crystallites. The relative amounts of the three structures were determined by deconvolution of the calorimetric peaks. The values of the melting cooperative units (theta) and the thickness of the crystalline lamellae (pitch heights) for starches were determined using mathematical models describing the melting processes. The values of the B for milky, waxy, and completely maturated starches were calculated as 18 and 29 anhydroglucose residues, respectively. The thickness of the crystalline lamellae of B-type crystals in the milky, waxy, and completely maturated starches were calculated. Structural changes in starch granules during maturation of wrinkled pea are discussed.