Functionality of chemically modified waxy, partial waxy and wild-type starches from common wheat

Abstract

Waxy wheat (Triticum aestivum L.) starch contains little or no amylose. Partial waxy wheats have amylose concentrations intermediate between those of waxy and wild-type (normal) starches. A factorial design was used to compare waxy, wild-type, partial waxy, and blends (10 and 17% amylose) of waxy and wild-type starches in native states, and after cross-linking with phosphorus oxychloride, substitution with propylene oxide, and a sequential modification procedure using both approaches. In analyses via the Rapid Visco Analyser (RVA), native waxy wheat starch reached peak viscosity at a significantly lower temperature, and displayed significantly higher viscosity (>3000 cP), than starches of all other genotypes and blends. Hydroxypropylation of waxy wheat starch increased peak viscosity to >3500 cP. In contrast, native and hydroxypropylated wild-type starches demonstrated peak viscosities of 1000 and 1500 cP, respectively. Cross-linked waxy starches demonstrated stable viscosities, with no breakdown or setback. With both native and modified starches, partial waxy pasting curves displayed viscosities intermediate between those of waxy and wild-type, though the same effect was obtained via use of the 17% blend. The 10% native starch blend displayed pasting properties intermediate between those of the partial waxy/17% blend group, and the waxy sample. The results suggest that appropriate selection of amylose contents, ideally formed by blending of waxy and wild-type starches, and chemical modification method, can result in wheat starches with predictable functional properties for a variety of food and industrial uses.