Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/21/1996
Publication Date: N/A
Interpretive Summary: Starch is the primary component of wheat flour, and consequently, plays an important role as a determinant of food product quality. Most of the functional attributes of starch can be related to the interactions of starch with water during heating in the processes known as gelatinization, pasting, and gelation. Pasting generally refers to changes in viscosity associated with these events. In this report, the variation among starches from different wheat varieties for gelatinization, pasting and gelation are shown to be primarily governed by the content of amylose and amylopectin in the starch. The content of amylose corresponds well with the presence of amylose synthesizing enzymes associated with three genes in wheat. When one or more of the proteins are absent, the content of amylose is reduced and the properties of the starch are altered markedly.
Technical Abstract: The starch of wheat (Triticum aestivum L.) flour affects food product quality due to temperature-dependent interactions of starch with water during gelatinization, pasting, and gelation. The objective was to determine the fundamental basis(es) of variation in gelatinization, pasting, and gelation of prime starch derived from different wheat varieties. Seven U.S. varieties, Kanto 107, and six near-isogenic hardness lines (NILs) were examined. A complete pasting curve was obtained using the Rapid Visco Analyzer. Apparent amylose content ranged from 17.5 to 23.5%; total amylose content from 22.8 to 28.2%. None of the parameters measured consistently correlated with onset of gelatinization and other RVA curve parameters that preceded peak paste viscosity. Higher peak paste viscosity, greater breakdown, lower final viscosity, negative setback, and less total setback were associated with lower apparent and total amylose contents. Each 1% reduction in apparent or total amylose content corresponded to an increase in peak viscosity of about 22 and 25 RVA units, respectively. The lower amylose varieties Penawawa and Klasic were missing the granule-bound starch synthase (GBSS) protein associated with the Waxy gene locus on chromosome 4A (Wx-B1 locus); Kanto 107 was confirmed as missing both the 7A and 4A waxy proteins (Wx-A1 and Wx-B1 loci); and the hardness NILs were also null at the 4A locus. We concluded that reduced quantity of starch amylose due to decreased GBSS profoundly affects starch gelatinization, pasting and gelation properties.