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Document Type

Dissertation - University Access Only

Award Date

2014

Degree Name

Doctor of Philosophy (PhD)

Department / School

Plant Science

First Advisor

William A. Berzonsky

Abstract

The impact of wheat flour starch components affecting end-use quality in food products is not well understood. However, the breeding of waxy wheat lines having low levels of amylose starch has provided new possibilities to characterize the impact of starch on end-use food quality and functionality. The unique rheological characteristics of waxy wheat may improve food texture and shelf-stability, by producing softer products that exhibit delayed staling. These advantages may be evident in the production of wheat flour tortillas, a type of flatbread which represents a rapidly growing segment of the US end-use industry. This study was conducted to determine the impact that low-amylose, waxy wheat starch has on dough expansion, flour tortilla functionality, and tortilla quality. A low-amylose, full waxy wheat breeding line was used to produce five waxy blends (0, 25, 50, 75, and 100% waxy) with a wild-type flour. Having waxy flour in a blend resulted in increasing the mean protein content. Also, it increased water absorption, while it decreased dough consistency as determined using a Mixolab. Tortilla diameter and rollability were improved by the addition of low-amylose flour in the formulations; whereas, tortilla brightness, bake height and specific volume were negatively impacted. Waxy wheat flour also improved fresh tortilla texture, as evidenced by the increase in extensibility observed in blends that included a high waxy flour component (≥ 75% waxy). However, this improvement in texture was not evident at 7 d storage at ambient temperatures, indicating that low-amylose flours do not necessarily extend the shelfstability of wheat tortillas. Several Mixolab characteristics as measured in the blends were highly correlated to wheat tortilla physical properties. There was a highly significant, negative correlation between tortilla diameter and stability (-0.84, p < 0.001), while baked tortilla height was highly correlated to the Mixolab C3 value (0.68, p < 0.001), and tortilla rollability and brightness were correlated to water absorption (0.67, p < 0.001 and -0.61, p < 0.01, respectively). The physical characteristics of tortillas were correlated with texture, and the Mixolab is evidently a good predictor of the physical, but not necessarily the textural attributes of wheat flour tortillas. Low-amylose, waxy wheat flour produced doughs that exhibited a significant higher expansion under a low vacuum pressure. There were also significant correlations between Mixolab characteristics and dough expansion in a vacuum chamber, suggesting that the dough expansion system is sensitive enough to detect differences due to low-amylose starch, and that its use has the potential to adequately predict traditional pan bread loaf volume. Approximately 800 doubled haploid (DH) lines were produced by hybridizing a low-amylose, full waxy wheat genotype with 22 spring and winter wheat genotypes predicted to have unique combinations of endosperm protein subunits. These DH lines can be used in the future to help determine the exact combination of low-amylose starch and protein subunits that optimize wheat flour functional characteristics and tortilla quality.

Library of Congress Subject Headings

Tortillas
Flour
Cooking (Wheat)

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

144

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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