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Instrumental methods for the evaluation of corn tortilla texture
xiv, 182 leaves : illustrations ; 28 cm.
Objective techniques (rollability, bending, tensile,
puncture, and stress relaxation) that evaluate control
tortillas and tortillas containing 0.75% CMC and 0.005%
barley malt were developed and evaluated. The abilities of
the objective techniques to detect texture differences in
corn tortillas containing different additives were evaluated.
The potential of using the objective technique to monitor
tortilla texture in industrial settings was also evaluated.
Objective rollability, bending and tensile techniques were
more highly correlated to subjective rollability and
flexibility than the puncture and stress relaxation test.
Puncture technique measured the ability of tortillas to
resist puncture, while stress relaxation measured the
viscoelastic properties. The variability of the objective
techniques was significantly affected by the uniformity of
the sample (thickness, moisture content, and the extent of
puffing), however, among homogenous samples, the
variabilities were low. The bending technique produced low
variability data on the commercial tortillas sampled on site
or from selected Texas markets. It detected textural
differences between table tortillas produced on different
work shifts and between tortillas prepared for table
consumption or chip use. The bending technique data on the
commercial tortillas supported and were in accordance with
the data collected on the laboratory tortillas. The
variability in texture values of corn tortillas available on
the market was detectable using both objective and subjective
techniques. The objective techniques supplemented the data
obtained in the subjective rollability tests and provided
adequate information to help explain the changes in textural
properties during storage or those caused by additives. The
choice of the objective technique used depends on the
application needed. For research and quality control in
industrial settings, the bending and tensile techniques are
recommended. They are fast, simple, perform as well in a
laboratory facility as in an industrial production facility,
and have potential to become a significant tool in monitoring
texture in industrial settings. The stress relaxation
technique is recommended for fundamental research in an
academic setting. The technique provides information about
viscosity and elasticity of corn tortillas that were not
"Major Subject: Food Science and Technology".
Issued also on microfiche from University Microfilms Inc.
Includes bibliographical references: pages 140-147.