Staling in corn tortillas prepared from nixtamalized corn flour
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Effects of forming method and storage on starch and texture of corn tortillas were evaluated. Texture of tortillas was evaluated subjectively using rollability and crinkle methods and objectively using bending and extensibility methods on a texture analyzer. Absorption, starch solubility at 95'C, and starch pasting properties were evaluated. Alcohol, grinding, centrifugation, and an oven at 50'C were utilized to quickly stabilize and dehydrate gelatinized starch during processing. Analyses of starch-related properties were conducted on the dried flour. The hot-press method caused tortillas to puff extensively during baking which imparted an attractive appearance and excellent texture, however, hot-pressing did not affect the staling rate. Hot-pressing is an alternative method to produce corn tortillas. More changes in starch functionality related to texture changes of tortillas occurred during the initial 24-h period than during the rest of the storage time. RVA pasting viscosities below 65'C were substantial in fresh tortillas and decreased during the initial 24 h of storage; those between 75-90'C increased significantly during the initial 24 h of storage. Smaller changes in viscosities were observed upon further storage. Solubility of amylose and amylopectin decreased during the initial 24 h of storage. Starch and texture changes during storage of acidic and alkaline commercial tortillas containing carboxymethyl-cellulose (CMC) were monitored. CMC improved stability of tortillas stored for 15 days, and interacted better with starch during processing and storage of alkaline tortillas. Amylose or amylopectin were substituted for 20% of nixtamalized corn flour. Partially retrograded amylose stabilized the initial tortilla structure and induced rapid changes in starch pasting properties after baking. Amylopectin retrograded slowly and imparted softness and extensibility when present in a gelatinized state. Extensive amylopectin retrogradation occurred after 24 h storage, yielding a brittle, less flexible tortilla. Reheating renewed desirable textural properties lost during staling at 22'C for 15 days. Corn tortillas underwent staling during storage, corresponding to rapid changes in starch functionality, amylose solubility and amylopectin crystalinity. Texture in fresh tortillas corresponds to increased RVA viscosity at low temperatures. Monitoring texture and starch properties provided insights into staling and effects of reheating on renewing desirable texture.
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Includes bibliographical references: p.128-133.
Issued also on microfiche from Lange Micrographics.
Fernandez de Castro, Deborah Ann (1998). Staling in corn tortillas prepared from nixtamalized corn flour. Master's thesis, Texas A&M University. Available electronically from
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