Specific enzymes have been used to improve flour quality for bread but enzyme action in tortilla flour has not been investigated. Two different wheat flours were prepared into tortillas using laboratory-scale, commercial equipment with fixed processing parameters. Dough and tortilla properties were evaluated using subjective and objective methods. Tortillas were stored in plastic bags at 22°C for evaluation. The effects of nine enzymes (amyloglucosidase 1, amyloglucosidase 2, bacterial 1, bacterial 2, fungal, maltogenic 1, maltogenic 2, malted barley and xylanase) on quality of wheat flour tortillas were evaluated. Dough absorption was adjusted to attain uniform dough for tortillas. Enzyme addition to tortilla flour did not significantly affect tortilla weight, moisture and pH. Bacterial 2 amylase extended shelf stability while maltogenic 1 and xylanase exhibited smaller improvements in shelf stability and other tortilla properties. Addition of 0.05 activity unit bacterial 2 amylase improved tortilla diameter and improved tortilla shelf life from 12 to 28 days. Maltogenic 1 at 280 ppm improved tortilla diameter, opacity and shelf life. Addition of 100 ppm of xylanase effectively improved tortilla diameter and shelf life. Bacterial 1 amylase at 60 ppm improved tortilla diameter but did not improve shelf stability. Amyloglucosidase 2, maltogenic 2 and malted barley amylase did not improve tortilla quality at any of the evaluated levels. Amyloglucosidase 1 and fungal amylase reduced overall tortilla quality at all the evaluated levels. Bread-making quality of wheat flour is correlated with the damaged starch present in the flour. Damage was induced by grinding the samples for 0, 1, 4 and 8 hr to determine the effects of starch damage on tortilla quality. Processing increased starch damage of control tortilla flour from 5.4% to 12.6%. Damage starch increased dough water absorption, toughness and press rating and reduced diameter and opacity of tortillas. Damage starch improved tortilla rollability at higher levels but did not improve tortilla properties in combination with bacterial 2 amylase. Overall tortilla quality was not improved due to additional starch damage. Improved tortilla quality using bacterial 2 amylase at very low levels could be commercialized.

Diss.--Microbiology--Göteborg--Göteborg university, 2002. / Bibliogr. en fin de chap.

Reproduction de : Thèse de doctorat : Biochimie et biologie moléculaire : Reims : 2005. / Résumé en français et en anglais. Titre provenant de l'écran titre. Bibliogr. f. 199-218.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: Brian J. Bahnson, Dept. of Chemistry & Biochemistry. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 133-138).

Thesis (Ph. D. in Molecular Plant Sciences)--Washington State University. / Includes bibliographical references.

Thesis (doctoral)--University of Helsinki, 1986. / Includes bibliographical references (p. 31-38).

Thesis (Ph. D.)--University of Michigan. 1904. / Cover title. Reprinted from Contralblatt f. bakteriologie, parasitenkunde u. infectionskrankheiten. II. abt., XIV. bd., no. 9/10, 1905.

Thesis (Ph. D.)--University of Hong Kong, 2009. / Includes bibliographical references (leaves 188-220). Also available in print.

Includes bibliographical references (p. 159-174).