(6) Flavones, The flavones are water-soluble pigments. Markley and
Bailey state that flavones have long been known to exist as glucosides and
from their study it appears possible that they will be found as esters of the
fatty acids. The flavones are colorless in acid or neutral mediums but
develop a greenish yellow tint in alkaline reactions.
Enzymes
Wheat and flour contain many enzymes, some of which are important
because of their action during fermentation of cracker and bread doughs.
Others become active in the sprouted grain, hence affect bread making only
rarely when some sprouted grain is included with sound wheat in milling.
Of the numerous enzymes, the diastases or amylases and the proteinases are
the most important from the standpoint of baking.
Diastases. Andrews and Bailey state that the chief function of the
starch enzymes of wheat and flour is changing starch to sugars. In sound
normal wheat and flour the diastatic activity is due primarily to the action
of beta-amylase. When wheat germinates, a second "diastatic factor," termed
alpha-amylase, is produced. Accompanying the activation of alpha-amylase
are the phenomena of dextrination and liquefaction. Both amylases convert
starch to reducing sugars, the alpha-maltase yielding alpha-maltose and
the beta-amylase producing the corresponding beta sugar. The maximum
398 FLOUR AND BREAD
activity of beta-amylase occurs at pH 4.5 to 5.1, whereas that of alpha-
amylase is at pH 5.6 to 5.8.
Proteinases. Until lately little was known about the proteolytic enzymes
of flour except that they brought about hydrolysis of flour proteins. Balls
and Hale have not only reported a method for estimating the proteolytic
enzymes in flour but also the action of these enzymes. They state alteration
of flour that takes place in bleaching and storage in air is due to a diminu-
tion of the proteolytic activity, brought about by the oxidation of the
activator of the flour proteinase. j0rgensen states that wheat flour contains
powerful proteolytic enzymes which are usually latent but activators such
as glutathione or yeast-water stimulate these proteinases of flour. Such sub-
stances as KBrOs and ascorbic acid, because they depress the activity of
the proteinase, have been found to be good improvers of baking strength of
wheat flour. J0rgensen has applied for a patent in the United States for
such a use of ascorbic acid.
Cellulose
The greater part of the cellulose of the wheat kernel is removed in
milling, so that the amount in white flour is small.
Bran. Bran contains considerable cellulose and cellulose absorbs water
slowly. Rahn describes the Schlueter process by which bran is steeped in
hot water and treated for some time with moist heat. During this treat-
ment the cellulose membranes are sufficiently hydrolyzed so that the cell
contents are more readily digestible. The bran is then dried and put
through a crusher and a fine grinding mill. In contrast to ordinary bran,
the treated bran is said to keep indefinitely and absorbs water more readily
and in larger quantity.
The Moisture Content of Flour
Page 322
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(6) Flavones, The flavones are water-soluble pigments. Markley and
Bailey state that flavones have long been known to exist as glucosides and
from their study it appears possible that they will be found as esters of the
fatty acids. The flavones are colorless in acid or neutral mediums but
develop a greenish yellow tint in alkaline reactions.
Enzymes
Wheat and flour contain many enzymes, some of which are important
because of their action during fermentation of cracker and bread doughs.
Others become active in the sprouted grain, hence affect bread making only
rarely when some sprouted grain is included with sound wheat in milling.
Of the numerous enzymes, the diastases or amylases and the proteinases are
the most important from the standpoint of baking.
Diastases. Andrews and Bailey state that the chief function of the
starch enzymes of wheat and flour is changing starch to sugars. In sound
normal wheat and flour the diastatic activity is due primarily to the action
of beta-amylase. When wheat germinates, a second "diastatic factor," termed
alpha-amylase, is produced. Accompanying the activation of alpha-amylase
are the phenomena of dextrination and liquefaction. Both amylases convert
starch to reducing sugars, the alpha-maltase yielding alpha-maltose and
the beta-amylase producing the corresponding beta sugar. The maximum
398 FLOUR AND BREAD
activity of beta-amylase occurs at pH 4.5 to 5.1, whereas that of alpha-
amylase is at pH 5.6 to 5.8.
Proteinases. Until lately little was known about the proteolytic enzymes
of flour except that they brought about hydrolysis of flour proteins. Balls
and Hale have not only reported a method for estimating the proteolytic
enzymes in flour but also the action of these enzymes. They state alteration
of flour that takes place in bleaching and storage in air is due to a diminu-
tion of the proteolytic activity, brought about by the oxidation of the
activator of the flour proteinase. j0rgensen states that wheat flour contains
powerful proteolytic enzymes which are usually latent but activators such
as glutathione or yeast-water stimulate these proteinases of flour. Such sub-
stances as KBrOs and ascorbic acid, because they depress the activity of
the proteinase, have been found to be good improvers of baking strength of
wheat flour. J0rgensen has applied for a patent in the United States for
such a use of ascorbic acid.
Cellulose
The greater part of the cellulose of the wheat kernel is removed in
milling, so that the amount in white flour is small.
Bran. Bran contains considerable cellulose and cellulose absorbs water
slowly. Rahn describes the Schlueter process by which bran is steeped in
hot water and treated for some time with moist heat. During this treat-
ment the cellulose membranes are sufficiently hydrolyzed so that the cell
contents are more readily digestible. The bran is then dried and put
through a crusher and a fine grinding mill. In contrast to ordinary bran,
the treated bran is said to keep indefinitely and absorbs water more readily
and in larger quantity.
The Moisture Content of Flour