27 Bakery and Cereal Products 619tic dough is formed that can entrap the gas formed
during the subsequent fermentation. The amount of
water absorbed by the flour is dependent upon, and
therefore must be adjusted to, the integrity of the
starch granules and the amount of protein present. A
high proportion of damaged granules, as found in
hard wheat flour, results in greater water absorption.
The unique elastic property of the dough is due to
the nature of the gluten proteins. Hydrated gliadin is
sticky and extensible, whereas glutenin is cohesive
and plastic. When hydrated during the mixing
process, the gluten proteins unfold and bond to each
other by forming a complex (gluten) as kneading pro-
ceeds, with an increasing number of cross-
linkages between the protein molecules as they
become aligned. Disulphide bonds (-S-S-) break and
re-form within and between the protein molecules
during mixing.
Gluten does not form spontaneously when flour
and water are mixed; energy must be provided (i.e.,
in the actual mixing process) in order for the molecu-
lar bonds to break and re-form as the gluten structure.
At this point, the dough stiffens and becomes smooth
and shiny. The gluten is now composed of protein
sheets in which the starch granules are embedded. In
addition, free polar lipids and glycolipids are incorpo-
rated in the complex by hydrophobic and hydrogen
bonds. The properties of the dough are determined by
the amount of protein present and by the relative pro-
portions of the gluten proteins.Table 27.1.Bread Additives
Dough Additive Role
Cysteine. Sodium sulphite and Reducing agent. Aids optimal dough development during mixing
metabisulphitea by disrupting disulphide (–S–S–) bonds. A “dough relaxer.”
Amylase Releases soluble carbohydrate for yeast fermentation and Maillard
browning reaction. Reduces starch retrogradation.
Ascorbic acid Oxidizing agent. Strengthens gluten and increases bread volume by
improving gas retention.
Potassium iodate, calcium iodate; Fast-acting oxidants; oxidizes flour lipids, carotene and converts
calcium peroxide; sulphydryl (–SH) groups to disulphide (–S–S–) bonds.
azodicarbonamidea
Potassium and calcium bromatesa Delayed-acting oxidants: Develops dough consistency, reduces
proofing stage.
Emulsifiers, strengtheners/ Dispersion of fat in the dough. Increase dough extensibility.
conditioners and crumb softeners Interact with the gluten-starch complex and thereby retard
staling.
Soy flour Increases nutritional value, bleaches flour pigments, increases in
loaf volume, increases crumb firmness and crust appearance,
promotes a longer shelf life.
Vital wheat gluten and its Increases gluten content, used especially when mixing time or fer-
derivatives mentation time is reduced. Water adsorbant. Improves dough
and loaf properties.
Hydrocolloids: Starch-based Regulates water distribution and water-holding capacity and there-
products from various plants by improves yield. Strengthens bread crumb structure and
improves digestibility.
Cellulose and cellulose-based Source of dietary fiber.
derivatives
Salt Enhances flavor (ca. 2% based on flour weight) and modifies
mixing time for bread and rolls. Increases dough stability, firm-
ness and gas retention properties. Raises starch gelatinization
temperature
Source:Compiled from Stear 1990, Williams and Pullen 1998.
aNot allowed in all countries.