The storage proteins of wheat are unique because they
are also the functional proteins. The wheat prolamins
(prolamins 40–50%) are extremely sticky and responsible
for the viscosity and extensibility in a dough system
whereas the glutelins provide elasticity. The prolamins
and glutelins combine through covalent and non covalent
bonds to form the gluten complex resulting in viscoelastic
dough that has the ability to retain gas and produce a light
baked product (Lindsay & Skerritt, 1999). Rice on the
other hand has very little prolamins (2.5–3.5%), as a result
a viscoelastic dough is not formed when rice flour is
kneaded with water. Therefore the gases produced during
proofing and baking cannot be retained and the resulting
product has a low specific volume, which does not
resemble wheat bread. The incorporation of hydroxypropylmethylcellulose
(HPMC) in rice flour has made it
possible to produce bread from rice flour (Gujral et al., 2003, Gujral et al., in press, Haque & Morris, 1994 and Nishita et al., 1976)
with a specific volume comparable to that of wheat bread.
The HPMC is able to provide the rice flour
dough with the film forming and CO2 entrapping properties
resulting in a product with a high specific volume.