Observation of the particles by optical microscopy indicated that
single and compound starch granules formed in starch heated in
water (Fig. 8A) and in water with OVA (B). However, compound
starch granules were formed, including even larger aggregates,
when starch was heated in soy globulin solution (C) or in soy
globulin solution with OVA (D).
These results indicate that slurry peak viscosity increased for
rice flour and soymilk upon addition of OVA because the OVA
caused single starch granules to form compound starch granules,
and the soy globulin caused the compound starch granules to
merge and form aggregations. Addition of OVA increased batter
viscosity by creating a greater number of large starch granules,
which prevented gas cells from merging. However, the proteins
used in soy globulin solution were in a native form, unlike soymilk
that underwent heat treatment. In the present study, although in-
teractions between OVA and starch and soy globulin were
confirmed, the effect of the state of aggregation, caused by heating
soy globulin, on the viscosity of the batter is unknown and will be
investigated in the future.
Adding OVA to soymilk increased gas cell membrane thermal
coagulation, and produced gelatinization viscosity greater than that
of batter made with water and rice flour. This may inhibit the
merging of gas cells in the center of the batter and prevent hol-
lowing of the crust. Furthermore, in soymilk batter with greater
than 2.5% added OVA, oven spring was believed to occur as the
increase in viscosity reduced the amount of water escaping from
the batter, which in turn raised the water vapor pressure within the
batter.