batter density was significantly different to that
containing 50%TS substitution (0.459 g/cm3) as
shown in Table 2. To confirm the explanation of
the relationship between the batter density and
bubble size and distribution, images of the cake
batters are shown in Figures 2a–2c. The bubble
size distribution was dependent on the batter
density as well as on the level of TS substitution
for WF. The smaller bubble size with more uniform
appearance was observed in the batter samples
prepared from WF only, due to the higher batter
viscosity with higher WF content (Table 2). The
bubbles in the batters containing TS with lower
batter density (0.467–0.459 g/cm 3) exhibited a
wide variation in bubble size distribution due to
the low viscosity of the batter containing TS having
lower gluten content which affected the larger
number of air cells initially incorporated during
mixing (Sahi and Alava, 2003). A higher number
of larger air bubbles was observed in the
photomicrographs of cake batters containing
higher TS contents. The larger air bubble sizes
that existed in the batters containing TS with lower
viscosity were expected to reveal evidence of
coalescence where two or more bubbles had
merged to form a larger bubble (Irene et al., 2006)
during the aeration stage before baking.