emulsifier addition increased the volume of incorporated air
by maintaining the mean size of the bubbles while increasing
the number of bubbles. On the other hand, as the level of oil
substitution in cakes with no emulsifier was increased, the
bubbles were smaller in number but larger in size. Psimouli
and Oreopoulou (2013) and Rodriguez-Garcia et al. (2012)
also observed a smaller size of bubbles in cakes prepared with
shortening and oil, respectively, compared to those with a fat
replacer. These authors attributed this effect to the ability of oil
to stabilize bubbles by forming a film in the air-matrix interface.
Furthermore, Lee et al. (2005), when preparing cakes
with lower amounts of shortening replaced by ƒÀ-glucan
amylodextrins, also found that the number of entrapped air
bubbles decreased. The emulsifier performs the function of
stabilize the bubbles in the case of batters with less oil content,
thus improving the structure. It is known that structures with
smaller and more uniform bubbles are more stable, and these
bubbles tend to remain in the final cake to a greater extent
(Stauffer 1990). Consequently, it is expected that the batters
with emulsifier will lead to a higher volume in the final cake.
Concerning the viscoelastic properties of the batter, in the
frequency range tested the so-called plateau relaxation zone
was observed for all the samples. The plateau region is characterized
by physical entanglements in the polymeric materials
(Ferry 1980). All batters showed a higher elastic modulus
than viscous, indicating the solid nature, with both moduli
depending on frequency but following a different pattern
(Calero et al. 2013) as the different values of a and b coefficients
indicated. The trend observed with the a coefficient for
both cakes with and without the addition of emulsifier, and in
the b coefficient for cakes with emulsifier, is to decrease from
2/3 replacement, indicating a less frequency-dependent modulus.
Although the same trend is observed for both coefficients,
higher values are exhibited for the b coefficient, which
might suggest higher frequency dependence of G compared
to GŒ counterparts. For each of the levels of fat replacement, GŒ
and G significantly increased with the addition of emulsifier.
Rodriguez-Garcia et al. (2014a) and Sahi and Alava (2003)
also found an increase in the moduli of low fat cakes with
emulsifier and other fat replacers. Rodriguez-Garcia et al.
(2014a) suggested a stronger structure promoted by the
water-binding capacity of the emulsifier. Nonetheless, the
greater air incorporation and the distribution of this air in the
form of fine bubbles generated by the emulsifier may also
affect the rheological measurements of the batters. In fact, it
has been found that the viscoelastic properties are also dependent
on the concentration of air trapped during mixing
(Kalinga andMishra 2009). In this research, GŒ and G moduli
were correlated (p