3.4.3. TAG migration analysis for chocolate chips baked in sand
TAG profiles were obtained from chocolate chips baked in sand and
palm oil mixtures (Table 4). As for chocolate chips baked in cookies,
the levels of PLO, POO, POP and PLP increased and the levels of SOS
and POS decreased in the chip after baking, indicating that fat migration
occurred in both directions between the chocolate chip and the
sand. The amount of migration was greatest for the chip baked in
sand with the highest fat content.
The degree of migration was calculated using Eqs. (1) and (2).
About 10% fat in the sand mixture was needed to prevent bloom, so
approximately 40% oil migration was required in order for bloom to
be inhibited (Fig. 7). This was a noticeably higher degree of migration
than the 16% migration required to inhibit bloom on chocolate chips
baked in cookies. It is unclear why a higher degree of migration was
required to inhibit bloom on chocolate chips baked in sand. It appears
that when fat is the only ingredient in the system, much more fat is
required to inhibit bloom. This suggests that other ingredients in the
cookie dough may also contribute to bloom inhibition.
Structural differences, such as particle size, shape and surface characteristics
between in the cookie dough and the sand model system
may explain the variation in migration levels observed. Also, the chocolate
chips baked in sand reached higher temperatures and melted faster
than chocolate chips baked in cookie dough, which may have resulted
in more total oil migration. In addition, unlike cookie dough, the sand
mixtures contained no water. The absence of polar interferences from
water in the sand matrix may allow the fat to migrate more efficiently.
Overall, the complex microstructure of cookie dough may impede fat
migration compared to the simple sand-fat system.
4. Conclusion
To better understand why chocolate chips generally do not bloom
in cookies, potential factors affecting chocolate chips were examined.
It was demonstrated that chocolate chips in cookies melted completely
during baking. Thus, crystal memory effect was not a factor in the
observed bloom inhibition on chocolate chips. Fat migration was
shown to be the primary factor that influenced bloom formation on
chocolate chips baked in cookies. When the fat content of the cookie
dough was sufficiently high, enough fat migrated into the chocolate
chip such that, upon cooling and storage, bloom was inhibited. The
degree of migration necessary to inhibit bloom on chocolate chips
was similar for cookies made with palm oil shortening and olive oil,
even though the amount of fat added to the cookie dough was not
the same.
Bloom inhibition also occurred on chocolate chips baked in a
model system of sand and fat mixtures. A higher level of fat migration
was required for palm oil to inhibit bloom on chocolate chips baked in
the sand system compared to chocolate chips baked in cookies. This
indicated that other ingredients in cookie dough may play a role in
bloom inhibition on chocolate chips.
Although fat migration clearly contributes to bloom inhibition in
this case, the exact mechanismbehind this inhibition is still unknown.
Based on the soft texture of chocolate chips in cookies after baking,
we speculate that the phase behavior and change in crystallization/
polymorphism of the mixed fat system is responsible for bloom