Why do we add extra acid to make white cake batters

If the sodium bicarbonate element of the raising agent is not completely neutralised by the acid component then the excess bicarbonate will cause some degree of caramelisation of the sugars during baking. Indeed this occurs in all cakes but because the crumb of many cakes is tinted yellow either with egg yolks or egg colour the slight degree of discoloration largely passes unnoticed.

In the case of a white cake where no egg yolk is present the slightest discoloration would be noticed. To prevent this therefore, additional acid -cream powder or cream of tartar - is added to make sure that all the bicarbonate of soda is neutralised.

10.33 We have been experiencing problems with collapse of our sponge sandwiches which leaves the product with a depression forming on the top of the cake and an area of coarse cell structure in the crumb. What causes this problem?

The area of coarse cell structure that you have observed in your collapsed sponge cake is often referred to as 'core' formation. Sometimes this might be observed in the crumb even though the top of the cake has not collapsed.

The primary cause of your problem is instability of the air bubbles in the batter. When the sponge batter reaches the oven and the gas bubbles begin to expand it is important that they do not coalesce until the right moment in the later part of the baking process. To remain separate from one another the stabilising film must stretch as the air bubbles expand under the influence of heat and because of the carbon dioxide gas that is diffusing into them as the result of the accelerating baking powder reaction. If the stabilising material is not able to stretch sufficiently then it ruptures, allowing adjacent gas bubbles to coalesce and form larger ones -the coarse component of the cell structure. At the same time the displaced stabilising material will join with other materials to form areas devoid of air cells -the thick cell wall material which also looks darker in colour.

While there is only one primary cause there are many contributing factors, including the following:

• The presence of traces of fat or oil in a non-emulsified sponge recipe. Ensure that all traces of fat or oil are removed from the mixing bowl and whisk by using boiling water to wash the utensils.

• Too little emulsifier in an emulsified sponge recipe. Try increasing the level to about 0.75% of the batter weight (see 5.15).

• Too much baking powder in the formulation (see Fig. 30). Reduce the baking powder level and if the cake lacks volume increase the mixing time to lower the batter relative density or increase the emulsifier level.

• Batter relative density too low, especially with low levels of emulsifier. While the batter may be stable at low temperatures it is during the baking that bubble stability is most important.

• The particle size of the flour being too large (Cauvain and Hodge, 1977).

One factor known to contribute to this problem is the presence of 'anti-foaming' agents such as silicones. Even levels as low as 2 ppm have been shown to induce core formation in sponge cakes. The effective level depends to some extent on the level of emulsifier present but 5 ppm silicon will destabilise most sponge cake batters. Traces of silicone may come from a number of different sources, including the following:

• Barrier creams used for hands.

• Flour, most likely from the wheat.

188 Baking problems solved 5.0

Continue reading here: Level of baking powder of batter weight

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