When making sponge drops we find that the last ones to be deposited are not as good as the first ones Why is this
Once a batter has been mixed changes in its properties occur with time. The nature of these changes varies according to the manner in which the batter is treated and the length of time that elapses before it is deposited. The main change is related to the stability of the air bubbles in the batter and the evolution of carbon dioxide gas from the baking powder in the formulation.
Once mixing starts, the acid in the baking powder begins to dissolve and react with the sodium bicarbonate present. The rate of the reaction depends on the type and nature of the acid and the temperature of the batter. The reaction proceeds more rapidly at higher temperatures whatever the acid being used. Some time after the baking powder reaction has begun the carbon dioxide gas diffuses into the air bubbles in the batter and they begin to inflate. Some may become so large that they can rise in the batter and escape at its surface. The stabiliser in the batter (e.g. emulsifiers) helps prevent this from occurring.
As the batter standing time before depositing increases, more carbon dioxide is evolved and eventually some of it can escape from the batter. If too much of the carbon dioxide is lost the batter relative density begins to increase, that is the batter becomes less well aerated and the sponge drops in volume. The length of time that has to elapse before this situation is reached depends on the particular baking acid being used but can occur with all acids. The potential for 'de-aeration' of the batter increases if the batter is agitated or subjected to shear. The longer that the batter stands, the greater will be the potential de-aeration effect from any agitation.
We suggest that you examine the length of time that the batter stands and see if this can be shortened. This may require the production of smaller batches mixed more frequently. Avoid excessive agitation of the batter once prepared, e.g. try to minimise the degree of scraping down of hoppers because this incorporates 'old' batter which contains less gas. Alternatively, consider using a slower-acting acid in your baking powder.
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