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QUESTIONS - p. 265

1. What is the function(s) of starch in baking powders?

The functions of starch in baking powder are:
a) to act as an inert filler. It acts as a buffer between the active ingredients and prevents their going into reaction when exposed to moisture.
b) to standardize the strength of the baking powder so that different brands produce the same amount of CO₂ per volume.
c) to absorb moisture and help keep the powder dry. Cornstarch is frequently used for this purpose.

2. What is the legal requirement concerning baking powders and their yield of CO₂?

In Canada, Food and Drug states that baking powder shall yield not less than 10% of its weight in CO₂ as determined by official methods.

3. To what components of baking powders do the terms "single acting" and "double acting" refer? What do the terms describe?

The terms refer to the nature of the acid ingredient. Single acting baking powders contain only one acid salt which is fast acting. The acid dissolves readily in cold water and CO₂ is released as soon as the baking powder comes in contact with cold liquid. The acid ingredient is usually potassium acid tartrate or mono calcium phosphate ( Magic ).
Double acting baking powders contain two acid ingredients resulting in two separate reactions which produce CO₂ gas. The fast acting acid, mono calcium phosphate, reacts when the baking powder is dissolved in cold water. The slower acting acid, sodium aluminum sulfate (SAS) requires heat to produce CO₂ as it reacts in hot water only. This reaction takes place for the most part in the oven. SAS reacts with the hot water to form sulfuric acid which then liberates CO₂ from the soda which was left unneutralized by the mono calcium phosphate.

4. What are the recommended amounts of single and double acting baking powder to use per cup of flour? Why the difference?

According to Freeland and Graves "Foundations of Food Preparation" the amount of singleacting powder needed is 1 ¹/₂-2 tsp per cup flour, and the amount of doubleacting powder needed is approximately
1 ¹/₂ tsp per cup flour. Singleacting baking powders produce nearly 3/4 of the available CO₂ in the cold batter as it is being mixed. By the end of mixing, only 20-30% of the CO₂ is retained in the batter.

Doubleacting powders release only 1/3 of the available CO₂ into the cold batter, the rest being released during baking. Therefore, slightly more single-acting baking powder may be required to produce a quality product.

5. What other factors affect the amount of baking powder required?

The amount of baking powder required may also be affected by:
a) what other methods of incorporating air into the batter were used, such as creaming the fat or adding as egg white foam.
b) the altitude. At higher altitudes less baking powder is required due to the lower atmospheric pressure. Because the boiling point of water is lower, steam is formed more quickly and the gases that are formed expand more because there is less atmospheric pressure bearing down on them.
c) the thickness of the batter. Thicker batters lose less CO₂ during mixing.
d) the amount of mixing required. The more the batter is mixed, the more CO₂ is lost.

6. What type of baking powder is best if the mixture must stand? Why?

Slow acting baking powder is best used for a batter that must stand as only 1/3 of the CO₂ is released into the cold batter.

7. What could you substitute for baking powder in a recipe? State amounts.

One cup of fully soured milk used with l tsp of baking soda releases an amount of CO₂ equivalent to 2 tsp of baking powder.