Can you go buy me yeast please?
ask your mom. In the supermarket you
have a problem of size. Indeed,
your mom didn't specify you if she
wanted chemical yeast or baker's
yeast. Is this equal?

• the chemical yeasts

- 25% of sodium bicarbonate:  NaHCO3

- 60% potassium Hydrogenotartrate :  COOH - CHOH - CHOH - COOK

- 15% of corn starch

To act, chemical yeasts must be under particular humidity and heat conditions. What is the reaction ?

We simply have an acido basic reaction. Indeed, the sodium bicarbonate is a basis and the potassium Hydrogenotartrate is an acid. The corn starch serves to the yeast conservation.

In presence of water and heat we have the following acido-basic reaction :

COOH - CHOH - CHOH - COOK  +  NaHCO3  -------  COONa - CHOH - CHOH - COOK  +  CO2 + H2O

It is the CO2 clearing that makes inflate bread

• The baker yeast

Bakery yeast is a living product. This cells possess the property to transform the naturally present sugars in flour in alcohol and in carbon dioxide.

In the absence of oxygen, glucose is transformed in ethanol (alcohol) and CO2 (carbon dioxyde) by the yeast, it is the alcoholic fermentation:

The CO2 manufactured by the yeast during cooking makes inflate the dough. you'll notice that there is also ethanol manufacture. Does It mean that our breads are alcoholized? No!.... because ethanol is evaporated during cooking.

NB: If you need more information on baker's yeast and on the process of bread inflation click here

Conclusion

We can say that the difference between the chemical yeast and the baker yeast resides in the fact that the carbon dioxide produced by baker yeast is largely obtained before cooking whereas the carbon dioxide produced by the chemical yeast obtained during cooking.
So, chemical yeast or baker yeast?

Chemical yeast can be used fo to the Genoese doughs but cannot be used for breads, pizzas, sweetbreads.