Yeast belongs to the fungus kingdom. It is a single celled organism that is responsible for fermentation i.e. converting sugars and starch into CO2 and alcohol. For over thousands of years, this magical ingredient has been used in the baking and alcohol industry. The commonly used terms for it in the culinary and alcohol industry are Baker’s yeast and Brewer’s yeast. Both of these belong to the Saccharomyces Cerevisiae strains. It is ivory colored and in a brick form or granulated.
This word evolved from the Sanskrit word ‘yas’ which means to bubble or foam. In 1680, Anton Van Leeuwenhoek first observed yeast but it was only in the late 1850’s, Louis Pasteur discovered yeast and studied the fermentation process and cultivation. The yeast was earlier made by Germans in the form of a cream and later made into solid bricks and over a period granular.
- Baker’s Yeast – There are many types of baker’s yeast like Fresh yeast, Compressed yeast, Creamed yeast, Active dry yeast, Instant yeast and Rapid rise yeast. They are used in the bakery industry primarily for leavening bread.
- Brewer’s Yeast – This is used to produce alcohol and bubbles in beers
- Wine Yeast – This is used in the wine industry to convert the sugars in the fruit juice into alcohol and carbon dioxide.
For the commercial use, all kinds of yeasts are packed in vacuum bags in bulk but for home use It is often sold in premeasured dosage as per usage in small sachets or small compressed bricks.
How Yeast Works ?
Through the process of fermentation, yeast produces alcohol and carbon dioxide which are useful for the food production. Alcohol produced is a value addition in the wines and the beers. It is also produced in the breads but it evaporates during the baking. The Carbon dioxide produced as a byproduct is responsible for adding the bubbles and the fizz in wines and beer. It is one of the important characteristics of the products. In breads, when the dough is made and left for proofing after fermentation carbon dioxide produced is entrapped between the gluten network and forms the tiny bubbles that we visibly see in bread. When baked the carbon dioxide is released leaving the spaces empty thereby giving it a spongy and soft texture.
It is important to first add some warm water to the yeast along with some sugar. Let it rest for about 10 – 15 minutes or till it starts bubbling. Sugar is very important for this step as it is the food for yeast. The yeast will only get activated in it’s presence. This is also a test to check if the yeast is active or not.
Critical points – Moisture (Humidity), Food (sugar / starch) and Temperature (warm/ 45oC).
Salt plays a very important role in controlling the fermentation. It prevents over fermentation of the dough.
Yeast performs a common function in most of the foods i.e. fermentation of sugars.
- Bread making – Fresh Baker’s yeast is the most commonly used and preferred one by the bakers and also for home use as it brings optimum results. Approximately 5g fresh yeast is used in 200g refined flour to make bread. It is used by crumbling the yeast in luke warm water along with a little sugar and adding this paste to the dish. The proportions of yeast, sugar, salt, fat and flour is very important in the bread making to get a perfect bread as each ingredient has a role to play in relation to yeast.
- Alcoholic beverages – Alcoholic beverages are those which contain ethanol. Ethanol is also a byproduct of fermentation and is a characteristic of beverages like beer, wine and distilled spirits. The yeasts used in these products act slower than in the bread. Home brewing is a hobby in United States and many brewer’s yeasts are available at retail stores.
Fresh Yeast Bread, Doughnuts, Cinnamon rolls, Croissants, Indian Breads like naan and kulcha, Pizza, pretzels, Pita, Etc.
The quantity of yeast in each recipe along with the fermentation time will vary from recipe to recipe.
Methods of Use in Bread making
- Mixing and kneading - Once the yeast is added to the flour and other ingredients. It is kneaded well to develop the gluten network needed for bread making.
- Fermentation - fermentation is done in a warm place and the dough is covered with a moist cloth to activate the yeast. This is done till the dough doubles in size.
- Knock back - This is done to remove all the large air bubbles formed and then resulting in even rising of the dough.
- Proofing - The dough is shaped and again left for rising for a shorter period.
- Baking - This has a great impact on the yeast as the bread first rises till the yeast is killed. Once the yeast is killed, the interior of the bread is cooked and then the top crust.
Yeast is a common ingredient in food supplements as it is a good source of protein and B-Complex vitamins. It does not have any nutritive value addition.
All year round
How to select
Select the yeast as per usage. Fresh yeast will last only for one week where as Active dry yeast or Instant yeast will last for a much long time. Both kinds of yeasts are easily available at retail and specialty shops. It is very important to check the expiry date while purchasing.
How to store
Yeast should not be frozen as it will killed. Active/ Instant yeast should be stored in a cool dry place, preferably the refrigerator.
It is a FDA approved ingredient
- There are over 200 species of yeast in thousands of different strains.
- Rapid rise yeast takes half the time for fermentation than ordinary yeast.
- It is used to make Yeast extract which is used to enhance flavors and as a food additive. It is often used the same way as Monosodium Glutamate.
- Rapid rise yeast is easily available under the brand name Fleischmann’s.