What is Yeast? : The baker's best friend
In the olden days, the bakers and the brewers used to use hops or boiled potatoes for making wild yeast as a fermenting culture, and the fermentation process used to take a very very long time.
However, now yeast is easily grown and is one of the most important ingredients used in bread making when it comes to fermentation. It's also known by the scientific name as “Saccharomyces cerevisiae” also commonly known as brewer's or baker’s yeast. The yeast plays a crucial role in several food products making processes such as baking, brewing, and winemaking.
However, in this article, we'll understand what yeast is and what different usable forms it is available in the market close to their application in baking.
Yeast is the heart and soul when it comes to bread making, providing the ideal chewy textured bread crumb with a crisp and crackly crust.
For making bread, the dough is fermented for two main reasons, they are :
A. Production of CO2 gas, that gives volume to the bread creating porous texture in the bread crumb.
B. For conditioning of the gluten so that the bread gets a good holding structure. Gluten is the protein that provides the dough elasticity and stretchability hence more the gluten more you can stretch the dough easily without breaking it at stretch unlike the dough made from millet grain like sorghum.
More about the yeast,
Yeast is a unicellular (single cell) plant belonging to the fungi family. It requires food, moisture, and a moderate climate for its growth and reproduction.
It multiplies or reproduces by the budding method. Yeast is sugar-loving. It is found on the surface of fruits like grapes, figs, peaches, plums. Its cells are spherical and oval and consist of a cell wall, cytoplasm, nucleus, and other bodily parts.
Each cell is very active at a temperature of 78 to 80 degree F (25 to 26.66-degree Celsius) and at 120 degrees F (48.88-degrees Celsius) their life is in danger and are usually killed at 138 to 140 degree F (58.88 to 60 degrees Celsius).
Their activity slows at low temperatures but below 40 degrees F (around 4 degrees Celsius) their growth is completely stopped.
ENZYMES IN YEAST:
The yeast contains certain enzymes that play an important role in the fermentation activity. E.g., food digested by certain enzymes converts complex starch into simple sugars.
An enzyme does not affect the chemical composition of the product substrate but helps in speeding a certain reaction in a process. It is also known as ‘Catalytic Agent’.
In the fermentation, process yeast contains four important enzymes namely Invertase, Maltase, Protease, and Zymase.
- Invertase enzyme helps convert cane sugar or sucrose into a simple sugar known as Invert sugar, a combination of dextrose and fructose.
- Maltase enzyme converts maltose sugar (a disaccharide) into dextrose.
- Protease enzyme mellows (makes soft) the action on flour proteins, thus helping in better stretchability, which gives the bread a better volume and structure.
- Zymase enzyme is the actual fermenting enzyme in yeast. It attracts the invert sugar & dextrose which was produced by the action of invertase and maltase, gets converted into CO2 gas, a small amount of pure alcohol, a small amount of glycerin, and succinic acid. These produced compounds are responsible for giving a pleasant peculiar flavor to the bread.
Apart from being a leavening agent in bread making, yeast is nutritious and contains essential minerals, vitamin B, and vitamin C.
TYPES OF YEAST :
Speaking about the different types of yeast that are available are:
A. DRY YEAST :
Dry yeast is available in the form of dry round granules. Further, it has two types :
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Dry Yeast: Granular form |
I. ACTIVE DRY YEAST:
Active dry yeast is the round spherical granules. This active yeast requires a process to activate it before using it in bread making. The process is also known as "Flying Ferment".
To know more about preparing the flying ferment, read more on …………………………………..
II. INSTANT DRY YEAST:
This can be added directly while making bread dough and does not need a proofing step since it is already in its active stage.
Dry yeast is manufactured from fresh yeast with the help of a vacuum drying method.
To say around, 1 kg of fresh yeast after drying gives a quarter kg of dry yeast. Therefore, if we are using dry yeast the quantity to be used is very little as compared to the fresh yeast.
B. FRESH YEAST OR COMPRESSED YEAST:
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| Fresh Or Compressed Yeast |
Unlike dry yeast, this comes in a moist cake form, creamy in color, cool to touch. And breaks with a clean fracture. And has a peculiar but pleasant aroma of ripe apples.
Since it is in the cake (wet) form its shelf life is less likely as compared to dry yeast. Fresh yeast also needs the proofing step to activate it before use.
The comparison between the dry yeast and the compressed yeast :
How yeast is manufactured on an industrial scale?
There are 2 such ways:
The first one is,
A. GRAIN METHOD:
It's a small batch method involving various steps.
a. Barley is the primary ingredient used. Here the barley grain is first washed and cleaned thoroughly.
b. Soaking and sprouting stage:
> The barley grain is soaked in water for 24hrs. The water is then drained out.
> The water which has been absorbed helps in sprouting. Sprouting is allowed to continue for about 3 days (72hrs).
c. When the sprout attains ¼ inch of length, the sprouted grains are heated in special ovens to kill the sprouts completely, and eventually, the sprouted grains begin to dry.
d. The dried sprouted grain is ground to a powdered form and sieved to get the fine uniform particle size.
e. The next stage involves the preparation of yeast,
> The barley powder is dissolved in water to make a solution. This solution is then heated to gelatinize the starch (where the starch swells and hydrates itself). The enzyme Invertase acts on the starch and converts it into sugar.
> Cooking continues for about 30hrs and you get a clear solution which means that all the starch is converted.
> It is cooled and the cooled yeast solution is then passed through a filter where most of the water is removed and you get a plastic sheet of yeast. This is kept in cold storage.
> Then it is shaped into half kg blocks which are wrapped in wax paper and stored at 32 degrees F (0 degrees Celsius) and the fresh yeast is ready.
> This fresh yeast is dried to convert it into dry yeast granules, a more stable form of yeast with help of a vacuum drying method.
B. MOLASSES METHOD:
A more advanced level used for bulk preparation of yeast eventually helps in the cost reduction of the produce.
a. In this, the starter seed yeast is preserved in the laboratory by biochemists. It is then transferred to the sterile conical flask containers.
b. These flasks are kept aside for 48hrs.
c. The 2nd stage involves the preparation of ‘wort’. This word is commonly used in the wine and brewing industry.
(Wort means the sweet infusion of grain or malt prepared before fermentation.) It is a liquid prepared from fruit juice or any sugary substance free from any wild yeast. This wort has a sugar content of about 25%. It also contains minerals, simple proteins, and some sugars. This liquid is ready for the preparation of yeast.
d. The wort which is prepared in bulk is transferred into fermentation tanks. These tanks have an operating temperature of about 38 to 40 degrees Celsius.
e. Air is also pumped inside the starter yeast for aeration and allowed to ferment for 72hrs. Yeast cells form a layer on top and float on the surface.
f. The layer is then transferred to cooling tanks. Here, the yeast layer is washed and excess water is drained off. It is then pressed through a filter to get blocks.
Usually, they are made available in 500gms rectangle-shaped blocks. These are then wrapped in wax paper and stored.
The usefulness of yeast as an ingredient in bread making has made lives easier than ever before.
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Always CraveDip☺!!!
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