yeast

Chemistry

2022

We explain what is yeast, alcoholic and lactic fermentation. Also, its various uses and the types of yeast that are traded.

Yeast is capable of initiating decomposition processes.

What is yeast?

A yeast or ferment is called a set diverse of mushrooms, usually microscopic and unicellular, capable of initiating the decomposition (fermentation) processes of different organic substances, particularly sugars and carbohydrates, and obtaining other specific substances (such as alcohols).

Yeasts are of various types, exist in various habitats, and reproduce both sexual (by spores) as asexually (for gemmation or sprouting). In a nutritionally favorable environment, a new litter of them is produced in just 90 minutes, since they are organisms simple and effective.

The fermentation is the process that this type of fungi carries out to obtain Energy and, in general, it can be of two different types, according to the by-product obtained:

  • Alcoholic fermentation. It is an anaerobic decomposition process (in the absence of oxygen (O2)), which converts carbohydrates (glucose, sucrose, fructose) into alcohol (ethanol (CH3CH2OH)), along with carbon dioxide (CO2), two molecules from ATP (adenosine triphosphate) and NAD (nicotinamide dinucleotide), according to the following chemical equation:
  • Lactic fermentation. This type of fermentation is carried out by some organisms (protozoa) and animal tissues, also in the absence of oxygen (sometimes as a process for obtaining emergency energy in muscle tissue). Lactic fermentation occurs through the breakdown of glucose (glycolysis) and the reduction of pyruvate (C3H4O3), thus obtaining less energy and producing lactate (C3H6O3), as substance of waste. Everything is given by the following chemical formulas:

What is yeast good for?

Yeast is usually used in making bread.

Yeast is widely used by the human being in various industrial and biotechnological processes. For example, in the making of bread, in the preparation of alcoholic beverages such as beer and wine, or in the production of birch sugar.

Many types of yeast naturally secrete antibiotics to combat their microscopic enemies, which is why they are used to obtain these substances for medical and pharmaceutical purposes.

As if that were not enough, the biological simplicity of yeasts makes them ideal for experimentation in the genetic and protein fields, since they are cheap, easy to reproduce and simple in their cellular functioning.

Types of yeast

Pressed yeast is usually diluted in water before being used.

Commercially, four types of yeast are handled (especially for bakery tasks), which are:

  • Compressed yeast. It is also known as fresh yeast, as it must be kept cold and is pressed into blocks of pasta. It must be diluted in Water before use, and is usually composed of bacteria of the kind Saccharomyces cerevisiae.
  • Dry yeast. Similar to pressing, but in vacuum sealed, dehydrated and granulated (powder) presentations, they can be added directly to the bread dough. In addition, it tends to have longer expiration times.
  • Natural yeast. Called "sourdough", it should be left to rest in a piece of bread dough, before using it in the whole preparation.
  • Chemical yeast. Using chemicals such as baking soda and baking powder, the same effect is achieved as with biological yeasts, by means of an artificial emulsifier that is usually incorporated in some self-rising flours. It is not really a yeast, therefore.
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