We call yeasts fungi that are unicellular – formed by just one cell – and are not visible to the naked eye, that is, they can only be seen with the aid of a microscope. Most yeasts have an oval shape, and their reproduction occurs asexually by means of budding, that is, one yeast does not need another to generate other individuals. They reproduce faster than molds, since they are more efficient in making chemical changes because they have a larger area / volume ratio.
Also unlike algae, yeasts do not photosynthesize, nor are they protozoa, as they have a rigid cell wall formed by chitin.
From the Latin levare , the name yeasts comes with the meaning of growing or making it grow, since the first yeasts found were those associated with the bread fermentation process, which causes an increase in dough through the release of gases and foaming.
The life of yeasts – Disease transmission
Living in places with the presence of organic matter, or even as parasites in other living beings – including humans -, yeasts can cause disease. Among the best known, is Candida albicans , which causes the disease called candidiasis – it mainly affects the female genitals.
Its life cycle is predominantly diploid and its ascospore is the haploid cell in the cycle. However, distinct species also have varying life cycles.
However, yeasts do not only play a negative role. They can be used in the food and beverage industry. As an example, we can mention wine and beer that use a certain species of yeast in some stages of their production. In addition, some species are also used in the dough fermentation process.
Microorganisms are also grown in distilleries for the production of ethanol through cane sugar, while for the production of bread, they are grown from sugarcane molasses. Explored for thousands of years by men, yeasts continue to be used for food production purposes.
Types of yeasts
With approximately 850 species, yeasts are separated into approximately 78 genera. However, within this great variety, we can highlight the brewer’s yeast and that of bread.
The yeast used for the production of alcoholic beverages is a natural yeast used in the fermentation of the must, which is a mixture of barley, water and hops to, finally, produce beer. These are from the genus Saccharomyces , the main species of which is Saccharomyces cerevisiae . Source of high protein content, yeast cells have other types of fats, in addition to being a source of B vitamins.
Bread yeast is one that allows it, when added to the dough, to grow and then be taken to the oven for baking. Growth takes place through the yeast transformation process, which when mixed with the dough, which contains sugars, begins to reproduce and perform glycolysis. The next step is the transformation of pyruvic acid into ethanol that releases a gas that, by creating bubbles in the mass, causes its volume to increase.