When it comes to baking, few things are as controversial as yeast. Except for the great and terrible gluten. For example, there are regular reports on the web that regular yeast can cripple healthy intestinal microflora, destroy gastric mucosa, and cause all digestive organs to fail at once.
There are even more rumors about quick dry yeast, it seems that due to its artificial origin it has a rare survivability, it does not burn in the fire and survives in the oven, and settling inside us, build colonies, poison everything inside with toxins and can even cause cancer.
And what does science say about this? We asked two experts to tell us about the secret life of yeast and shed light on its activities in the depths of bread crumbs and our bodies.
What kind of yeast is used in baking?
“The so-called baking yeast, or Saccharomyces cerevisiae, is a specific and well-studied class of single-celled fungi. For centuries they have been used not only in baking, but also in the alcoholic beverage industry to support the natural fermentation process. This culture of yeast fungi reproduces by budding and under favorable conditions shows an avalanche-like growth, which causes the rise of dough. Scientifically, the process is described as follows: In the presence of oxygen, the yeast cells enzymatically oxidize sugars, releasing carbon dioxide. That is, by saturating with oxygen and feeding on sugars, the yeast actively pumps carbon dioxide bubbles from within the dough and lifts it.
Until the 1970s, only fresh yeast, in other words live yeast colonies in the form of pressed briquettes or “yeast milk” (a water suspension), was used in baking. Today, so-called dry, rapid or instant yeast is also in use. First, they are less prone to disease, which is very important for baking on an industrial scale, because one virus can wipe out a colony of live yeast and stop the production of an entire bakery for a while. And secondly, rapidly accelerate the process of rising dough, are responsible for the formation of porous crumb.
How does dry yeast differ from fresh yeast?
“Quick dry yeast is no longer a complex of living organisms, but the isolated contents of highly purified cells. Fast yeast production begins with an individual yeast culture that first grows in a test tube, then combines with a high-sugar mass – molasses – and grows in an oxygenated sterile environment, and finally is filtered and dried under certain conditions. In simpler terms, fast yeast is a sterile squeeze of live, ‘slow’ yeast in which its working qualities are enhanced.
Can yeast enter our bodies with bread?
“The main accusation against artificially grown, fast yeast is that it supposedly has thermophilic properties, i.e. increased resistance to high temperatures, it settles in the gastrointestinal tract together with bread and can cause damage to the natural microflora. But is this really the case?
Any single-celled fungi consist of protein and water. The comfortable temperature for the development of yeast fungi is no higher than 36 degrees. Their thermostability reserves are quite low: at 40-45 degrees, any yeast is guaranteed to lose the ability to reproduce. At temperatures above 55 degrees the protein denatures, that is, folds, irreversibly losing its original properties. Any housewife who mistakenly added too hot milk to the dough leaven could see this for herself. Such dough lost its ability to ferment and rise, because the yeast in it was killed. Considering that during baking the temperature inside the bread crumb reaches 95-98 degrees, closer to the crust – 180 degrees, then the yeast in it remains only a protein trail. No kind of yeast can survive at these temperatures. Conclusion suggests itself: there can be no yeast cells in baked bread, therefore, they can not get into our body with the bread.
Do the rumors about “thermophilic” yeast circulating on the Internet have any real basis?
“Thermophilic microorganisms do exist. There are classes of pathogenic hyperthermophilic bacteria that can reproduce at 200 degrees or higher. There are heat-resistant bacillus spores. There are certain types of mold fungi: for example, hay bacillus spores can withstand heat up to 120 degrees. But specifically to baking yeast, all this aggressive microzoop has nothing to do with baking yeast. In the process of baking, any bread, whether with or without yeast, becomes essentially yeast-free because the yeast is completely deactivated.”
And if you pinch off a piece of raw dough and eat it, will the yeast get into the perfect environment and multiply and multiply?
“In theory this could be allowed, but in practice no one would eat a whole loaf raw. That minuscule amount of live yeast contained in a piece of dough will meet a barrier of gastric juice and the body’s natural microflora. So raw dough – if only a potential threat, then only for people with a seriously weakened immune system or with severe intestinal or stomach disorders, a healthy person such dabbling at most threatens a slight flatulence.
Much more tenacious are the mycelia that live, for example, in moldy cheeses. The blue and white molds in cheese are fungi of the genus Penicillium (roqueforti and candidum, respectively). These fungi secrete antibiotics during their life, which help them inhibit the development of all other bacteria in the vicinity. Therefore, the consumption of moldy cheeses in excessive amounts can indeed cause harm and dysbacteriosis and, consequently, the development of undesirable flora in the intestines.
By the way, yeast is a natural inhabitant not only in raw dough, but also in all fermented foods without exception, including sauerkraut and kefir, but we perceive it as natural probiotics and considered beneficial, and, unlike baker’s yeast, for some reason does not cause such a storm of outrage and horror stories on the Internet.
Can I be allergic to yeast?
“Food allergies to baker’s yeast, if they occur, are extremely rare and scientifically unproven to be dangerous, unlike gluten allergies. On the contrary, all Saccharomyces yeast cultures (saccharomycetes) contain a group of B vitamins, including vitamin B12, which can fight inflammation and thus reduce allergic reactions. It is true that baker’s yeast does not contain as much B12 as, for example, brewer’s yeast. Not without reason brewer’s yeast is used in medicine as a dietary supplement.
So sourdough bread is healthier than bread made with yeast?
“In an ideal world, yes. But that’s if the sourdough was grown on pure cultures. All home bakers know how dangerous the presence of introduced, so-called wild yeast in sourdough can be, which can not only ruin bread, but also act as a pathogen to our body. Unchecked sourdough that has matured without sanitation can introduce uninvited microorganisms, including those that cause “dirty hands disease.” For example, pathogenic thermophilic bacteria, spores of mold or yeast-like fungi, E. coli and hay bacillus, which are all the more dangerous because they penetrate the dough during kneading and can survive in the depths of the crumb.