What is yeast block?

In this brief guide, we will answer the query, “What is yeast block?” and will discuss the different types of yeasts.

What is yeast block?

Differently from active dry yeast, which contains about 95% dry matter, yeast block is also known as cake yeast or fresh yeast. Bakers typically utilize fresh yeast, a block of yeast cells that has roughly 70% moisture. Pale beige, soft and crumbly like a soft pencil eraser, and with a yeastier fragrance than dried yeast (1).

What is yeast?

Yeasts are single cell, eukaryotic microorganisms classified in the fungi kingdom. These microscopic fungi are generally about 3–4 μm in size, have a nuclear membrane and cell walls, but unlike plants, they contain no chloroplasts. Yeasts are characterized as heterotrophs in which they rely on living and dead organic material as sources of energy and nutrients. obtain their nutrition by producing and releasing various proteolytic, glycolytic, or lipolytic enzymes to digest organic matter, or by absorbing amino acids and monosaccharides through the cell wall. Reproduction occurs by budding and fission. Budding occurs when a parent cell increases in size, and a protrusion forms along the cell wall to form a “bud”, which breaks from the parent cell or is partially conjoined in elongated cells. Fission also occurs when a parent cell divides into two daughter cells (1).

Mushrooms and molds are members of the same fungal family as yeast, which is a single-celled microbe. We only utilize one kind of yeast for baking: Saccharomyces cerevisiae, often known as “baker’s yeast” or “sugar eating” yeast. There are hundreds of different kinds of yeast. Yeast rises because it consumes the sugars and starches included in the bread dough, turning them into carbon dioxide gases that give the bread its characteristic light and airy feel. The term “yeast” is a perfect description of what this yeast does. When the dough is cooked, the rising process is interrupted and finished.

There must be a reason why there are so many distinct kinds of yeast. The yeast used to be available only in one form: fresh, but in 1941, food manufacturers discovered a way to dehydrate it, resulting in a shelf-stable product for the general public.

What is the process for making yeast?

Commercial baker’s yeast, on the other hand, is a specially produced, cultivated, and processed strain expressly designed for baking. To cultivate yeast, it is necessary to use a liquid containing molasses, nutritional salts, and B vitamins, which may be found in anything from growth tubes to culture tanks to fermenters. Fresh yeast is extracted from the tanks and put into little squares that may be purchased at the supermarket after being filtered, squeezed, and firmly compressed. When fresh yeast is dried, you obtain both active dry and instant yeasts, with active dry having a lower percentage of living yeast cells than instant yeast.

Yeast is grown in large fermenters by the fed batch process. The fermenters are equipped with cooling coils and with means for vigorous aeration to maintain highly aerobic growth. The growth rate is restricted to a growth rate coefficient of less than 0.25. In the fermenter liquid 4-6% of yeast solids can be produced. Post Fermentation processing begins with centrifuging to produce a concentrate (yeast cream) with 18-20% solids. The yeast cream is washed and either pressed or filtered to a semisolid yeast mass of 30% solids. This press or filter cake is packaged as a crumbly mass in bags or extruded in blocks that are wax wrapped. It is cooled and shipped refrigerated to bakeries. Some bakeries also accept shipment of the pumpable, refrigerated yeast cream (2). 

Fresh yeast

After the fermentation process to grow yeast, the yeast cream containing 18~20% yeast solids is quite viscous, but is still pumpable. At concentrations of 23% solids it cannot be pumped, and at concentrations of 27 ~ 30% the yeast assumes a semisolid plastic consistency (2). A crumbly, firm block of fresh yeast is made from a slurry of yeast and water. Bakers prefer fresh yeast because it has a richer, slightly sweeter taste and a better “rising” character than dried yeast, which is preferred by novice bakers.

Fresh yeast is simple to work with once you get the hang of it, despite its scary appearance. Before you begin baking, make a starter by dissolving fresh yeast into warm liquid and letting it “bloom.” Stir the yeasty liquid into the dry ingredients of your bread recipe after the new yeast has begun to bubble and froth.

When to use fresh yeast?

Baked goods with lengthy, sluggish fermentation and rising times are best served by using fresh yeast rather than dried since their active reaction lasts longer than that of dried yeast. These braided bread with herbs and this handmade flatbread are two examples of recipes that benefit greatly from many proofs. In the same way, if you’re making something sweet like jelly doughnuts or cinnamon buns, you’ll have to spend a lot of time waiting for your dough to rise, but it’s well worth it in the long run.

Active dry yeast

Ground and dehydrated active dry yeast are known as “active dry” products. If you’re a novice baker, you’ll find it in the majority of supermarkets. During World War II, active dry yeast was created to overcome the refrigeration shortage. It has a “dormant” yeast in it that may be stored at room temperature for many months before being used as a starter ingredient. Active dried yeast may be stored in the refrigerator or freezer for up to a year in a dark container.

Active dry yeast comprises 15–25 billion live yeast cells (colony forming units; CFU’s) per gram. The three most common processing methods include tunnel dried yeast (granular powder), fluid-bed dried yeast (quick rise yeast in oval shaped spheroids), and rotolouver dried yeast (produces small spheres or balls). The tunnel dried and fluid-bed drying methods are most common in the U.S., while the rotolouver drying method is more common in Europe and Latin America. Of these drying processes, fluid-bed drying has become the most popular because it causes less damage to yeast cells, and thus, maintains their viability (2).

Activated dried yeast does not need to be proofed before being added to bread dough, contrary to common assumptions. To make bread, this yeast may be applied straight to the dry components, rather than the wet ones. Although some home bakers prefer to add it to the rest of the ingredients after mixing it with a little quantity of warm water first. Before using this yeast, be sure to read the directions on the packaging carefully.

You may test your dried yeast’s viability by adding half a teaspoon to a cup of warm water and a few grains of sugar. If the yeast is still active, it will bloom (foam and bubble) after about ten minutes. 1 gram of active dry yeast should have the same bake activity as 3.1 grams of cake yeast (2).

When should you use active dry yeast?

Yeasts have three functions in baking. They produce the leavening gas that expands the dough; they affect the rheological properties of the dough and they contribute the typical fermentation flavor of yeast-raised products (2).

Even though active dry yeast is the preferred choice of most home bakers, some insist on not using it. Is it because the term “fresh” conjures up images of fluffy, bubbly yeast? Both of these yeasts are indistinguishable when treated correctly. If you want to use fresh yeast, it’s always a good idea to keep a supply of active dry yeast on hand.

It’s a time-saver since it doesn’t need to be proofed before use. These handmade morning cherry rolls, adorable Marzipan challah hedgehogs or this hearty fig-walnut bread are a great way to convert your skeptical, fresh-yeast-only pals.

Instant yeast

Active dry yeast is coarser than instant yeast. It is almost similar to active dry but is advertised as dissolving and activating more rapidly (thus the “instant” portion). Additionally, it may be labeled as “rapid-rise yeast” or “fast rise yeast,” depending on where you look.

Doughs start fermenting as soon as a yeasted dough is mixed, and fermentation continues throughout makeup and proofing until about 8 to 10 minutes after the proofed loaves enter the oven (2). To make the dough rise even quicker than fast, you may also locate them with extra enzymes, which means you can skip the initial rising period and instantly form a loaf after kneading. No blooming is necessary for quick yeast, just as for active dried yeast.

Is it possible to use two different kinds of yeast in the same recipe?

To put it simply, substituting various kinds of yeast for each other isn’t an issue since the yeasts all perform the same functions and are packaged differently. For effective swaps, there are just a few things to modify and keep a watch on.

Instant and active dry yeast may be used interchangeably. Using active dry yeast in a recipe that calls for instant yeast will need you to increase the rising time somewhat. You should use two times the quantity of dry yeast called for in a recipe if you’re using fresh, and the other way around. Just remember that new yeast must be proofed before being added to the rest of the ingredients, so keep that in mind. It’s possible to skip the proving step entirely if you use fresh yeast instead of dried.

Other types of yeast

Liquid yeast

Liquid yeast is just yeast in a more convenient form. Some bakeries do use them for baking, although they’re more typically employed for brewing beer than for anything else. To activate the yeast, you just mix the yeast with the nutritional solution that comes in separate bags. At the end of the fermentation, the yeast cell concentration of 4-6% solids and this is increased to about 20% by centrifugation. By this concentration, the yeast is still creamy and pumpable and some bakeries accept shipment of the pumpable, refrigerated yeast cream (2).  

Brewer’s yeast

Beer is a beverage made predominantly from malt by fermenting an extract of malted barley and hops using a special strain of yeast. Yeast plays an important role in the brewing process not only by converting the fermentable sugar in the wort to ethanol and carbon dioxide but also by producing a variety of volatile and nonvolatile constituents mostly in trace amounts that contribute to the overall flavor of the beer (2).

Yeast production is a complex process, and brewer’s yeast is at the heart of it all. It’s not utilized in baking but instead is well-known for its beneficial effects on health. A powder, capsules, pills, or pre-mixed with a variety of other items are all ways to receive the supplement. Brewer’s yeast includes B vitamins and other minerals and is thought to benefit your skin, hair, neurological system, and immune system.

Nutritional yeast

Deactivated yeast, like nutritional yeast, will not aid in the rise of any bread or pastry. It may be purchased as flakes or as a powder and used as a condiment or spice. Because of its cheesy, nutty flavor and high concentration of B vitamins and minerals, nutritional yeast is particularly popular among vegans. Nutritional yeasts are used as supplements in animal feeds due to their relatively high protein and amino acid, energy, and micronutrient content compared with common feed grains and oilseed meals. Other important yeast-based products contain nutraceutical compounds present in yeast cells and cell walls (i.e. β-glucans, mannan oligosaccharides, nucleotides) that have generally been shown to improve animal growth performance and health (1).

 Interested? We’ve got a vegan spinach and mushroom lasagna with nutritional yeast that you should try.

Other FAQs about Yeast that you may be interested in.

Does nutritional yeast expire?

How long does yeast last?

Does Nutritional Yeast Have MSG

Can you use active dry yeast in a bread machine?

Conclusion

In this brief guide, we answered the query, “What is yeast block?” and discussed the different types of yeasts.

References

1. Shurson, G. C. Yeast and yeast derivatives in feed additives and ingredients: Sources, characteristics, animal responses, and quantification methods. Anim feed sci technol, 2018, 235, 60-76. 
2. Reed, G., Nagodawithana, T.W. 1991. Baker’s Yeast Production. In: Yeast Technology. Springer, Dordrecht.