Across the world, yeast has been a crucial part of cooking for thousands of years, with different types used for different tasks. But for novice bakers, using yeast, and even knowing whether it’s still good, can be quite confusing.
If that’s you, no fear. You just need to learn how to proof it.
What is yeast?
Yeast is a single-cell fungus called Saccharomyces cerevisiae. It’s very much alive, which, despite its microscopic size, becomes evident once you give it food, warmth and moisture. It feeds off sugar and starch, which it converts into carbon dioxide and alcohol through fermentation.
There are over 500 species of yeast, which all fall more generally into 2 categories: brewer’s yeast and baker’s yeast. Brewer’s yeast is a wet yeast well suited to producing alcohol through fermentation, while baker’s yeast is used as a leavening agent because it’s better for producing carbon dioxide. It’s the carbon dioxide that creates air bubbles in bread and other baked goods, causing them to expand (or rise). Baker’s yeast comes in two types: fresh yeast and dry yeast.
Fresh yeast generally comes in a compressed cube. These are made of fresh yeast cells and are high in moisture, which means they perish quite quickly. However, they are generally preferred by bakers.
Dry yeast, as you might expect, keeps much longer. It’s therefore better suited to have stocked for very occasional bakers. It comes in two types: active dry yeast and instant yeast.
Despite its name, active dry yeast is actually dormant and should be activated before use – as does fresh yeast. This process is known as proofing. Instant yeast is so called because it needs no such activation.
What does proofing yeast mean?
As mentioned above, proofing your yeast simply means activating it before use. Although not always necessary, you will usually get a better rise from yeast that’s been proofed first. More importantly, however, it means testing your yeast before wasting time and effort baking (or brewing) with yeast that won’t ever ferment.
Yeast is a living organism. If it’s nearing or past its expiration date or hasn’t been stored properly, there may not be enough living cells left for it to have the desired effect. This goes for dry yeast as well as fresh.
Every baker knows how heartbreaking it can be to spend time and effort on a recipe that doesn’t even begin to rise, so it’s generally a good idea to proof your yeast first.
Do all yeasts need to be proofed?
The short answer is no. A healthy yeast will still ferment even if it hasn’t been proofed first, so long as there's enough moisture in the recipe (as there is in bread). Proofing is still a good idea though, for the reasons given above.
However, some yeasts shouldn’t be proofed at all. In the case of instant yeasts, you may disrupt the qualities that make them rise quickly if you dissolve them in liquid first. Always read the instructions on the packet if using instant yeasts you’re unfamiliar with.
How to proof dry yeast
To proof active dry yeast, you will need:
1 cup of water for every packet (¼ oz) of yeast
1 teaspoon of sugar (or honey) for every packet (¼ oz) of yeast
Remember, your yeast will need moisture, warmth and food to activate. With that in mind:
Warm the water to around 105°F (40°C) to 115°F (45°C). Pour the water into the bowl.
Add the yeast and sugar to the warm water and give it a stir.
Wait for 5–10 minutes. After that time, the yeast should be causing the water to bubble on the surface. If it doesn’t bubble at all, your yeast is no longer usable. If it only bubbles slightly, you may still be able to use it if you give your baked goods more time to rise.
How to proof fresh yeast
There are two methods you can use to proof fresh yeast. The first method is largely the same as the dry yeast proofing method above. However, you should only warm the water to around 100°F (38°C). Fresh yeast thrives at slightly lower temperatures to dry yeast.
The second method for proofing fresh yeast is simply to mash your cube of yeast together with a teaspoon of sugar on a plate. It should start foaming up after 5–10 minutes, at which point it’s ready to be added to your recipe. If not, your yeast may be unusable.
Recipes with yeast
Yeast is a fun ingredient to learn how to use. And the best part is all the fresh bread you get to eat, still warm from your oven.
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