Week 9: Yeast

1.5 lbs of Instant Yeast

After this week, you should have 1.5 lbs stored. This is the program goal. This is the only week we address Instant Yeast.

Yeast has been used in baking and brewing for thousands of years. There are at least 1,500 'species' of yeast, all of which are technically living organisms. Yeast occurs naturally in the environment and is in the same biological family as fungi such as mushrooms. The most common use of yeast has been in the making of bread. The yeast reacts with oxygen and helps leaven bread, or make it rise. There is evidence the ancient Egyptians used yeast to make bread around 4,000 years ago.

Yeast is a single-cell egg shaped organism (fungus), called Saccharomyces cerevisiae, which needs food, warmth, and moisture to thrive. It converts its food, sugar and starch, through fermentation, into carbon dioxide and alcohol. It's the carbon dioxide that makes baked goods rise. Yeast is only visible with a microscope. It takes 20,000,000,000 (twenty billion) yeast cells to weigh one gram. To grow, yeast cells digest food and this allows them to obtain energy. While there are over 500 'varieties' of yeast, 3 types are most commonly available.

Fresh, Active Dry, and Fast-Acting (aka Instant):

  • Fresh Yeast, also known as compressed or cake yeast, is active yeast. It's sold in tiny cakes in the refrigerated section of many supermarkets. It has good rising qualities and produces excellent-tasting bread, croissants and Danish pastries. Fresh yeast does not keep well; it will last about two weeks if refrigerated, and up to 3 months if frozen. Fresh yeast should be proofed in tepid water (check manufacturer’s directions, but usually 80-90 degrees F). This yeast type is a good choice for breads requiring a long cool rise, or for breads made using the sponge method.

  • Active Dry Yeast is the most commonly available form for home bakers and is available in ¼ oz packets or jars. Active dry yeast has a larger particle size than Instant Active Dry Yeast, and is also dormant, making it necessary to proof and re-hydrated before using. Active Dry yeast should be stored in a cool dry place. Store open containers in the refrigerator. If unopened, active dry yeast will keep well beyond its expiration date printed on the package, for up to one year at room temperature. It will keep longer if frozen. Place directly in the freezer in its vacuum sealed container. If frozen, you can use it directly without thawing. If opened, active dry yeast will keep 3 months in the refrigerator and 6 months in the freezer.

  • Fast-Acting or Instant Yeast is a dry yeast that comes in very fine granules (smaller granules than active dry yeast), absorbs liquid rapidly, and doesn’t need to be hydrated or proofed before being mixed into flour. It can be added directly to the bread flour and mixed in along with the other ingredients. When using Instant Active Dry Yeast, the bread recipe only needs one rise. What would otherwise be known as the first rise is replaced by a ten-minute rest, and you don’t need to “punch the dough down” afterwards. The second rise (or only rise in this case) takes place after the dough has been shaped into a loaf. This makes bread making simple. It will take approximately one hour in a warm place (longer in the refrigerator as a slow rise) until the dough is just about doubled in size.

A very common instant yeast is LeSaffre Saf-Instant Yeast. This is high potency, fast acting yeast that can be added directly to your dry ingredients without it having to proof (activate) first. Saf-Instant Yeast is already active. Exposure to oxygen, heat or humidity decreases the activity of the yeast, and using overly hot water will kill it completely (Bosch recommends 110-120° F). After opening, store in an airtight container in the back of the refrigerator, away from drafts. It should be good for about a year. Unopened in a dry cool place and it should be good for 5-10 years. Unopened in the freezer and you can get 10-20 years (some say indefinitely).


You can substitute one type of yeast for another but the quantities need adjusting. For dry active yeast, you generally need to use half the quantity of fresh yeast stated in the recipe and for instant yeast, you need to use 1/4 of the quantity of fresh yeast. So, if the recipe calls for 30g (1 ounce) of fresh yeast, then you can use 15g (½ ounce) active dry yeast or 7g (¼ ounce) instant yeast instead. Most of the yeast packages give basic guides as to how much yeast you need to add to certain quantities of flour, but if your recipe contains a lot of salt, egg, butter or other fats, then you will need to use slightly more yeast, or allow a longer time for rising, as these will tend to slow down the action of the yeast. So basically: 1 oz Fresh Yeast = ½ oz Active Dry Yeast = ¼ oz Instant Yeast.

Measuring Yeast:

You do not need to be exact in measuring yeast. Remember it’s going to multiply like crazy anyway. A little less is fine; the dough will rise more slowly and may taste better. If you're going to error, error on the shy side. Too much yeast will give an unpleasantly yeasty flavor and aroma.

Testing Yeast:

Sugar is used in testing yeast. To test yeast: Add ½ teaspoon of sugar to the yeast when stirring it into the water to dissolve. If it foams and bubbles within 10 minutes, you know the yeast is alive and active.

Page updated: 10/13/20