Friday, January 21, 2011

All about yeast

Disclaimer: This is not my work. As I mentioned earlier in one of the posts that I had a document saved from a bread baking forum many years back. Unfortunately, I don't have any info on the source. I had copied and pasted the topics that I needed on to a word document. If someone knows the source of this, please let me know so that I can post the link here.

This piece of information is about yeast. Like before, my notes are in the parenthesis.

History, biology and nutrition:
Bread yeasts are one-celled fungi found all around us, in our kitchens and outside, in the air, in the soil, and on grains, fruits and vegetables. People have been capturing and propagating these wild yeasts for thousands of years in sourdough starters. Scientific breeding of our domestic strains of bread yeasts really started with Louis Pasteur in the 1800s.

Bread yeast ferments carbohydrates producing alcohol and carbon dioxide gas in the process. The gas bubbles, trapped within the elastic dough are what make dough rise, giving us light flavorful bread. Flavor and texture are not the only benefits. Yeast itself is an excellent source of B-complex vitamins and Thiamine and the action of fermentation makes grains more digestible (these are good reasons to prefer yeasted breads rather than quick-breads as a daily diet.)

Bread yeast is an amazingly versatile and adaptive organism: shut off its oxygen supply and it will still reproduce anaerobically; deprive it of moisture and it will go dormant, but still live. Modern yeast factories capitalize on these characteristics to produce yeast in several forms for the home and professional baker.

Forms of commercial yeast:
You may remember the little foil wrapped cubes of compressed yeast (yeast in a starch medium) that required refrigeration during its 3 week life and needed proofing before use in a recipe. Compressed yeast has been almost entirely supplanted by various kinds of dry yeast (pure yeast that has been air dried into dormant granules) packaged in air tight containers with long shelf lives (look for the "use by" date printed on the package.)

Active Dry Yeast (commonly found brands are Fleischmann's and Red Star) is called active to distinguish it from Nutritional or Brewer's Yeast which is also dry. Nutritional Yeast is dead; it has no leavening power. It may be a nutritious food supplement, but it has no place in breadmaking (The Laurel's Kitchen Bread Book says that even a small amount added to dough will decrease the effectiveness of the active yeast and make gummy bread.) Active Dry Yeast is usually sold in those little 3-part envelopes in every grocery store. It requires proofing (dissolving in water) before use.

Rapid Rise Yeast made by Fleischmann's is also sold in envelopes or jars. It probably is a kind of instant yeast, since it doesn't need to be dissolved in water first. (This one acts like instant yeast)

Instant Active Dry Yeast
is a new product from Red Star. They have made the granules of their traditional yeast smaller so that dissolving in water is not necessary. (Breadmachines recommend you to use this type of yeast and I use this type even though the brand is different)

Instant yeast is not commonly available in super markets. But it is well worth seeking out at wholesale grocers like Smart & Final or bakery supply houses. Instant yeast is dried at a much lower temperature which keeps more yeast cells alive. It requires no proofing and responds very quickly, rising quite high. This is a professional's yeast. This is the yeast called for in all my recipes on these pages. Commonly available brands are Red Star and Fermipan. Substitution measurements for compressed or active dry yeast are given on the packages.

Why use instant yeast?
A major reason is economy. At $2.00 per pound you could throw most of it away and still save money compared to those little 3-part packages of regular yeast. My total ingredient costs would double if I used the active dry yeast available in the supermarkets. Another reason is convenience: it is always there in the refrigerator, ready to use with no mess or fuss. It lasts more than a year in the refrigerator and longer in the freezer (no need to thaw before using.) (If you live in U.S, buy from costco or B.J's and Sam's. I can get yeast enough for 2 years for me for about 4 dollars. I do bake bread every week so it is well worth it for me. Even if you threw away half of it, it still is cheaper than buying 1/8th of the same quantity for 8 dollars sold in a jar)

Care and feeding of yeast:
Before use, keep your yeast cool and dry. When the yeast is in a dough or batter, it does best in evenly warm and humid surroundings (75 - 90 degrees.) I will keep growing, at a much slower rate, at cooler temperatures, even refrigerated. If an emergency interrupts your baking session, punch down the dough, cover it with plastic wrap and refrigerate it until you can get back to it. Then, transfer the dough to a warm bowl and let it warm slowly to continue rising. This is an emergency method only. But emergencies do occur. There are recipes designed to include overnight rising in the refrigerator. See also The Laurel's Kitchen's Bread Book for detailed directions on using sponges (starter doughs) to adjust rising times to fit your schedule. In general, the lower the temperature the slower the rise and the more flavorful and nutritious the bread. (I store good amount in the refrigerator and the bulk in the freezer. They work just fine even after 2 years of opening the package)

Instant yeast doesn't need proofing but, if you are in doubt about some year old yeast, it doesn't hurt to prove it. Put 1/2 cup of warm water (105-115 degrees) in a bowl or glass container with plenty of room for expansion. Add a pinch of sugar or flour, then sprinkle the yeast and stir to dissolve. I use a knife for stirring; it's easier to clean than a spoon. Let the mixture sit for 10 minutes. If it still hasn't foamed up after 15 minutes, discard. Yeast does not need to be fed sugar; it will make its own sugars from flour. Yeast doesn't like honey, but will tolerate it mixed in with the other ingredients of the dough. Yeast does better with a succession of rising periods rather than one long one. Each time you punch down the dough and briefly knead it, the yeast is exposed to new food.

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. I wouldn't increase the yeast measurements in the recipes on these pages; they are already at the high end. Way too much yeast will give an unpleasantly yeasty flavor and aroma.

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  1. So much to know about yeast! Awesome post Champa! please keep more such posts coming!

  2. superb post with all details about yeast ... thanks for sharing this info

    Super Yummy Recipes

  3. so much material about yeast!! wow!! thx for posting!

  4. Very good info, Champa!
    Guess what? I tried my hand with yeast first time this weekend! The outcome was great!!
    And the recipe was of course, from ur blog :)
    Will post it on my blog soon... Thank u so much!


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