Yeast

I haven't written in a couple days due to trying to convert the yeast in a recipe.  Yes, the conversion of a single ingredient can be a slog at times, especially dealing with something as crucial and volatile as yeast.  I Came across a recipe I wanted to try that called for instant yeast (which was an improvement over other recipes calling for instant biscuit mix).  Being a bit of a traditionalist, I wanted to use fresh yeast, which wouldn't be an issue except the measure was in tablespoons!

If I may rant slightly, when it comes to cooking, metric or imperial, always, always, always eventually convert your ingredients to weight measures if you are taking notes for the sake of writing a recipe!  The consistency of your results will improve, and adjusting the size of recipes becomes simple math.  The metric system is by far the superior system for this - especially when you get into recipes calling for tenths of a gram of something - any product measured in tenths of a gram will have huge result differences if you stray.  Nothing against imperial - being a Canadian, I am inexplicably tied to it - I have no clue my height or weight in metric, but I buy my gas by the litre, fruits and vegetables by the pound, compare prices in the store by increments of 100 grams, and my oven is in fahrenheit (I also spell flavour and colour with "our" - take that spellcheck!).  I do my best to include both systems in my recipes as well as convert measurements to weight, but depending how the recipe came to my hands, I may be a bit behind in my homework.  Whenever I write a recipe, it's weighed out in grams.

Back to yeast - I was faced with a tablespoon of instant yeast and wanted to use fresh.  I went to the cupboard and scooped and weighed a tablespoon of active dry yeast - how much difference could there be with instant?  Then I thought "what if?" and consulted the all knowing internet.  I went to www.convert-to.com - a very useful site - and did confirm that the weights should be the same.  Of course, that was only part of the equation, so here's the results of the rest of my research.

Fresh or compressed yeast:

 - needs to be refrigerated (will last 2-3 weeks)
 - does freeze well (for a reasonable period of time)
 - has about 70% moisture

Active dry yeast:

 - a dry good - can be stored several months in the cupboard (check best before date)
 - needs to be rehydrated in warm water (110F / 43C) before using - use a portion of the liquid that will already be going into the recipe

Instant or quick rise dry yeast:

 - a dry good as well
 - needs to be mixed with the dry ingredients then activated with warmer water (125-130F / 52-54C)
 - will get killed at temperatures above 138F / 59C - so be careful
 - rises faster than active dry yeast

Conversion notes:

 - instant yeast is slightly stronger than active dry yeast - if substituting active dry for instant you may want to add up to 20% more.  If substituting instant for active dry, remove up to 20%.  This is often done for speed, and if using active dry, not the end of the world to keep the measures the same and give it the extra time to rise.  Going the other way, using instant instead of active dry, it will rise faster, so keep an eye on it or it will explode!  (not really)

 - both dry yeasts are stronger than fresh yeast.  The most common conversion is to multiply the weight of instant yeast by 3 to calculate how much fresh yeast to use (and maybe slightly less if converting from active dry).

Using yeast:

 - fresh yeast should be light coloured, crumbly and fresh smelling - if dark, sour smelling or slimy, don't use it
 - blooming yeast (fresh or active dry) should result in a foamy top on the liquid after some minutes
 - yeast is a living thing, so it has a temper - too much heat will kill it, too little will slow the rising
 - a well proofed bread will be slow to spring back when you poke it
 - if you overproof - best to punch it down and re-shape your bread or you'll have huge holes inside
 - with all the variables, especially if you've switched the yeast in a recipe, if you weren't satisfied with the results, better to analyze the recipe and procedure and make adjustments for next time rather than switch to a new recipe you've never done before (unless it was a total disaster and something was clearly wrong with it to start with) - this is also the way to finding and creating those recipes classified as "the best" - there is wiggle room in baking and pastries, you just have to make baby steps over time and take and compare notes.