Using sponge method with bread machine.
It seems to me that bread-machine recipes, and the machines themselves, are designed around using 1 packet, (7 grams, or 2-1/4 teaspoons) of instant dry yeast. Or... anywhere from 2 to 3 teaspoons of yeast.
It occurred to me that if you want to save yeast, you might be able to make a sponge first, using perhaps 1/8 tsp yeast, and some water and flour, and maybe sugar, taking the water/flour out of the total recipe amount.
The flour/water/sugar would then grow or cultivate the 1/8 tsp yeast to an amount equivalent to the 2-1/4 tsp.
Then the sponge is added in to the rest of the recipe, (keeping total flour and water the same as original recipe) and in effect saves 2-1/8 tsp of yeast, per loaf.
Timing, temp, and type of flour would be critical.
Going from 1/8 to 2-1/4 is a factor of 17. So it's a 16x, or 1600% "increase." Or, doubling 4.09 times if I did the math right: log (base 2) of 17.
Has anyone done this? Are there any rules of thumb to use for estimating growth rates for IDY? (Currently looking at sourdough yeast rates.)
I found this: http://www.thefreshloaf.com/node/59477/sourdough-yeast-growth-rates-various-temperatures Where the first graph is commercial yeast.
So, assuming a .3x _increase_ per hour (1.3 multiplication factor), at 21 C room temp, doing some math, it looks like 2.65 hours to double the yeast cells, and I would need to double 4 times, about 10.6 hours. Does anyone see any glaring errors in that logic or in the math?
I"m trying exactly this to conserve yeast used by my regular "Zo" bread machine recipes. But the doubling logic isn't working in practice - I got 2 flat loaves in succession. I used 1/4 tsp yeast in 1/3 cup water with some sugar and flour, left loosely covered at room temp 70 deg F for 6+ hours, before adding to the machine with the balance of ingredients. Loaves came out 1/3 or 1/4 proper height.
Interesting, as my Panasonic 2500 recipe book tends to use 1/2 to 1 teaspoon of yeast. Maybe it depends on which country you are in? I am in England.
The logic looks OK to me idaveindy. For yeast calculations, the weekend bakery has put together a compendious table (no idea how much experiments went into it). I have found that these ovenight proofing things seem to be quite tolerant of a range of initial innoculations. 1/8 tsp looks about right for an overnight ferment, I am sure I have read recipes that suggest just that amount.
I have been experimenting with making hybrid sourdough/yeast breads in the bread machine. I have been using 40 or 50% pre-fermented flour in a poolish or biga (fermented using sourdough) and then sticking it on top of the remaining ingredients in the breadmaker and letting it do its stuff. (Since doing that, I read a recipe for breadmaker sourdough which suggested giving the ingredients an initial hand mix in the breadmaker bowl before setting it off, which seems sensible, but it worked OK without.) With a straightforward breadmaker loaf I would use around 1/2 to 1 tsp for a "small" (400g flour) loaf, which is about 1.4 - 2.8 g, with the hybrid version I add 0.5-0.8 g yeast when loading the breadmaker, and I am thinking maybe I don't need to add any yeast. Results are OK, but I am not quite getting the flavour I get with a more laborious all sourdough recipe.
So I have done the sponge in the breadmaker, but not exactly how you are proposing. I can't see why it shouldn't work though.
TIM