November 16, 2008 - 9:50am
What is the weight of a cup of 100% hydreation sourdough starter?
I am just a little bit dense here and confused at the same time.
What is the weight of a cup of 100% hydration sourdough starter? 240 grams? 300 grams?
Depends on the activity of the yeasties, Bill. If they've been working hard and there's lots of CO2, then it would be lighter than if it were just mixed up. It's nothing that can be definitely nailed down, I don't think. That's why things are specified by weight, because volume is not reliable, especially in this case, where you have an arbitrary amount of gas in the volume.
Why, I wonder, do you want to know the weight of a cup of starter?
Paul: Thanks for the response. And, you are right. Depends. But, the reason I ask is because a lot of recipes I run into (some in well known books like Beth Hensperger's The Bread Bible and some on the Internet) call for 1 cup of starter (no weight given).
And, if you want to play around and increase the starter to say 1-1/2 cups, how do you do that if you do not have a starting point for the weight of the cup of starter?
Rose Levy Beeranbaum in her book, The Bread Bible, says that a "scant" cup of liquid (100% hydration) starter weighs 240 grams.
Peter Reinhart in his The Bread Baker's Apprentice says that a cup of his "seed" starter (88% hydration) wieghs 7 ounces or 198 grams.
And, lastly Jeffery Hamelman's Bread: A Baker's Book of Techniques and Recipes recipe for Vermont Sourdough says that two tablespoons of liquid (100% hydration) weighs 1 ounce. So 16 Tablespoons in a cup means that this cup weights 8 ounces or 226 grams.
So, who's right. Or is it as you say, "It depends..."
To keep things easy, I'm going to say that a cup of liquid starter (100% hydration) weighs 230 grams (that's an average between Rose and Jeff).
Thus, based on this weight, a cup of liquid starter would contain 115 grams of flour and 115 grams of water.
It's a place from which to start.
Sounds good. You might also try weighing a cup of your starter...
Jeff's calculation wrong as 8 oz is 0.5 lb which is 0.5*453.6=226.8 which is closer to 227g. the 100 percent hydration (approximately twice as much flour as water by volume). a cup of water weighs 237g and the 100% hydration flour is 237g so after almost doubling in volume, it will weight at least 237g, so the 240g figure is probably accurate for 100% hydration. at 88% hydration it is going to be 240g of flours + 211g of water which is going to be at least 226g and probably more like 256g considering its smaller size. i'd stick with 240g/cup (which is convenient as AP and bread flour weigh 120g/cup and water weighs almost 240g/cup).
The accurate formula is total weight divided by twice (from doubling in size) the volume of the initial combination. so you can measure the initial combined volume, double it and divide the sum of weight of water (1 liter= 1000g, 1 cup = 8.32 oz) plus the weight of the flour (120g bread wheat flour/US Cup or 0507g/ml (multiply by .94 for whole wheat (113g/C or 477g/L) and .88 for rye (106g/C or 447/L)) by that (doubled value).
I weighed it a while ago, and it's 280 grams for my starters.
As to starter varying depending on how active they are, in the interest of consistent volumetric measurement you should stir down the starter before measuring it.
OK, I admit that I'm as dense as a loaf of poorly made whole wheat bread but would there be much if any difference in weight of active vs inactive starter?
Volumn sure, but CO2 gas is not going to give any lifting effect like say, helium, would it? And if it did, would any of the scales we all use pick up such a small difference in weight? I'll bet if I weigh an empty balloon, then blow it up to 3X it's empty volumn, my scale would not regisrter the added CO2 & moisture. And are'nt the little beasties CONVERTNG the existing weight of sugars to CO2? Not ADDING new weight?
I'm giving myself a headache.
It's weight per volume. No, the starter isn't going to float away. Imagine egg whites. How much volume do six egg whites take up? What is their weight? Now whip them and ask the same two questions - different volume/weight ratio in your answers, eh?. If your initial question was "how much does a cup of egg white weigh?" then, in order to answer it, you would have to know if they were whiped or not. Same with the starter. If you're asking "how much does a cup of starter weigh?" you need to know how gaseous that starter is in order for the answer to be meaningful.
Your egg white example brought it into clarity and makes me wonder why I did not grasp the concept right away (must be getting old!).
Now this begs the question; should you always 'stir-down' a starter before measuring it by volumn?
Mike's the man to listen to on that, and he says:
"As to starter varying depending on how active they are, in the interest of consistent volumetric measurement you should stir down the starter before measuring it."
what is the weight of water for your cup? Note. Cups vary throughout the world. Then stir down starter to pop any bubbles, tare the cup, fill and weigh.
And... You can save "stirring down" by pouring a liquid starter in a small stream from at least a foot high, the bubbles will pop in the pouring.