what makes sour dough sour?

a sourdough starter does make a sourdough sour.

http://en.wikipedia.org/wiki/Sour_dough

I hope it helps.

Sourdough Starter is a flour water and ??? combination mixed, and allowed to set for awhile to ferment naturally. Adding in measured ingredients (feeding) on certain days, and allowing the mixture to ferment to the proper level. Then the mixture is called the "MOTHER", some is removed to make bread, the rest sets and is "fed" to maintain the process. Much like Amish Friendship Bread (a sweet bread) but fermented just the same, and fed on certain days to keep it alive, and baked on certain days, and sharing part of the Mother Starter with Friends along with the instructions and a recipe.

It is called a Mother which is a starter made with bread flour, yeast and water. Letting it ferment and then add to dough you are making but always refill the starter as it will last forever. Keep refrigerated.You can also use yogurt, vinegar for a more sour flavor.

It does a lot of sitting, and rising. It is not really sour but it is called sour since it sits out so long.

Obviously it is the yeast that causes the chemical reaction, it is used in a lot of bread. So why isn't every bread "sour"? Well know it all's? Get out of the kitchen and into a classroom. The amount of fermentation, like one person mentioned, is what earned it the name "sour dough". Like I said from sitting and allowing the chemical reaction to take it's time. What happens when you leave milk out? It sours. What happens when you leave out un-pasteurized goats milk? It sours, but unlike cows milk it is used in many things and tastes great.

Well it looks like this is a show down. I have managed to get the most thumbs down. This is just weird.

Yes Richard K and Wize woman, those are techniques used in making sourdough. Good job!!! That wasn't the question. *sigh*. Also, people shouldn't just leave links to Wikipedia. It's a great source of info but if people wanted to fumble through a 10,000 word discourse from an internet based encyclopedia to find a little bit of info they want then they wouldn't use Y!A. The point is to answer their questions as best as possible. I would rather give the best answer I can than run around tossing links and saying look it up yourself. Add a link as your source or as an addition to what you display.

I hope I answered you question, I am sorry your answer was disclaimed by my banter towards the peanut gallery below.

bitter DOUGH STARTER a million pkg. energetic dry yeast 2 c. lukewarm water 2 c. flour a million/2 c. sugar a million c. water a million c. milk In a huge glass jar or crockery pot dissolve yeast in heat water. upload flour; beat until tender. enable stand in one day at room temperature for 5 days. Stir each and on a daily basis. On 5th day upload sugar, water and milk. Refrigerate, stirring each and on a daily basis for yet another 5 days earlier utilising. Starter may well be stored in refrigerator indefinitely. continually replace used element with equivalent quantity of flour and water. bitter DOUGH ROLLS OR PIZZA CRUST: a million c. flour 3/4 tsp. baking soda 2 tsp. baking powder a million/2 tsp. salt a million/2 c. vegetable oil combine all ingredients; combination nicely. shape dough right into a million a million/2 inch balls. Bake on greased sheet at 425 ranges, 10-quarter-hour or in muffin tins at 350 ranges for 25-35 minutes. For pizza, separate dough gently and unfold in pizza pan. Bake 425 ranges 10 minutes. get rid of from oven and proper as needed. Bake until cheese melts and meats are cooked.

Pretty sure it's the sour stuff.

I believe it is the effect of fermentation process

The yeast and how long it takes for the bread to rise.

http://www.io.com/~sjohn/sour.htm

http://en.wikipedia.org/wiki/Sourdough

It is the yeast and bacteria and how it is made.