I feed starter with a 50-50 mix of water and flour. Usually 1/2 cup water 1/2 cup flour for a small container. You can eyeball the ratio. It isn’t critical to get it perfect.
If you keep the starter in the fridge you can get away with feeding it twice a week depending on your yeast strain. You can do this by eye…if the starter starts to look ugly when you take it out to feed, you should feed it a little more often.
One thing I will say is that you can resurrect a starter that seems long past edible. The starter will get a cloudy fluid on top of the batter and develop a really strong smell if you let it go too long. My personal experience is that you can pour off the watery fluid and some of the batter if need be. Then add a good feeding of flour and water. It will take a little longer than usual to build up again. Yeast is a very durable critter.
The difference between flour marketed as Bread Flour and flour marketed as All Purpose (at least in the US) is the type of wheat from which it is milled, and therefore the protein percentage in the flour, a p/l value close to 1 which gives proper plasticity to the dough, and a large enough falling number to allow long fermentations.
At least the US, all flour marketed as either All Purpose or Bread Flour should be suitable for bread making, although bread flour will permit greater gluten development due to the higher protein level.
The yeast or bacteria in a bread starter eat the starch (after it has been converted to sugar by enzymes present in the flour), which is the bulk of the grain, whether the wheat is winter or summer, hard or soft, red or white.
Also, the way the bag is labelled is as much a marketing issue as a technical issue. For example, in the US, King Arthur brand all purpose flour is nearly as "hard" (high in protein) as other common brand's (such as Gold Medal) bread flour.
Use either all purpose or bread flour, as you choose.
Best Answer
Sourdough bread is bread that has been all or partially risen with the help of wild yeast. It is made sour because of wild lactobacilli that are picked up with the wild yeast. Where the yeast eat sugar and produce CO2 for rising- the bacteria create acid and other compounds that make the bread sour and distinctly flavored.
Because of the wild nature of the microbes, the bread will taste a little different in every place that it is made. The lactobacillus that gives San Fransisco sourdough bread its characteristic flavor is actually named Lactobacillus sanfranciscensis.
The starter can be a hassle to make and to keep. It requires almost daily attention to feed it and can waste a fair amount of flour unless you bake bread frequently. You can freeze the starter but it will require a few days of feeding before it can be used again. Many baked recipes besides bread are also delicious with sourdough starter. Sourdough waffles or coffeecake are fantastic.
Whether it is worth the effort is a personal decision. Many people don't like the flavor and you would have to love the flavor enough to make almost every bread with that flavor to justify the starter upkeep. Personally- I used to keep a starter but my kids don't like the flavor and I got tired of all my bread tasting the same. I just buy a loaf for the 2-3 times a year that I am craving a Reuben sandwich.