Sourdough not sour at all…

I have gathered that younger starters don't have the same oomph as older starters when it comes to complex flavor.

One thing you could try would be using a recipe that allows for a long, slow ferment of a portion of your dough in the refrigerator overnight.

Unforunately what you have baked just isn´t sourdough bread. The starter will become a true sourdough starter populated with other types of yeast cells (i hate the term wild yeast) and also lactic acid producing bacteria.

The sourness in sourdough bread comes exclusively from the lactic acid producing bacteria (they produce acetic acid too and various esters). So if you keep your starter and feed it daily for a week or two and then make that loaf again I am sure you will get a bread with at least a tidbit sourness to it.

First off, commercial yeast is a very strong strain of yeast. It is difficult for wild yeasts (I like that term and don't know why Kuret doesn't) to outcompete and take hold. It may be difficult to get the correct sourness from the commercial yeast that will continue to thrive as you feed it. So you may want to either start with a simple flour/water (or pineapple juice) type starter that uses no commercial yeat, or a mail order one that just needs to be refreshed and you are on your way.

That said, besides the particular strain of yeast (which can be a major factor), there are other factors that affect sourness. One is the age of the starter (young starter is not as sour). Another is the starter consistency. A firm starter will be more sour than a liquid/batter type starter. The last thing I can think of off the top of my head (and there may be others) is whether or not the dough was retarded in the refrigerator. Retardation slows the fermentation and creats a more sour dough. But there is also the fact that if you refrigerate after mixing/kneading, it will be different than if you retard after shaping.

The first step IMO is to get a starter that does not use any commercial yeast. Otherwise it really is a poolish or biga (both very good ways to make bread, but not truley a 'sourdough').

One more thing... If possible use bread flour for refreshing. It has more gluten than AP flour, so there is more food for the yeast to eat.

The recipe you are using really doesn't give the pre-ferment enough time to develop much flavor, sour or otherwise.  I recently learned that until my wild yeast pre-ferment reaches the age of three (or more) weeks it just doesn't have anything that I can call a sour component.  

(first post, since I've been lurking awhile :))

If anyone has input on this, I'd love to hear your thoughts.  The first starter I made a few months ago, I also started with commercial yeast, and had the same reaction: where is the sour?  I looked at a ton of information online, and also read up here on the forum, and it stuck with me that adding acidic juice (pineapple, oj, etc) was all trying to bring the pH down so that the beasties we wanted would thrive, especially the LABs.... why couldn't you just add a dollop of unflavoured yogurt with live active culture, since isn't that essentially what they are?

I took some of the original starter (with commercial yeast) and stirred a little yogurt (about 1TB) into it and fed it, and now it has burbled happily into a boozy smelling culture (which I have named Boozy Baby).  At the same time, I started a new starter (KAF, no yeast added) and a touch of yogurt, and it developed into an incredibly pungent starter as well (now named Toxic Ooze, since that's what it smelled like to me!).

They're both currently about 3-4 months old, and I've been feeding and using them regularly (much to DFs dismay), and last week baked a loaf with each starter, using the same formula and same durations of time.  We found that Toxie tasted significantly...cleaner.  The sour was much more pronounced and somewhat sharper, than Boozy.  Boozy baked up with a very creamy sour taste, which was also nice, but more mild (I guess?) than Toxie.

So maybe what you might try doing is the same thing?  A tablespoon or so of yogurt into the commercial yeast starter, and a few days and few feedings later, it should help?