What cuases bitterness in sourdough?

Hi, long time ago I had a firm starter that, although 3 months old and well growing, developed a lot of bitterness in the bread. I dropped that starter and passed to a liquid one, but the curiosity remains because a lot of people keep on lamenting the bitterness. What causes it? Nico

Not sure what you mean by "bitterness" (sour?), but here's some good reading on the topic of fermentation and the resultant acids.

http://www.thefreshloaf.com/node/10375/lactic-acid-fermentation-sourdough

I mean bitter, not sour ;) I know that thread, but there's no explanation of the bitterness I experienced. Maybe better ask directly to her.

mini

especially for whole grain flours. The oils in whole wheat flour, for example, make it turn rancid quickly and can result in bitter-tasting loaves.

- Jackie

Very interesting, I'll do that test. Yet I'm not sure that in my case the flour was old; moreover it was white, not wholemeal. The taste didn't feel like rancid, but it's still possible of course.