So, I have read that for a more sour bread to use less starter. I did just that but, the bread was not as sour as others I have made nor the one I made the day before with 5x the starter.
Recipes used:
500g flour
314g water
50g starer
10g salt
500g flour
344g water
250g starter
12g salt
-Mix rest 1 hr, mix it salt and remaining water rest 1 hr and then 4 stretch and fold every 30 min and put into refrigerator.
-First dough was left in fridge for almost 36 hrs then rested 2 hrs before oven
-Second dough was left in fridge for 24 hrs then rested for 1 hr before oven
**Starters are at 100% hydration
The more mature, the colder the conditions it's kept in, the longer the gap between builds, etc. etc., the stronger it will be.
Was the starter ripe when you used it? What flour did you use? Have you tried a lower hydration? There's a long list of factors that can influence sourness.
It's not just a matter of cold retarding.
It might be worth putting a couple of hours aside to use TFL's search tool and give yourself an in-depth education on how to develop sourness in starters and doughs.
1. use a levain rather than just starter and put in all of the liquid
2. use your first formula, include 25% of the total flour in the levain plus all of the water plus your 25g of starter
3. ferment the levain for at least 10 hrs and preferably 16 hrs at a warm room temperature (78-86°F)
4. add the remaining flour, combine, autolyse for 20 min, add salt and mix until you are happy with gluten development.
5. bulk ferment warm, divide, rest, shape, proof at room temperature, bake, cool
6. tell us how it tastes.
7. repeat using an 8 hr/overnight retard/proof at ~65°F if you can arrange it. Lower temp for longer time up to 24 hrs @ 40°F but watch it so that it doesn't over proof.
8. if that is not sour enough for you, replace 5-10% of the flour with white whole wheat (or red whole wheat if you like) but the crumb will be more dense.