I’m in the UK. I have tried making sourdough bread twice now and seem to have come up against the same problem on both occasions. I’ll describe the second attempt…
My starter was about 10 days old since inception. I took it out of the fridge in the morning, and fed it immediately. Within two and a half hours, it had doubled and was bubbling well, so I decided it was a good time to use it within the next 90 minutes.
I mixed my flour and water (560g of 100% Allinsons white bread flour, with about 72% hydration) for a minute or two (the water had a tablespoon of sugar and a tablespoon of olive oil added before mixing). I then let it autolyse for an hour before folding in 100g of my starter (thick batter consistency) and 12g salt.
Over a further two hours, I carried out 4 stretch and folds. The gluten developed well and by this time, the dough was holding some shape reasonably well, strong and elastic, and coming away from the sides of the mason bowl. No other kneading was carried out.
I then left it to prove at about 24/25 degrees C for a further 5 hours, covered in cling film.
When I looked next, bubbles were appearing on the top, and the volume of dough had increased by a half, but the surface was not domed, and the dough had lost its structure and turned sticky again (almost looking like gloopy honeycomb, if that paints a picture). As soon as I tipped it out of the mason bowl onto a floured surface, of course it just collapses into a spongy mess.
This is almost exactly what happened first time – it is the batch rise that seems to scupper everything. The only option I have at this point is to add a load of flour to make it even partly workable, but there’s just no surface tension left in the dough at all (as I'm used to with a dry yeast), and there's no way I can lame the dough, so whilst it bakes, the end product is on the dense side and poorly aerated.
Any thoughts on where I might be going wrong ?
I think you might be going too fast in the initial stages. If I am making any type of sourdough bread i give my starter a feed first thing in the morning and leave it until the evening (or at least 8 hours) when I then do an overnight ferment with the aount of starter I need for the loaf, some water and some flour (quantity depends on the sixe and type of bread I am making. The next day (or day 2) I mix in the rest of my flour water salt etc.. and fold and stretch. etc...(leaving an hour between each fold and stretch and doing it about four times. I then quite often, if I'm making a white or wholemeal loaf leave it in its baneton for another night in the fridge ( to develop even further) and put it in the oven on day 3! Even with a simple Rye loaf I feed in the morning, do an overnight ferment and mix and bake on day 2. Hope this helps.
As an after thought, why are you adding the sugar? It shouldn't be necessary, you only need four, salt and water for sourdough bread generally.
I am a total beginner, only started during lockdown, however,I have experienced your problem and I believe it is over proofed!!! In this warm weather, after my last stretch and fold, I go to pre-shape when it has risen about 20% normally about 90 mins to 2 hours.