I find that my sourdough starter’s smell is noticeably more yogurty (lactic acid) and less tangy (acetic) when I add a tiny amount of food grade calcium to the water. There’s a similar effect on the final bread as well, but there are other factors (eg fermentation time/temperature) that probably have a bigger effect on the final loaf.
I believe the calcium feeds the lactic acid producing bacteria, favoring their growth.