I have done sourdough for ever. The secret is the more you use it the more the sour comes out. Feed it ,place back the amount you have taken out. Refrigerate it. as you keep pulling out the starter to make a new batch you will start to see "Grey liquid" on the saved starter. This makes your "sour". Stir it into the starter. it and carry on. At some point if it gets really sour my recipe includes adding baking soda to tone it down. Also when you need to stop using the sour dough starter, freeze it. Does well, or you can spread it out on wax paper or parchment paper and let it dry. Crumble it up and add 1 cup of liquid, let it sit until it is all rehydrated and then start the process all over again for baking bread. Also never use anything metal with it. It will take the taste of the metal.