Is butter a neutral substance

Answer 1

My guess, knowing something about the diary butter making process (charning acidified milk = buttermilk) is that the pH is somewhat lower than 5, not neutral anyhow, but slightly acid, though you can't taste it in the 15% water phase. pH in the 85% fat phase is not an issue because pH is defined for aquous solutions and acids do NOT ionise or protolyse in fat (hydrophobic).

When butter becomes old and rancid the pH gets lower and is tastable!