Acids help to weaken the surface proteins of meat, making the texture softer and tender. However, strong acids like lemon juice can make it mushy. Plain, unstrained, or Greek Yogurt is often used in Indian cuisine for flavor but also to tenderize. The natural organic and lactic acids created by the living cultures of bacteria when fermenting the dairy product can more gently marinate the meat. This is good news if you want to prep the chicken in advance to cook it the next day.