Since tzatziki is a yogurt-based sauce, the brand of yogurt you buy is really important to the taste of the sauce. Some are tangier than others. Using those may make the tzatziki dip taste more sour. That's why we don't recommend blending the lemon juice in with the yogurt and other ingredients. That way, you can taste the yogurt sauce after it's blended and change the amount of lemon juice if needed. If you taste it and think the tzatziki is sour from the yogurt, add less lemon juice.