Hello R!
If you fry the garlic flakes for a long time, definitely they will taste bitter. Pour some oil in the kadai and fry the garlic flakes in it on slow fire. After a few seconds, the color will slightly change and you can feel the garlic flakes very light if you take them in the spoon. You can take away them in that stage. You will feel the difference if you grind them for a chutney recipe.