Yes, spices can definitely be over-toasted. Over-toasting can result in a bitter or burnt flavor, ruining the intended taste profile.
Toasting spices is a fantastic way to enhance their flavor and aroma. The heat releases essential oils, making them more potent and complex. However, this process requires careful attention. When spices are exposed to heat for too long or at too high a temperature, the delicate oils can burn. This burning process transforms the pleasant, aromatic compounds into bitter, acrid ones. The result is a spice that tastes unpleasant and can negatively impact the overall flavor of your dish. The key is to toast spices gently, using low to medium heat and constantly monitoring them. You'll know they're ready when they become fragrant and slightly darker in color. Remove them from the heat immediately to prevent burning.
Use a dry pan over low heat and continuously stir or shake the pan while toasting spices. This ensures even toasting and prevents hot spots that can lead to burning.