Yes, you can eat 20-year-old spices, but they likely won't add much flavor to your food.
While spices don't "expire" in the sense of becoming unsafe to eat and making you sick, they do lose their flavor and potency over time. According to Serge Krikorian, chef and co-owner of Vibrant Occasions Catering, "they do lose their potency and flavor over time," although this process can take years (20-Feb-2024). So, while the spices might not harm you, they probably won't enhance your dishes either.
Here's a breakdown:
- Safety: 20-year-old spices are unlikely to cause food poisoning or make you ill.
- Flavor: The primary issue is the loss of flavor and aroma. The volatile oils that give spices their distinctive characteristics degrade over time, especially when exposed to air, light, and heat.
- Effectiveness: They won't have the same impact on your cooking as fresher spices.
Therefore, while technically edible, replacing 20-year-old spices is recommended for optimal flavor in your cooking.