Many recipes that call for nuts or seeds specify toasted nuts or seeds. What this means is that you are expected to have bought the nuts in a raw state (not roasted) and toast them yourself. Toasting helps bring out the flavor of nuts or seeds, making it deeper and richer. Toasting, in essence, makes nuts taste more nutty.
The reason toasting does this is because of chemical reactions that take place, just like they would if the nuts were roasted. It brings oils to the surface, and also initiates the Maillard browning reaction of sugars and proteins. As well, it darkens the color and makes the nuts or seeds more crisp. If the nuts are slightly stale, toasting will freshen them up! In fact, even if the nuts or seeds have already been toasted, or roasted, it will help to toast them a few minutes yourself, to bring out their flavor and freshen them up in case any staleness has begun. There are two basic ways to toast nuts, and the method you choose will probably depend on the amount of nuts you need.
Toasting Nuts (or Seeds) in a Skillet
For most home cooks, the skillet method of toasting will probably be preferable. This works best if you only need a small amount of nuts or seeds. Place a heavy skillet on medium heat and place the nuts or seeds you want to toast in the pan. Do not put in more than will just cover the bottom of the pan. You do not want more than one layer, so if you need to toast a large amount with this method, do it in batches.
While the nuts are toasting in the pan, turn or toss them constantly so that they do not scorch or burn. When you start to notice a nutty, caramel, sweetish smell wafting up from the nuts, they are ready. This will take from five to seven minutes, depending on the level of heat. If you want to achieve a deeper toast without burning the nuts and seeds, turn the heat down a bit and toast them more slowly. The skillet method is preferable to the oven method below because you are able to constantly monitor you nuts and smell them as they are toasting, so that you’ll know when they are toasted to perfection. However, a nice quality thick skillet or frying pan will work much better. Also, a gas flame stove will work better than an electric one.
Remember, do not oil the skillet or spray it with cooking spray. This is toasting, not frying, and nuts and seed already have plenty of their own oils. They will not stick.
Oven Method for Toasting Nuts or Seeds
Preheat the oven to 325 to 350°F. Spread the nuts and seeds in a single layer on a sheet pan. Toast the nuts in the oven for five to ten minutes, checking often to monitor their color. Look for a light brown color but do not push it way past into a dark brown, as the residual heat will continue to darken the nuts and you could end up with bitter flavors. Well toasted nuts and seeds should have a nice nutty and sweet flavor, not a bitter one. Once your nuts or seeds are done toasting, remove them from the hot pan immediately so that the heat of the pan does not continue to cook the nuts. The advantage of oven toasting is that the nuts toast evenly so they are less likely to scorch on one side. However, as long as you constantly move your nuts and seeds during the stove-top method, there is no reason to fear scorching.
Do I Have to Toast Nuts?
No, you do not absolutely have to toast nuts, even if a recipe calls for it. However, your dish will probably not taste as good as it would have, and, as well, the nuts will not be crisp. Most chefs almost always toast nuts and seeds before using them in a dish. I would advise that, even if your recipe does not specify that you toast the nuts and seeds, you go ahead and do so to bring out their flavor.