When it comes to the classifications of nuts, nuts have a bit of an identity crisis. Botanically, a nut is a fruit, but botanists will tell you that some of what are labeled "nuts" on your grocer's shelf are misidentified. They aren't true nuts in the scientific sense. Many of the nuts in your local market are considered seeds or kernels, and some nuts don't fall into either category. For example, peanuts are considered legumes, like peas.
However, if you ask chefs or registered dietitians, they would tell you not to be so picky. To them, taste, texture, and nutritional content matter much more than the intricacies of scientific classification.
Botanical Nuts and Bolts
Because true nuts are scientifically categorized as tree fruits, that puts walnuts in the same category as apples. The two fruits differ in the way their outer casing, or ovary, ripens. With a nut, the ovary hardens as it ripens and becomes a shell. Inside the shell, the fruit's seed, or kernel, develops. With certain types of nuts, that seed becomes an edible treasure. (With other fruits, the ovary develops into a more delicate skin that protects the soft flesh.) Although nuts contain seeds, most seeds are not, from a botanical standpoint, true nuts. Most of the "nuts" you eat (except for peanuts) are actually the seeds of tree nuts.
There are many classifications of tree nuts, but most of them don't have delicacies hidden within their shells. Of the 11 types of nut trees -- wingnut, beech, oak, stone oak, alder, birch, hornbeam, walnut, pecan, chestnut, and hazelnut (filbert) -- only the last four produce edible seeds. The beauty of a tree nut is that the shell acts as a natural preservative and protects the seed from disease and from the elements.
From a purely culinary standpoint (as well as from the perspective of this book), the definition of a nut is painted in much broader strokes. Food experts classify nuts as any edible kernels encased in shells.
In our next section, we'll discuss one of the most popular nuts -- almonds.
To learn more about nuts, see: