By Robert L. Wolke
Wednesday, April 11, 2007
It's spring. Time to dig holes in the soil of a farm, garden or window box and insert little beads of matter that in a few weeks or months, with the aid of nothing but sunlight, air and water, will turn into food.
What a revelation that must have been to the first human who related a plant to its seed. A tiny seed can turn into a living, breathing (respiring) plant, from a diminutive radish to the proverbial mighty oak. A seed is the promise of a miracle.
Take a close look at a seed -- any seed, from a coconut to a lettuce seed not much bigger than the period at the end of this sentence. The mission of a seed, once part of a fruit, is to make another fruit. And so goes the cycle. Inside the seed's hard coat is the embryo of a whole new plant -- miniature root, shoot and all -- plus enough food to keep the embryo growing until it has external root cells to imbibe the water, leaves to absorb the carbon dioxide, chlorophyll to absorb the sunlight.
Though often dry by the time we encounter it, a seed is alive, albeit dormant. It may sleep for weeks, months or even years (centuries, in some cases), biding its time until it finds itself in a favorable environment, usually one with warmth and moisture -- although some require intense heat and must await a brush fire. Then it will germinate, thrusting its embryonic shoot through its coating and soon above ground. And whose spirits are not lifted by the sight of those first green shoots that emerge in the spring?
That said, we don't have to plant our seeds and wait for them to produce edible plants. Along with birds and many other animals, we can eat the seeds themselves for the nutrients they have been hoarding.
Nature creates and disperses vastly more seeds than will ever germinate, and this profligacy provides an important food source on its own. Grass seeds such as wheat, corn and rice are the primary nourishment of much of the world's human population. The seeds' carbohydrates break down into glucose, which can be used by virtually all organisms to generate energy at the rate of four calories per gram. The seeds' fats, at nine calories per gram, are an even more concentrated source of energy that is primarily stored for longer-term use.
These vegetable fats, so different from animal fats -- they're generally high in the "good" unsaturated kind -- supply us with the essential fatty acids we cannot manufacture in our own bodies. We routinely press or chemically extract the oils from some three dozen kinds of seeds, from almond to walnut. (Botanically speaking, a nut is a whole, hard-surfaced fruit containing a seed, although we refer to many of the seeds alone as nuts.) Along with two legumes -- soybeans and peanuts -- nuts are the richest in oils among our common edible seeds. Some of their approximate percentages of oil: almonds, 50; hazelnuts, 60; English walnuts, 65; peanuts, 50; and soybeans, 20. We use these oils for cooking and for making soaps, cosmetics, lubricants and, most recently, even automobile fuel (biodiesel, from restaurants' discarded deep-frying oil).
But man shall not live by fat alone. Nuts are also high in fiber. And many seeds play yet another important role in our foods: Even in tiny amounts they add spice, aroma and zest to otherwise humble dishes. Where would we be without our anise, annatto, caraway, coriander, cumin, fennel, mustard, nutmeg, poppy and sesame seeds?
Seeds were so valued by the authors of the Bible that in the story of Genesis (1:11-12), God awarded them third-day priority. "And God said, 'Let the land burst forth with every sort of grass and seed-bearing plant. And let there be trees that grow seed-bearing fruit. The seeds will then produce the kinds of plants and trees from which they came.' And so it was. The land was filled with seed-bearing plants and trees, and their seeds produced plants and trees of like kind. And God saw that it was good."
And so do we.
Robert L. Wolke (http://www.robertwolke.com) is professor emeritus of chemistry at the University of Pittsburgh and author of "What Einstein Told His Cook: Kitchen Science Explained" (W.W. Norton, 2002). He can be reached firstname.lastname@example.org.