Monday, February 20, 2012
Is chia (Salvia hispanica L.) a grain or a seed?
People have been calling chia a grain, but that simply is not correct. It is a seed. Here is an explanation of the difference between a grain and a seed from a botanical standpoint.
A grain has its fruit wall and seed coat fused, so you cannot separate them. So each grain is technically an individual fruit (called a caryopsis) containing a single seed. When processed, the fused ovary wall (fruit coat) and seed coat are the "bran," the embryo is the "germ," and the endosperm is the part full of carbohydrates that we eat. Of course, if you eat whole grains you get the bran, germ and endosperm together. So on an ear of corn or the head of a grain, each grain is an individual ovary with a seed inside.
Seeds are fertilized/ripened/mature ovules (that are found within ovaries), and the seed coat is made of the maternal tissue called integuments. The ovary is part of the flower that contains the ovules. So in fruits, like watermelon, the rind and what we eat is all ovary, and the "seeds" are the black things inside (to confuse matters, the little white things are ovules that did not get fertilized). Most plants have true seeds, but in some plants, like wheat, rice, and corn what we see and use is really the fruit and seed combined. Interestingly what have often been called ancient grains (amaranth, quinoa and buckwheat) are actually seeds!
Chia grows multiple seed heads on a single plant, within each head the seeds are singular within a capsule or husk, which is formed at each flower. If you hand strip the head from the plant, the capsules come off, rubbing them in your hand the seed comes out. The husk is what is left of the ovary (fruit) coat. You have just a single seed per ovary in chia, which is not uncommon in plants. The capsule or husk is the ovary, with the individual seeds coming from ovules in the ovary.
So in summary: Seeds just have a seed coat, embryo and endosperm/cotyledons, whereas grains also include the ovary.
Hence chia (Salvia hispanica L.) is technically a seed, and because if the high oil content, is an oilseed.