A few underground stem vegetables are notable for retaining some crunchiness after prolonged cooking and even canning. These include the Chinese water chestnut, lotus root, bamboo shoots, and beets. Their textural robustness comes from particular phenolic compounds in their cell walls (ferulic acids) that form bonds with the cell-wall carbohydrates and prevent them from being dissolved away during cooking.
From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee. By permission of Scribner, a division of Simon & Schuster, Inc.