I've talked about texture quite a bit in this blog, including the importance of texture as a sensory property, my talk on texture at the Culinary Institute of America and the use of trigeminal irritants to create novel texture perception (which, I assure you, parts 2-n will be posted soon!). One area that I haven't dabbled in too much is the use of gums and hydrocolloids to create texture. These are substances that are added to foods to emulsify and create interesting mouth feel and diversity in texture, raising interest in the item being consumed. The picture to the left is raw, unprocessed gum arabic, for example. It is used as a thickener in many food items.
Two fun properties of thickeners that are of interest to food scientists and culinarians are both shear thickening and shear thinning. Basically, a thickener that exhibits shear thickening behavior thickens under stress. The following video shows that under stress (the stress of the "hit" from these feet) that corn starch becomes a solid. Once the initial stress subsides though, a person can sink.
Ketchup, on the other hand, is a perfect example of a shear thinning fluid. This is the reason you beat the side of the (rigid) ketchup container with your hand to get it out - you apply stress, and the fluid thins and begins to flow.
Culinarians have been using starches and gums forever, readily available from suppliers such as TIC Gums (among others). However, recently the molecular gastronomy movement has invigorated the desire to assemble familiar foods in novel ways. Famous blogs such as Khymos and Ideas in Food have popped up with pages and pages of illustrations of applications of these substances to create amazing food. And just today, a fantastic (free) book was released by the people responsible for Khymos going over all of the different hydrocolloids used in food, their properties, and example recipes. It is a highly suggested reading and reference material, and is available here: Texture: a hydrocolloid recipe collection, edited by Martin Lersch.