“Texture can be used to describe the rigidity or gel of the product. It might describe the surface texture or appearance, such as dry or glossy,” says Celeste Sullivan, technical manager—food applications, Grain Processing Corporation, Muscatine, IA. “It might describe the way the product falls from the spoon, such as long, stringy, gloppy. Texture provides a unique mouthfeel, or mouth coating, such as smooth or gummy or chalky.”
Viscosity, or thickness, indicates a product’s resistance to flow, but tells consumers much more. “Thickening is important for body and mouthfeel, as well as enhancing the cling,” according to Sullivan. “It might prevent separation or contribute to shelf life of the dressing. Suspension is important for particulates, vegetables and spices. Thickening and body relate to suspension.”
Starch search
Starches are composed of two polymers: straight-chain amylose and branched-chain amylopectin. Straight chains group together into bundles for a rigid gel that yields a stiff texture often prone to syneresis. Branched chains do not align as closely, resulting in less gelling, creamier texture and greater moisture retention.
Composed almost entirely of amylopectin, waxy starches are excellent low-cost thickeners for salad dressings, according to Rachel Wicklund, associate food scientist, Tate & Lyle, Decatur, IL. Dent corn starches’ amylose will contribute a slightly gelled texture that is especially desirable for spoonable dressings.
Starches are often modified to optimize viscosity, texture and stability during processing and shelf life. In fact, Wicklund suggests modified starches are used almost exclusively over native starches in the formulation of salad dressings. “Chemical crosslinking provides the starch granule stability to heat, acid and shear, all of which are present in a heat-processed salad dressing,” she says. “Substitution opens and expands the starch granule structure, which adds viscosity, improves the water holding and stabilizes the texture during the shelf life of the dressing.”
Starches can also be modified to be functional for dressings that are cold-processed. “Pregelatinized instant starches are manufactured by cooking and drying the starch, which results in broken granules,” Wicklund explains. “Granular instant starches, also referred to as cold-water-swelling (CWS), are processed in such a way as to swell the starch granule and dry it, while keeping the granule intact. The intact granules create a smooth, glossy appearance that is characteristic of many dressings, whereas broken granules may result in a rough, grainy appearance. The intact granule also has greater stability in the high-shear, low-pH system.”