Fast-food chains waste no time vaunting their all-beef hamburger patties, a measure intended to quell any cynical speculation about what they use bind their ingredients. And if you're preparing a meal at home from scratch, you exert full control over what goes into your food, and have the liberty to add binders and other ingredients as you see fit. Binders help tie ground and minced ingredients together, giving them a smoother, more appealing texture and helping them retain moisture. Depending on your priorities, you can choose from several options.
The Mighty Egg
Eggs lead the way as the most useful of binders, because of their complex chemistry. The rich yolks contain natural emulsifiers, such as lecithin, which bind water-based and fat-based ingredients, and help create a smooth texture. The egg's whites, rich in protein, coagulate during cooking and help give substance and structure to the finished food. Eggs also lend richness and flavor in their own right, adding to their usefulness.
Sticky and Starchy
Starch-based binders also play multiple roles in your food. Starches act by forming an invisible web that immobilizes liquid into a sort of gel, which in turn lends structure to your dish. It also keeps the moisture in your foods, another highly desirable result. Most starches can be used in this role, including bread and cracker crumbs, oatmeal, cooked rice and even plain old wheat flour. They'll take the moisture they need from your meat and other ingredients, though, so they're best used in conjunction with eggs, dairy products or other binders.
The Dairy Case
It might not be the first option that springs to your mind, but milk is also useful as a binder. Milk's proteins, especially its casein proteins, coagulate during cooking in much the same way as the proteins in egg whites. The milk's liquids, for their part, add moisture and help activate the binding effect of starch-based ingredients. Evaporated milk, which contains less liquid and therefore a higher percentage of protein, proves especially effective.
Gels and Gums
If you need to avoid eggs and dairy for dietary reasons, you'll need to look a little farther afield. One alternative protein-based binder, gelatin, works with foods that will be served cold or at room temperature. Gum thickeners such as guar gum and xanthan gum can also take over the binding role and are often used that way in commercially manufactured foods. Even common fiber supplements such as inulin and psyllium can be useful. Anyone who's ever whisked either substance into a glass of juice understands how effectively they bind up liquids.
Advanced chefs and food manufacturers can call on a number of additional binders, as needed. For example, an enzyme called transglutaminase acts as a sort of glue to bind meat cells together. Alginates and carrageenan from seaweeds, and whey or casein proteins from milk, play a role in the industrial production of foods as diverse as ice cream and deli meats. Even some forms of cellulose derived from wood are used. This isn't as strange as it sounds, because it's very similar to the insoluble fiber you'd find in beans, oatmeal and other familiar foods.