Not Just Filler

• If you've ever tried to make a meatloaf without any fillers, you already understand that ingredients such as milk and breadcrumbs play a significant role in the loaf's texture. An all-meat loaf is dry and coarse, lacking in flavor and moisture. The combination of breadcrumbs, milk and egg -- called the "panade" in classical cuisine -- civilizes the dish, binding the ground meat together, smoothing its texture and helping it retain moisture. The proteins in the milk and eggs, combined with the starches in the breadcrumbs, create a gel that traps moisture in the loaf and prevents its natural juices from escaping.

Soy Versus Dairy Milk

• Dairy milk is made up mostly of water, with a small percentage of fat and a healthy allowance of proteins, vitamins and minerals. Soy milk, despite its origin in beans, is surprisingly similar. It's slightly lower in fat and calories, contains none of milk's cholesterol, and is slightly higher in protein than dairy milk. Its vitamin and mineral content is different from dairy milk's, but each is a healthful and nutritious beverage in its own right. In meatloaf, they're functionally identical. Substituting soy milk for the dairy milk will have no detectable impact on the finished dish, as long as you remember to use plain -- not sweetened or flavored -- soy milk.

Making Your Own

• If you avoid processed foods, or just prefer to make your own, it's not difficult to make soy milk in your own kitchen. Start with dried soybeans, soaked or par-cooked so they can be pulverized. Process them in your blender with hot water for a few minutes at high speed, until they make a milky, grainy liquid. This pulverizes the beans, so the water can extract their fats, proteins and nutrients. Strain the liquid through several layers of cheesecloth, squeezing as hard as possible, to extract the liquid. Simmer the resulting soy milk for 20 minutes to minimize its "beany" flavor, then refrigerate it for later use.

A Bit of a Stretch

• If you choose to make your own soy milk at home, don't be in a hurry to discard the chunks of soybean you've got leftover in the cheesecloth. Although the milk-making process extracted some of its vitamins and minerals, this soy meal -- often referred to by its Japanese name, okara -- still retains lots of fiber and nutrition. Use it to stretch the ground beef in your meatloaf, adding protein with minimal extra fat. Combining 1 part okara to 4 or 5 parts ground beef is all but undetectable. Freeze any extra okara for later use in other dishes.