At a fundamental level, bread is a simple thing. All you need to make a loaf are flour, water, salt and yeast, and some time and effort. Any alteration in those basic ingredients can have far-reaching effects on the final result. For example, changing from white to whole-wheat flour results in a denser, coarser loaf with a strong, wheaty flavor. Substituting milk for the recipe's water makes further changes, sweetening and softening the bread.
Why Wheat Bread Is Different
Switching from white to whole-wheat bread involves a number of changes, aside from the obvious darkening of its color. All-purpose white flour has the grain's germ and bran milled away, while whole-wheat flour includes them. The oils, fiber and B-vitamins in wheat flour make it more healthful than white flour, but they also complicate your life as a baker. For one thing, those oils are prone to oxidation and spoilage. That's one reason why wheat bread sometimes has an unpleasantly bitter edge to its flavor. Wheat bread also tends to be denser than white, because the sharp-edged flakes of bran slice through the strands of gluten that give your bread its rise.
Better and Better
Your loaf of bread requires water to activate the yeasts and stimulate the development of gluten in the dough. Plain water works just fine, but as an alternative you can turn to milk. It's mostly made of water, so it's equally effective at moistening your dough, but it brings more to the table. Milk adds noticeably to the bread's protein levels, and adds a number of other nutrients including vitamins A and D and minerals such as calcium. If you're making wheat bread for its health benefits, that alone makes milk worthwhile. But milk also plays a structural role.
Crust and Crumb
Switching from water to milk has an immediate impact on the texture of your loaf's crust and crumb. Milk's proteins lend the dough strength and help the gluten strands support the loaf's weight. It also contains small quantities of fat, natural sugars and emulsifiers, which help soften the bread and its crust. Instead of a dense and crusty loaf, wheat bread containing milk is softer and more delicate. Its hint of natural sweetness improves the bread's flavor, masking any bitterness from the oils. The sugars in the milk also feed and stimulate the activity of the yeast, helping produce better rise in your bread. Finally, the sugars and proteins the milk help contribute to the development of a richly golden-brown crust.
The Enzyme Thing
Some bread recipes, especially older ones, suggest you should scald the milk before using it to bake bread. That's partially a holdover from the days before pasteurization, when raw milk might carry dangerous foodborne diseases. That's no longer an issue, but a second factor still applies. Natural enzymes in your milk have the effect of weakening gluten, and can take away some of the dough's natural lift. The effect might or might not be noticeable, depending on your flour and the dairy's processing methods. Try identical batches, one with plain milk and one with the milk scalded and then cooled. If there's a noticeable difference, keep using the scalded milk.
A Few Further Tips
If your goal is to have a soft loaf of whole-wheat sandwich bread, you can take a few other steps to soften the bread. A tablespoon of oil or an egg -- or both -- will enrich the bread and soften it noticeably, giving it a finer texture. To lighten the bread and help it rise more effectively, look for vital wheat gluten at a bulk foods store, and add a spoonful or two to each batch. This strengthens the gluten and counters the deflating effect of the bran, giving you a lighter and higher loaf. Wheat flour is more absorbent than white flour, so if you're adapting a white bread recipe you'll need to increase the quantity of liquid slightly.
- On Food and Cooking: The Science and Lore of the Kitchen; Harold McGee
- Epicurious: Bread Recipes and Tips
- Healthaliciousness: Nutrition Facts Comparison Tool -- Whole Milk
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