Soaking Pasta - Food Science - Exploratorium

Cooking instructions on a typical package of dry spaghetti read as follows:

• Bring 4 quarts of water to a rolling boil.
• Add 1 pound of dry spaghetti.
• Cook 10–12 minutes, stirring frequently.
• Drain.

This method is straightforward and relatively foolproof. However, it uses large amounts of both water and energy. Imagine you’re camping and short on cooking fuel. Is there a more energy-efficient way to cook that pasta?

Two things happen when dry pasta cooks: 1) it rehydrates by absorbing water and 2) the starches and proteins in the pasta flour break down. When you cook pasta in boiling water, it seems like these two processes go together—but they don’t have to. Pasta absorbs water at any temperature; it just does so quicker at higher temperatures. Dry spaghetti rehydrates in about ten minutes in boiling water, and in around two hours in room-temperature water, so you can soak your spaghetti for a couple of hours to complete the first half of the process without using energy to boil water. Once it’s rehydrated, the spaghetti will be soft and pliable (shown in the photo below), but you wouldn’t want to eat it—it’s not fully cooked.

To be fully cooked, the starches in the spaghetti need to break down, a process called starch gelatinization. The proteins in the flour also need to be broken down, or denatured, from tight globs to relaxed chains that humans can easily digest. Both of these processes require heat: they occur somewhere in the range of 55–85°C (130–185°F), which, crucially, is below the boiling point of water (100°C, 212°F). These reactions require some water, but far less than boiling a pot of spaghetti the traditional way does—as long as the spaghetti is in some liquid and heated to 85°C, it will cook completely. This method also takes less energy; the pasta is already hydrated, and can cook in just a minute once it’s been heated. You can tell when the necessary reactions have taken place by noting the color of the pasta. After rehydrating but before it’s been heated, the pasta looks pale and opaque. After heating, the spaghetti is yellowish and translucent, like spaghetti cooked the traditional way (see photo below). It should taste the same too, since it’s now fully cooked.

With a little planning ahead, you can save yourself the trouble and energy cost of heating a large pot of boiling water to cook dry pasta. In fact, there’s no need to heat any water at all. Simply heat your favorite sauce, add the rehydrated pasta, and let it sit for a minute. Dinner is served!