What do most packaged breads (even those claiming to be whole wheat or multigrain), as well as many pastas, baby foods, and frozen French fries have in common? They're highly or ultra-processed foods.

Foods don't have to be prepackaged snacks, desserts, or sauces to qualify as highly processed.

If you're wondering about the level of processing of foods in your refrigerator or pantry, there’s now a simple test to identify those you should not buy again.

According to the Tufts University Food Is Medicine Institute, you can drop a piece of a starchy food into a glass of water and then go back to look at it in three to four hours, and you'll know if it's highly processed or unprocessed.

If the food has turned into a mushy blob that's floating in cloudy water, it's highly processed.

The mushiness happens because cellular walls of the foods’ fibers are not intact. Therefore, it dissolves quickly. And it will do the same in your digestive tract.

In contrast, if the food is soggy but undissolved you know that when you eat it the food will take a good while to digest and will not spike blood sugar. It's essentially unprocessed.

Another good measure is to read nutrition labels. Foods should contain at least 1 gram of fiber for every 10 grams of carbs, says Dr. Dariush Mozaffarian, head of the institute. If a food doesn't have that fiber-to-carb ratio, don't buy it.

For great recipes using fresh, unprocessed foods, check out my "What to Eat When Cookbook."