Name: Kids DIY Ketchup
Total time: 13 h 30 min
Ingredients: 2¼ pounds grape tomatoes; 1 garlic clove , peeled; ½ cup red wine vinegar; ½ cup packed dark brown sugar; 2 teaspoons table salt; ½ teaspoon pepper; Pinch ground allspice

Why This Recipe Works

This recipe takes everything we love about store-bought ketchup and packs in even more tomato flavor with fresh tomatoes. Cooking all of the ingredients on the stovetop lets their flavors meld, while blending and straining leave you with a smooth sauce. As their ketchup cools, impress your young chef with some ketchup science. While they might be used to seeing store-bought ketchup in a squeeze bottle, for most of the 1800s and 1900s it was served in a glass bottle. When you turn a glass bottle of ketchup upside down, the ketchup stays stubbornly in place. But if you give the bottle a good whack, you get a ketchup landslide on your plate. It’s hard to get ketchup out of a glass bottle because ketchup is a non-Newtonian fluid. Newtonian fluids (named after famed scientist Sir Isaac Newton), such as water and oil, pour in a steady, even stream. Non-Newtonian fluids don’t behave as nicely. Some of them, such as ketchup, mayonnaise, and toothpaste, won’t start flowing unless you apply a force to them—like that whack on the bottle. The added force changes ketchup’s texture from thick to thin.

Before You Begin

You can use cherry tomatoes instead of the grape tomatoes, but because they are juicier, you will need to cook them a little longer. In step 3, increase the cooking time to 12 to 15 minutes.

Instructions

Add all ingredients to 12-inch nonstick skillet. Use rubber spatula to stir to combine.

Bring tomato mixture to simmer over medium-high heat (small bubbles should break often across surface of mixture). Reduce heat to medium and simmer, stirring occasionally and scraping bottom of skillet, about 20 minutes.

Reduce heat to low and continue to cook until almost all liquid has evaporated and rubber spatula leaves distinct trail when dragged across bottom of skillet (see photo, “Step-By-Step: Leaving a Trail,” below), 5 to 10 minutes. Turn off heat. Let mixture cool for 15 minutes.

Ask an adult to carefully transfer tomatoes and liquid to blender jar. Place lid on top of blender and hold lid firmly in place with folded dish towel. Turn on blender and process mixture until smooth, about 1 minute. Stop blender.

Set fine-mesh strainer over medium bowl. Pour tomato mixture into fine-mesh strainer. Use rubber spatula to stir and press on mixture to push liquid through strainer into bowl. Discard solids left in strainer.

Let ketchup cool completely, about 30 minutes. Pour ketchup into jar with tight-fitting lid. Place in refrigerator until chilled and thickened, at least 12 hours. (Ketchup can be refrigerated for up to 1 month.)