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Many recipes call for mixing different ingredients together, but sometimes you need special techniques to combine ingredients that don’t mix easily.
In certain foods called emulsions, like mayonnaise, you can force oil and water to mix. To make an emulsion, you need to add a third ingredient (such as eggs, in mayonnaise) that sticks to both water and oil, holding the mixture together.
You can even make mixtures with an invisible ingredient: air. With air whipped into a liquid to make bubbles, foams (like frothy milk on cappuccino) add new flavors and textures to food. But eat quickly – as the bubbles pop, the foam disappears.

INGREDIENTS

• Balsamic vinegar
• Vegetable oil
• Mustard
• Two small jars
with tight caps

DIRECTIONS

Add 2 tbsp. balsamic vinegar to each jar.

Add 5 tbsp. vegetable oil to each jar.

Add 1 tsp. mustard
to one jar.

Cap both jars,
shake well,
and observe
the mixtures.

WHAT'S COOKIN'

When you shake the jars, the vinegar breaks up into small droplets that can mix with the oil. But over time, these droplets combine again, and the vinegar sinks down to the bottom. The mustard makes the emulsion last by keeping the vinegar droplets from coming back together.