Nanoparticles are present in many foods, including:

Milk: Casein micelles, which are nano-sized protein spheres, are naturally present in milk.

Sweets and baked goods: Titanium dioxide (TiO2) is often added to these foods as a white pigment.

Salt, spices, and icing sugar: Silicon dioxide is added to these foods to improve their flow.

Green tea: Ground to nano-sized particles to improve its antioxidant properties or flavor.

Nanoparticles can also be intentionally added to foods for a variety of purposes, including:
Delivery systems
Nanoparticles can be used to deliver nutrients, flavors, colors, preservatives, and nutraceuticals.
Modifying food
Nanoparticles can be used to change the appearance, texture, or stability of food.

Nanoparticles can also be present in foods as a result of food processing, such as grinding, homogenization, and cooking. Nanoparticles can also leach into food from packaging materials.

Some scientists have raised concerns about the safety of nanoparticles in food. For example, titanium dioxide has been shown to accumulate in the liver, spleen, kidney, and lung tissues of rats.