Nature created oil and water specifically so they would not mix, then peppered the food supply with a whole range of other ingredients to help the two mix well
Technology is helping food companies create efficient emulsifiers—among the most critical aspects in the formation of successful emulsion-based food and beverage products. Without emulsifiers, most of the sauces and condiments consumers enjoy, and many of the beverages, would not be possible. When thinking of emulsifiers, one has to include desserts, dressings, dips, creams, milk-based products, sauces, and even soft drinks.
In principle, food emulsions are one of the simplest forms of oil-in-water emulsions, consisting of small oil droplets dispersed within an aqueous medium. There are, however, a number of challenges associated with developing successful commercial products. Ingredients appropriate for emulsion-based products to be marketed as healthful and natural also tend to fluctuate and cause changes in the properties and stability of finished products.