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There’s no reason to worry — it’s just a few molecules that have changed places. It’s a matter of… efflorescence.
A few years ago, a small bakery had a problem. A day or so after baking chocolate chip cookies, the chocolate chips would develop a unpleasant white filml.
Confused, the bakery owner contacted Richard Hartel, professor of food science at the University of Wisconsin, looking for an explanation.
Hartel studies foods like chocolate and ice cream, and receives questions like this constantly, says . So what was going on with those chocolate chips?
Chocolate can appear uniform and solid to the naked eyebut if we looked at it under a microscope we would see that it is actually a particle mixture of cocoa, sugar crystals and (in milk chocolate) milk powder, all held together by cocoa butter.
Sometimes, some of these ingredients moveand this is what makes the chocolate white, or “efflorescent”. There are two main types of efflorescence in chocolate: sugar efflorescence and fat efflorescence.
Sugar efflorescence: the refrigerator effect
When we take a cold chocolate bar out of the refrigerator and leave it unwrapped on the counter, water from warmer air surrounding can condense on the cold surface of chocolate, like condensation on a cold window pane.
This humidity dissolves part of the sugar on the surface of chocolate. When the water evaporates, the sugar is left behind in the form of tiny crystalscreating a white, powdery coating.
This is called sugar efflorescence. Chocolate is still good to eat, it’s just not very pretty.
To avoid this, Hartel says that “the chocolate must be well wrapped to be stored in the refrigerator or freezer, and then allowed to warm to room temperature before unwrapping”, which prevents condensation from forming on the chocolate.
Fat efflorescence: when chocolate becomes stale or hot
Chocolate can also turn white even when not stored in the refrigerator. “Imagine thatleaves a chocolate bar in the car on a hot summer day,” says Hartel. “Once it cools, it often develops a dull, white coating.”
This dull white covering is called fat efflorescenceand it happens when the cocoa butter inside chocolate slowly changes shape.
Cocoa butter is made up of fat molecules that can be organized into six different crystal formswhich chemists call “polymorphous“.
The chocolate makers want a special form, the so-called Form V, because it gives the chocolate that special shiny appearance and that texture that melts on the tongue. They create this shape by carefully heating and cooling the chocolate in a process called temperagem.
But over time, especially in hot locationslike a sunny windowsill or a hot car, Form V can transform in a more stable form called Form VI. These larger crystals scatter light rather than reflecting it, making the chocolate appear dull and white.
Hartel explains that fat efflorescence “can form in chocolate practically any temperaturealthough it generally slows down as the temperature drops.” This is why chocolate brands recommend storing chocolate in a fresh atmosphere.
Some chocolates are more susceptible to fat efflorescence than others.
In a 2008 study, scientists from Canada and Sweden observed chocolate under a microscope. The study authors found that chocolate with a microscopically rough surface was more likely to form fat efflorescence. All those little cracks create more places for fat crystals to grow.
Os filled chocolatessuch as those with peanut butter centers, are even more likely to erupt. The liquid fat from the filling can move into the chocolate shell, speeding up the process and making the chocolate soft and sticky.
In conclusion… if your chocolate has suddenly turned white, there is no reason to worry.
