White stuff on your dates?

What you see: White patches on dates you’ve had for a while What it is: Sugar crystals! Eat or toss: It’s just sugar. The dates will probably be harder and drier than when you first bought them. Steer clear if you smell anything off, but as long as you don’t see fuzzy mold, which is quite unlikely, you should be fine. You can even heat them in a pot with a little water to freshen them up.

The story: Dates, packing lots of sugar and relatively little moisture, are generally quite shelf stable. But if they’re stored for too long and exposed to lots of changes in temperature and humidity, their surfaces can develop a white and crusty landscape.

Such “sugaring” or “sugar bloom” can also show up on raisins, particularly on the ridges of the wrinkles. The Raisin Production Manual notes that this is likely "because the skin’s greater permeability in this area allows the migration of soluble solids to the exterior.”

Indeed, take a close look at the date pictured above, or the ones you may be contemplating eating. You'll probably notice that the snowy sugar dots concentrate on the tops of ridges.

You can even revive dried out dates and eliminate the sugaring at home. A little water soak will help, possibly with a little heat from the stove, advises Elhadi M. Yahia, a professor at the Autonomous University of Querétaro in Mexico who has written about the science of harvesting and processing dates. Before the water gets hot enough to boil, the sugar crust should dissolve away and the dates should soften, he said.

Fungal growth is unlikely The white crusty spots you might find on dates in your kitchen are highly unlikely to be mold. That's because dates generally don't pack enough water to support mold growth. According to a USDA report, “Molds are of little consequence in the spoilage of commercially packed dates except in very moist lots. They may cause large losses before and just after the fruit is harvested if rains or periods of high humidity occur at that time.”

So, while mold formation isn’t impossible, it’s an issue that date farmers, not consumers, are much more likely to encounter. It is possible that yeast could grow on dates in your kitchen but you’d probably smell alcohol or something sour. They would also not taste right, their color might be off and they might be puffy. Any white stuff from yeast would be more likely to show up in creases of the date, not in the ridge-top patches more common with sugar crystallization.

To extend shelf life, keep your dates in the fridge (or even the freezer if you aren’t going to eat them for a while). Dates with higher moisture content in particular will benefit from cool temperatures.