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We bought some sweet potatoes from the store and a few days later we chopped them up to make some roasted veggies.

To our surprise, the insides of the potatoes were full of holes or cavities. There was also a small amount of milky white substance that would gather in tiny droplets around the edge of the cut.

I had no idea what was going on so we threw them out. What's the deal? Were these bad? Was throwing them out the right thing to do?

The outside looked pretty normal, so I'm not sure how to identify this in the future.

holy potatoes

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    It might be related to hollow heart, but I have never seen it look quite like that. Might want to take it to gardening if someone here cannot identify. In any case, it looks extensive enough that I would not have considered the sweet potato salvageable. Guess would be growth related, but it is possible that was bacterial and unlikely the taste would have been right in any case. – dlb Aug 9 '17 at 15:35
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    The milky substance you referred to is normal. It is the sap. Many times when baking whole sweet potatoes this sap will ooze out and look like syrup. It's quite sweet. Many years ago we were told that the more sap a sweet potato has, the sweeter it would be. – Cindy Aug 9 '17 at 15:56
  • Hi JPhi1618, we prefer titles to be boring and informative. I know that it is fun to write them with puns, and that they are better clickbait. But this makes it very difficult to find the question again in the search function, or to see at a glance what it is about when it is shown in a list in the sidebar, and such functionality is the main way of making Stackexchange more informative than other platforms. So sorry, but I had to edit it. – rumtscho Aug 9 '17 at 15:57
  • @Cindy, Thats interesting. I've never seen it seep out like that after cutting. Maybe the cavities concentrated it near the surface? – JPhi1618 Aug 9 '17 at 15:58
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    To be honest, I don't see it as much nowadays. Back years ago it was normal to see a lot of it when cutting or baking them. I think what makes the difference is the commercial methods of storing. Farmers used to cure and store them for long preservation. I was always told that the longer they were cured, the sweeter they would be. – Cindy Aug 9 '17 at 16:05
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Okay, after looking around a bit, I think the proper description of the sweet potato in your picture is 'pithy'. And I saw some pics where this condition had progressed much further than it had in yours. It seems that what causes this is temperatures too high during the storage time. I found references to this in several places.

From the University of Arkansas :

Sweet potatoes: proper curing improves quality, shelf life By Will Hehemann The Cooperative Extension Service U of A System Division of Agriculture

PINE BLUFF, Ark. – Sweet potatoes are not very sweet when initially harvested, Shaun Francis, extension horticulture specialist for the University of Arkansas at Pine Bluff, said. Farmers should cure their sweet potato crop for a period of time to ensure the correct taste and a longer shelf life.

“Sweet potatoes remain metabolically active after they are harvested,” Francis said. “As the tubers continue the respiration process, their starches are converted to sugars, hence the sweet taste.”

Another purpose of the curing process is to heal any abrasions or bruises the sweet potatoes sustain during harvesting, he said. As the potato cures, a corky layer of cells develops just below the surface of the abrasions, which serves as a barrier against disease-carrying organisms.

The curing process can begin immediately after sweet potatoes are harvested. First, remove them from the field as soon as possible to prevent sunscald damage.

“If you are harvesting during moist conditions, allow the soil around the roots to dry for an hour or two,” Francis said. “Though you can remove excess soil around the roots, remember not to wash freshly harvested potatoes.”

Store the potatoes in a warm, humid room for four to seven days. Ideal conditions for curing are a temperature of 85 degrees Fahrenheit and a relative humidity of 90 percent.

“As these conditions may be difficult to establish inside a household, consider using a shed on the farm or a garage,” Francis said. “Some farmers can achieve the correct conditions for curing in a room with a space heater, thermostat and humidifier.”

If the temperature decreases during the curing process, increase the number of days the sweet potatoes spend curing. If it is 80 degrees Fahrenheit outside, let the potatoes cure for up to 10 days, he said.

Good ventilation is also important in the curing process, as it can prevent a buildup of the carbon dioxide that is released by the tubers. The circulation of air also enables excess condensation to escape, which prevents rotting.

After sweet potatoes have cured for the correct amount of time, they should be stored at an approximate temperature of 60 degrees Fahrenheit and a relative humidity range of 85-90 percent, Francis said.

“Keep the storing conditions constant, as fluctuations will cause the deterioration of root quality,” he said. “Low temperatures cause the potatoes to develop too tough a center, while high temperatures will cause the roots to sprout, shrivel and become pithy.”

Francis said sweet potatoes stored in cool, constant conditions have a shelf life of up to several months.

For more information on cultivating and preserving sweet potatoes or other tubers, contact your local county extension agent or visit www.uaex.edu.

(Emphasis mine.)

So, while they probably wouldn't have hurt you, they were obviously inferior quality and most likely wouldn't have tasted very good. Good call on tossing them!

  • The skin wasn't broken, so I didn't really think it was insects or mold, but like you said - I assumed they wouldn't have tasted good, and we wouldn't have been able to stop thinking something was wrong. – JPhi1618 Aug 9 '17 at 17:23

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