Cure sweet potatoes - sprout during cure process + white coating

Question

Variety: All Purple. To cure I managed to build a heat incubator. I made it as an expanded polystyrene box, I put electric heat tape inside to maintain temperature. Washed, wet tubers have been packed into plastic bags with a few small holes, then put to plastic fruit crates. All of that is placed inside expanded polystyrene, hermetic (almost hermetic) box together with electric heat tape + thermo regulator to maintain the temperature inside. Polystyrene box is a very good isolator, so it's easy to maintain the required temperature inside.

I also have some temperature sensors. The first one, directly inside the box, is connected to temperature regulator and it's set to +32 °C (89 °F). Sensor inside plastic bags, with tubers inside shows 30-31 °C (86-88 °F) and humidity 90-95% so, the conditions look fine.

However, after 2 days tubers started sprouting, and some new, thin, white roots appeared on them, while the cure process is definitely not finished yet.

Does this sound ok? Have you experienced similar issues with sprouting? Is that really a problem? Am I doing anything wrong? How long should I wait to be sure they are cured correctly? And how do I know it's enough for them.

I guess sprout is not my only problem, I have no idea what's that on them:

It does not look like mold, but not looking good. Only some of them were affected.

Answer 1

My thoughts would be that the tubers are too warm and too wet. They think conditions are right for vegetative growth, not curing.

I harvested my sweet potatoes (Georgia Jet) about 10 days ago. They go straight into a passively ventilated bin, no washing, kept dry, in the house where the temperature ranges from 20-25C and humidity is 60-70% RH currently. They stay in this bin until needed for cooking in a couple of months time. Never any sign of sprouting, and after a few months they are very sweet. As we progress into winter the RH drops to about 40% at which point they will refuse to sprout at all even when you need them to do so.

Commercial growers need a marketable product as soon as possible, so they hasten the conversion of starches to sugars by tweaking up the temps and RH under control of excellent meters. My experience of temperature and RH meters and sensors is that they can be unreliable (particularly RH) and perhaps what your meter sees as 90-95 is likely 100% particularly given the zero ventilation.

Of course it depends on where you live and your living space, but my course of action would be to pull them from the bags in the warm, dry them off, place loose and cool in a bin and be prepared to wait a bit longer than the book says for curing to complete. Assess curing stage with taste test.