It turns out that the sprouts do contain potentially harmful concentrations of glycoalkaloids, compounds that can have toxic effects. But sprouted spuds aren’t necessarily duds: the root itself is likely still safe to eat, so long as you cut away the little growths.
In a paper published in the Journal of Agricultural and Food Chemistry, USDA research chemist Mendel Friedman explains that “glycoalkaloids are produced in all parts of the potato plant including leaves, roots, tubers, and sprouts.” When consumed in large enough doses, glycoalkaloids can have some pretty nasty effects, like nausea and vomiting. The levels of these compounds in the root itself are generally too low to have any bad effects. But “sprouts contain higher levels than do leaves or tubers,” therefore it’s best to avoid them.
Friedman mentions that “light and heat or mechanical injury stimulates glycoalkaloid synthesis,” which is why it’s a good idea to store your potatoes in a dark place. Light also encourages chlorophyll formation, which is harmless in itself. But it causes potatoes to turn green in the same areas that are at the most risk for being poisonous, acting as a visual clue for the parts you should avoid.
The USDA recommends that “if a potato has begun to grow sprouts, cut off the sprouts before cooking” and to “cut off any skin that started to turn green.” The remainder of the potato should be safe for consumption. If you do notice an unusually bitter taste in the potato, however, this could be a sign of increased glycoalkaloids in the root. It should not be eaten.
https://www.chowhound.com/food-news/54631/are-sprouted-potatoes-poisonous/
Potato sprouts are considered toxic due to their potentially high concentration of glycoalkaloids, which can exert their toxic effects on the nervous system by interfering with the body’s ability to regulate acetylcholine, a chemical responsible for conducting nerve impulses.
In addition, when potatoes sprout, the starch in the potatoes is converted into sugar. If the potato is firm, it has most of the nutrients intact and can be eaten after removing the sprouted part. However, if the potato is shrunken and wrinkled, it should not be eaten.
Sometimes potatoes develop a green tinge – a potato exposed to light, sprouted or unsprouted, may itself have an increased concentration of glycoalkaloids. If this is the case, the toxic area will turn green. You can cut the green part off and eat the rest of the potato.
When buying potatoes, pick firm ones and do not buy if they have sprouted or have a green tint to the skin. As for storing, keep potatoes in a cool dry spot for longest storage.
https://www.rachaelray.com/2011/08/30/is-it-safe-to-eat-sprouted-potatoes/
Any reference to a toxic potato is based on solanine, the toxin that potatoes have when their skins turn green, (its also in the leaves) other plants that contain this are other nightshade varieties including peppers, tomatoes, and tobacco. The sweet potato is a relative of the morning glory and not a nightshade. Check at http://www.nightshadejournal.com for info on solanine content of many plants. See here http://www.clovegarden.com/ingred/mg_mglory.html for the reference to sweet potatoes as a morning glory family member, there is also additional information on the site about yams and other false sweet potatoes.
http://www.eufic.org/jpage/en/page/faq/faqid/sweet-potatoes-green-sprouts-safe-to-eat
See above link for exactly whether or not the sprouts of sweet potatoes are poisonous.
https://skeptics.stackexchange.com/questions/28020/are-sprouted-sweet-potatoes-safe-to-eat
Sweet Potatoes are Different from Peruvian (White) Potatoes
White potatoes are stem tubers in the nightshade family. I wrote a post about those recently: Why do Potatoes Sprout and how can You Stop Them? Sweet potatoes are not related—they are root tubers in the Morning Glory family. Root tubers do not have buds, nodes and internodes, and scaly leaves right on the tuber, and the ability to develop chlorophyll when exposed to light, as stem tubers do. This article is all about sweet potatoes.
Why Cure Sweet Potatoes?
Sweet potatoes need to cure before storage, and the curing conditions are different from those needed for storage. Good curing enables the sweet potatoes to store for six months or even longer.
Immediately after harvest, field drying, sorting and crating (within an hour or two), take the boxes of sweet potatoes to a warm, damp indoor space to cure. Curing helps the skins to thicken, cuts to heal, and some of the starches to convert to sugars. Uncured sweet potatoes are not very sweet, will not bake well, and are best used in dishes with other foods (if you can't wait).
As well as promoting the healing of wounds acquired during harvesting and handling, the curing conditions also help the development of a protective cork layer over the whole root. And a waxy material (suberin) is produced by the roots' outer cells and covers the skin. This layer acts as a barrier to disease organisms, and prevents excess moisture loss.
Ideal Sweet Potato Curing Conditions
Curing involves optimizing three factors: temperature, relative humidity and ventilation. Ideal curing conditions are 85°F–90°F (29°C–32°C), and 80–95% humidity for 4–7 days. Curing takes longer (as much as 3 weeks) if conditions are less than perfect. Dry air does not lead to good curing. If the air is below 66% humidity, timely good healing will not take place, and the sweet potatoes will not store well unless more time is allowed. The loss from decay in sweet potatoes cured at 50% humidity is twice that of those cured at 82%. (Storage of sweetpotatoes, Jacob Martin Lutz, USDA, 1958)
In the past we tried using our greenhouse to cure sweet potatoes, but it really is too hot, sunny and dry in the daytime, and too cool at night. Nowadays we use a heated basement. We stack our 4” (10cm) deep boxes of roots on pallets, with wood spacer bars between boxes in each stack, to ensure air flow. We use box fans to improve the airflow, and the basement already has some natural ventilation. We reckon on 10–14 days under the conditions we can provide.
We get quite good temperatures, but keeping humidity up is difficult for us. We cover the flats with newspaper to hold in some moisture. Some people use perforated plastic. We have unsuccessfully tried using domestic humidifiers and hanging strips of wet cloth from the ceiling. The best result seems to come from splashing water on the concrete floor several times each day.
To test if curing is complete, rub two sweet potatoes together. If the skins scratch, they need to cure longer. Keep an eye on their progress—curing longer than needed leads to sprouting.
Sweet Potato Storage
Sweet potatoes can be stored in the same room they are cured in, if you can cool the room evenly and fairly rapidly from the curing temperature of 85°F–90°F (29°C–32°C), to the storage temp of 55–60°F (13°C–16°C) in 10 days or fewer. Otherwise, find a different storage space.
Above 60°F (16°C), shrinking, pithiness, and internal cork (if that viral disease is present) may occur, and below 55°F (13°C), a permanent chilling injury (Hard Core) can happen. The potatoes remain hard no matter how long you cook them, and are useless. Do not ever let the temperature drop below 50°F (10°C).
Ideal storage conditions for sweet potatoes include 60–70% humidity, up to 85%, with one air change each day. If the heat circulation is uneven, hot spots can develop in front of the heaters and cause severe losses. Never let hot air blow directly on the sweet potatoes. Do not store in airtight containers, sweet potatoes need one complete air change per day.
Ken Allan, in Sweet Potatoes for the Home Garden, informs us that at about 60°F (16°C), the metabolism of the sweet potato slows to near zero, meaning it won’t grow. Temperatures above 70°F (21°C) are conditions that allow growth: although slow at 70°F (21°C), the rate increases to fast at 100°F (38°C).
To store our sweet potatoes, we use a rodent-proof “cage” in our basement. We stack the boxes directly on top of each other and this seems to keep enough moisture in. This way, assuming we had a good enough harvest, we can still have sweet potatoes into May and early June. Shrinkage occurs at 1–2% per month if cured, 2–5% if uncured. In some cultivars, pithiness also increases with length of storage.
Sweet potatoes do not need to be in the dark. Dormancy is generally broken by moisture and warmth, not daylight. Green sweet potato sprouts are edible, not toxic, as white potato sprouts are.
The Effects of Ethylene on Sweet Potatoes
Ethylene is a naturally occurring, odorless, colorless gas produced by many fruits and vegetables, but it can also be produced by faulty heating units and combustion engines. Propane heaters should not be used, as propane combustion produces ethylene. Incomplete combustion of organic fuels can result in the production of ethylene, toxic carbon monoxide and other byproducts. Do not use any unvented hydrocarbon fuel heaters near stored produce.
Ethylene is connected with ripening, sprouting and rotting. Some crops produce ethylene in storage—apples, cantaloupes, ripening tomatoes all produce higher than average amounts. Chilling, wounding and pathogen attack can all induce ethylene formation in damaged crops.
Some crops, including most greens, are not sensitive to ethylene and can be stored in the same space as ethylene-producing crops. Other crops are very sensitive and will deteriorate in a high-ethylene environment. Potatoes will sprout, ripe fruits will go over the top, carrots lose their become bitter. Sweet potatoes are sensitive to ethylene and should not be stored with any crops or any heating systems that produce ethylene. Symptoms are difficult to diagnose, but ethylene can cause internal darkening and pithy areas, as well as sprouting.
Accidental Sprouting of Sweet Potatoes
If your curing or storage conditions were not right, you may get early sprouting. If this happens, fix the problem, then snap off the sprouts and use the sweet potatoes as soon as possible. If the sweet potato also has soft and wrinkly flesh, it's an indication that it has lost nutrients. Left longer, sprouted sweet potatoes become mushy and turn brown or black.
https://www.motherearthnews.com/organic-gardening/sweet-potato-sprouting-zbcz1801