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All low acid foods to be canned must be processed under pressure to destroy Clostridium botulinum spores. Starches slow the transfer of heat to the center of a canning jar; therefore avoid canning any potato product that would prevent heat transfer during processing. Do not can mashed potatoes, creamed potato soup, or mushy overcooked potatoes that settle to the bottom of the jar.
When done properly, new white potatoes may be safely canned. Penn State Extension Let’s Preserve Potatoes has complete instructions for canning potatoes.
When canning new white potatoes remember:
- Select small to medium-size mature potatoes of ideal quality for eating.
- Tubers stored below 45ºF may discolor when canned.
- Treat with ascorbic acid to prevent surface darkening (3000 mg or 1 teaspoon to 1 gallon of water).
- Potatoes need to be firm enough that they do not become mushy when placed into the jars. There needs to be space between the potato pieces so that water can circulate around the potatoes pieces while they are being processed.
- Do not use these directions for canning sweet potatoes.
Storing Fresh Potatoes
Fresh potatoes have a long storage life when handled correctly.
- Store potatoes in a cool, humid, but not wet, environment that is dark and is well ventilated. The ideal storage temperature is 45 to 50ºF. Potatoes stored below 40ºF as in the refrigerator will develop a sweet taste.
- Cold temperatures convert the starch in the potato to sugar. This increase in sugar will cause potatoes to darken when cooked—especially at high temperatures. It is more of a problem when making fries than when boiling potatoes.
- Storing potatoes in the refrigerator is not recommended; but if you do, allowing the potatoes to warm gradually to room temperature before cooking can reduce discoloration.
Green on Potatoes
Prolonged exposure to light causes potatoes to turn green. You may see this on homegrown potatoes that are partially above the soil surface. Commercially packaged potatoes in clear plastic bags may turn green from exposure to light in the store. Potatoes packaged in heavy paper with the viewing window underneath the bag are less likely to have shades of green underneath the surface of the skin.
The green on the skin of the potato is the build-up of a chemical called solanine. It produces a bitter taste; and, if eaten in large quantity, can cause illness. Because of the bitter taste, one is unlikely to eat enough to cause illness. If there is slight greening, cut away the green portions of the potato before cooking and eating it.
Sprouting indicates that the potato is trying to grow. Cut the sprouts away before cooking the potato.