Going green: why we throw away almost half of the potatoes we buy

According to a report in today’s paper British households throw away almost half of the potatoes that they buy. That’s almost 2.7 million spuds binned every day, making the potato second only to bread in the food waste league tables. Much of the waste is down to us not getting around to cooking with them before they begin to turn green, develop sprouts or wrinkled skins. Although a potato past its best doesn’t look very appealing, is it safe to eat and should we be doing more to ensure we eat more of them and waste less?

Potatoes begin to turn green when they are exposed to light – it’s why gardeners ‘earth up’ their potato plants as they grow, to ensure that all the tubers are kept in darkness beneath the soil. The green colouration is due to the formation of chlorophyll, an essential pigment that allows plant leaves to absorb sunlight for photosynthesis. The chlorophyll itself is harmless, but its development in the potato indicates that other, more toxic, chemicals may also be present. These chemicals, known as alkaloids, can cause digestive problems if eaten in small amounts and, more seriously, drowsiness and neurological issues if consumed in large amounts, although this is very rare. The low doses you’re likely to get from eating the odd potato that has starter to turn green shouldn’t cause any problems, but it’s recommended that before cooking a potato with green patches, they should be peeled and any remaining green cut away. This is probably a good idea, because even if there’s not enough of the alkaloids there to poison you, the green areas are likely to have a bitter taste… not what you’re wanting from a plate of mash.

When a potato starts to form sprouts it is simply trying to grow, form a plant and make more potatoes. Every spring, up and down the country, gardeners stand their seed potatoes in egg boxes on cool, light windowsills to chit them. This is pretty much the same process as the unintentional sprouting of potatoes stored on the vegetable rack. It kicks off the growth of a new plant. As the sprouts form, the starch stored in the potato is converted into sugars to provide energy for all this new growth. After a while, the potato will start to wrinkle and shrivel, and by this stage it’s probably fit for nothing more than the bin. But if you catch it sooner, the sprouts can be removed and the potato will be fine to cook with. The alkaloids associated with green potatoes are also present in, and at the base of the sprout, so make sure you cut away a chunk of potato around the sprout, just to be on the safe side.

Getting the longest shelf life from potatoes is largely down to storage. Keep them in a cool, dry, dark, well ventilated place. Check regularly and remove (and use) any that look to be turning green or sprouting. And take a look at the Love Food Hate Waste website for lots of facts, recipes and more storage tips for potatoes.


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