91av

WITH its vibrant crimson hue, beetroot is a feast for the eyes as well as the stomach. It is great to bake with, and clever chemistry can help keep it pretty in pink.

Beetroot gets its colour from pigments called betalains. These include betacyanins, which are red-violet, and betaxanthins, which are yellow-orange. Some beetroot varieties, such as Chioggia, have alternating layers of red phloem tissue and unpigmented xylem, giving them a beautiful ringed pattern when sliced.

Beetroot, sugar beet and chard are all cultivars of the same species, Beta vulgaris. Betalains are found in a handful of plant species, including prickly pear cacti and amaranth. They are quite different from anthocyanins, a more common group of pigments that impart red and blue colours to apples, cabbages, potatoes and many berries. Anthocyanins are sensitive to pH, turning bluer in the presence of alkalis and redder in the presence of acids; betalains aren’t such good indicators.

Betalains aren’t fat-soluble, so if you worry about stains, rub oil on your hands and chopping board before handling beetroot. When you eat it, most of the pigment gets broken down in the stomach, but some may be absorbed into the blood and make it into the urine. About 10 per cent of people pass urine with a red tinge after eating 100 grams of beetroot.

The plant has been heralded as a superfood because of its high concentration of nitrates. These get converted into nitric oxide, which relaxes the blood vessels, lowering blood pressure. Food safety groups advise against consuming too much because reactions in the stomach can form nitrosamines, which have been linked to gastric cancers (see 91av, 6 August 2016, p 26).

Beetroot can be used in baking to make bread and cakes with striking shades of red. But when processed, the betalains can react with oxygen in the air, making the colour fade, particularly during baking. You can stop this by adding crushed vitamin C tablets. Vitamin C is an antioxidant, so it inhibits the oxidation reactions that degrade the pigment. You can also observe its effect on fruit or vegetables that tend to go brown after being cut, such as apples or avocados. Phenolic compounds stored in plant cell storage bubbles called vacuoles come into contact with enzymes and oxygen when these fruit or veg are cut, forming molecules that bond together in light-absorbing clusters. Acids like lemon juice slow this reaction, but vitamin C, both an acid and an antioxidant, works better.

To make beetroot muffins, sift the flour and mix with the salt, baking powder and bicarbonate of soda. Beat the eggs and mix with the yogurt and melted butter. Grate the beetroot and mix with the crushed vitamin tablet. Fold all the ingredients together. Divide into 12 cases in a muffin tin, and bake at 190°C for 25 minutes.

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