This scrumptious purée makes a great side dish and will keep for some weeks. It will ferment quickly so if you don't like tart ferments, keep it in the fridge. The lactic acid bacteria in the ferment acts as both a bio-preservative and a provider of great nutrients. Buy ready to eat beetroot or boil it yourself until soft. Both tomato and beetroot are rich in antioxidants. However, beetroot is an oxalate containing food. By fermenting it, you are removing the oxalates as the microbes in the ferment will eat the oxalates as fuel. The longer you leave it to ferment, the more oxalates they eat.