Peel bananas, retaining about a quarter of their skins. Put bananas and skins in a muslin or cheesecloth bag, place in a large pan or boiler with 5.7 litres of water and simmer for half an hour.
Squeeze juice from orange and lemon.
Place sugar, orange and lemon juice, chopped raisins, tannin and citric acid in a plastic bucket.
Pour the liquid from the bananas into the bucket and stir until the sugar is fully dissolved.
When cool, squeeze as much juice as possible into the bucket. Add the yeast and nutrient.
Cover the bucket and stand in a warm place for 7 days, stirring daily.
Strain juice into fermentation vessel and fit airlock.
When fermentation is complete, rack into a clean container, add 1 crushed Campden tablet and refit airlock.
