Slice the bananas and sprinkle with lemon juice. Roast cumin seeds in a dry pan, shaking or stirring constantly until brown. Crush or grind. Combine the yogurt with all the ingredients except the banana. If desiccated coconut is used, moisten it first by sprinkling with about 2 tablespoons water and tossing it with the fingers until it is no longer dry. Fold banana into yogurt mixture. Chill and serve.