Purple grapes are available all year round. If you buy grapes, look for a plump grapes, with fruits firmly attached to the stems. See detailed pictures above, they are the best examples of newly picked grapes.
Here’s how to frost grapes: Dip a small bunch of grapes into a beaten egg white and deep it again in caster sugar. Leave them dry on a rack or platter. Use as garnish for desserts. For fruit salad, do not peel black or purple grapes as it tends to colour the syrup.