Put ripe fruit into a pan with vinegar and simmer for 15 minutes. Strain through a sieve, pressing out the juice, and return liquid to pan. Add the salt, mustard and spice, and simmer for 30 minutes. Strain again through a sieve and stir in the sugar. Simmer for 30 minutes, put into hot bottles and seal. Sterilize for 30 minutes in a water bath.