In a large saucepan, combine fruit, sugar, vinegar, mustard and onion. Cook and stir over high heat until mixture comes to a full boil. Continue to stir and boil for 1 minute. remove from heat. Immediately stir in liquid fruit pectin. Skim off foam. Stir and skim for 5 minutes to cool slightly. Pour quickly into sterilized jars. Seal while hot with new 2 piece lids or 1 cm hot paraffin. Makes about 5 cups.