Place allspice on a double thickness of cheesecloth. Gather corners of cloth to enclose seasonings; tie securely with string. In a small bowl, mix 3/4 cup water, vinegar and maple syrup until blended; set aside. In a small saucepan, mix flour, cornstarch, mustard, turmeric, salt and remaining water until smooth. Gradually whisk in vinegar mixture. Add spice bag. Simmer over medium heat until thickened, 5-10 minutes, stirring occasionally., Discard spice bag. Transfer to a covered container; cool slightly. Refrigerate until cold. Store in refrigerator for up to 1 month.