At the liquor store, I demanded a small bottle of cheap whisky. The clerk rattled off names and prices. I informed her that I was making grapefruit marmalade. She rolled her eyes and I settled for Black Velvet.
This season, I have failed miserably to preserve citrus fruit. The marmalade wouldn't gel. In a last ditch effort, I searched the Internet for recipes and found Australian Annabel-Langbein's Blog for making grapefruit marmalade without commercial pectin. The grapefruit contain enough of its own pectin. The preparation of the fruit takes about 45 minutes and the actual cooking time is about 1 hour and 35 minutes. It makes almost a gallon of marmalade.
You need about 10 medium sized grapefruits (about 5 lbs/2 kg), 5 lbs sugar, and a 1/2 cup of whisky is optional. Quarter the grapefruit and cut thinly. Put the fruit in the big non-corrosive pot you'll use for cooking. Add 4 cups (1 liter) of water and let stand overnight.
The following day, put the grapefruit pot on the stove on high heat until boiling, turn down the heat, and let it simmer for 40 minutes. After the 40 minutes are up, stir in the 5 lbs of sugar, bring to a boil, turn down the heat, and let simmer for an additional 55 minutes. Now you are done cooking.
To prepare your jars and lids, simply put them in the dishwasher on high heat. This takes care of the sterilization as far as I am concerned. I like to seal my jars with a layer of wax that I heat in a double boiler consisting of two sauce pans with boiling water in the larger and the wax melting in the smaller one inserted in the large pan. Do not overheat.
If you want to test to see if the marmalade is really going to gel, chill a saucer in the fridge, remove it after a few minutes, and drop a teaspoon of your marmalade on to it, and tilt it a bit. Annabel writes that is should form a thin wrinkly skin on the surface of your marmalade and it's done.