We harvested many large green heirloom tomatoes before the freeze.
A brown bag, three overripe apples, two days, and ripe! Grandma taught me the trick, but I don't know if she understood that it was the ethylene gas put out by ripening fruit that spurs further ripening. Apples pump out a good amount, and at the right time for green tomatoes. If you want to keep your fruit from ripening, you should keep them away from other fruits, especially ripe ones.