Normally, fresh chunks of apple frozen in ice cream are as hard as a rock. But if you infuse them with a sugar solution, they remain soft and tasty. This sugar solution acts like a kind of anti-freeze because it has a lower freezing point than the apple (see graph below for the explanation).
This I'ble will show you how to achieve this. You will end with a subtle ice cream: at first you just taste the cinnamon, but once you bite trough a piece of apple, it's like suddenly a second flavor is released (apple).
The fastest way of infusing this sugar solution into apple is by using a vacuum chamber (look here for my previous Instructable).
However, in the case of apple, there's a secret: you don't need vacuum, just a little bit more time!
It took me quite some time & effort to get this recipe right. I froze many batches of infused apple in which I varied: vacuum pressure, infusion temperature, time, sugar concentration and chunk size.
By coincidence I discovered that a reference sample that was merely soaked for a long period (without vacuum) showed nice results. It should be noted that this is true for apple. For more details on the process, see step 2 of this I'ble.