Geoffrey S. Mendelson wrote:
>
> Thanks, I wasn't clear, I wanted to cook the applesauce in the sealed
> cans, with the outcome of apple butter in a still sealed can.
>
> I meant to ask about storing the unopened cans.

Delche de leche can be made inside unsealed cans by cooking them in a
slow cooker. I do not believe it will work for converting apple sauce
into apple butter.

Last year we made apple sauce and apple butter in a slow cooker directly
from apples. Core, skin and dice apples to fill the crock. Cook to
reduce and refill. Cook over night and the result is apple sauce. Can
them using the big boiling canning set up. To make apple butter instead
of cooking over night we turned the lid a little to let steam escape
and cooked all of that day. Enough water evaporated to reduce the apple
sauce to apple butter.

Some of the additional cooking process would have caramelized the sugar
in the apples the way flan is made inside a can of condensed milk but I
think most of it was allowing the extra water to evaporate.