well, it depends on the context.

In the contadino tomato sauce the first meaning coming in mind is that it is suggesting that those tomatoes grew in a very safe way, without chemicals added, as the tomatoes that the contadini were growing for their own use.
And a very common way to preserve them was to cook them , then put them in bottles, and finally to boil for at least one hour. Someone still does at home. I give it up about tomatoes, but I do the same with red hot peppers.