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High altitude jam

We have a bumper crop of black currants. Anybody got good advice on what aspect of jam making (with commercial liquid pectin) needs to be modified for altitude? We’re at 1517 meters/4979 feet.

Katja

4 Comments

  1. Richard Masoner

    I make pickles, not jam, but the same principle that altitude = lower boiling temperature applies for any water bath processing. You have to add time to the processing. Sorry, I don’t know how much time for jam.

    Reply
  2. Katja (Post author)

    Here’s what I found, for canning in general:

    Because of the lower boiling point of water at high altitude, increase the processing time 1 minute for each 1,000 feet above sea level if the time is 20 minutes or less. If the processing time is more than 20 minutes, increase by 2 minutes per 1,000 feet.

    (Colorado State University Cooperative Extension Resource Center)

    But for the actual jam-making part, as opposed to the processing, the following would seem to apply:

    To prevent excessive water evaporation, cook the syrup to a final temperature lower than that given for sea level. Decrease the final cooking temperature by the difference in boiling water temperature at your altitude and that of sea level. This is an approximate decrease of 2 degrees for every increase of 1,000 feet in elevation.

    (Colorado State University Cooperative Extension Resource Center)

    This dovetails with advice given in Putting Food By, which is my old tattered canning book, in which they say that the greater evaporation at altitude will give you a too-stiff jam or jelly if you follow sea level directions. The pectin gives directions in terms of “rolling boil”, as in “bring to a rolling boil that cannot be stirred down, add the pectin, and boil for exactly one minute”. I’m not sure how to convert/adjust one minute of rolling boiling to a lower temperature. Or maybe I get the lower temperature for free by being higher.

    Reply
  3. MICHAEL

    Thank god you included our altitude in meters.

    Reply
  4. Katja (Post author)

    Don’t mock.
    :-)

    Reply

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