The only foods that may be safely canned in an ordinary boiling water bath are highly acidic ones with a pH below 4.6, such as fruits, pickled vegetables, or other foods to which acidic additives have been added.
Ainsad toidud, mida võib tavalises keevas veevannis ohutult konserveerida, on tugevalt happelised ehk mille pH on alla 4,6, nagu puuviljad, marineeritud köögiviljad või muud toidud, millele on lisatud happelisi lisaaineid.