"The trick is to sterilise the jars and instruments by cooking them for a minute or two."
That's where I get worried about home recipes. There are critters that will survive WAY more than a minute or two in boiling water, or even two minutes in an autoclave.
"Bacteria, however, are not as easily destroyed. The bacteria, Clostridium botulinum produces a spore that makes a poisonous toxin which causes botulism. This spore is not destroyed at 212° F. In addition, bacteria thrive on low acids in the absence of air. Therefore, for a safe food product, low-acid foods need to be processed at 240° F. This temperature can only be achieved with a pressure canner."
from Presto®: Pressure Canning Introduction
which echos a number of government and university sites.
I made the mistake of putting up some garlic on oil once. Fortunately the pretty colors made me throw it out untasted, apparently garlic and naything else dug out of the ground can be guaranteed
to have botulism spores in it. I know, good fresh mozzarella has just come out of a long hot water bath, but I'd really hate to be really ill at sea.