In NZ, it is not customary to waterbath jams and jellies, not even low acid fruit jams like strawberries or apricots.
I regularly make cranberry sauce with just half the weight of sugar to fruit - weigh the berries, barely cover with water and I use both orange zest and orange juice, bring to the boil and when the berries just start to pop, add the sugar and hard boil until the sugar is fully dissolved.
Pour into clean jars that have been kept warm in a 50C
oven to with 2mm of the rim, screw top down immediately and invert for 10 minutes then turn right way up to completely cool.
I
reuse commercial jars so long as the twist top lids are undamaged - not scratched inside or dented around the sides. New lids are readily available
online from companies that
sell jars.
If a
spoon is inserted under the lugs and levered up, it breaks the vacuum without damaging the lids so that they can be re used.
Once opened, I store my preserves in the fridge but otherwise, they are kept in our garage until needed.
I am in my 60's and my mother preserved all her jams without water bathing them and myself and all three of my siblings have survived to tell the tale😉