Start by peeling your mangoes and discard the peel. Keep the mangoes (with the seed core attached) in a big cooking pot.
Pour all the sugar over the mangoes and mix everything well.
This step is optional. Wash your lemon/lime and cut into half. Press out the juice and pour over the mangoes. Throw the lemon rind into the pot with the mangoes. Lemon rind adds natural pectin to the jam making and it helps to set the jam.
Heat up your pot on low heat and stir the fruits. Cook on low heat for about 30 minutes or until you see the rolling boil happening. The fruit flesh will completely detach from the seed core and only the strings will be left.
Reduce heat and cook until jam is set. Use a thermometer in doubt: The setting temperature is 105 Celsius/220 Fahrenheit. You can also test if the jam is set by using a frozen plate or spoon and by dropping some of the hot cooked jam on the frozen part. That will cool the drop of jam instantly and you will be able to see if the jam has set or not. If the jam is still running, cook it a bit more and repeat the test until the jam has set. Always keep an eye on the cooking Jam as to not burn the jam.
Pick out and discard the lime/lemon pieces and the Mango seed cores with the strings attached to the cores (some mango types don't have strings which are all the better, in that case, see Recipe Notes below).
Grab a sterilized Jar and fill it up with the jam up to the rim. Drop a few drops of alcohol into the cap so that it gets disinfected. Seal the jars and turn it upside down and leave it like that for a few hours before you store the mango jam jars in a cool and dry place. Keeping the jam jars upside down for a while creates a vacuum and helps in preserving the jam all the longer.
Make sure to label your jam with jam name, date and best before date. The jam will be good for about 1 year if unopened. Store in the fridge once opened.
When choosing mangoes pick a mango variety with fewer fiber/strings and undamaged mango. If you use a mango variety which doesn't have fibers and only fruit flesh, cut off the fruit flesh from the seed core and discard the seed core. You only need to cook the seed core with the mangoes if the mangoes have fiber strings because you don't want those in your jam and they remain on the seed core like a layer of hair.
Use only untreated/pesticide free lime/lemon because the whole lemon halves are used to cook up the jam as it provides natural pectin.
Store jars filled with jam in a dry, cool and dark place. Once you open the jars, store in the fridge.
You can reduce the sugar in this mango recipe but you will need to consume the mango jam in the next 1-3 days. The sugar in the mango jam and the lime/lemon help the jam to preserve for months if ripe fresh mangoes are used.
1 medium Mango weighs about 200 grams/ 7 ounces with the seed core.