Citric acid is another name for tartaric acid. It is obtained synthetically, has no odor, but has a very sour taste. It is used to preserve jelly, jam and marmalade.
The recommended ratio is to add one teaspoon of citric acid to 1 kg of sugar. This means that if you make a large amount of jam, which requires more than 1 kg of sugar, you should also increase the amount of citric acid - 2 kg - 2 tsp, 3 kg - 3 tsp. etc.
If you add more than needed, there is a danger that the jam will acquire an unpleasant taste. Usually the citric acid is added to cooked and ready jam, just 1-2 minutes before removing it from the heat and distributing it into jars.
Citric acid can be put in water, in which the sliced fruit for the jam are dipped in. That way they won't darken. Apart from for making jams and marmalade, citric acid is also used in the production of desserts, ice cream and juices.
See how you can make some citric acid jams: Green Tomato Jam, Pear and Peach Jam and Oven-Baked Peach Jam.
