Based on my experience with how very EASY, it was to make this bergamot-orange jam, I decided to make a new portion of citrus jam, this time based on red grapefruit (Star Ruby sort).
I started by weighting the grapefruit, so I would have an idea about the amount of sugar needed to make this jam. As initial starting point I started with 1 to 1 ratio of grapefruit to sugar. However, with this sugar level, the bitterness in the jam was too strong for me. Therefore I decided to increase the ratio to one part of grapefruit to 1½ part of sugar. With this sugar level I found the balance between bitterness and sweetness to be quiet interesting, so I to took the decision to stop the sugar addition here. However, you should consider to use a level of 1 part of grapefruit to 2 part of sugar, if you find the bitterness gin tonic to strong for you.
I also noticed, that I should make adjustments to the cooking time of the citrus fruit depending on the firmness/softness of the citrus fruit, which you are putting into the cooking pot. I cooked the grapefruit for 1 hour, which was too long, as the grapefruit was turned into a pure without any fruit pieces at all during the blending process. I think, that 40-45 minutes would have been better to target as the cooking time. So with firm citrus fruit, you should target 1 hour as cooking time, where you with softer citrus fruit should reduce the cooking time to 40-45 minutes.
As this jam as well is made from citrus fruit and the sugar amount is quiet high, where is not need for adding pectin gelling powder, as the citrus fruit is a natural source of pectin.
Red Grapefruit Jam:
- 2 (red) grapefruit = 550 g
- 825 g sugar or 1100 g sugar, if more sweetness is preferred
- Wash the grapefruits.
- Place the grapefruits in a small cooking pot, which when is filled with water.
- Place the lid on the cooking pot. Let the citrus fruits boiled (softly) for 40-60 minutes.
- Remove the grapefruits and place them in a blender.
- Add sugar on top of the citrus fruits.
- Blend everything into a homogeneous mass.
- Prepare the jam glasses by filling them with boiling water. I do not use any preservatives in my home-made jam, so this is important to increase shelf-life of your jam. Another thing you can do is to store the jam cold afterwards.
- Fill the glass with jam and close the glass.