Lemonade Marmalade

The Lemonade Tree , Citrus limon x reticulata, is a citrus. From the name, it appears to be a cross between a Lemon, Citrus limon, and a Mandarin, Citrus reticulata. Daley's describe it as a "Small well shaped tree of moderately vigorous growth, suited to the home garden. Bears a large crop of fruit over a long period. The fruit is pleasant to eat and ideal for fruit drinks." You can add to that, it makes a superb marmalade.

Fig 1:

Fig 1 shows the fruit of the Lemonade Tree.


The following assumes that the fruit has a sugar content of about 12°Bx. Lemonade fruit is sweeter and less acidic than lemons.

The mix is 25:75 fruit:sugar, a relatively low fruit content.

The calculator above can scale the recipe, just complete one of the yellow fields and hit ENTER or SPACE, and the rest will be calculated.


Wash and clean fruit, remove any skin blemishes. Cut fruit and remove seeds, then rough chop fruit in food processor in the water.

Simmer the fruit in the water slowly until skins are soft, 20-40 min, yielding about 1.7kg (170%) of cooked fruit mix. As it cooks, the mixture becomes thicker and requires frequent stirring to prevent sticking. Longer cooking time seems to yield higher Pectin.

Adjust pH to within the range 3.0 to 3.3. Use Sodium Bicarbonate to increase pH or Citric Acid to reduce pH.

Test the Pectin content by placing a few drops in a small dish of alcohol (Methylated Spirits is fine). The fruit mixture should clot and form a lump that can be lifted out of the dish with a fork. If the Pectin is weaker than that, additional Pectin may be needed to cause the jam to gel.

Heat the fruit mixture and add the sugar.

Cook the jam, stirring frequently to prevent sugar burning on the bottom of the pot, and until mixture reduces, Brix= 68°Bx or boiling temperature elevated by 5°C over that of water.

The endpoint can be determined several ways, including:

The first method is the most accurate, the second uses simple equipment and is good, the others work better with experience.

Fig 2:

It is important to adjust the absolute endpoint temperature for altitude. Fig 2 shows the jam endpoint boiling temperature vs altitude. For example, at an altitude of 600m, the endpoint is about 102.9°C. A good procedure is to measure the boiling point of water just prior to making the jam, and write down the endpoint for the jam to be 5°C higher, this automatically captures the altitude / barometric adjustment.

Be careful to not overcook the jam whilst testing it, take it of the heat. You can always cook it some more, you can't cook it less.

If the jam reaches the endpoint Brix degree or corrected boiling temperature and does not gel when a few drops are put on a plate, its pH is wrong, or it lacks sufficient Pectin. Boiling the jam further will not fix the problem, in fact it risks a new problem, burning the sugar.

For longer keeping, add Sodium Metabisulphite (E223) for a concentration of 50ppm in the final product. Add 0.23g (0.023%) of Sodium Metabisulphite (E223) dissolved in a little water for a concentration of 50ppm. 

A practical method of measuring such a small quantity is to dissolve 10g of Sodium Metabisulphite in 20ml of water to make 27ml of 37% solution. If using a refractometer to adjust the 37% w/v solution, it has SG=1.12 or 28°Bx. Then add just 0.6ml of the 37% solution to 4.6kg of jam (use 1ml pipette or syringe for dispensing).

Table 1: Sugar calculations
Component Mass (kg) °Bx Total Soluable Solids (kg)
Fruit 1.00 10 0.10
Water added 1.00 0 0.00
Sugar 3.00 100 3.00
Water  evaporated -0.41 0 0.00
Yield 4.56 68 3.10

The yield is 4.56kg (456%).

Cool jam to 82° - 85° and fill sterile jars. Close jars with sterile lids and invert jars for three min before turning them right way up.

Fig 3:

Fig 3 shows a sample of the Lemonade Marmalade. It is a bright yellow colour with strips of peel in suspension. The test batch gelled well without additional Pectin, but subsequent batches have needed some Pectin. All batches required a little increase of pH.

Links / References

Endpoint to boiling a sugar solution

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Last modified 17 May 2018 14:31.

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