Rhubarb syrup with the Thermomix® only works with one intermediate step that many recipes skip: after the first cook, the rhubarb is strained and only the rhubarb water is cooked on. If you leave the pieces in, you end up with a thick, cloudy compote rather than syrup.
We have been making rhubarb syrup for years and made exactly this mistake at the start. The recipe said “cook for 8 minutes, then continue cooking for 35 minutes” and we left everything in the pot together. The result was cloudy, full of fibres and turned thick and sticky after two weeks in the fridge instead of staying syrupy.
Rhubarb Syrup with the Thermomix®
Ingredients 0 / 5 ✓
- 1300 g rhubarb
- 600 g water
- 300 g sugar
- 20 g lemon juice
- 2 tsp vanilla extract Optional: 2 sachets of vanilla sugar
Instructions 0 / 4
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1
Rhubarb.
Wash the rhubarb, trim both ends and peel carefully. Cut into pieces, place in the mixing bowl with the water and heat for 8 min / 100°C / speed 1.
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2
Cook the rhubarb.
Remove the measuring cup, place the simmering basket on top as a splash guard and cook for 35 min / 90°C / gentle stir setting.
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3
Strain.
Line the simmering basket with a clean tea towel and strain the rhubarb through it. Catch the rhubarb water and squeeze the rhubarb firmly in the cloth. Rinse the mixing bowl. Return the rhubarb water to the mixing bowl, add the sugar, lemon juice and vanilla extract, place the simmering basket back on top as a splash guard and cook for 35 min / 100°C / speed 2.
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4
Fill into bottles.
Meanwhile sterilise the bottle with boiling water, fill with the syrup and leave to cool.
Tip: To taste, pour some syrup into a glass and top up with cold sparkling water or Prosecco. Serve with ice cubes and fresh mint leaves for an even more refreshing drink.
Video
Nutrition per serving
Why the rhubarb must come out after the first cook
Rhubarb releases its aromatic compounds and red colour into the water during those first 8 minutes at 100°C. That is the point at which the extraction is at its peak. The 35 minutes at 90°C afterwards only draw more pectin from the fibres, and that makes the syrup go jelly-like as it cools. Exactly like jam, except that we are not using jam sugar here.
That is why you strain after the first cook: line the simmering basket with a tea towel, catch the rhubarb water, and squeeze the rhubarb pieces firmly in the cloth. Only the clear rhubarb water goes back into the mixing bowl. The pieces can be discarded or used for compote.
90°C instead of 100°C for the second cook
The second cook runs at 90°C on the gentle stir setting, not at 100°C. The reason is the sugar: at 100°C, sugar caramelises on the bowl walls and burns. At 90°C it dissolves completely and the syrup stays clear. The 35 minutes on the gentle stir setting reduce the volume by roughly a third and make the syrup shelf-stable.
Keep the simmering basket on top as a splash guard. Without it the syrup boils over and sticks to the lid. The simmering basket prevents that while still letting steam escape.
Peeling rhubarb is essential
The outer fibres must be removed before cooking. They do not break down during cooking and will end up as tough strings in the syrup. Wash the rhubarb, cut off both ends, then peel the skin from top to bottom with a knife. The red stalks colour the syrup better than the green ones, but both work.
The pieces can be cut roughly, about 2 to 3 cm. The exact size does not matter because the rhubarb is strained out afterwards.
Vanilla extract instead of vanilla sugar
The recipe uses vanilla extract or 2 sachets of vanilla sugar as an alternative. We use extract because vanilla sugar adds extra sugar and the syrup becomes too sweet otherwise. 2 tsp of homemade vanilla extract works perfectly. The vanilla note is subtle rather than dominant and complements the tartness of the rhubarb.
Lemon juice brightens the flavour and prevents the syrup from oxidising and turning brown during storage. 20 g is enough.
Storage and dilution
Sterilise the bottle with boiling water, fill with the hot syrup and leave to cool. Stored in the fridge, the syrup keeps for at least 6 months. To serve, pour about 50 ml of syrup into a glass and top up with 200 ml of cold sparkling water or Prosecco. Ice cubes and fresh mint leaves make it even more refreshing.
If the syrup becomes thicker after a few weeks in the fridge, warm it briefly. That dissolves the sugar crystals again.
More syrup recipes
- Lemon Ginger Syrup
- Iced Tea Syrup
- Blackcurrant Syrup
- Sugar Syrup
How other recipes differ
Goes well with: Prosecco, vanilla ice cream and yoghurt.
Also a great match: Solero Cocktail Thermomix®.
Most rhubarb syrup recipes for the Thermomix® use green rhubarb and around 200 g of sugar per 900 ml of rhubarb water, which gives a pale, mildly sweet syrup. We deliberately use red rhubarb, because only that delivers the deep pink colour that actually looks like spring in the glass. Instead of citric acid from a sachet, we use fresh lemon juice, which protects both the colour and the flavour at once. For straining, we skip the standard sieve and use a cotton cloth, otherwise the syrup stays cloudy. The base is also easy to adapt into variations with strawberry, ginger or vanilla, as well as an Aperol Spritz alternative or a homemade rhubarb lemonade.
