Making yacon syrup at home is straightforward: you juice fresh yacon tubers, then slowly simmer the liquid until it reduces into a thick, dark syrup. The process takes several hours but requires minimal equipment. Yacon syrup has roughly one third the calories of regular sugar, with a low glycemic index, thanks to its high content of fructooligosaccharides (a type of prebiotic fiber your body doesn’t fully digest). Here’s how to make it from scratch.
Choosing and Preparing Yacon Tubers
Yacon tubers look like sweet potatoes with thin, papery skin. If you’re growing your own, harvest them as late in the season as possible, ideally right after the first frost, to maximize their natural sweetness. Research on yacon grown in Central Europe found that growers harvested 153 to 172 days after planting, timed to the first frost for peak sugar content. Once harvested, process them quickly. During storage, the beneficial fructooligosaccharides in yacon break down into simple sugars, which defeats much of the purpose of making the syrup.
If you’re buying yacon tubers from a market or specialty grocer, look for firm roots without soft spots. Plan to process them the same day you bring them home.
Preventing Browning
Yacon flesh turns brown almost immediately after cutting, similar to apples. This happens because enzymes in the tuber react with oxygen the moment the flesh is exposed. Browning doesn’t make the syrup unsafe, but it produces a darker, less appealing product with slightly off flavors.
The simplest home solution is a citric acid bath. Dissolve about a quarter teaspoon of citric acid powder per cup of water, then drop your peeled, sliced yacon pieces into the solution as you work. A 15 to 20 minute soak is enough to slow the browning enzymes significantly. Lemon juice works as a substitute since it’s naturally high in citric acid, though it adds a faint citrus flavor. Research on yacon processing found that a 0.15% citric acid solution soaked for 20 minutes was the most effective single treatment for preserving the tuber’s original pale color.
Extracting the Juice
Start by peeling the yacon tubers. The skin comes off easily with a vegetable peeler. Slice the peeled tubers into chunks and run them through a juicer, or blend them with a small amount of water and strain out the pulp. Many home producers prefer blending because standard juicers sometimes leave too much liquid behind in the pulp. If you go the blender route, add just enough water to get the blades moving.
Once blended to a smooth pulp, pour everything through a fine mesh sieve lined with cheesecloth. Squeeze the cheesecloth firmly to extract as much juice as possible. You can also do a second extraction: return the leftover pulp to the blender with a bit of hot water, blend again, and strain a second time. This mirrors the commercial technique of using heated water to pull remaining sugars from the ground roots. The two batches of juice get combined before cooking.
Expect roughly one cup of juice per pound of fresh tubers, though this varies with the juiciness of your particular roots.
Cooking the Juice Into Syrup
Pour the strained juice into a wide, heavy-bottomed pot. A wider pot means more surface area, which speeds up evaporation considerably. Bring the juice to a gentle simmer over medium-low heat. You do not want a rolling boil.
Temperature control matters here. The fructooligosaccharides that give yacon syrup its prebiotic value and low glycemic profile start breaking down into simple sugars at higher temperatures. Studies on fructooligosaccharide stability show measurable degradation at 90°C (194°F) and above, with losses accelerating at 100°C and 110°C. Keep your simmer gentle, closer to 85°C (185°F) if you have a thermometer. This is below a full boil, with small bubbles forming at the bottom of the pot but not vigorously breaking the surface.
Stir occasionally to prevent scorching on the bottom. As the liquid reduces, it will darken from pale gold to a deep amber or molasses-like brown. The syrup also thickens gradually and can scorch more easily in the final stages, so reduce the heat further and stir more frequently as it approaches the desired consistency.
The whole process typically takes 2 to 4 hours, depending on how much juice you started with and how wide your pot is. You’re done when the liquid has reduced to roughly one eighth to one tenth of its original volume and coats a spoon the way maple syrup or honey would. If you have a refractometer, you’re aiming for around 70 to 73 Brix (a measurement of sugar concentration). Without one, the spoon test works well: dip a spoon in the syrup, hold it sideways, and watch how it flows. It should run slowly, not drip like water.
Yields to Expect
Yacon tubers are about 85 to 90% water, and the juice itself is mostly water too. As a rough guide, 10 pounds of fresh yacon tubers will yield around 10 cups of juice, which cooks down to approximately 1 to 1.5 cups of finished syrup. This low yield is why commercially sold yacon syrup tends to be expensive. Knowing this ahead of time helps set expectations so you don’t think something went wrong when your large pot of juice reduces to a small jar of syrup.
Storing Your Finished Syrup
Let the syrup cool to room temperature, then transfer it to a clean glass jar with a tight-fitting lid. Refrigerate it. The high sugar concentration and relatively low pH help preserve the syrup naturally, but homemade versions lack the standardized processing of commercial products, so cold storage is the safest approach.
Properly reduced yacon syrup stored in the refrigerator keeps for several months. You’ll know it has gone off if you see mold on the surface, notice fermentation bubbles, or detect a sour or alcoholic smell. Using a clean, dry spoon each time you scoop from the jar helps prevent contamination. For longer storage, you can process the syrup in small canning jars using a water bath method, just as you would with any fruit syrup.
Using Yacon Syrup
Yacon syrup tastes like a mild molasses with hints of caramel and apple. It’s noticeably less sweet than honey or maple syrup, so you may find yourself using a bit more of it. It works well drizzled over oatmeal, stirred into smoothies, or used as a sweetener in salad dressings. Because high heat degrades the prebiotic compounds, it’s best used as a finishing syrup or in no-bake recipes rather than in cookies or cakes that spend 30 minutes in a hot oven.
With roughly one third the calories of table sugar and a very low glycemic index, yacon syrup is particularly popular among people managing blood sugar levels. The fructooligosaccharides pass through the upper digestive tract largely intact and feed beneficial gut bacteria in the colon, which is why yacon is often described as a prebiotic food. A tablespoon of the finished syrup contains roughly 20 calories, compared to about 50 to 60 for the same amount of honey or maple syrup.