How do I make a syrup thicker?

Making syrup thicker is a common need when baking or cooking. Thicker syrup leads to better consistency and texture in desserts, glazes, fruit toppings, and more. Luckily, there are several easy ways to thicken syrup at home.

Table of Contents

Using Cornstarch

One of the easiest and most effective ways to thicken syrup is by using cornstarch. Cornstarch is a thickening agent that inhibits liquid mobility and increases viscosity. Here’s how to thicken syrup with cornstarch:

In a small bowl, whisk 1-2 tablespoons of cornstarch with 2 tablespoons of cold water until smooth and lump-free. Set aside.

In a saucepan, bring your syrup to a simmer over medium heat. If starting with a cold syrup, bring it to a boil first.
Once simmering, slowly drizzle the cornstarch slurry into the syrup while whisking vigorously. Whisk continuously for about 1 minute as it thickens up.
Remove from heat and allow to cool slightly before using or serving. The syrup will continue thickening as it cools.

A good rule of thumb is 1-2 teaspoons of cornstarch per cup of syrup. Start with less and add more as needed. Too much cornstarch can lead to a gummy texture.

Tips for Using Cornstarch

Make sure the syrup is simmering first – this helps activate the cornstarch thickening power.
Whisk the slurry well before adding – this prevents clumping.

Add slowly and whisk vigorously – this ensures even distribution and thickening.
Allow to cool slightly – syrup will thicken more upon cooling.

Cooking the Syrup Longer

Another simple way to thicken syrup without additives is by cooking it down. The longer a syrup simmers, the more water will evaporate, resulting in a thicker consistency. Here’s how it works:

Pour your syrup into a wide saucepan and bring to a simmer over medium heat.
Let the syrup gently bubble, keeping an eye on it to prevent burning.
As water evaporates, the syrup will slowly start to thicken. Allow to reduce to desired consistency, anywhere from 5-15 minutes.

Remove from heat and let cool before using.

Be careful not to overcook, as syrup can quickly go from just thick enough to too thick and sticky. Go slowly and make small reductions at a time until desired consistency is reached.

Tips for Cooking Syrup Longer

Use a wide pan – more surface area means faster evaporation.

Stir occasionally – this helps moisture escape evenly.
Watch carefully – syrup goes from thin to thick quickly.
Remove from heat before target thickness – syrup will thicken more upon cooling.

Adding Gelatin

For an extra thick, fudgy syrup, gelatin can be used. Gelatin is a natural protein derived from collagen. It acts to bind liquid, increasing viscosity and body. Here’s how to use it:

In a small bowl, sprinkle 1-2 teaspoons gelatin powder over 2 tablespoons cold water. Allow to soften 5 minutes.
Heat syrup to a simmer in a saucepan. Remove from heat.

Microwave gelatin for 10 seconds to melt, then whisk into hot syrup until dissolved.
Return to heat briefly, stirring, until fully combined. Remove from heat.
Pour into container and refrigerate 2+ hours to fully set. Stir well before using.

Start with a small amount of gelatin and add more to reach desired thickness. Too much can make syrup gummy. Refrigeration is key for gelatin to activate.

Tips for Using Gelatin

Bloom gelatin in cold water first – this prevents clumping.
Heat syrup before adding – hot liquid dissolves gelatin best.

Whisk thoroughly – ensures no gelatin bits remain.
Chill completely – allows gelatin to set syrup.

Adding Fruit Puree

Fruit purees are a great way to infuse syrup with flavor and thicken it up naturally. Fruits contain pectin, a soluble fiber that acts as a gelling agent. Here’s how to do it:

Puree fruit of choice in blender or food processor until smooth. Berries, stone fruits, and citrus work well.
Push puree through a fine mesh sieve to remove solids and seeds.
In a saucepan, combine 1/4 to 1/2 cup fruit puree per cup of syrup over medium heat.

Bring to a brief boil, then reduce heat and simmer 5 minutes, until slightly thickened.
Remove from heat and let cool. The syrup will thicken further upon cooling.

Berry purees add vibrant flavor and color while citrus purees like lemon or lime infuse brightness. The natural pectin provides thickness.

Tips for Using Fruit Puree

Use ripe fruit – overripe is best for maximum pectin.
Simmer briefly – too much heat destroys pectin.
Start with less – can always add more puree to reach desired thickness.

Strain out solids – for smooth syrup.

Making a Reduction

One technique that professional chefs use is reducing syrup down to a super concentrated state. The basic method is:

Pour syrup into a wide saucepan and bring to a boil over high heat.

Once boiling, reduce heat slightly to maintain a rapid simmer.
Allow syrup to simmer vigorously, uncovered, until reduced significantly, up to 85% its original volume.
Syrup is ready when it coats the back of a spoon and holds a line when you run your finger through it.

This concentrates the sugars and flavor compounds, resulting in a very thick, luxurious syrup. Be extremely careful towards the end as syrup can quickly burn. Watch it like a hawk and remove from heat immediately once reduced enough.

Tips for Making a Reduction

Use a large pan – more surface area speeds reduction.
Stir frequently – prevents burning on bottom.

Remove from heat before target – syrup will continue to thicken slightly.
Cool before using – thickens more upon cooling.

Adding Honey or Maple Syrup

For a foolproof way to thicken and add flavor to syrup, mix in some honey or maple syrup. Both contain more dissolved sugars than plain sugar syrup, instantly increasing viscosity and richness. Here’s how to do it:

Make basic simple syrup by dissolving equal parts sugar and water.
Allow simple syrup to cool slightly so it won’t melt honey or maple syrup.
Add 1/4 to 1/2 cup honey or maple syrup per cup of simple syrup.

Whisk or stir well to incorporate fully.

The syrup will immediately take on some thickness from the honey or maple syrup. Simmer briefly to blend flavors if desired.

Tips for Using Honey or Maple Syrup

Use real maple syrup, not pancake syrup, for best flavor.

Experiment with mild vs. bold honey varieties.
Add syrups at the end – extended cooking dulls flavors.
Store refrigerated – helps prevent fermentation.

Making an Inversion

Inverting sugar syrup is a common technique in candy making and dessert sauces. It creates a thick, smooth syrup with high moisture retention. Here’s how it works:

Make a simple syrup by dissolving sugar in water over heat.
Add an acid like lemon juice or cream of tartar once dissolved and bubblinng.

Simmer for 10-15 minutes once acidic ingredient is added. Syrup will start to thicken.
Remove from heat and stir in a pinch of salt once slightly cooled.

The acid plus heat breaks down sugar molecules, reducing water activity and increasing thickness. Salt balances flavor. Use immediately or refrigerate up to 2 weeks.

Tips for Making an Inversion

1/8 tsp cream of tartar or 1/2 tsp lemon juice per cup of syrup works well.
Simmer for full time to properly invert sugars.
Stir frequently – inversion darkens syrup slightly.

Add flavorings after – heat can diminish flavors.

Using a Refractometer

For precise control over syrup thickness, many professional confectioners use a refractometer. This tool measures the refractive index of a liquid, called degrees Brix. Follow these steps:

Purchase a refractometer calibrated for the range of your syrup. Common is 58-82% Brix.

Cook syrup to desired flavor and approximate thickness.
Allow sample to cool slightly so it won’t damage refractometer.
Place 1-2 drops on the prism, close the lid, and look through the eyepiece. The line where the blue and white fields meet is the Brix percentage.

For a thicker syrup, continue cooking to increase the reading. For a thinner syrup, dilute with water.

Target Brix values:

Simple syrup: 50-60%

Medium syrup: 60-70%
Heavy syrup: 70-80%

Tips for Using a Refractometer

Ensure proper calibration – instructions come with unit.

Only needs a drop or two – don’t overfill prism.
Take multiple readings – check different areas of syrup.
Look closely – readings can be subtle.

Making a Slurry

Another pro pastry technique is making a starch slurry. Combining starch with a liquid before adding to syrup provides instant thickening power. Here’s how:

Mix 2 tablespoons cornstarch, tapioca starch, or flour with 2 tablespoons cool water in a bowl.
Heat 1 cup of syrup in a pan until simmering.

Once simmering, slowly whisk in slurry. Keep whisking as it comes to a boil.
Boil 1 minute, then remove from heat and let cool slightly before using.

The slurry disperses evenly in the hot syrup for an instant thickening effect. Letting it boil activates the starch. Cool slightly as it will thicken more upon standing.

Tips for Slurry Thickening

Combine slurry in separate bowl first.
Add slowly while whisking vigorously.
Make sure syrup is hot to activate starch.

Use right away – slurries can start to separate.

Conclusion

Syrup that is too thin can negatively impact recipes and desserts. Luckily, many simple methods exist to improve syrup’s thickness and viscosity. Cornstarch, gelatin, fruit purees, extended cooking, reductions, and slurries are all reliable options. Use a refractometer for precise fine-tuning. With the proper technique, you can easily take syrup from thin and runny to luxuriously thick and rich.