How to Keep Strawberry-Rhubarb Filling from Becoming Watery for Crumble Bars

Strawberry and rhubarb are a classic pairing for many desserts, come spring, and if you can find the rhubarb stems in any local store, we highly recommend buying and baking a batch of crumble bars. While we have a recipe on our website for that, there’s one big issue with these bars – the filling becoming watery and ruining the crust. Whether you’re preparing a strawberry-rhubarb pie, crumble, or jam, a runny filling can be frustrating and ruin the shape and sturdiness of your dessert. But don’t worry, there are several tricks to prevent your strawberry-rhubarb filling from turning into a watery mess and in the end running the crumb.

Use a Thickener

One of the most effective ways to prevent a watery filling is by using a thickening agent, such as cornstarch, arrowroot powder, or flour, all of these are quite good at absorbing excess liquid during baking. Cornstarch is the most commonly used thickener for fruit fillings. It creates a smooth, glossy finish and helps hold the fruit’s juices together without being too noticeable. Arrowroot powder is a great alternative to cornstarch and works well at lower cooking temperatures. It creates a clear, glossy filling and works wonders for delicate pies. Flour is also a good option, though it’s a bit heavier than cornstarch and can result in a more opaque filling. Use about 1 tablespoon of either of these thickeners per 1-1.5 cups of fruit.

Pre-Drain the Fruit

Rhubarb and strawberries both release a lot of moisture during cooking, and too much liquid can cause the filling to become soupy. To avoid this, chop them both up and place them in a colander over a bowl, then sprinkle a small amount of sugar over the fruit and let it sit for 15-30 minutes. The sugar will draw out excess liquid, especially the strawberries, which you can discard. After draining, pat the fruit dry with a paper towel to remove any remaining moisture. The less liquid you start with, the less likely your filling will be watery.

Cook the Filling to Reduce Liquid Content

Another effective method to thicken the filling is to pre-cook the fruit filling before adding it to your dessert. This step helps the juices to evaporate and the thickening agent does its job more effectively. After the draining process, add the chopped strawberries and rhubarb into a saucepan over medium heat, and cook for 5-10 minutes until the fruit begins to soften and release its juices. Take care for it to not overcook, you want the fruit to stay intact, once the fruit has softened, add the thickening agent, and stir until it has absorbed the liquid and thickened. Let the mixture cool slightly before using it in your recipe.

Use Less Water and Sugar

Both water and sugar can contribute to excess moisture in your strawberry-rhubarb filling, so be mindful of how much of each you’re using this is especially for the water. As for sugar, while it helps bring out the natural sweetness of the fruit, using too much of it can cause the fruit to release more liquid. Start with a modest amount of sugar, taste and only add more if needed. If your strawberries are particularly sweet, you might not need much sugar at all. On the other hand, rhubarb can be less sweeter, so a little extra sugar may be necessary to balance out.

Let the Filling Cool Before Assembling

After making your strawberry-rhubarb filling, it's crucial to let it cool before adding it to your dessert. Hot filling can release additional liquid when it hits the dough or crumble mixture, leading to a soggy crust. Once your fruit filling is prepared, allow it to cool to room temperature or slightly warm before assembling your dessert. Cooling the filling allows it to set up more firmly, preventing it from releasing too much liquid once it’s in the crust or topping.

Avoid Over Mixing the Filling

Overmixing your fruit filling can cause it to become too mushy, resulting in more liquid being released during baking. Mix the fruit gently with your thickening agent and sugar, just enough to coat everything evenly. Stir the fruit gently, and don’t mash it unless the recipe specifically calls for it. You want to preserve some texture in the filling so that it doesn’t turn into a watery mess.