You can thicken plum jam by continuing to cook it to evaporate more liquid, adding pectin, or using a thickening agent like cornstarch.
Plum jam typically thickens as it cooks down due to the natural pectin in the fruit, the sugar added, and the evaporation of water. However, sometimes the jam doesn't set to the desired consistency. When this happens, there are a few methods you can use to achieve a thicker jam.
One common method is simply to continue cooking the jam over medium heat, stirring frequently, allowing more liquid to evaporate. Be careful not to scorch it. You can test for readiness by placing a small spoonful on a cold plate; if it sets as it cools, it's done.
Alternatively, you can introduce additional thickening agents or pectin. Adding commercial fruit pectin according to package directions is a standard way to ensure a firm set, especially if your plums are low in natural pectin or you used less sugar.
Using Cornstarch to Thicken Plum Jam
Another effective way to thicken jam, including plum jam, is by using cornstarch. As a common thickening agent for various recipes like sauces, soups, and glazes, cornstarch is also a viable option for jam recipes.
- According to the reference provided, cornstarch is also a viable option for jam recipes with less added sugar or ones that feature fruits with naturally less sugar or pectin. Plums can sometimes be lower in natural pectin, making cornstarch a suitable choice, particularly in reduced-sugar recipes.
Here's how you can typically use cornstarch to thicken jam:
- Create a Slurry: Do not add cornstarch directly to hot jam, as it will clump. Instead, mix 1-2 tablespoons of cornstarch with an equal amount of cold water or fruit juice in a small bowl to create a smooth paste or slurry.
- Add to Jam: Bring the jam to a gentle simmer. Gradually whisk the cornstarch slurry into the hot jam, ensuring it's well incorporated.
- Simmer and Stir: Continue to simmer the jam for another 1-2 minutes while stirring constantly. The jam will begin to thicken as the starch granules swell.
- Check Consistency: Remove from heat and let it cool slightly to check the final consistency. If it's still not thick enough, you can repeat the process with another small amount of cornstarch slurry, but be cautious as too much can result in a cloudy or gummy texture.
Using cornstarch is a quick fix for runny jam and works particularly well when you haven't used traditional pectin or need a fast result without prolonged cooking.
