Tips and tricks.
How many times has your beautifully flaky and crisp piecrust gotten soggy because you didn’t properly tend to your fruits and let their juices run out like teenagers in the night? It’s time to reel in that water, activate that pectin, and slice a clean piece of pie.
The innate thickener in all fruits is pectin, a carbohydrate in plant cell walls that releases at high heat. Boiling fruit with sugar causes pectin molecules to hold on to each other as they disperse throughout the filling. While at a boil, the chains of pectin get tangled up with the sugar that’s suspended in the fruit’s water molecules. The molecules chill out as the filling cools after baking, and as they settle, water gets trapped inside the pectin, forming a gel and yielding a perfectly set filling.
Pectin content varies by fruit and is most plentiful in a plant just before it’s fully ripe. And even when their pectin content is high, not all fruits have enough to produce a beautifully set filling. This is where thickeners come in. Starch thickeners absorb water molecules and restrict water movement as they grow, helping to form a fruity gel or thicken a custard. -Aralyn Beaumont
Cornstarch is super fine and contains no protein, so it disperses and absorbs water without restriction. It’s a strong binding agent and activates at boiling temperature. Its downsides are that acids tend to break down its starch molecules, it’s not completely flavorless, and it can produce a cloudy color, so it’s best in a well-seasoned custard pie.
This is your grandma’s favorite thickener, but maybe it’s best left in her pantry. Because of its high protein content, it has a weaker concentration of starch (75 percent), which increases the risk of clumping while the rest of the filling stays runny. It’s suitable for sturdy fruits like apples that require a long baking time.
Gelatin is a product of heated collagen, which is found in animal skin, connective tissue, and bone. It’s a long, thin structure that is really attractive to water, and when the two combine, they settle into an elastic structure that can readily support air bubbles—ideal for chiffons and mousses. Gelatin sheets and powder have to be activated (bloomed) in water before being added to a filling.
Tuber starches (tapioca, potato, arrowroot)
These starches contain no protein, so they’re effective even at low concentrations. They activate at low temperatures, yield a silky texture, and have no flavor. They’re ideal for light and watery fruits like berries. They are much more delicate than other starches so treat them with respect (refrain from overstirring and overheating). Dotting the filling with small pieces of butter can help prevent boiling and thus keep your delicate starches from breaking.
Apples have so much pectin that grating them into your berry pies gives a boost to whatever thickening agent you’re using.
Helpful Tips For Thickening
Fruits with high pectin content include apples, cranberries, gooseberries, plums, and grapes. Keep in mind that pectin content will vary by species.
Fruits with low pectin content include apricots, blackberries, blueberries, cherries, peaches, pears, raspberries, and strawberries.
For fruit pies, macerate the fruit for an hour to release some of the juices. Discard excess juice and mix the fruit with thickener and spices.
Mix the thickener with whatever dry ingredients you’re adding to the filling. This way the flavoring and thickening agents will disperse throughout the entire pie, leaving no clumps or bland spots behind.
The tighter you pack the fruit, the less room for the juices to travel and the tighter your filling will set.
Smaller pieces of fruit cook more quickly, which is good for delicate starches.