There is obviously no shortage of literature on how to make apple pie, so this discussion will be condensed into two main points: 1) an endorsement of J. Kenji Lopez-Alt’s technique of par-cooking apples at 160F to produce a crisp, firm apple filling and 2) the rejection of the classic nutmeg/cinnamon flavor profile for a lighter, more sprightly combination of honey, peach jam, and lemon zest.
I realize that cooking apples sous vide probably requires a bit of explanation. I’ve offered two below, a simplified version and a complete one.
Explanation without scientific jargon: Pectin is a sugar found in cell walls that helps to hold the plant cell together. By par-cooking the apples at 160F, we encourage a chemical reaction that converts pectin to a form that is more stable under heat without adding so much heat that the pectin itself degrades. The result is an apple filling that holds together and keeps a firm texture throughout the baking. In this case, sous vide is used as a matter of convenience as it is the simplest way to precisely regulate temperature.
Explanation with scientific jargon: Pectin is a complex polysaccharide that acts in concert with cellulose to maintain the structural integrity of the plant cell wall. At normal cooking temperatures, pectin is not heat stable, leading to an applesauce-like mush upon baking. Pectinesterases are naturally occurring enzymes in the apple that catalyze the de-esterfication of pectin, allowing them to cross-link with calcium and other divalent cations to increase intracellular cohesion. The result is a heat-stable form of pectin that will keep the apple filling firm throughout the bake. By immersing the apples in a 160F water bath, heat is provided to the pectinesterase reaction without raising the temperature to the point that the enzyme is denatured. In this case, sous vide is used as a matter of convenience as it is the simplest way to precisely regulate temperature.
On a related note, there are many traditional apple pie recipes that call for 1-2 tablespoons of lemon juice to be tossed into the filling. The biochemical rationale behind this is that both intrinsic pectin stability and pectinesterase activity (it’s a bit more complex than that but the statement holds true within this pH range) are increased with decreasing pH . This highlights another advantage of the par-cook strategy in that it’s no longer necessary to add an unpalatable acid to the pie just to stabilize the pectin.
Aside from this extra par-cooking step, the only other major variation in this recipe is to omit nutmeg and cinnamon in favor of honey, peach jam, and lemon zest. This combination of flavors is inspired by the traditional Korean tea yujacha, or honey citron tea (sold as a marmalade that is stirred into hot water), which has a very similar flavor and can also be used in the filling. The citrusy undertones of the lemon zest, or yuzu peel, if opting to use honey citron tea, complement the sweet tartness of the apples much more than cinnamon or nutmeg ever could.
There is no correct way to make apple pie (although there probably are a few incorrect ones). This method produces a firmer texture than most recipes, and whether that is a desirable property is up to personal preference. Nevertheless, it is always a worthwhile effort to to gain a better understanding of the physical and chemical properties behind different cooking techniques.
For a comprehensive review of the techniques and rationale behind baking apple pie, please refer to The Food Lab’s excellent collection of articles on apple pie.
pie // sous vide apples + lemon zest
Portioned for a 9" pie pan
- 325g (2½ cups) all-purpose flour
- ¾ cup (1.5 sticks) unsalted butter
- 1 tsp salt
- 1 tbsp white sugar
- 1 egg, beaten
- 8 apples of your choosing
- 3-4 tbsp peach jam, 1 tbsp honey, and zest of one lemon or 3-4 tbsp yujacha (honey citron tea).
- 2 tbsp cornstarch
- ½ cup sugar
Preheat the oven to 425F.
Measure and sift 325g (2½ cups) of all-purpose flour into a mixing bowl with 1 tsp salt and 1 tbsp sugar. Working quickly, roughly cube ¾ cup (1.5 sticks) of butter and place them at the bottom of a food processor. Pour the flour mixture into the food processor and pulse several times, while drizzling cold water through the feed tube, until it reaches the consistency of coarse, moist sand. Divide the dough into two balls of equal proportion. Flatten into discs, wrap with parchment paper, and chill the discs in the fridge for at least 30 minutes. At this point, the dough can also be frozen for later use.
Meanwhile, peel 8 apples and slice into thin strips. In a large mixing bowl, toss the apples with ½ cup sugar, 2 tbsp cornstarch, and either 3-4 tbsp peach jam, 1 tbsp honey, and the zest of one lemon, or 3-4 tbsp of yujacha. Vacuum seal and immerse in a 160F water bath for 1 hour. Transfer the contents of the bag to a large pot or dutch oven and cook under medium heat until the juices thicken, stirring frequently with a rubber spatula or wooden spoon. Arrange the apples in a single layer on a baking sheet and set aside in the fridge until completely cool.
While the apples cool, roll out the bottom crust so that there are a few inches of overhang off of a 9″ pie dish and install into place, using kitchen shears to remove any extra overhang. The top crust can either be a top shell, a lattice, or any other design of your choice – it can be rolled out prior to adding the filling and set aside for later. Additional details such as the leaves can be made by cutting out the shapes from flattened dough. At any point during this time, the dough and crust can be re-chilled in the fridge to prevent melting – just wait 5-10 minutes for the temperature to decrease and begin working again.
When the filling has completely cooled, transfer it over the bottom crust and install the top crust of your choice on top of the filling. With a brush, apply a beaten egg wash to any exposed dough to assist with the browning of the crust.
Bake in a pre-heated oven at 425F for 20 minutes. Reduce heat to 375F and bake until deep golden brown, about an additional 30 minutes, checking occasionally to ensure that the outer rim of the crust does not burn. Take the pie out of the oven, allow to cool, and serve.
Recipe adapted from Serious Eats – Gooey Apple Pie