US biophysicist Amy Rowat has shared the science behind creating a perfect sweet pie at the World Science Festival, recently held in New York.
Amy, who co-developed the internationally acclaimed Harvard Science and Cooking Course, deconstructed an apple pie and examined every aspect of its chemistry, including steam vents, pie geometry, thickening molecules and fat chunks. Here are some of Amy’s findings, as reported by The New York Times.
Colour Chemistry: The famous Maillard reaction – the chemical reaction that occurs between amino acids – and is essential for colour and flavour happens faster at a higher temperature. For a browner, more flavourful crust, set the oven to at least 190°C and before baking, brush the pie with egg wash with heavy cream mixed in to increase protein and lactose.
Crust Composition: When flour meets water, a gluten protein network forms, which gives dough structure. However, bakers don’t want gluten to form so extensively the crust becomes tough. Replacing a portion of water with alcohol – such as rum or vodka – or vinegar can help impede gluten formation.
Building Flakiness: Butter, which consists of tiny water droplets dispersed in a matrix of fat, is a crucial source of flakiness. The water droplets turn to steam during baking and become trapped in the crust, resulting in air pockets. Butter with a slightly higher water content and less fat works well for pies. Butters from the US usually have higher moisture contents and yield a flakier, more porous crust compared with European butters.
Apple Slice Structure: As a pie bakes, water from the apples converts from liquid to gas and air pockets expand. Simultaneously, the apples shrink in volume and soften, often falling into crevices. This can result in a sizable space between crust and filling. For a truly fruit-packed pie, slice apples flat instead of cutting them into wedge, and pat them down in the crust to make sure they lie flat, which minimises collapse.