Fat rendering — the slow conversion of solid animal fat into liquid cooking fat — is one of the oldest food preparation techniques in existence. López-Alt's scientific approach identifies the precise conditions that produce fully rendered, clean-tasting fat versus partially rendered, gummy, or off-flavoured results.
The application of low heat to solid animal fat (pork belly skin, duck skin, chicken skin, lard, beef suet) to melt and separate the pure fat from the connective tissue, water, and proteins. The goal is maximally rendered fat with minimal protein browning and no remaining gummy connective tissue.
- Start in a cold pan with no additional fat — the fat will render into its own liquid. A hot pan sears the exterior before the interior fat has time to melt, trapping it inside - Low heat throughout — high heat browns the protein components before the fat has fully rendered, producing a gummy rather than crispy result. The exception is the final browning stage after the fat has rendered - Score skin deeply before rendering — this provides channels through which the liquid fat can escape from the fat layer beneath the skin - Add a small amount of water at the start (for duck and pork belly) — the water prevents scorching while the fat begins to render and evaporates before the final crisping stage [VERIFY: approximately 1cm of water in the pan] - The two stages: slow rendering (low heat, fat liquefies and escapes) followed by crisping (medium-high heat, protein structure browns and crisps in the rendered fat) Decisive moment: The transition from rendering to crisping — when the skin looks deflated, the fat has mostly rendered out, and the pan contains a pool of clear liquid fat. At this point increase heat to begin browning the now fat-free protein structure. The skin will crisp in its own rendered fat.
THE FOOD LAB (continued) + THE DUCHESS BAKE BOOK