Caramelization

Caramelization is the simplest browning reaction — pure sugar, heated until it breaks down into hundreds of new compounds that produce the characteristic color, aroma, and bittersweet complexity of caramel. Unlike the maillard-reaction, no proteins are involved.

The process

When sucrose is heated above ~330°F/165°C, it melts into a thick syrup and begins to decompose. The sugar molecules fragment and recombine into a cascade of products:

• Organic acids (acetic acid and others) — contribute sourness
• Sweet and bitter derivatives — the bittersweet complexity of caramel
• Volatile aromatic molecules — butterscotch (diacetyl), nutty (furans), sherry-like (acetaldehyde), fruity (esters), and the distinctive caramel note (maltol)
• Brown polymers (melanoidins) — the color

The process is progressive: light yellow (mild, mostly sweet) through amber (complex, bittersweet) to dark brown (increasingly bitter, eventually burnt). The cook’s job is to stop at the right point.