On Food and Cooking

cooking domesticates them: heat breaks down
and softens their pectin-rich cell walls, and
the astringent tannins become bound up in the
debris, so the taste softens as well. Quince
paste firm enough to slice is a traditional
product of Spain (membrillo) and Italy
(cotognata), and in Portugal a quince preserve
was the original marmalade (marmalada). The
16th-century alchemist and confectioner
Nostradamus gave several recipes for quince
preserves and observed that cooks “who peel
them [before cooking] don’t know why they
do this, for the skin augments the odor.” (The
same is true for apples.)
Quinces have another enchanting quality:
when slices are slowly cooked in sugar over
several hours, they turn from a pale off-white
to pink to a translucent, deep ruby red. The
key to this transformation is the fruit’s store
of colorless phenolic compounds, some of
which cooking turns into anthocyanin
pigments (p. 281). Pears contain the same