On Food and Cooking

centuries cheese has been melted in a
communal pot at the table and kept hot over a
flame for dipping bread, it’s well known that
wine can help keep melted cheese from
getting stringy or seizing up. The ingredients
in a classic fondue, in fact, are just alpine
cheese — usually Gruyère — a tart white
wine, some kirsch, and sometimes (for added
insurance) starch. The combination of cheese
and wine is delicious but also savvy. The wine
contributes two essential ingredients for a
smooth sauce: water, which keeps the casein
proteins moist and dilute, and tartaric acid,
which pulls the cross-linking calcium off of
the casein proteins and binds tightly to it,
leaving them glueless and happily separate.
(Alcohol has nothing to do with fondue
stability.) The citric acid in lemon juice will
do the same thing. If it’s not too far gone, you
can sometimes rescue a tightening cheese
sauce with a squeeze of lemon juice or a
splash of white wine.