Ice cream that has been through a freeze-thaw cycle tastes wrong. Not just softer — texturally different. Gummy, icy, coarse. The damage is not just thermal; it is structural.
During the initial freeze, ice crystals nucleate rapidly in a matrix stabilized by emulsifiers, proteins, and partially coalesced fat. The ice crystals are small because nucleation happens quickly. During a thaw-refreeze cycle, the small crystals melt and recrystallize into fewer, larger crystals. This is Ostwald ripening — the thermodynamic tendency for small particles to dissolve and deposit onto larger ones, because larger crystals have lower surface energy per unit volume.
The fat network, meanwhile, has its own damage trajectory. Partial coalescence of fat globules during churning creates a fragile lattice that gives ice cream its body. Thawing allows this network to relax and partially collapse. Refreezing doesn't rebuild the original fat network — it creates a new one with different geometry, different air cell distribution, and different mouthfeel.
The two structural systems — ice crystals and fat network — degrade through different mechanisms on different timescales. Ice recrystallization is a thermodynamic process driven by crystal size distribution. Fat network collapse is a rheological process driven by stress relaxation. Both are irreversible in practice, but for different physical reasons.
The texture of ice cream is not a property of its ingredients. It is a property of its process history — a frozen record of every thermal event the material has experienced.