During warm-cold shipping abuse, what do tiny ice-cream gums mainly fight?

Answer: Large crystal growth

Thicker first spoonful — Not quite. Gums can thicken the mix and change mouthfeel, so this is a tempting answer. But in warm-cold shipping abuse, the bigger quality threat is not the first spoonful feeling slightly thin. It is heat shock: small crystals disappear and larger ones grow until the whole pint tastes coarse.

Large crystal growth ✓ — Right. Guar, locust bean gum, cellulose gum, xanthan, and similar stabilizers are often used at tiny levels to slow ice and lactose crystal growth. The payoff is not that they make ice cream magically premium; they buy insurance against large crystals. A craft pint with perfect ingredients can still arrive icy if distribution lets the crystal network coarsen.

Slower surface melting — Not quite. Stabilizers can slow meltdown, so this is related. But the classic shipping problem is repeated warming and cooling that coarsens the ice-crystal network. A pint can melt slowly on the counter yet still become icy after weeks of temperature cycling.