Why is sorbet icier than ice cream?
Sorbet isn't a lower-effort ice cream -- it's solving the same ice-crystal problem with one fewer tool available.
The kitchen answer
Ice cream has fat to coat and protect its ice crystals. Sorbet has none, which means sugar concentration has to do that entire job alone -- and getting it wrong in either direction shows up immediately, as either an icy block or a slushy mixture that won't set.
What's actually happening
In ice cream, fat (see Cold & Freezing) coats small ice crystals and physically slows how easily they merge and grow. Sorbet has no fat at all, so it's relying entirely on sugar concentration and churning to keep crystals small -- there's no second line of defense once churning is done.
Sugar concentration is also doing double duty in sorbet: too little sugar and there's not enough dissolved solids to depress the freezing point meaningfully, so it freezes into a hard, overly icy block; too much sugar and the freezing point drops so far the mixture barely sets at all, staying slushy. Ice cream's fat content gives it a wider margin for sugar level to vary within and still turn out fine -- sorbet's margin is much narrower.
What does that mean for your recipe
Good sorbet recipes are precise about sugar content for a real reason, not out of fussiness -- professional sorbet bases are often built and checked against a target sugar concentration (sometimes measured directly with a refractometer) rather than "to taste," because taste doesn't reliably tell you whether the concentration is actually in the workable freezing range.
What can go wrong
- Sorbet frozen into a rock-hard, icy block: too little sugar -- not enough freezing-point depression, and no fat to fall back on.
- Sorbet that never firms up: too much sugar -- the freezing point has been pushed down past what the freezer can counteract.
- Adjusting sweetness without checking texture: tasting "less sweet" and adding more fruit or less sugar changes the freezing behavior just as much as the flavor.
- Comparing sorbet unfavorably to ice cream on iciness alone: a fair comparison needs fat-free ice cream (or gelato with less fat) as the baseline, not full-fat ice cream.
Try it yourself
Same fruit purée, two sugar levels:
- Make one batch of sorbet base at a standard sugar level.
- Make a second batch with noticeably less sugar, same fruit and volume.
- Churn and freeze both identically.
Watch for: the lower-sugar batch freezing distinctly harder and icier despite identical churning -- direct proof that sugar concentration, not just churning, is controlling the outcome here.
Go deeper
This is the same colligative-property relationship as freezing point depression covered in Cold & Freezing, just pushed to a tighter tolerance because there's no fat buffering the result -- sorbet is arguably the purest kitchen demonstration of that one mechanism working (or failing) entirely on its own.