Overrun is not a term most people encounter outside of a production kitchen, but it is one of the most significant variables in the quality of any frozen dessert. Understanding it explains a lot about why gelato from a good shop tastes different from a supermarket tub.

What overrun actually means

Overrun is the percentage increase in volume that occurs when air is incorporated during churning. A mix that starts at one liter and ends at two liters after churning has 100% overrun. Commercial ice cream in the United States can legally have up to 100% overrun, meaning half of what you are eating is air. Gelato is typically churned to between 20% and 35% overrun. The result is a denser, heavier product that melts differently and delivers flavor more directly.

How the machine affects overrun

The Carpigiani LB 502G we use at Isle Brook Crest is a batch freezer, not a continuous freezer. Batch freezers give you more control over churn speed and time, which means more control over overrun. We run our batches at a churn speed that produces approximately 25% overrun for dairy flavors and slightly less for sorbets, which have no fat to trap air. The exact settings vary by base, and we adjust them seasonally as the milk fat content shifts.

Why low overrun changes the eating experience

Less air means the gelato melts faster on your tongue, which sounds like a disadvantage but is actually what allows the flavor to reach your palate more quickly and completely. It also means the product is heavier by volume, which is why a scoop of gelato feels more substantial than a scoop of ice cream of the same size. The density is not a side effect. It is the point.

The shelf life trade-off

Low overrun gelato does not keep as long as high-overrun ice cream. The denser product is more susceptible to ice crystal formation over time, which is why gelato is best consumed within a few days of production. We make new batches on a rolling schedule and retire flavors when the batch is gone rather than holding product for weeks. This is not a marketing position. It is a consequence of making gelato the way it is supposed to be made.

If you want to taste what low overrun actually produces, come in any day Wednesday through Monday. The current menu is posted every Wednesday morning at islebrookcrest.com.