Frozen yogurt stays soft because added sugars and constant churning prevent large ice crystals from forming.

The smooth texture of frozen yogurt is a result of freezing point depression and mechanical aeration. When water freezes, it naturally forms a crystalline lattice structure. By adding solutes like sucrose, fructose, or corn syrup, manufacturers lower the temperature at which the liquid turns to ice. This ensures that even at freezer temperatures, a portion of the mixture remains liquid syrup, which coats the solid ice crystals and prevents them from binding together.The churning process, often referred to as 'overrun' in the dairy industry, is equally critical. As the yogurt base is chilled, rotating blades constantly scrape the sides of the freezing canister. This action incorporates air bubbles into the mix and physically breaks down ice crystals before they can grow larger than 50 micrometers. Crystals smaller than this threshold are undetectable by the human tongue, resulting in a velvety mouthfeel.Stabilizers such as guar gum or carrageenan are also frequently added to maintain this structure over time. These ingredients bind to water molecules and increase the viscosity of the unfrozen portion. This prevents 'heat shock,' a phenomenon where small ice crystals melt and refreeze into larger, crunchy grains during temperature fluctuations. Research from food science departments, such as those at Cornell University, emphasizes that the balance of sugar, air, and stabilizers is what differentiates premium frozen yogurt from a simple frozen block of dairy.