Grades 6–8 · Everyday Life
Why can thawed fruit be softer than fresh fruit?
A fresh berry feels firm partly because its cells and cell walls form a supporting tissue. Much of the berry is water. When it freezes, some of that water becomes ice, and growing ice crystals can disturb the delicate cell structure.
In the diagramIce can change a fruit’s cell structureEqual windows of a schematic plant tissueFresh tissueSlower freezingCell walls support tissueLarger crystals can damageAfter thawing, damaged fruit can leak juice and feel softer.
Freezing rate matters. Under otherwise comparable conditions, faster freezing generally creates smaller crystals, while slower freezing allows larger crystals to grow. Larger crystals can cause more damage. When the berry thaws, the ice returns to liquid water, but disrupted cells and tissue do not simply rebuild themselves. Juice may leak out, and the berry can feel softer.
This is why a reversible change of state can cause a change that is not fully reversible in the whole food. Freezing also slows many changes responsible for spoilage, but it does not sterilize food or stop every chemical reaction. Different foods respond differently because their structures, water content and other ingredients differ. The drawing compares crystal-size tendencies, not an exact prediction for a particular fruit.
About this explanation
Starting knowledge: Know that plant tissue contains water-filled cells and that water can freeze into ice.
Sources
- University of Minnesota Extension — Preserving food at home: Freezing
- University of Georgia National Center for Home Food Preservation — Summer is a Good Time to Think About the Cold