Fresh Cranberries Bounce Like Rubber Balls

The remarkable bounciness of a fresh cranberry is due to the four small air pockets located inside the fruit (Review). These tiny chambers not only give the berry its signature spring but are also the reason cranberries float in water. This buoyancy is essential for the most common harvesting method, where growers flood the bogs, dislodge the berries from their vines, and corral the fruit as it floats to the surface. Over 90% of the cranberry crop is gathered this way, primarily for products like juice and sauce.

The discovery of this unique sorting method has a charming history. In the 1880s, a New Jersey farmer named John "Peg Leg" Webb reportedly spilled a bucket of cranberries down a flight of stairs (Review). He observed that only the firmest, freshest berries bounced all the way to the bottom, while the soft or spoiled ones remained on the steps. This simple observation led to the invention of the bounce board separator, a device still used in the industry today to sort the highest quality fruit.

For cranberries destined to be sold as fresh fruit, farmers often employ a "dry harvesting" method using mechanical pickers. After being harvested, these berries are graded based on their ability to bounce. The berries that are firm and bounce effectively are packaged for sale in grocery stores, while those that fail the test are processed into other cranberry products. This ensures that the fresh cranberries you buy are of the highest quality.