In the experiments reported below, strawberries of uniform size and colour were collected from a commercial farm and stored briefly at 20 degsC or higher.
Some were then immersed in water at 1 degsC (hydro-cooling) and removed once their temperature had reached 20 degs, 15 degs, 5 degs or 1 degsC, while others were cooled to 1 degsC by forced-air cooling.
Fruit from each of these treatments was compressed by applying a constant load using a convex-tipped probe. Other fruit was dropped onto a steel plate or hit with a steel ball to assess the effect of impacts.
Compression produced less bruising when the fruit was cold. By contrast, cold fruit bruised more in the dropped-fruit tests, especially when it was cooled by forced-air cooling.
The results suggest that fruit should be picked early in the day, when its temperature is still low. It should be transported in containers in layers no more than three fruit deep in order to minimise compression bruising.
Transfer points should be minimised during grading and packing so as to avoid impact injury and, if forced-air cooling is used, the fruit should be graded and packed before cooling.
Strawberry Bruising Sensitivity Depends on the Type of Force Applied, Cooling Method and Pulp Temperature by Ferreira, Sargent, Brecht and Chandler (2009). HortScience 44 (7): 1953-1956. ISHS members can view HortScience from the website www.ishs.org.