Improvement of the postharvest quality of strawberries

Methods for the improvement of the postharvest quality of strawberries are being studied in a joint research project between VTT, MTT, domestic producers and Finnish packaging and refrigeration companies during 1995–1997. The aim of the project is to find the main factors affecting the postharvest quality of strawberries and to develop the methods that can be used to prolong the shelf life and improve the quality.

Results of the 1995 season trials showed that the degree of ripeness had a significant effect on the shelf life of strawberries. Although the berries were effectively pre-cooled, transported and cold-stored, they kept their quality only one to two days, at best three days, if they were picked as full ripe. By picking them as ¾-ripe, the shelf life was prolonged at least to three days, at best even to seven days. On the other hand, the initial sensory and nutritional quality of ¾-ripe strawberries was not as good as the quality of ripe strawberries.

Pre-cooling of strawberries had an effect on the shelf life and injury of strawberries during transport. In a vibration test, pre-cooled strawberries were injured slightly more than non-cooled strawberries. The effectiveness of forced air cooling could be improved by perforation of packages. Perforation of corrugated board cases and cellular containers or cartons increased the stream velocity of air between berries and made the cooling more effective.