The key factors in the harvest and postharvest treatments of strawberries.
Mokkila, M., Sariola, J. and Hagg, M.
VTT Tiedotteita Year: 1999 Issue: No. 1955 Pages: 55 pp. Ref: 6 pp. of ref.
1999
บทคัดย่อ
This handbook discusses the main factors affecting the postharvest quality of strawberries and describes the methods that can be used to prolong shelf life and improve quality. It also summarises the differences between the quality and shelf life of 10 different strawberry cultivars cultivated in Finland (Bounty, Dania, Elsanta, Honeoye, Jonsok, Korona, Lambada, Nora, Polka and Senga Sengana). The significance of each postharvest step is illustrated with examples that were obtained as the result of a joint research project which was carried out between VTT, MTT, domestic producers and Finnish packaging and refrigeration companies, during 1995-1997. Because every single treatment of strawberries can cause mechanical injury to the berries, they ought to be picked straight into the selling package as carefully as possible. The degree of ripeness has a significant effect on quality and shelf life. By picking when partially ripe, berries do not become damaged by transport vibration as severely as if
picked when fully ripe. The amount of mouldy berries is then less and the shelf life can be several days longer. On the other hand, the initial sensory and nutritional quality of partially ripe strawberries are not as good as the quality of ripe strawberries. The most critical factor influencing postharvest quality is temperature. Precooling as soon as possible after harvesting and storage at low temperatures are essential for decelerating the respiration rate of strawberries. Cooled strawberries have also proved not to be damaged by transport vibration as severely as uncooled strawberries. Perforation of the cardboard cases as well as the containers and cartons increases the stream velocity of the air between the berries and makes forced air cooling more effective. Two different kinds of forced air-cooling systems that are practicable at farms were constructed and tested during the project. A storage and transport temperature of 2 deg C is recommended for strawberries. Although there are no significant diff
erences in the shelf life between storage temperatures of 2 deg C and 5 deg C, the amount of mouldy berries increases faster at 5 deg C. Spring suspension has an influence on the intensity of vibration of the trucks. Because low frequencies of vibration are the most injurious for strawberries, trucks with air springs are recommended instead of trucks with leaf springs for transport of strawberries. In the markets strawberries ought to be stored in a cold store and selling at a cold counter is recommended.