Quality preservation of fresh berries after harvest: strawberries, raspberries, blackberries - the challenge and the opportunities
Berries ( strawberries, raspberries, blackberries) are one of the few product categories growing in retail sales every year in Europe. Improvements in handling, availability and taste, as well as their superb health properties make them very atractive to the consumer.
This fruit category has several aspects in common , that makes it difficult to handle after harvest, since they:
• are very perishable: average shelf life of strawberries and raspberries at optimum temperature ( 0C) is 7 days, blackberries is 5 days.
• are all hand-harvested, one by one
• have a very thin skin, and are very sensitive to pressure or bumps
• are very susceptible to fungi, especially Botrytis sp.
• do not stand free moisture in their surface. When condensation in the fruit surface occurs as a consequence of fruit being moved out of cold storage, free moisture deposits in the fruit surface and fungi grow very quickly, even at low temperatures
These factors force producers to take stricter post-harvest handling measures than with other fruits. Berries are certainly the most perishable fruits of the fresh produce category.
Therefore some measures are key for a successful berry transport and distribution, such as:
• ensuring proper sanitation in the field, avoiding any kind of inoculum from decayed fruit
• ensuring good drainage and avoiding water accumulation in the field, to avoid postharvest diseases
• timely field fungicide applications, to reduce fungi spore load, especially in high humidity days
• field packing, to avoid double handling
• ensuring harvest to cooling time does not exceed two hours; delays in cooling have a dramatic effect on quality reduction
• eliminating field heat from berries through a fast temperature pull down ( less than 1 hour)
• ensuring a rapid fruit distribution, ensuring that inventories move quickly out of cold storage into customers retail shops
• ensuring a well coordinated harvest program, avoiding fruit peaks that eventually need to be sold at a discount or discarded
Due to their very perishable nature, specific packaging technology has been developed for berry quality preservation. In particular, the use of modified atmosphere packaging that maintains a high CO2 concentration (10%-15% CO2) allows the storage and distribution of berries for an additional 3-4 days without fungi decay.
An additional innovation has been the development, over the last 5 years, of new berry varieties that have better flavor and shelf life, while maintaining other eating qualities ( sugars, etc). The evolution of berry plant breeding continues actively by all major berry companies and will deliver varieties with better taste and longer life after harvest in the next years.
Copyright 2011 Dr. Manuel Madrid