Saturday, January 23, 2021

Post-harvest of blueberries

The method of harvest and postharvest handling can have a large impact on fruit quality and storage life.

Blueberries ripen rapidly on the plant, going from 50% pink to fully blue in 2 to 3 days, but require several days following full color development to develop sweetness and flavor.

The berry yield per bush is between 8 and 12 kg, which requires up to ten pickings by hand during the harvest season. However, in countries with high labor costs, blueberries are first picked manually 3–5-times, and after a several-day interval, the rest of the fruit is collected by a fruit harvester.

Machine-harvested fruit are usually processed as frozen fruit. Mechanical harvesting of highbush or rabbit eye fruit is conducted by over-row harvesters that use rotary, sway, or slapper mechanisms to remove the fruit from the bush, while lowbush blueberries are harvested with hand or mechanical rakes.

Fresh market fruit is generally harvested by hand. This allows selection of ripe fruit with little bruising. Pickers carry five-quart collection buckets on their belts. When filled, the worker will empty the buckets or exchange it for empty buckets with a harvest supervisor.

Handling and physical abuse during and following harvest must be minimized to maximize market life.

Fruit quality loss during postharvest handling is primarily the result of decay, physiological breakdown, physical abuse, and dehydration. Fruit must be of high initial quality to maximize storage life.

After being harvested, regardless of the picking method, blueberries are immediately sorted and placed in cold storage (for either long storage or processing by hydrocooling technology with the addition of sodium hypochlorite solution) at the optimum storage temperature of 0 °C to reduce respiration and fruit dehydration. Most of the fruit is directly intended for fresh consumption.

Controlled or modified atmospheres reduce decay of blueberries with optimum concentrations of CO2 ranging from 10% to 12%. Reduced O2 concentrations of 1% to 2% have been recommended but there is little evidence that O2 reduction is beneficial.

In countries that are large blueberry producers, blueberries not intended for fresh consumption are most often frozen in fluidized tunnel freezers. In the world markets, fresh blueberries are sold in retail packages, and frozen blueberries are sold in bulk packages.
Post-harvest of blueberries

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