How are blueberry fruits harvested? A detailed guide to the methods
How are blueberry fruits harvested? Please advise. 1. Harvesting lowbush blueberries. Lowbush blueberry fruits ripen fairly uniformly, and the early-ripening fruits generally do not drop, so you can wait until all the fruits are ripe before harvesting. In the Changbai Mountain area of China, the fruits ripen in mid-to-late July. Lowbush blueberry fruits are relatively small, making manual hand-picking rather difficult...
How are blueberry fruits harvested? Please advise.
1. Harvesting lowbush blueberries
Lowbush blueberry fruits ripen fairly uniformly, and the early-ripening fruits generally do not drop, so you can wait until all the fruits are ripe before harvesting. In the Changbai Mountain area of China, the fruits ripen in mid-to-late July.
Lowbush blueberry fruits are relatively small, making manual hand-picking rather difficult. The most widely used, quick and convenient option is a comb-toothed manual harvester. After harvesting, remove twigs, leaves, stones and other debris, then place the fruits into containers.
In the United States and Canada, lowbush blueberries are mostly harvested mechanically. The harvesting machine is also a large comb-toothed harvester, equipped with a shaking device; during harvesting it swings up and down and side to side to detach the fruits, which are then transported by conveyor belt to a cleaning unit.
2. Harvesting highbush blueberries
In highbush blueberries, the fruits of the same cultivar, on the same bush, and even on the same cluster do not ripen entirely uniformly, and harvesting generally lasts 3-4 weeks, so harvesting must be done in batches. Normally, fruits are picked once every 1 week. When the fruits are to be sold fresh for raw consumption, hand-picking is used. After harvesting, they are placed in plastic food boxes, then in shallow trays, and transported to market for sale. Bruising, sun exposure, wind and rain should be avoided as much as possible. Generally, one adult laborer harvests about 40 kg per day. During hand-picking, fruits can be graded directly according to fruit size and ripeness.
In the United States, handheld electric harvesters are used when harvesting rabbiteye blueberries and highbush blueberries to save labor. The harvester weighs about 2.5 kg and consists of an electric vibrating device and 4 extending harvesting teeth, powered by dry-cell batteries. When working, a movable fruit receiver is placed on the ground beneath the bush, the harvester's 4 harvesting teeth are inserted deep into the bush, and the power is switched on to vibrate the fruiting branches for about 3 seconds. Using this harvester requires 3 people working together, making its efficiency equivalent to 2-3 times that of manual harvesting. Before the fruits go to market, they need to be graded and packaged.
Fruits should be harvested at the right time, not too early. If harvested too early, the fruits are small and poor in flavor, which affects fruit quality. But they should not be harvested too late either, especially for fresh fruit shipped long distances; harvesting too late reduces storage and transport tolerance. When blueberry fruits ripen it is midsummer, so take care not to harvest in the rain or immediately after rain, to avoid mold and rot.
3. Mechanical harvesting
In developed countries, due to the shortage of labor resources, mechanical harvesting is receiving increasing attention in highbush blueberry production. The main principle of mechanical harvesting is shaking the fruits off. A large mechanical harvester comprising a vibrator, fruit receiver and conveyor belt device can harvest more than 0.5 ha in 1 hour, equivalent to the workload of 160 people. This greatly reduces costs. However, mechanical harvesting has several problems: first, yield loss; it is estimated that mechanical harvesting loses about 30% of the yield compared with manual harvesting; second, mechanically harvested fruits must go through a grading and packaging process; third, the initial investment is relatively large. In China, it is not suitable when farmers operate on a small, scattered scale, but mechanized harvesting should be considered for large-area, intensive cultivation.
4. Fruit grading
After harvesting, once fruits have gone through primary mechanical grading, they still contain stones, leaves, unripe fruits, and fruits that are crushed or bruised, so further grading is needed. After harvesting, fruits are graded according to their ripeness, size and so on. The grading standards for highbush blueberries mainly include: berry pH 3.25-4.25; soluble sugar <10%; total acid 0.3%-1.3%; sugar/acid ratio 10-33; firmness sufficient to withstand vibration of 170-180 revolutions/second; fruit size, diameter >1 cm; color that has not reached the inherent blue indicates the fruit is not yet ripe, while a pigment content >0.5% in the fruit means it is overripe. In practice, grading is mainly based on fruit firmness, specific gravity and refractometric reading.
Grading by specific gravity is the most commonly used method, and it relies on two principles. One is air separation. Blueberry fruits pass through an air stream, and light objects such as small twigs, leaves and dust are blown away, while ripe fruits and heavier, high-specific-gravity objects are retained and move on to the next grading step. The next grading step is generally done manually. The other method is water separation. Water separation gives better results, but its drawback is that the loss of bloom affects appearance quality.
5. Packaging
On the market, blueberry fresh fruit is usually packaged in non-toxic plastic boxes, generally with a fruit weight of 120 g per box, or 500 grams. They are then packed into cardboard boxes for storage and transport.
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