Blueberries, due to their delicate skin and plump flesh, are prone to damage and squeezing during the sorting process if not handled with care, affecting the quality and shelf life of the fruit. To achieve lossless sorting of blueberries, scientific control is required in multiple aspects, from tool selection and operating techniques to environmental control. The following is a detailed operating guide.

The first step in sorting blueberries is thorough preparation, which is essential for preventing damage.

When choosing tools, prioritize soft, smooth containers, such as food-grade plastic baskets or shallow bamboo baskets. Choose plastic baskets with smooth edges and no internal protrusions. For bamboo baskets, ensure the weave is even to prevent sharp thorns from scratching the fruit. Avoid using iron containers or hard plastic boxes. These are rigid and can easily collide with the blueberries during handling and sorting, potentially damaging the skins.

Also, clean your work area in advance, ensuring it's clean, tidy, and free of grease and debris. You can place a food-grade silicone mat or soft cotton cloth about 1-2 cm thick on the surface to cushion the impact of placing the blueberries, further reducing the risk of damage.

Also, observe the blueberries' freshness before sorting. Freshly picked blueberries should be placed in a cool, well-ventilated area for about 30 minutes to allow some of the surface moisture to evaporate naturally. Because the blueberry skin with water droplets is more fragile and easily damaged by friction, sorting it after letting it stand can effectively reduce damage.

For large-scale blueberry growers or processors, mechanical sorting is an important means of improving efficiency, but it requires careful equipment commissioning and maintenance to prevent fruit damage.

When choosing equipment, a dedicated blueberry sorter with a soft conveyor belt and adjustable speed is preferred. Food-grade rubber is preferred, and the surface should have a certain degree of elasticity and friction to ensure smooth conveyance of the blueberries while reducing friction between the fruits. Before formal sorting, a test run is essential: adjust the conveyor belt speed to 1-1.5 meters per minute. This speed ensures efficient sorting while allowing sufficient time for the fruits to be identified and graded, minimizing collisions and crushing caused by excessive speed.

Also, check the sorter's grading baffles to ensure smooth edges and a reasonable gap between them and the conveyor belt. Excessive gaps can easily cause fruit to fall, while too small gaps can cause fruit pinching. Generally, the gap should be 2-3 mm larger than the maximum diameter of the corresponding grade of blueberries. Furthermore, the sorter should be regularly cleaned of impurities and residual fruit to prevent damage caused by friction between impurities and fruit. During the mechanical sorting process, dedicated personnel are assigned to monitor the equipment's operating status in real time. Any problems such as conveyor belt deviation or loose baffles should be detected and immediately shut down for maintenance to prevent extensive fruit damage caused by equipment failure. After each day's sorting, the equipment should be thoroughly cleaned and lubricated to ensure smooth operation of all components and minimize damage to the blueberries caused by equipment stalling.