How does automated sorting affect blueberry quality?

The design of the machines through which fruit passes during the packing process affects the quality of blueberries reaching customers. We tested how the construction of the MXM BN.2 blueberry sorter translates into fruit firmness. How do competing sorters compare?

Quality is king!

Year-round fruit availability has made quality and taste the key differentiators for blueberries. A glance at the packaging is enough to assess the first parameter. Transparent punnets make it easy to spot damage, dents or abraded bloom, and customers put back on the shelf even packages with minor defects. Conversely, large, firm, unblemished fruit is treated by retailers as a premium product.

The pressure for volume often wins out over gentle fruit handling. In an era of global production and widespread automation, fruit deterioration is partly the result of how blueberries were treated before reaching the consumer. Mechanical harvesting, intercontinental transport, the packing line, logistics to the store – at each of these stages blueberries lose their firmness and bloom.

Damage on the journey from bush to punnet is a fact. It is worth remembering, however, that packing companies – through their choice of machines – have an influence on how significant the quality decline will be. The example of the MXM BN.2 sorter illustrates this perfectly.

Blueberry damage and science

The impact of physical shocks on blueberry quality is not a new topic. Scientists have been studying it for years, using specific measurement methods. Among the most notable research in this area are the works of:

• Yudong Bao, Jiasai Zeng, Yuying Liu; Dynamics and damage analysis of blueberry fruit collisions; 2026;

• Rui Xu, Fumiomi Takeda, Gerard Krewer, Changying Li; Measure of mechanical impacts in commercial blueberry packing lines and potential damage to blueberry fruit; 2015.

The key conclusions for practitioners are as follows:

1. The primary determinant of damage is the drop height correlated with the impact speed of the fruit against the surface. The lower the total drop height on the line and the height of the highest individual drops, the better for the product.
2. Greater fruit protection is provided by the use of soft materials (e.g. silicone components, foam) that absorb impact energy. Depending on the variety and the cushioning used, this translates to a reduction in impact energy of approximately 50–70%.
3. The presence of the fruit itself also cushions impacts. The more blueberries passing through the machine, the lower the impact energy. A collision with a hard surface (e.g. stainless steel) is significantly more damaging than a collision between two blueberries, as the energy concentrates at the point of contact rather than dispersing between similar structures (fruit).
4. Resistance to damage depends on the variety – some are noticeably more susceptible.
5. Damage is also correlated with blueberry weight. The heavier the fruit, the lower the impact force (G) required to cause damage.

Why is the MXM BN.2 sorter so gentle on fruit?

Because we designed it with blueberries in mind and with full awareness of how destructive passing through a packing line can be for this fruit. How does this translate specifically into the sorter’s construction?

The MXM BN.2 has the lowest total drop height (about 15 cm) of any machine currently available on the market. As fruit passes through the machine, it comes into contact with three surfaces. We describe each of these below.

1. The first point of contact between the fruit and the sorter is the entry ramp. The ramp is lined with an absorbing material, and additionally, at the point of first impact, we removed the steel substrate beneath the mat. The result of these measures is a significantly reduced impact on the fruit.
2. In the second stage, the fruit moves from the entry ramp onto a monolithic belt made from high-quality TPU. This belt is fitted with guiding channels made from a lower-hardness material, which further contributes to maintaining product quality. The belt does not rotate the fruit, meaning its bloom is even better protected. The channels on the belt ensure the fruit travels along a defined path, allowing it to subsequently achieve the flight trajectory required by the vision system.
3. Fruit assessment takes place in flight, without contact with any part of the machine. Blueberries that fail to meet the criteria are directed by compressed air onto the rejection belt, while those destined for packing land on a profiled exit ramp covered with impact-absorbing material. They then travel along the ramp to the next machine, such as an inspection table or conveyor.

You can find out more about the construction of the MXM BN.2 blueberry sorter by watching the video with Piotr:

We ran the tests. What do the numbers say?

Inspired by the scientific research, we conducted our own tests. For this purpose, we used a Techmark IRD 500 sensor, the equivalent of the BIRD sensor used by Xu, Takeda, Krewer and Li. The tests covered 3 devices – the MXM BN.2 blueberry sorter and 2 competing machines, which we will call Sorter A (a conventional sorter) and Sorter B (a grader). The tests were carried out under packing facility conditions, with fruit on the line.

During the tests, the same criteria were applied throughout. The sensor was placed among the fruit on the feed conveyor, from where it entered the sorter, and after landing beyond the sorter it was removed from the line. Measurements were taken multiple times (MXM BN.2 – 4 trials, Sorter A and Sorter B – 5 trials) in order to average the results.

Bao and colleagues state that a blueberry can withstand a maximum impact force of 2.00–3.00 N. Above these values, irreversible fruit damage may occur. At an average fruit weight of 2.9 g, for 2–3 N the G values fall in the range of 71 G–106 G. To simplify, we can assume that impacts below 71 G are safe for blueberries, while the 71–106 G range can be treated as the critical zone in this study.

Here are the results:

The collected data shows that the MXM BN.2 is the gentlest on blueberries. In the case of our sorter, the tests recorded an average of just 4 impacts per pass through the sorter, while the other machines generated 10 and 13 contacts with the surface. Equally significant is the fact that only 12.5% of the 16 impacts recorded in total during the MXM BN.2 tests fall within the zone above 71 G. The remainder are below the 71 G threshold, with no impact exceeding the 106 G level.

How do the competitors compare?

Sorter A: during a single pass through the sorter, the sensor recorded an average of 10 contacts with the machine; 37.3% of these impacts fall into the risk category (between 71 G and 106 G), and 29.4 percentage points exceed the 106 G threshold.

Sorter B: generated an average of 13 impacts, of which 60.0% were in the risk zone and as many as 44.6% exceeded 106 G. The maximum recorded impact (288.6 G) is more than 2.5 times higher than the upper limit of the critical zone.

How does physics affect the blueberry business?

When choosing a blueberry sorter, throughput and sorting optics alone are not enough to consider. The machine’s construction and its impact on fruit quality are highly significant variables – particularly today. Blueberry supply is growing, yet not every grower is able to deliver fruit at the required quality level. Mechanical harvesting and multi-day transport from other continents cause fruit quality to decline – and this is visible to the naked eye. If you are an importer or a packing company, you have limited influence over what happens to the input before it reaches you. You do, however, take responsibility for how your machines affect the firmness and bloom of the blueberry.

If you export fruit to distant markets, the way you handle blueberries has a direct impact on their shelf life in the weeks that follow. By using sorting equipment that bruises blueberries, you risk that by the time a container of your product reaches another continent, the fruit will be soft or damaged. That is the most straightforward path to losing contracts.

Choosing the gentlest blueberry sorter is an investment in the quality of the product you offer your customers. Fewer damaged berries mean fewer complaints, less paperwork and logistics associated with returns – and in turn, greater trust from retail chains and more time spent packing the next orders. It is also an opportunity for shoppers on the shop floor to actively seek out packaging with your logo – even if it costs a little more.

The impact of sorting on blueberry quality – let’s talk about your line

The test results described above are very concrete arguments. This is precisely our approach to blueberry packing optimisation – reliable, data-driven, and drawing on years of practical experience. If you would like to discuss blueberry sorting and how this process affects fruit quality as well as the overall efficiency of your line, fill in the form below and book a consultation with one of our advisors – free of charge, with no obligation and at a time that suits your schedule. We look forward to hearing from you!