When designing and setting up a blueberry packing line, a great deal of attention is usually paid to sorter capacity, weighing accuracy and the speed of the entire process. In practice, however, packing efficiency is also determined by much simpler elements. One of them is the way the fruit enters the final package.

If the punnet is not positioned correctly, the fruit stream is too wide, or the next package does not arrive under the dispenser at the right moment, some blueberries may fall outside the package. With a single punnet, the loss may seem insignificant, but during many hours of production the same situation can occur hundreds or thousands of times.

For this reason, reducing fruit spillage should be treated as one of the elements of optimizing the entire packing process.

---

Why do blueberries spill during filling?

There is usually no single cause. The problem is most often the result of several factors combined: the shape of the package, its position in relation to the drop point, the way the fruit is guided and the speed of the entire line.

Even a small change can make a difference. A punnet that is only a few millimeters narrower than the one used previously may cause fruit at the edge of the stream to miss the opening.

The same applies when the height of the package changes. If its upper edge is lower, the fruit has a longer free-fall distance, increasing the possibility of blueberries bouncing off other fruit or the edge of the package.

The most common causes of spillage include:

• a fruit stream that is too wide,
• incorrect positioning of the punnet in relation to the dispenser,
• too much distance between the drop point and the package,
• incorrect guides or narrowing inserts,
• too much fruit entering the package at one time,
• package transport that is too fast,
• unstable positioning of the punnets,
• changing the package type or dimensions without readjusting the line,
• overfilling the package.

---

The package must be positioned precisely under the filling point

One of the basic requirements for correct filling is repeatable package positioning. If the punnets move sideways on the conveyor or stop in slightly different positions, the fruit stream will not always enter the center of the package.

The problem can be particularly noticeable with small packages. The smaller the opening of the punnet, the smaller the margin for error between the product stream and the edge of the package.

It is therefore worth checking not only where the package stops, but also whether the guides keep it in the same position throughout operation.

The blueberry stream should match the width of the punnet

If the fruit falls from a wide conveyor directly into a much narrower package, some blueberries may already be outside the outline of the punnet before they begin to fall.

In such situations, suitable guides, narrowing inserts or other directing elements are used to concentrate the fruit stream before the filling point.

However, these elements should not compress the blueberries too aggressively or create blockages. The narrowing section should guide the product smoothly and as gently as possible.

Changing the type of package requires particular attention. An element adjusted correctly for a wide punnet may not provide suitable guidance when a smaller package is introduced.

---

The lower the drop height, the easier it is to control the fruit

A blueberry entering a package does not stop immediately. It can bounce off the bottom of the punnet, the fruit already inside it or the edge of the package.

The greater the drop height, the greater the energy of the fruit when it reaches the package. This increases both the risk of bouncing and the possibility of mechanical damage.

For this reason, the distance between the end of the dosing system and the package should be kept as short as reasonably possible, provided that the machine design and package transport system allow it.

Reducing the drop height is important not only for keeping the area around the machine clean. Gentler fruit handling also helps maintain quality during subsequent storage and transport. More information about maintaining blueberry quality can be found in our article on how to increase blueberry shelf life after harvest.

Avoid temporarily overloading the package

Even if the average amount of product entering the punnet is correct, the way it is dosed is also important.

A large portion of fruit released at once may behave very differently from the same mass delivered more evenly. Blueberries falling onto one another can bounce, move toward the edges and eventually fall outside the package.

For this reason, stable product feeding is just as important as the accuracy of the final weight.

---

Not every package behaves in the same way

Changing the punnet may seem like a minor modification to the process, but from the machine’s point of view it changes the geometry of the product receiving point.

Factors that may be important include:

• the width and length of the package,
• the height of its walls,
• the shape of the upper edge,
• the rigidity of the package,
• the way it is guided on the conveyor,
• the position of the center of the package in relation to the dispenser.

After changing the package type, it is therefore worth carrying out a test with real product and checking the entire process at normal operating speed. It should not be assumed that a setup that works correctly with one punnet format will automatically be suitable for another.

Overfilling the punnet can also cause spillage

The problem can also occur near the end of the filling process. When a large amount of fruit is already inside the package, subsequent blueberries no longer fall onto a flat bottom, but onto the irregular surface created by the fruit already inside.

The fruit can then roll toward the edge and fall onto the conveyor. This is more likely if the package is filled very high or if the final portion of fruit is too large.

This is why correct dosing and weighing are directly connected. Excessive filling not only increases product usage but can also increase the risk of fruit spilling outside the package.

---

Line speed should be matched to the entire process

Increasing the speed of the package conveyor does not always increase the actual capacity of the packing facility. If the system does not have enough time to correctly position, fill and discharge the punnet, the amount of spilled fruit may increase.

As a result, operators have to stop the line, collect fruit or correct the position of the packages. A machine running at a higher nominal speed may therefore produce fewer finished punnets per hour.

When optimizing the process, it is worth looking at the capacity of the entire line rather than the speed of a single machine. We discuss a similar principle in our article on how to increase blueberry sorting efficiency.

Regularly observe the filling point

Spillage is not always a constant problem. It may occur only at a certain operating speed, with larger berries, with a particular type of package or when the amount of product supplied to the dispenser changes.

For this reason, when adjusting the line, its performance should not be evaluated on the basis of only a few individual punnets. It is better to observe the process for a longer period and pay attention to situations that occur only occasionally.

Testing with an actual batch of fruit is also useful, because blueberry size and the way the fruit moves influence its behavior during package filling.

---

What should you check when blueberries fall outside the package?

1. Check whether every package stops in exactly the same position.
2. Compare the width of the fruit stream with the width of the punnet opening.
3. Check the adjustment of the guides and narrowing inserts.
4. Assess the product drop height.
5. Observe whether too much fruit enters the package at one time.
6. Check how the line behaves during the final stage of filling the punnet.
7. Reduce the speed and check whether the problem still occurs.
8. After every change of package format, check the filling point adjustment again.

Small losses repeated thousands of times become a significant cost

A few blueberries falling outside a single punnet may seem insignificant. However, if the line prepares thousands of packages every day, even a small loss repeated during every cycle begins to have an economic impact.

In addition to the value of the fruit itself, there is also the time required for cleaning, the possibility of production stoppages and the additional risk of damaging fruit that falls onto machine components or the floor.

For this reason, a correctly adjusted filling system should be treated as an integral part of an automated sorting and packing line, not merely as a minor detail at the end of the process.

---

Summary

Reducing blueberry spillage during package filling primarily requires the machine to be correctly adjusted to the punnet being used. The position of the package, the width of the product stream, the drop height, the dosing method and the line speed are all important.

Particular attention should be paid whenever the type of package changes. Even a small difference in its dimensions may require the guides or filling point to be readjusted.

A correctly configured line not only reduces product loss. It also helps keep the work area clean, reduces downtime and increases the actual efficiency of the entire packing process.

More information about automating blueberry sorting and preparation for packing can be found on the Green Sort blueberry sorter page.