Baking quality doesn't start in the barn, but in the field

Although frying quality is often directly related to storage, the foundation for it is laid much earlier. What happens during the growing season often still affects the color of the fries or chips months later. During storage, we can correct a number of things, but not restore everything.

The role of sugars

The color of fried potato products is largely determined by the content of reducing sugars, such as glucose and fructose. During frying, these sugars react with amino acids in the potato. This so-called Maillard reaction causes the product to brown.

A limited amount of sugar is normal, but when the sugar content becomes too high, it results in fries or chips that are too dark. Processors therefore set strict requirements for frying color. Controlling the sugar content is essential, especially for potatoes intended for fries and chips.

Potatoes remain living products even after harvest. Processes continuously take place within the tuber in which starch is converted into sugars and vice versa. The conditions during growth, harvest, and storage largely determine how these processes proceed.

The foundation is laid on the land

Many problems with baking quality originate in the growing season. Stressful conditions such as drought, heat, or large fluctuations in growth can make tubers more susceptible to quality problems during storage. In fact, the storage period begins in the field immediately after desiccation. High or low temperatures after desiccation already affect baking quality in the field.

The mineral status of the soil and the crop also plays a role. A balanced potassium supply contributes to good tuber quality and better storability. In addition, uniform ripening is important. Tubers that have not ripened sufficiently are not only more susceptible to damage and loss of quality, but also start the storage period with a poorer frying color, and this deficiency persists throughout the storage season. It frequently occurs that the cause of problems with frying color is not due to temperature or CO2, but to the harvesting of an unripe crop.

"The color of the fries is not determined solely by the temperature range during storage. What happened during the growing season and how a batch breathed during storage are ultimately reflected in the frying test," says a storage specialist at Tolsma-Grisnich.

Storage: more than just temperature

After storage, wound healing is paramount. Damage sustained during harvesting must heal as quickly as possible. It is recommended to maintain a product temperature of approximately 15 degrees for ten to fourteen days for this purpose.

Next comes the cooling phase. It is precisely here that mistakes are frequently made. Cooling down too quickly can cause extra stress and increase the risk of sugar buildup. Therefore, the advice is Tolsma-Grisnich storage specialists to cool down gradually, by a maximum of 0,2 to 0,3 degrees per day, especially for sensitive varieties.

For most processing potatoes, the storage temperature ultimately lies between approximately 6,5 and 8 degrees. Lower temperatures can be beneficial for dormancy and respiration, but at the same time increase the risk of cold sweetening.

In addition to temperature, the CO₂ content also plays an important role. During storage, potatoes inhale oxygen and produce carbon dioxide. If this CO₂ is not sufficiently removed, it can affect the physiology of the tuber and ultimately compromise frying quality.

Especially in modern, well-insulated storage sheds, CO₂ levels can rise unnoticed when there is little ventilation. Therefore, not only temperature is measured, but also the CO₂ level in storage. For processing potatoes, it is generally recommended to keep the CO₂ level below an average of 2.000 to 3.000 ppm. At higher concentrations, the risk of poorer frying color increases.

Cold sweetening remains a point of attention

A well-known phenomenon in French fry potatoes is cold sweetening. When potatoes are stored at low temperatures for extended periods, part of the starch is converted into reducing sugars. The result is that the potatoes fry darker.

The challenge for growers is to find a balance between sprout inhibition, storage losses, and baking quality. Lower storage can have benefits for shelf life, but at the same time increases the risk of sugar buildup.

Slowly warming a batch prior to delivery can break down some of these sugars. However, this is not always fully successful because processes run less optimally at the end of the storage period, especially when sweetening due to aging plays a role. Sugar (sucrose) is an important indicator in this regard. Measuring the trend in this sucrose content provides information on whether aging is imminent or if safe reconditioning is possible. After all, prevention is always better than cure. A good storage process tailored to the variety, storage purpose, and delivery time remains the best strategy.

Practical tips

To maintain good baking quality, a few basic rules are important. First, ensure a healthy and sufficiently matured batch before it enters the storage shed. Subsequently, prevent damage as much as possible during harvesting, transport, and storage.

Pay attention to proper wound healing, then gradually cool down the batch and monitor not only the temperature but also the CO₂ level. Do not store potatoes colder than necessary and avoid large temperature differences within the batch. Additionally, regularly check the frying color and sugar content during the storage season, doing so more intensively after January leading up to delivery.

Perhaps the most important lesson is that frying quality cannot be viewed separately from cultivation. Conditions in the field often continue to affect storage for months. Especially in a market where quality is once again a more significant factor, it pays to keep an eye on the entire chain. After all, a good fry color does not start in the factory, or even in the barn, but already during the cultivation of the potato.