In order to ensure a perfect shelf life, packaging must meet various requirements. Our expert and EUROSAC member, Uwe Vogelskamp, explains how the shelf life of a paper sack is determined and how the choice of material and the sack construction contribute to preserving the quality and properties of a product, also when stored for several months.

Which factors are relevant for a long shelf life?

With shelf life we refer to the ability of packaging to protect a specific product for a longer period of time. The packaging is responsible for preserving the quality and the special properties of the goods it holds and prevents them from deterioration and spoilage. Therefore, it is important to consider those product properties when choosing the most suitable packaging. If you want to store products such as cement that react with water, you need packaging which acts as a barrier to moisture. One of the key factors for shelf life is how much humidity and moisture the packaging can withstand.
Products containing oil or fat, such as cocoa or milk powder, must be protected from heat and light, as these can change the fatty substances in the product. In addition to the product properties other factors have to be taken into account, e.g. the distribution channels, the expected time until the product is used as well as the climatic conditions during transport and storage.

Which features of a paper sack contribute to a long shelf life?

First, the choice of material has an impact on shelf life. We mainly use sack kraft paper made from virgin fibres. The long, strong fibres provide high mechanical strength, which means that breakage of the paper sacks is less likely to happen. Secondly, the right type of barrier, adhesive or coating keeps external influences such as light, heat, oxygen, moisture or foreign matter from impairing the product quality. Thirdly, the construction of the paper sack adds to a long shelf life: from sealable valves and different gluing techniques to special bag construction. Finally, it is important to handle the paper sacks properly during transport and storage. Your paper sack producer will advise you which sack solutions meet your individual requirements and how to properly handle the sacks.

What advantages do paper sacks offer?

The main benefit is that paper sacks are made from natural resources. They are recyclable and biodegradable. Even when a plastic barrier is needed to improve the shelf life of a specific product, we use paper whenever possible and only as much plastic as necessary. Our industry also offers innovative moisture-resistant sack constructions that avoid the use of plastic entirely. Moreover, paper sacks are very tear-resistant, which is a prerequisite for a long shelf life. Paper protects against UV radiation and can withstand high temperatures up to about 100 degrees Celsius. It has low thermal conductivity, which means the external heat is not transferred to the product inside. Thanks to their natural porosity, paper sacks can “breathe”. Warm or hot contents, such as cement that is heated during filling, can cause condensation during contact with external cold. This doesn’t happen in paper sacks because they allow the moisture to escape. Their breathability also prevents the formation of mould on products such as flour or starch, which need to be in contact with air and moisture.
Thus, paper sacks offer a long shelf life and advantages in terms of sustainability, at the same time – a great benefit in times of climate change and rising expectations on companies’ ethical conduct. Paper sacks, depending on each country’s regulations, can be recycled and have a second life. The virgin fibre is excellent for recycling and can be recycled up to seven times.