According to FAO estimations, fruit and vegetables account for 45-50% of global food losses. The loss in the post-harvest period is particularly severe, as it also means that the inputs used for the production (land use, energy, etc.) are lost.

Fresh products such as fruit and vegetables are metabolically active post harvest. They consume oxygen, while generating heat, carbon dioxide, water vapour and aromatic compounds, and therefore spoil easily. In order to be able to prevent quality losses in the post-harvest by means of improved process design, we first need to understand the physiological and physical properties of the respective products and know how they respond to certain environmental influences.

Packaging is to protect the product and extend its shelf life by providing the optimum gas composition and moisture in the packaging. Our goal is to better understand the mechanisms of water vapor and condensation dynamics in packaged fresh products and to develop optimized packaging on this basis. 

For example, we are investigating the absorption kinetics of moisture-regulating packaging made up of several layers of film. Moreover, we are increasingly focusing on biobased packaging materials such as cellulose or polylactic acid (PLA), which we are investigating with regard to their suitability for MAP (modified atmosphere packaging) and moisture-regulating packaging design. Using mathematical modelling, we develop tailor-made packagings for fresh produce, taking into account product respiration rates and the transfer dynamics of gases during their passage through the packaging film.

The gas composition within the package can have a strong influence on the quality of the fruit. The use of packaging gases such as nitrogen or carbon dioxide creates optimised storage conditions within gas-tight packaging (such as Modified Atmosphere Packaging MAP or MAHP) - similar to the atmosphere in large storage halls with controlled atmospher (CA). This protective atmosphere slows down the ripening process and thus extends the shelf life of the products by days or even weeks while maintaining their high quality.

The plant's natural ripening hormone ethylene, even in the smallest traces, can cause undesirable rapid ripening and decomposition of fruit and vegetables. Removing ethylene from the storage atmosphere is one of the major challenges in the post-harvest period. Conventional techniques can only 'buffer' ethylene, but are unable to decompose it. We have developed a novel photocatalytic filter technology (using UV light and titanium dioxide as catalyst) for ethylene degradation to efficiently remove the undesirable ripening gas from the storage atmosphere.

For a better monitoring of product quality in post-harvest, we investigate and develop new methods and procedures for the automated analysis of quality parameters in real time. The focus of our research is on optical methods such as fluorescence or reflection spectroscopy, and also on new methods such as laser backscattering, which in the future could indicate changes in tissue structure and components of stored fruit. The analysis of the aromatic compounds (VOCs) in the headspace of packaged fresh products can also be an indicator of initially invisible quality changes. 

In order to record the physiological activity and thus the degradation processes of fresh products in the post-harvest quickly and easily, we have developed a small, flexible measuring device. O₂, CO₂, temperature and relative humidity sensors enable a continuous, non-invasive online monitoring of the effects of temperature, gas composition and storage time on the respiration rate and respiration quotient of the product. The modular sensor system is also suitable for continuous monitoring of environmental conditions in storage rooms and transport vehicles.

More on our research: WG Packaging and storage