The idea of the doctoral thesis was born from the author reading scientific literature. ‘By that time, I had already written my first research article on the suitability of plastic packaging for food, and I wanted to write about a more environmentally friendly solution,’ says Kristi Kõrge. ‘I like challenges and was given the perfect opportunity to go abroad to a laboratory, more precisely to the Slovenian National Institute of Chemistry to make and test these packaging materials myself.’

Estonia has great alternatives to chestnuts

The choice fell on chestnut (which is not related to our local horse chestnut!) because the results of the research would be beneficial both for Slovenia and for other Mediterranean countries, where chestnut trees grow in abundance.

‘Chestnut is one of the most common biomasses in the Mediterranean and contains a large amount of water-soluble polyphenolic compounds, which enables us to make the biomaterial film UV-resistant, mechanically stronger and active. Activity is the property of a material to release a certain degree of active components (polyphenols) and thereby inhibit or prevent, for example, microbiological contamination of food,’ explains the recently-awarded doctor.

Kristi confirms that a suitable replacement for chestnuts can be found in Estonia. ‘Besides chestnut extract, many other active ingredients have been used and it is certainly possible to replace it with a good alternative found in, for example, Estonia.’ 

Suitable for short-term packaging

Kristi also sees great potential in such packaging, both in Europe and in Estonia. ‘Large and exemplary companies in this field already exist, but not in our region. Some of the best examples are Apeel (America) and Lactips (France),’ lists Kristi, who believes that there is still the need to be realistic when it comes to organic packaging. ‘These materials will not replace all the solutions that need plastic materials, but they are ideal, primarily for products that need short-term packaging. And there are plenty of those! At this point, we also have to deal with changing the habits and behavioural culture of our society,’ emphasises Kristi.

Laboratory work in Slovenia was also affected by the pandemic

The aim of Kristi Kõrge's doctoral thesis ‘Biological Activity and Physicochemical Properties of Chitosan Film Cross-Linked with Chestnut Extract for Active Food Packaging Applications’ was to describe the physicochemical changes of these chitosan films depending on the film-forming solution (FFS) components, to use replacement models to model dependencies, and, based on the acquired calculations, to produce packaging for storing food with a medium-level moisture content. The purpose of the shelf-life tests was to investigate the change in the properties of the bio-packaging in contact with food, to determine the bioactivity of the packaging to ensure food safety depending on the physicochemical parameters of the packaging and to investigate the effect of packaging on the storage time of food.

According to Kristi, the most exciting part of the whole work was to monitor the development process of the material in the laboratory, i.e. to see how it is really possible to repeat the output of biomass-based material. The most difficult part, however, was conducting food experiments in a chemical laboratory when the pandemic was gaining worldwide momentum. ‘It was not allowed to use the help of students, therefore I had to do everything myself,’ says Kristi.