New biopolymer coating to help berries last fresh for longer

The Institute of Biology at the University of Latvia (UL) has developed new materials for treating fruits, especially soft berries, with biodegradable microbially synthesised polymer coatings, which will help preserve the quality of berries for longer and extend their shelf life.

Fruit and vegetable losses in Europe account for 45% of the total harvest. Losses and food waste can be seen as a misuse of natural resources. Food producers are under increasing pressure to produce foods with extended shelf-life in order to secure higher volumes and reduce production costs, but the use of chemicals in food processing has harmful effects on the human body.

“Our aim is to store fresh berries in a way that is safe for humans, but for longer than is currently possible,” says the scientific director of the project, Dr. biol. Pāvels Semjonovs.

Extending the shelf life increases the competitiveness of the producer and is an environmentally friendly solution.

Treated with a safe polymer coating

Berries can be given a longer shelf life by treating them with an effective, health-safe and biodegradable polymer coating made from microbially synthesised polysaccharides, their derivatives, and composites. To achieve this objective, the researchers carried out biotechnological studies on the specificities of the production of certain biopolymers from by-products of the agricultural and food processing industries, such as whey, hydrolysates of plant residual biomass, and molasses. The use of different by-products has led to significant cost reductions in the production of biopolymers. After preparation and sterilisation, bacteria capable of synthesising biopolymers were added to the culture medium under sterile conditions. This was followed by a cultivation process during which the bacteria consume nutrients in the medium and form biopolymers. The process concluded with the harvesting and purification of the biopolymer. If necessary, the polymer is mixed with other compounds and incorporated into a composite material.

During the experiments, the researchers not only developed and optimised the composition of the medium, but also performed the selection of the biopolymer producers. For example, one of the biopolymers is bacterial cellulose, a valuable compound with several potential applications such as medicine, food, packaging, and environmental restoration. Particularly high synthesis of bacterial cellulose can be achieved in apple juice medium using the bacterium Novacetimonas hansenii MSCL 1646, which is able to efficiently form the polymer from sugars present in the medium. Similarly, the most suitable bacteria were selected for other agricultural and food processing by-products, i.e., substrates.

Next step: Setting up a pilot plant

In the project at the Institute of Biology, researchers developed prototype technologies for biopolymer coatings and packaging materials with the right characteristics for their application, fruit coatings, biodegradable packaging materials, for both fruit and dairy packaging. The developed device, a rotating disc bioreactor, allows a much higher synthesis of bacterial cellulose compared to static cultivation in flasks, which is the classical approach. The use of the bioreactor allows to reduce the culturing time of biopolymers, to increase the polymer yield and to move towards large-scale biopolymer production in the future. The next step would be to set up a pilot plant to evaluate in more detail the cost-effectiveness of bacterial cellulose production.

The biopolymer coating would be available in the form of a solution that the consumer could eat with the berry, thus receiving an additional dose of prebiotic polysaccharides (biopolymers), and as absorbent pads and films similar to polythene bags, but which will eventually degrade naturally.

“We could largely replace fossil-based plastics with those derived from natural raw materials that are often not put to good use in factories, such as whey. It is good if large factories separate the protein from the whey and add it as an additive to various foods, but it happens that all the whey protein ends up in the environment and pollutes it. We can get biopolymers from whey, in which case we would need less oil and gas,” adds Semjonovs.

Such materials can also be obtained from low-quality apples or their processing residues, presumably also from other fruits or their residues.

The UL was the lead partner in the project “Obtaining biodegradable polymers from renewable resources for the development of fruit protective films and packaging materials”. The partners involved are APP Institute of Horticulture, AS Rankas Piens, SIA Probiotika LV, SIA Skoru dārzi, Auri Parish farm Pērles, and Valters Dambe.

The project “Obtaining biodegradable polymers from renewable resources for the development of fruit protective films and packaging materials” was implemented with the support of the state and the European Union under the measure “Support for the implementation of the European Innovation Partnership on Agricultural Productivity and Sustainability working group projects on agricultural productivity and sustainability”. The project started in October 2019 and ran until June 2022. The project is supported by the Ministry of Agriculture and the Rural Support Service.

Source: Press release (labsoflatvia.com). Photo: Toms Grīnbergs, University of Latvia