The aim of the study was to isolate lignin from organosolv, beech tree (Fagus sylvatica), and Japanese knotweed (Reynoutria japonica), to use it for paper surface and to replace part of the non-renewable product resources with bio-based ones. A total of nine coated samples with different lignin formulations and starch were compounded, prepared, and evaluated. The basic (grammage, thickness, specific density), mechanical (elongation at break, tensile, burst and tear indices), and barrier properties (contact angle, water penetration, water vapour permeability, kit test) of the coated papers were investigated. The analysis showed no significant difference in tensile properties between uncoated and coated samples. Furthermore, the decrease in water vapour transmission rate and the lower contact angle for coated samples were nevertheless confirmed. The novel coating materials show promising products with very good barrier properties. Finally, the correlation between structural, morphological, and (other) natural lignin-based factors was revealed, highlighting the importance of parameters such as the equivalence ratio of aliphatic and phenolic hydroxyl groups or the average molecular weight. Tuning functionality by design could optimise performance in the future.

Barrier properties are very important in food packaging; the better the properties, the longer the product can stay fresh in the packaging, which prolongs the shelf life of the product. One way of improving barrier properties is to modifying the existing coatings with the addition of metal oxides, nanoparticles, or natural extracts. The aim of the study was to compare the barrier properties between paper coated with starch and paper coated with starch and black cherry extract mix. Prunus serotina extracts were prepared by ultrasonic extraction in 60°C water. The extracts were then filtrated and evaporated to obtain a constant mass. The reference coatings were prepared by dissolving starch in hot water to obtain a solution of 30%. The experimental coatings were prepared by substituting 10% starch for black cherry extract. Coatings were applied on the paper by laboratory coater in two thicknesses: c.a. 7 and 15 g/m2. The papers were characterised by grammage, coating weight, porosity, and roughness. Barrier properties were tested by following methods: Cobb-Unger, KIT, water vapour transmission rate, and heptane vapour transmission rate. Papers coated with formulations including extract had better barrier properties against oils and waxes, better results in KIT, Cobb-Unger, and heptane vapour transmission rate tests. The results of the water vapour transmission rate test as well as porosity and roughness were the same for papers coated with and without extract addition, they were influenced by the thickness of the coating, not the extract addition. The addition of black cherry extract influenced the barrier properties of the coated paper, and the extract improved the properties against oils and waxes.