Properties of paper coated with Prunus serotina (Ehrh.) extract formulation

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.