Grain and beer production by-products (wheat bran, grain production residues and Saccharomyces cerevisiae) application in compostable packaging material. The impact on physical-mechanical and barrier properties
Authors: Markeviciute Zita , Lyytikäinen Johanna , Leminen Ville , Varzinskas Visvaldas 
Published: December 2023

Abstract

Renewable materials and material circularity are the key priorities of coming decades. Paper is the most used material in the packaging sector, however its applications in the food packaging are limited because of the low barrier properties. When coated with petrol-based polymer barrier coatings it becomes unrecyclable neither mechanically, neither biologically. Bio-coated and made from / with agricultural waste or by-products compostable paper packaging is environmentally favourable solutions that can benefit the biological cycle of the circular economy. The main objective of this study is to review the applicability of grain and beer production by-products application in compostable food packaging materials. The effect of different grain by-products (industrial wheat grain processing residues and wheat bran) particles and concentrations (15wt% and 40wt%) as well as the effect of brewer’s yeast (saccharomyces cerevisiae) of 10wt% concentration on the physical-mechanical and barrier properties on Northern bleached softwood kraft (NBSK) and chemithermomechanical (CTMP) pulps. The material composites were fabricated using standard sheet forming method. The physical-mechanical properties were analyzed through tensile strength, strain at break, tear resistance and bending stiffness tests. The barrier related properties were analyzed through roughness, air permeance and water contact angle tests. The result reveal that the vast majority physical-mechanical properties decreased with the increase of both type of grain production fillers. Industrial wheat grain processing residues resulted lower impact on physical-mechanical properties than wheat bran filler. Higher percentage properties decrease was absorbed in NBSK pulp than in CTMP. Roughness of CTMP can be improved by adding both – industrial wheat grain processing residues and wheat bran. Wheat bran particles can increase hydrophobicity. CTMP pulp strength properties can be increased with addition of yeast, however yeast additive effect on air permeance demonstrated resulted negative impact. In case of NBSK pulp which has higher primary strength properties, addition of yeast does not make any significant changes. The conducted experiments demonstrated that grain production by-products decreases physical-mechanical properties, but can be applicable and benefit compostable food packaging material production by saving raw materials. The pulp type and filler ratio in must be evaluated on an individual case. Beer production by-product saccharomyces cerevisiae does not make significant difference on material physical-mechanical properties – the yeast-containing samples are generally less mechanically robust but can exhibit flexibility. The effect on barrier properties varies – air permeability of these samples is generally higher however yeast has a positive impact on surface hydrophobicity – paper surface becomes more hydrophobic or less receptive to wetting by liquids.