Co-authors​ :

 Remo MERIJS-MERI (LATVIA), ZICĀNS Jānis (LATVIA), Tatjana IVANOVA , Juris BITENIEKS (LATVIA), Ivan BOČKOVS , Madara ŽIGANOVA , Linda MEŽULE , Viktorija DEŅISOVA  

Chitosan (C) is a natural polysaccharide derived by deacetylation of chitin, which is found in the exoskeleton of crustaceans or in the cell walls of mushrooms. Compared to crustaceans, mushrooms may offer certain advantages for producing chitosan, due to more sustainable process. In general, chitosan is known for its biodegradable, dietary, antimicrobial, antioxidant and other valuable properties, which determines multitude of chitosan applications in food, packaging, cosmetics, biomedicine, textile and other areas of national economy. Antimicrobial properties of chitosan are improved with increasing deacetylation degree (DD), whereas in the case of chitosan derivatives, antimicrobial activity mostly depends on the degree of substitution (DS) of the grafting groups. Chitosan oligosacharidides (COS), derivatives of low-molecular weight chitosan, also possess bioactive amino and hydroxyl groups and thus may be considered as potential antimicrobial agents. Consequently, in the current research high DD chitosans of different origins (mushrooms and crustaceans) have been used for modification of polybutylene succinate (PBS) and its copolymer with butylene adipate (PBSA) for expected application in antimicrobial food packaging. By considering attractiveness of melt based approaches for mass-production, the research has been focused on the development of technological approach for obtaining of C and COS modified composites with PBS and PBSA by melt compounding. Concentration of C or COS in the both polymer composite matrices has been changed in a range from 0 to 10 wt.%. Calorimetric, surface, rheological, mechanical, thermal and barrier properties of the obtained PBS and PBSA composites have been investigated by using differential scanning calorimetry, optical tensiometry, antimicrobial, rotational rheometry, dynamic mechanical thermal analysis, tensile stress-strain analysis, tear strength and welding strength measurements, as well as moisture vapor transfer and gas permeability measurements. It has been determined that the mushroom COS modified composites demonstrated higher antimicrobial activity, whereas the most promising for practical applications were the composites containing 7-10 wt. % of COS. Besides, it has been concluded that melt compounding temperature during manufacturing of the composites should be below 140oC in order to prevent thermal degradation of the biopolymer and chitosan additive. It was also determined that in the presence of C or COS barrier properties were not considerably affected. Finally it was observed that addition of C and COS contributed to the increased stiffness, without considerably diminishing ultimate elongation of the composites. In general, findings of the current research confirm the potential manufacturing of the C or COS modified PBS or PBSA based anti-microbial composite films by melt based approach.