Immobilization of β-cyclodextrin in ethylene-vinyl alcohol copolymer for active food packaging applications

Current developments in active food packaging are focusing on incorporating agents into the polymeric package walls that will release or retain substances to improve the quality, safety and shelf-life of the food. Because cyclodextrins are able to form inclusion complexes with various compounds, they are of potential interest as agents to retain or scavenge substances in active packaging applications. In this study, β-cyclodextrin (βCD) was successfully immobilized in an ethylene-vinyl alcohol copolymer with a 44% molar percentage of ethylene (EVOH44) by using regular extrusion with glycerol as an adjuvant. Films with 10%, 20% and 30% of βCD were flexible and transparent. The presence of the agent slightly increased the glass-transition temperature and the crystallinity percentage of the polymer, that is to say, it induced some fragility and a nucleating effect. The water vapor, oxygen and carbon dioxide barrier properties of the materials containing βCD were determined and compared with those of the pure polymeric material. Permeability to these three permeants increased with the addition of βCD due to the presence of discontinuities in the matrix and to the internal cavity of the oligosaccharide. Also the CO2/O2 permselectivity increased with the addition of βCD. Finally, the potential effect of the composites in the food aroma was analyzed. The materials with βCD preferentially sorbed apolar compounds such as terpenes. This characteristic could be useful in active packaging applications for preferentially retaining undesired apolar food components like hexanal or cholesterol.