Volatile antimicrobial absorption in food gel depends on the food matrix characteristics

The aim of this study was to investigate the influence of the food microstructure on the release, absorption and partitioning of the volatile antimicrobials from antimicrobial packaging film. Carvacrol loaded polylactic acid (PLA) film was prepared and tested on a food gel model simulating products like jellies, jams and dressings. Whey protein isolate/carrageenan gels with different microstructures were prepared by varying the NaCl concentration (50–250 mM): the higher the salt concentration the lower the gel consistency. Results showed carvacrol partitioning in the gel increase at higher concentration of NaCl. A 41% increase of carvacrol absorption after 7 days was found in gels prepared with 250 mM of NaCl, compared with the gels at 50 mM NaCl. The results can be explained by the differences in gel microstructures: gels with higher NaCl concentrations showed the small WPI-containing aggregates and large pores from confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) images, in turn facilitating carvacrol absorption by proteins in the gels. The physical properties of gels revealed that gels with higher NaCl concentrations showed lower strength and water holding capacity, pointing to a more loose structure of the gel. The results demonstrate that the microstructure of gels have a clear effect on carvacrol absorption and this factor should be taken into account for designing antimicrobial packaging for the preservation of the gel-like foods.