| High pressure processing (HPP) can be applied to either in bulk or prepackaged food in flexible or semi rigid packaging materials. Since the integrity of the package during and after processing is of paramount importance, this study investigated the effects of HPP on the barrier, mechanical, physical characteristics and sorption behavior of selected flexible structures.; In chapter 2 the “barrier properties” and in chapter 3 the “mechanical properties” were compared for high-pressure treated and non-treated pouches. After HPP, the permeability, tensile properties and sorption behavior of the materials were evaluated. Scanning electron microscopy (SEM), and scanning acoustic microscopy (C-SAM) measurements were also taken to investigate the presence of micro defects in the films. Films used in this study were PET/SiOx/LDPE, PET/Al2O3/LDPE, PET/PVDC/nylon/HDPEIPE, PE/nylon/EVOH/PE, PE/nylon/PE, metallized PET/EVA/LLDPE, PP/nylon/PP, PET/EVA/PET and PP. Results showed that the permeability of metallized PET was most severely affected by HPP. Permeability changes in the other materials were small compared to metallized PET. Tensile properties of the films were not affected. However, physical damage to the metallized-PET films was identified by SEM and C-SAM analyses.; In chapter 4 the sorption of d-limonene was evaluated in both the polymeric structures (PP, multilayer PE/nylon/EVOH/PE, and metallized PET/EVA/LLDPE) and the food simulants, in both the HPP and untreated pouches as a function of time. Results showed that d-limonene concentration, both in the polymers and in the food simulants for pouches made of PP and (PE/nylon/EVOH/PE), was not significantly affected by HPP. However, the metallized PET/EVA/LLDPE showed a significant difference in the amount of d-limonene between HPP and control pouches. As expected, changes in temperature significantly affected the sorption behavior of all polymers. While PP and PE/nylon/EV OH/PE films retained d-limonene amount, the metallized-PET did not. |
