POLYMERIC PACKAGING FILMS FOR THERMAL PASTEURIZATION PROCESSES

Kanishka Bhunia

Pasteurized ready-to-eat meals requires a refrigerated storage and/or in combination with aerobic environment as anaerobic spores are not inactivated during pasteurization processes. Use of low-barrier polymeric packaging material can create an aerobic environment inside the package, however, it causes oxidation in food. Barrier properties of polymeric packaging materials are affected by thermal pasteurization processes and causes further degradation of food quality. Microbial safety and quality degradation of packaged food are also dependent on amount of oxygen present at the package headspace and in food matrices. Therefore, storage temperature, barrier properties of polymeric packaging, oxygen at package headspace and oxygen diffusion in the food matrices together determine the shelf life of a pre-packaged pasteurized ready-to-eat food. Thus, the overall objective of this study was to evaluate the packaging criteria for pasteurized food product. In the first study, the effect of oxygen transmission rate (OTR) of polymeric packaging films on oxidation-reduction potential (Eh) (aerobic/anaerobic nature of food) and oxidative changes in ready-to-eat pasteurized blue mussels in red sauce and shredded carrots were evaluated during refrigerated storage. Mussels packed with higher OTR films showed significantly higher lipid vi oxidation. The Eh of pasteurized sauce was negative during refrigerated storage, indicating that it can support the growth of anaerobic spores such as Clostridium botulinum. Shredded carrots packaged in low barrier pouches showed significantly higher degradation in color and correlated to total carotenoid content and total phenolic content in the shredded carrots. The results from the first study suggested to store the pasteurized food in refrigerated temperature. In the second study, changes in gas barrier properties of polymeric packaging films was evaluated after hot water pasteurization and MAPS processes. The higher overall processing time of MAPS (52 min) compared to hot water pasteurization (36 min) caused higher reduction in barrier properties in hydrophilic Nylon-based multilayer films and it was attributed to the fragmented crystal structures and plasticization of Nylon due to absorbed water. In contrast, distorted crystal structures was responsible for reduced barrier properties of hydrophobic PET-based multilayer films after hot-water pasteurization process. In the third and last study, a non-invasive methodology was developed to study oxygen diffusion in model food gels at 22°C and refrigerated temperatures (4°C). It demonstrates that Oxydots can be used at multiple locations with in a food to determine the oxygen content. Oxygen diffusivity (????????2) significantly decreased with increasing gel (agar) concentration. Temperature significantly lowered the ????????2 in the model food gels. A combined obstruction and hydrodynamic model was used to explain the decreased ????????2 in gels with increasing gel concentration. The findings from the present study will be useful to select a suitable packaging films for pasteurization processes. It will also help to measure oxygen content in food and describe microbial growth and oxidation processes in foods.

POLYMERIC PACKAGING FILMS FOR THERMAL PASTEURIZATION PROCESSES

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