Performance evaluation of high barrier metal-oxide coated polymeric films intended for in-package thermally sterilized food products
Primary Author: Ashutos Parhi
Faculty Sponsor: Shyam Sablani
Primary College/Unit: Agricultural, Human and Natural Resource Sciences
Category: Agricultural and Natural Resource Sciences
Metal-oxide coated multilayered polyethylene terephthalate (PET) films are used for storing in-package thermally processed food products. However, these films can develop defects when exposed to retort and microwave assisted thermal sterilization (MATS) processes. This increases their oxygen and water vapor transmission rates (OTRs,WVTRs) reducing the shelf life of packaged food.
In this work, we evaluated four film pouches: MOA, MOC, MOE, MOF having layers of metal-oxide coated PET, Nylon 6 and polypropylene. We filled them with water and processed in a retort at 121°C (F0=6–9 min) and MATS at 124°C (F0=10.9 min). The processing times were determined based on solid food products packaged in flexible pouches. Subsequently, the pouches were emptied, dried, filled with an oxygen-sensitive gel, resealed and stored at 23°C for 180-days. The gel changed color at locations with defects and we extracted samples from those locations for scanning electron and confocal laser scanning microscopies (SEM, CLSM).
OTRs and WVTRs of the films increased significantly (P<0.05) after thermal processing with MOA showing the highest increase and MOF the least. Presence of additional layers of coating may have reduced the barrier deterioration in MOF pouches. MATS processed films showed a lower change compared to retort process. MOC, MOE and MOF pouches showed fewer defects than MOA, visualized through localized color change in the packaged gel as well as SEM and CLSM analysis. Overall, the MOF pouches showed least deterioration after thermal processing and will be ideal for shelf-stable food products with an extended shelf-life.