High oxygen and moisture barrier, metal oxide (MO)-coated multilayer polymer packaging can retain the quality of shelf-stable food products. However, the presence of defects such as cracks and pinholes in the coating layer of these films can increase their oxygen and moisture permeabilities. The defects have microscopic dimensions and can be present at random locations in the films’ coatings, making it challenging to find and characterize them using traditional sensors and microscopic techniques.
The study consisted of three sections. In the first part, a methylene blue and agar gel-based, color changing oxygen sensor was developed and field tested with four retort-processed MO-coated films. The sensor changed color from yellow to blue, at the locations with the defects in the films. Microscopic characterization confirmed the presence of defects, validating the technique. The sensor detected the defects efficiently at 23 ℃, however, it was unsuccessful when tested under accelerated conditions at 40 ℃.
In the second part, the sensor was tested with two ultra-high barrier MO-coated films containing two and three MO-coated-PET layers that were processed with retort and microwave assisted thermal sterilization (MATS) processes. The sensor functioned well and characterized the films’ barrier performance after exposure to thermal processing, thus proving its effectiveness as a characterization tool.
In the third and last section, the possibility of accelerating the detection process was explored by formulating the sensor using three different gelling agents: Agar, Gellan_ NaCl, Gellan_ CaCl2 and testing them at 23 ℃ and 40 ℃ with two MO-coated films. Gellan_ NaCl was faster than Agar and Gellan_ CaCl2 and could successfully detect the defects within 20 days at 40 ℃, reducing the detection period from 180 days at 23 ℃, as observed in the first study. Overall, the sensor could expeditiously detect the defects and thus, could reduce the cycle time needed for developing newer food packaging.
This session is part of the Scientific Discovery Workgroup Research Promotion (Pre-Tenured Faculty)