As part of the Environmental Security Technology Certification Program (ESTCP), Natick Soldier Research, Development and Engineering (NSRDEC) evaluated nanocomposite packaging for Meals, Ready to Eat (MRE) rations to demonstrate and prove the validity of the packaging systems’ ability to decrease the amount of solid waste produced by the military. The packaging was developed during previous projects under NSRDEC’s Environmental Quality Basic Research (EQBR) and Strategic Environmental Research and Development Program (SERDP). The film processing with industry and manufacturing of the pouches were conducted on conventional processing equipment at AmeriQual Packaging. The assembly operation occurred smoothly without any problems or delays. Performance objectives for shelf life, rough handling, insect infestation, recyclability and storage were evaluated. This investigation focused on three MRE components: the Meal Bag, the non-retort food pouch, and the retort pouch. The non-retort food item chosen for the storage studies was pretzels and the retort food item was vegetarian penne pasta. Storage studies were conducted for 3 years at 40, 80, 100 and 120 oF. Storage study testing consisted of: sensory analysis, oxygen concentration, hexanal analysis, and microbiological analysis.
The nanocomposite Meal Bag was fabricated from the same base resin as the existing control bag, but 7.5% nanoparticles was added for improved thermal and barrier properties. The thickness of the nanocomposite Meal Bags was seven mil versus 11 mil for the control bag. After testing and evaluation, it was determined that the performance objectives for the Meal Bag were all met. The nanocomposite Meal Bag’s integrity in comparison to the control Meal Bag was in the same acceptable range. This was measured by determining the seal strength at the top and bottom seals. The Meal Bags were also rough handled at different temperatures using tests corresponding to the military specification requirements, and these met the success criteria. Rough handling of the pallet load was also performed and minimal defects were found in both the control and nanocomposite Meal Bags. Another performance objective that the Meal Bags met was resistance to insect infestation. The control and nanocomposite Meal Bags were exposed to a variety of insects typically encountered during storage and samples were examined at predetermined time periods. There was no more than 20% failure for the Meal Bags. One of the performance objectives was to assure recyclability of the Meal Bag. This was demonstrated in the laboratory by re-melting and reprocessing the polymer nanocomposite with other virgin polymers. Also, the recycling company, TREX, confirmed that the Meal Bags could be utilized in their recycling facility. TREX also addressed color, rheology, and mixing of the Meal Bag material with TREX’s regrind. The weight savings, reduction of solid waste, and decrease in base resin are all approximately 30%; however, the addition of nanoparticles results in an increase in cost to the formulation.
For the retort and non-retort pouches, polymeric structures were used that had another protective layer for an oxygen barrier incorporated into the outer layer and also contained a nanocomposite layer. All of the same tests were conducted with the control and nanocomposite retort pouches as were performed with the non-retort samples, except a microbial evaluation was added. All the tests passed except for the recyclability. The microbial evaluation was conducted at time 0 and for every storage interval that a sensory test was conducted during both the accelerated and long term storage. The microbial evaluation was performed with five retort pouches of each sample and all samples were acceptable with no food safety issues. During recyclability testing, it was determined that the wide range of melt temperatures of the polymers in the non-retort and retort pouches would prevent recyclability.
A critical performance objective was for soldier acceptance of the packaging, which was demonstrated by a field study survey with approximately 100 soldiers. The acceptability of the packaging was comparable with the controls.
The reduction of solid waste was contributed to by the decrease in resin used to manufacture the Meal Bag. The reduction of solid waste for the retort and non-retort pouches is not significant because neither can be recycled, but there is a weight savings. The MRE food in the new nanocomposite packaging survived the airdrop even though the packaging had some defects. The inspection of defects on the nanocomposite packaging after the air drop and transportation studies was also successful with results comparable to the controls. The sensory panels conducted with consumer panels and technical panels were acceptable from the initial time to three years.
Since the military is moving toward Micro-wave Assisted Thermal Sterilization (MATS) methods, and foil structures cannot be utilized with MATS, the nanocomposite structures offer an alternative to the foil barrier layers found in the control non-retort pouch. MATS is a direct heating method that offers faster thermal penetration and better uniformity than conventional retorting or canning. Food is subject to high-temperature, short duration treatment allowing microwaves to penetrate the food, cooking packaged foods from the inside out and preventing burning around the edges. Preliminary studies have shown that these nanocomposite structures can successfully undergo MATS.
This project was presented to the Joint Service Operational Ratios Forum (JSORF) twice as informational briefings (2010 and 2012) and now work continues with the Combat Feeding Directorate (CFD) project “Barrier Coatings for Optimized Package Performance”, which is performing accelerated storage studies at 100 °C for other food items for retort and MATS sterilization. Overall, the nanocomposite packaging has been demonstrated to be comparable in performance to the current control packaging with a reduction in solid waste and hopefully this technology will transition to the Warfighter.