The Effect of Retort Conditions on Clear High Battier Laminated Structures

Kevin Lifsey

Presented by Dante Ferrari, Celplast Metallized Products Ltd.

Retorting refers to the thermal sterilization of low-acid foods, to extend shelf life
by killing bacteria and other microbial species in the food. It has traditionally been used to preserve foods packaged in metal cans or glass jars. Following WWII, flexible retort packaging was born, with the innovation of the meals-ready-to-eat (MRE) pouch for military rations. This replaced canned food, or C-rations, and today MRE pouches are still the packaging of choice for providing food to remote military personnel. They are made up of PET/nylon/foil/CPP or PET/foil/nylon/CPP 4-layer laminations. This is an extreme use requirement, as MRE’s require a shelf life of up to three years at 80°F or six months at 100°F, translating to OTR < 0.06 cc/m2/day and WVTR < 0.01 g/m2/day1.

Retorted pouches can be either pillow or stand-up pouches, and are lighter in
weight and easier to open than traditional cans or glass jars. In addition, retorted pouches offer improved food flavor over traditional rigid packaging. Since the pouch has more surface area and a thinner package than an equivalent volume jar or can, heat can be transferred through a retort pouch more quickly than a jar or can, allowing for quicker sterilization, which preserves the quality of the food2.

More recently, clear barrier films have gained acceptance in retort pouch applications. These are typically SiOx-coated or Al2O3-coated 48 gauge PET films,
which replace the 0.00035” foil layer in a standard retort pouch structure. Advantages offered by these films over foil are their ability to be used in a microwave, they allow the use of metal detectors during pouch filling, the customer can view the product inside the package, and they meet metal-free recyclability requirements. The barrier properties of SiOx coatings on PET film have been the focus of some recent studies in unlaminated film structures3,4, indicating factors that can be used to improve SiOx-coated PET barrier
properties. In addition, improvements in flex crack resistance and reduced pinholing leading to better barrier properties in a lamination have been achieved with at least one high speed electron beam web coater5.

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