Montmorillonite improves water vapor barrier of some low-moisture packaging systems.

A product's storage stability addresses one of the foremost problems faced by processors-how to stabilize a food once it is harvested. The purpose of storage stability testing is to provide evidence on how the quality of a product varies over time under the influence of environmental factors such as temperature, humidity and light. The information provided by such studies indicates how these factors may influence product quality, safety and acceptability.

A number of scientists have tested a nanocomposite consisting of low-density polyethylene (LDPE) and montmorillonite-layered silicates to see if it had better water vapor barrier properties than pure LDPE when used to package low-moisture foods. Montmorillonite is a very soft phyllosilicate mineral. Its microscopic crystals form a clay.

Researchers packaged cornflakes and crackers in both pure and nanocomposite LDPE in two thicknesses-2 millimeters and 6 millimeters. The investigators also included meal ready-to-eat (MRE) packaging in their study. The packaging was exposed to various environments for at least 19 days: conditioned air at 39 C, 90% relative humidity; 39 C, 50% humidity; and 23 C, 50% humidity.

The researchers monitored the moisture sorption during this time, and the packaging materials were compared against each other. The 2-millimeter nanocomposite LDPE had better water vapor barrier properties at 23 C and 50% relative humidity than did the pure LDPE. The 6-millimeter nanocomposite LDPE had better water vapor barrier properties at 23 C and 50% humidity, and at 39 C and 50% humidity than the pure LDPE.

Also, the 6-millimeter nanocomposite outperformed the MRE packaging system at 23 C and 50% humidity when it was used to package crackers. However, in all other cases, pure LPDE outperformed the nanocomposite LDPE, and the MRE system outperformed the 6-millimeter nanocomposite. So it appears that adding montmorillonite-layered silicates to LPDE improves the water vapor barrier properties of low-moisture food packaging systems under 23 C and 50% relative humidity conditions. However, this improvement was not obtained at higher temperatures or humidity levels.

Further information. Oladiran Fasina, Department of Biosystems Engineering, 214 Tom E. Corley Building, Auburn University, Auburn, AL 36849; phone: [phone]; fax: [phone]; email: [e-mail].