Since the contents are generally not consumed all at once, reclosability is a highly desirable feature. Dry ready-to-eat cereal needs to be safeguarded from
- Loss of flavour components
- Changes in moisture content
- Unwanted flavours/doors from added from the environment.
Plastic film inside a paperboard box meets these requirements. The film is a two mil (2 mm) thick co-extrusion of HDPE and EVA. At low cost, HDPE provides sufficient moisture barrier (about 0.3 g-mil/100 in2 day) together with toughness to withstand puncturing by sharp-edged particles. Where added ingredients require additional oxygen protection, EVOH or nylon are included in the co-extrusion.
With regard to plain rice, containment is a key package function, for which plastic bags and paper-board boxes are utilized. LDPE/LLDPE are the most frequently used packaging films that impart strength for 20 pounds of product besides offering puncture-resistance. At the same time, heat becomes sealable at a reduced cost. Most common include combinations of both, with LLDPE being utilized for further robustness. The dual-layer laminate causes the reverse-printing of the outer layer wherein the inner layer carries on the heat seal function.
As far as flavoured aromatic rice is concerned, a vacuum brick package using a 4.5 mil PET/nylon/LDPE construction or a PET/EVA pouch is used for providing an improved door barrier