This invention pertains to the art of food packaging, and more particularly to packages adapted for microwave ovens.
The invention is particularly applicable to a multilayer sheet material having a large number of small pinholes for cooking bread products and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and may be employed in cooking other food products.
U.S. Pat. No. 4,404,241 to Mueller, et al. issued Sept. 13, 1983 and is generally representative of the current state of the art in microwave food packaging. Additionally, this patent provides a concise explanation of some of the problems involved with packaging foods for cooking in microwave ovens. Specifically, Mueller, et al. teaches use of a single, one inch diameter circular aperture or four, 1/4 inch diameter apertures in a sidewall of a package to release or vent built-up water vapor or steam during heating or cooking. Although these aperture sizes adequately vent the package to limit pillowing or rupture, the enlarged openings do cause variations in the texture of the cooked product in the package. Bread products in particular have a tendency to become tough and overcooked at areas disposed adjacent these apertures and soft or undercooked at areas spaced away from the apertures.
Still other microwave packages utilize an adhesive to secure different portions of the package together. Although adequately securing the package, the adhesive may become liquid-like during microwave heating and enter vent openings in the package to contaminate the food product.
It is also generally known to employ microwave packaging of a multi-layer material in which one layer that forms the interior of the package s a metal. It is important to control the thickness of the metal layer since too great a thickness will tend to short out the microwave while a correct, predetermined deposit will facilitate heating. Again, provisions have previously been made to vent packages of this type to prevent rupturing or pillowing as a result of the vapor pressure that builds up during cooking. The large openings often utilized in structures of this type have the effect of unevenly cooking the food product.
The subject invention is deemed to provide a new and improved arrangement that overcomes the above referenced problems and others, and provides an improved package structure that evenly cooks a food product.