Microwave thawing package and method

#The present invention relates to devices and methods for thawing frozen materials by exposing same to electromagnetic energy, and more particularly to packaging systems and methods wherein thawed liquid is removed from exposure to the energy to prevent overheating the liquid.

#Many heat sensitive materials are frozen to prolong storage life. These include foodstuffs, pharmaceuticals, and particularly blood and blood products. It is often desirable to thaw these materials quickly, especially blood needed in emergency situations. At the same time, it is well known that it is very difficult to thaw frozen materials by microwave heating in a controlled and reproducible way, because the loss tangent of water is so much greater than that of ice. Once a small portion of the material is melted, that portion rapidly absorbs additional microwave energy and begins cooking.

#In the field of microwave radiation, it is well known that microwave ovens may be constructed to operate at either fixed or variable frequency. Owing to the coupling ability of 2.45 GHz microwaves to water, this frequency is often used for cooking foods, drying, and other purposes wherein the principal material to be acted upon is water. However, it is well known that a multimode cavity operating at fixed frequency will display significant nonuniformities in the spatial power density owing to the formation of standing waves (or the excitation of only a small number of microwave modes within the cavity).

#FIG. 1 is a schematic front view of an embodiment of the present invention wherein an upper section accommodates microwave heating while a lower, shielded section protects thawed liquid from further heating.

#FIG. 2 is a schematic cross-sectional side view through section A-A′ of FIG. 1.

#FIG. 3 is a schematic cross-sectional side view of a microwave heating section of an embodiment of the present invention showing a lossy (microwave-absorbing) layer having an essentially uniform thickness.

#Like reference numerals are used for like elements in the drawings.

#For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

#The present invention is designed to provide packages and methods for controlled microwave thawing of frozen materials while preventing thermal runaway in already-melted material. Some applicable processes include thawing of foodstuffs, pharmaceuticals, blood and blood products, biological tissue, other biological and/or chemical materials. Electromagnetic energy includes microwave, radio-frequency (RF), and infra-red (IR) types of energy.