Food or edible material: processes – compositions – and products – Processes – Cooling – freezing – or treating cooled or frozen product,...
Reexamination Certificate
2000-10-05
2001-09-25
Yeung, George C. (Department: 1761)
Food or edible material: processes, compositions, and products
Processes
Cooling, freezing, or treating cooled or frozen product,...
C426S241000, C426S565000
Reexamination Certificate
active
06294215
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to improvements in the microwave heating of frozen food products. In particular, the invention relates to a method for preparing frozen food products having enhanced coupling properties with microwaves such that the reconstitution time can be significantly reduced. The invention also relates to a frozen food product having such properties.
BACKGROUND OF THE INVENTION
Microwave heating of frozen food products is characterized by a slow and largely non-uniform reheating first step before the product is thawed, followed by a more rapid second step wherein the thawed parts of the product are heated. In fact, the non-uniformity of the heating before the thawing is translated and even amplified during the second heating step. Therefore, there is a need to focus on the frozen state and to modify the physical properties of the frozen product in order to increase the rate of thawing and to reduce the temperature gradients between the various parts of the food product during the first microwave heating step.
It has been found that frozen foods have very low dielectric parameters at the microwave heating frequency of 2.45 GHz, ranging from 1.1 to 2.5 for the real part of the permittivity, &egr;′, and from 0.01 to 0.0001 for the imaginary part, &egr;″ (microwave absorption). These values are both close to those of gases and air at ambient conditions. The microwave heating rate that is induced by dipolar absorption is proportional to the microwave absorption &egr;″, and therefore is very small for all frozen products. In addition, because of the low values for the dielectric parameters, the impedance of the whole frozen product does not affect the microwave field distribution in the oven cavity, resulting in a heating pattern that is largely non-uniform.
U.S. Pat. No. 4,428,971 to Havette et al. discloses a process for the preparation of a composition for frozen or deep-frozen soufflés. The patent relates to the incorporation of carbon dioxide in the proportion of 0.5 to 2% by weight of the souffle in order to promote better rising during baking in a conventional oven and to reduce the likelihood of the soufflé's collapsing when served. According to Havette, a small amount of carbon dioxide is fully dissolved into the soufflé base which is then stored in a freezer. The dissolution of the carbon dioxide is achieved by injecting carbon dioxide gas into the product or by mixing solid carbon dioxide with the soufflé recipe until complete dissolution of the gas is achieved. In both cases, the product obtained after this processing step is a “batter” with some gas dissolved in it. Macroscopically, this carbon dioxide gas does not form gas pockets in the “batter” because of the small quantity of solid carbon dioxide used and because of the way it is incorporated into the composition. In Havette, the carbon dioxide is mixed in small amounts at low speed until the gas has completely dissolved. When the frozen composition is reheated by baking, the dissolved gas expands so that the whole upper part of the soufflé rises and does not collapse when it is served. The method of cooking a souffle disclosed by Havette is adapted to conventional ovens, however, and would not be suited to microwave heating. The process of Havette does not utilize a structure which is microscopically modified so as to provide significant improvements for microwave heating.
U.S. Pat. No. 5,624,700 to Ogden discloses the incorporation of relatively large amounts of carbon dioxide in solid or semi-solid foods during the final processing steps for making a semi-solid or solid spoonable food. The food products as manufactured, however, are carbonated cream or ice cream products which are not intended to be processed in microwave ovens.
GB Patent No. 1,005,399 to American Machine and Foundry Company discloses a method of enhancing the flavor of a dairy dessert by introducing carbon dioxide into the dessert to lower the initial pH value of the mixture and provide a dessert having greater zest through carbonation.
JP 59146542 A1 to Sawaguchi Kazuore discloses a mixture for making carbonated ice cream, sherbet, or frozen yogurt.
JP 6062754 A to Kanebo Ltd relates to the production of carbonated ice candy.
Despite these disclosures, there remains a need for improved microwave reheatable frozen products, and the present invention satisfies this need.
SUMMARY OF THE INVENTION
The present invention relates to the preparation of a frozen food product having enhanced coupling properties with microwaves. In a preferred embodiment of the invention an amount of solid carbon dioxide at an initial temperature is added to a non-frozen food product, the solid carbon dioxide containing food product is frozen to a storage temperature, and the solid carbon dioxide is allowed to sublime and form gas bubbles to provide a frozen food product wherein the gas bubbles are distributed within the frozen food product and are of sufficient size to induce a more rapid and uniform absorption of microwave energy by the frozen food product. The difference between the initial temperature of the solid carbon dioxide and the storage temperature is typically from about 35 to 60° C., and preferably from about 35 to 50° C. The amount of solid carbon dioxide is typically at least about 3 percent by weight of the non-frozen food product.
According to one embodiment of the invention, the solid carbon dioxide is added to the food product as finely ground particles having an average size of from about 1 to 4 mm or preferably from about 2 to 3 mm. According to another embodiment of the invention, the majority of the gas bubbles that are formed have a size of at least 1 mm, and the sublimation of carbon dioxide results in less than 10 percent of the carbon dioxide escaping from the food product. The solid carbon dioxide containing food product is frozen to the storage temperature in less than 5 minutes. In another embodiment of the invention, the solid carbon dioxide containing food product is frozen first to a temperature lower than the storage temperature, preferably between about −45 to −39° C., and then slowly the temperature is increased over a period of time of at least about 25 minutes to the storage temperature, which is preferably between about −21 and −18° C.
The invention also relates to a frozen food product comprising an amount of carbon dioxide of at least 3 percent by weight of the food product in the form of gas bubbles wherein the majority of the gas bubbles have a size of at least 1 mm, wherein the amount of carbon dioxide is between about 3 to 6 percent by weight of the food product. This enables the frozen food product to be reheated in a microwave at least 30 percent more quickly than a frozen food product without carbon dioxide.
REFERENCES:
patent: 3503757 (1970-03-01), Rubenstein
patent: 4428971 (1984-01-01), Havette et al.
patent: 4738862 (1988-04-01), Bee
patent: 4891235 (1990-01-01), Mizuguchi et al.
patent: 5229157 (1993-07-01), Birch et al.
patent: 5624700 (1997-04-01), Ogden
patent: 5968582 (1999-10-01), Vaghela et al.
patent: 1005399 (1965-09-01), None
patent: 59-146542 A1 (1984-08-01), None
patent: 6-062754 (1994-03-01), None
Nestec S.A.
Winston & Strawn
Yeung George C.
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