Electric heating – Capacitive dielectric heating – Specific heating application
Reexamination Certificate
1999-04-13
2001-11-27
Leung, Philip H. (Department: 3742)
Electric heating
Capacitive dielectric heating
Specific heating application
C219S777000, C219S780000, C219S775000, C099S451000, C099S358000, C426S244000
Reexamination Certificate
active
06323473
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a prepackaged food sterilizing apparatus and a sterilizing method for sterilizing a so-called prepackaged food obtained by sealably packing various foods in a packaging container such as a plastic bag and a plastic tray by application of a high frequency.
BACKGROUND ART
So-called prepackaged foods are rapidly widespread such that various foods are sealably packed in a packaging container such as a plastic bag and a plastic tray, and it is true to say that such prepackaged foods contribute to the food style of modem society to a great extent. It has been a common practice to heat the prepackaged foods for sterilization after a food is sealed in a packaging container. A certain heating process (heat maturation process) is also applied to a certain kind of food, combined with heat sterilization, to improve tastes and flavors of the food.
At a last stage of heat sterilization, boiling and steaming are generally performed. However, boiling and steaming require a long time for processing, which lowers sterilization efficiency, and in addition, the flavors of the food may be degraded. The applicants of this invention have proposed a high frequency heating apparatus in which plural prepackaged foods are loaded in a flat sealed container and a high frequency power is supplied to the container by way of opposing electrodes in a pressurized state (Japanese Patent Application No. HEI 7-329296).
In the above high frequency heating apparatus, inside the container where the prepackaged food is loaded is brought to a sealed state by the opposing electrodes in contact with a peripheral portion of the container. Accordingly, it is possible to heat the inside of the sealed container (food loading chamber) at a temperature of 100° C. or higher to sterilize the food in a short time.
In the above high frequency heating apparatus, pressurizing means for pressurizing the inside of the container is necessary. Particularly, since plural prepackaged foods are loaded in the cylindrical shape container in the above apparatus, large size pressurizing means is necessary, which would raise the installation cost for the apparatus. Further, it is difficult to uniformly apply a high frequency to the plural prepackaged foods loaded in the container. Specifically, the heated temperature may vary depending on the loaded position of the prepackaged food which hinders uniform heating, and there may occur a situation that sterilization is not completed with respect to the prepackaged food that has been loaded at a lower temperature heating position. Incomplete sterilization eventually leads to non-sterilization due to growth of bacteria.
To enhance sterilizing ability, there is an idea of applying a high frequency to a prepackaged food for a longer time. However, this idea leads to energy cost rise which is not desirable in the economic viewpoint. Further, a new problem may be raised that the flavor of the prepackaged food is degraded due to over heating.
There have been proposed various sterilizing apparatuses by microwave radiation in which a prepackaged food is accommodated in a support housing member made of a synthetic resin having an inner configuration substantially equal to the outer shape of the prepackaged food (European Patent No. 0269073 (European Patent Application No. 8711732B.2), Japanese Examined Patent Publication No. HEI 7-51060, Japanese Examined Patent Publication No. HEI 7-114672, Japanese Utility Model Registrar No. 2539778, and Japanese Patent No. 2778165).
In view thereof, an object of this invention is to provide a prepackaged food sterilizing apparatus and a sterilizing method that enables assured sterilization to a prepackaged food while suppressing process cost for sterilization.
DISCLOSURE OF THE INVENTION
An aspect of this invention is directed to a prepackaged food sterilizing apparatus provided with a high frequency generating section to supply a high frequency voltage in order to sterilize a prepackaged food by dielectric heating. The apparatus is equipped with a food loading container including a pair of opposing electrodes having a first electrode and a second electrode to which the high frequency is applied, and an annular frame interposed between the pair of first and second electrodes. The container has at least one food loading chamber for loading the prepackaged food therein. The food loading chamber has such an inner shape as to substantially match an outer shape of the prepackaged food.
In this arrangement, the food loading chamber of the container defined by the opposing electrode pair and the annular frame is adapted for loading one prepackaged food. Unlike the conventional case where a large number of prepackaged foods are loaded in a food loading chamber of a large capacity to sterilize the foods by dielectric heating using a pair of opposing electrodes which may result in a drawback that the heated temperature of the prepackaged foods varies depending on the loaded position and the prepackaged foods with incomplete sterilization may be discharged, according to the inventive apparatus, performing serial process such that a certain number of prepackaged foods are loaded in the food loading chamber(s) one after another and taken out therefrom successively after dielectric heating enables reliable sterilization onto the prepackaged foods.
Further, since the food loading chamber has such an inner shape as to substantially match the outer shape of the prepackaged food, expansion of the food due to dielectric heating is prevented by an inner wall of the food loading chamber which obstructs breaking of a bag/tray constituting the container. This arrangement eliminates a necessity of pressurizing the inside of the food loading chamber on a large scale, as performed conventionally, with an attempt to prevent burst-out of the food, thereby contributing to installation cost reduction.
As another aspect of this invention, the first electrode and the second electrode may be each formed with an opposing plane shaped into a flat surface parallel to each other, and the annular frame may have such an inner shape as to substantially match a side surface of the prepackaged food. Thereby, the construction of the container can be simplified. Further, at least one of the opposing planes of the first and second electrodes may be formed with a recess of an inner shape substantially matching the outer shape of the prepackaged food, and the annular frame may be so shaped as to come into contact with an outer surface of the prepackaged food. In this case, the container can contain various types of prepackaged foods.
As a still another aspect of this invention, the annular frame may include a plurality of annular frame segments (first and second segments) placed one over another, and each of the annular frame segments may have such an inner shape as to match the side surface of the prepackaged food. Thereby, two prepackaged foods can be loaded in the container at once. The first and second annular frame segments may be dividably or integrally constructed.
As a yet another aspect of this invention, the prepackaged food sterilizing apparatus may further comprise a holding means operable to the opposing electrode pair to hold the shape of the food loading chamber. The holding means securely holds the closed state of the food loading chamber even if the inside of the chamber is pressurized by heating to prevent burst-out of the food. The holding means may include a pressing means for pressing the first electrode against the second electrode. The pressing means may preferably include a cylinder device.
As a still another aspect of this invention, the holding means may include an engaging means for restricting the first electrode away from the second electrode. Preferably, the engaging means may include an engaging portion and an operable tab to alter the position of the engaging portion between an engaged position of rendering the first and second electrodes in a pressingly held state and a release position of releasing the held state.
As a yet ano
Akesaka Yoshio
Kodama Junichi
Yamamoto Yasuji
Jordan and Hamburg LLP
Leung Philip H.
Yamamoto Vinita Co., Ltd.
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