Method of obtaining acceptable configuration of a plastic container after thermal food sterilization process

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container with an acceptable configuration, which comprises filling the container with food, sealing the container, either or both these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing, such as to permit reformation of the container bottom wall without significant side wall panelling, filling the container with food at a temperature, sealing the container, thermally sterilizing the packed container in a continuous retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents, and during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by controlling the pressure external of the container and the cooling conditions, said reforming step being effected in a continuous cooler at a pressure which is less than that employed during the sterilizing step, said controlling step including providing that the plastic of the bottom wall of the container is at a reformable temperature at which the plastic is soft while providing a pressure differential such that the pressure external of the container exceeds the pressure internal the container.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by establishing a preselected ambient gas pressure in the retort at the conclusion of thermally sterilizing, and controlling the ambient pressure and the cooling conditions, said reforming step being effected in the retort at the same or about the same pressure as that employed during the sterilization step, said controlling step including effecting cooling gradually such that as the pressure internal the container decreases, reforming occurs when the plastic of the bottom wall is at a reformable temperature at which the plastic is soft.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by establishing a preselected ambient gas pressure in the retort at the conclusion of thermally sterilizing, and controlling the ambient pressure and the cooling conditions, said reforming step being effected in the retort at a pressure moderately or slightly higher than that employed during the sterilization step, said controlling step including effecting cooling gradually such that as the pressure internal the container decreases, reforming occurs when the plastic of the bottom wall is at a reformable temperature at which the plastic is soft.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by establishing a preselected ambient gas pressure in the retort at the conclusion of thermally sterilizing, and controlling the ambient pressure and the cooling conditions, said reforming step being effected in the retort at a pressure which is less than that employed during the sterilization step, said controlling step including effecting cooling gradually such that as the pressure internal the container decreases, reforming occurs when the plastic of the bottom wall is at a reformable temperature at which the plastic is soft.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents in a continuous cooler, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by establishing a preselected ambient air pressure in the continuous cooler prior to the initial stages of cooling, and controlling the ambient pressure and the cooling conditions, said reforming step being effected in the continuous cooler at an ambient pressure which is less than that employed during the sterilizing step, said controlling step including providing a gradual rate of cooling such that as the container contents cool and the pressure and volume internal the container decrease, reforming occurs prior to sidewall panelling when the plastic of the bottom wall is at a reformable temperature at which the plastic is soft.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging of the container bottom wall, cooling the container and its contents in a continuous cooler, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by establishing a preselected ambient air pressure in the continuous cooler prior to the initial stages of cooling, and controlling the ambient pressure and the cooling conditions, said reforming step being effected in the continuous cooler at an ambient pressure which is about the same as that employed during the sterilizing step, said controlling step including providing a gradual rate of cooling such that as the container contents cool and the pressure and volume internal the container decrease, reforming occurs prior to sidewall panelling when the plastic of the bottom wall is at a reformable temperature at which the plastic is soft.

A method of thermal sterilization of a plastic container packed with food to obtain a thermally sterilized packed container having an acceptable configuration, which comprises filling the container with food, sealing the container, either or both of these steps including selecting an initial headspace volume and an amount of gas, taking into account an initial vacuum level, if any, at sealing such as to permit bulging and subsequent reformation of the container bottom wall without significant side wall panelling, thermally sterilizing the packed container in a retort operated at a temperature and pressure for a time sufficient to sterilize the container and its contents and to cause bulging and creep of plastic of the container bottom wall, cooling the container and its contents, and, during the cooling step, reforming the bulged container bottom wall to attain an acceptable container configuration by controlling the pressure external of the container and the cooling conditions said controlling step including providing that the pressure is about the same as or less than that employed during the sterilizing step, providing that the plastic of the bulged container bottom wall is warm while providing a pressure differential such that the ambient pressure external of the container exceeds the pressure internal the container, and utilizing the ambient pressure while said plastic is warm to reform the bulged bottom wall.