Patent SE-1430155-A1 (SE)
Inventor: GUSTAVSSON GUSTAV MARTIN
IPC: F24C15/00
Filed: 2014-11-04
Abstract: The inventor has performed tests with various valves on the market having opening pressures of 20-150 mbar. For some products in some packages, the valves do not open when the desired core temperature of the food product is reached. Examples of such food products are fish and meat, such as beef, pork and ham. This means that the off-aromas stay within the package.Vacuum may be formed at the same time as the product is sealed, but in such case, off-aromas stay inside the pack. If no vacuum is formed in the sealing process, the same amount of air remains in the pack after the process if the valve has not opened. Forming a vacuum in the sealing stage are for some products tricky as there is a risk that liquids or product ends up in the seal, thereby reducing the strength of the same. Letting air and steam out through a valve during cooking enables a safer, more convenient way to vacuum pack that also has organoleptic advantages.If, for example, a sealed food package is heated in an oven such that the gas phase temperature inside the package reaches 72 °C, the partial pressure of water vapor is 345 mbar. Adding the expansion of the air inside the package at this temperature, a valve having an opening pressure of 150 mbar should open. It has however been shown that this is not the case for many applications. The reason why the valve fails to open is probably that the material of the package stretches/expands and thereby increases the volume of the package and prevents the internal pressure from reaching the opening threshold. This is especially the case for a rigid package with a flexible sealing, such as a plastic film, or a completely flexible plastic package. The off-aromas and liquids may thus stay inside the package even when the temperature in the oven is 120-130 °C. The valve would perhaps open if the temperature in the oven was increased further, but in such case the food product would be overcooked. Another problem is that most available valves are composed of plastic and cannot tolerate temperatures above 140 °C.According to the present disclosure, the ambient pressure, i.e. the pressure inside the oven, is instead reduced at the end of the cooking process such that the relative overpressure inside the package increases. Thereby, the off aromas are released from the package already at temperatures that are compatible with available plastic valves and at which over-cooking of temperature-sensitive foodstuffs, such as fish or meat, can be avoided.The present disclosure thus provides a steam oven for cooking at atmospheric and sub-atmospheric pressure, said oven being operable in at least three different modes including: (i) dry heating at atmospheric pressure; (ii) moist heating at atmospheric pressure; and (iii) operation at sub-atmospheric pressure,wherein said oven comprises: a housing defining a cavity capable of receiving food packages;. at least one heating element;. a steam-generating arrangement for providing steam in the cavity;. an fan arrangement; and. a gas outlet connectable to a vacuum source for withdrawing gas from the cavity.There present disclosure also provides a method of cooking food arranged in a sealed package comprising a one-way valve that opens at an overpressure of 20-200 mbar in an oven, comprising: heating the sealed package in the oven at approximately atmospheric pressure for a first time period; and. reducing the pressure in the oven and subjecting the package to a sub-atmospheric pressure for a second time period.