#828: Au Courant: Commercial Cooking and Kashrus Concerns
Certain foods require bishul Yisroel (cooking by a Jew)* to retain their kosher status. The manner in which many kashrus agencies adhere to this standard is by having a Torah-observant Jew turn on the oven at the beginning of the workday, thereby aiding in the cooking process, thus rendering all food cooked during that cooking cycle bishul Yisroel.
The most modern ovens, however, have created an issue with this protocol; they are rigged with an energy-saving apparatus that extinguishes the heating element in the oven whenever it is opened and reignites it when the door is closed. In commercial settings, this may happen many times in one workday. This causes an obvious bishul problem, since the fire initially ignited by the Jewish worker is not continually maintained throughout the day.
Some authorities quote the Shach (17th century halachic commentator) that once a Jew begins the cooking process by turning on the fire, the food retains its status as bishul Yisroel, regardless of whether the pot remains continuously on the fire—it may be removed and returned to the heat source without Jewish intervention. Aside from the fact that many poskim disagree with the Shach, this solution seems insufficient to allay the issues with an automatic oven as there is no continuous fire—the heating element is extinguished and reactivated when non-Jewish workers swap uncooked dishes with those originally “cooked” by the Jew.
Some authorities maintain that since the Jew originally ignited the fire, the subsequent on/off action can all relate back to the original fire, but this heter (leniency) does not take into account the fact that it is only the electricity of the oven that is maintained throughout and not the actual heating element.
A popular heter to resolve the issue is that we may rely on the fact that even when the fire is extinguished by opening the door, a significant amount of heat remains in the oven—sufficient to cook food—and as long as this degree of heat is maintained, the fire going on and off does not affect the status of the food. Some kashrus authorities suggest another workaround to the issue by advocating for a supplementary heating element to be inserted in the oven by the Jew that is not subject to the automatic door action, but this element would have to provide enough heat to cook in order to provide any kashrus advantage (a tea light, for example, would be woefully insufficient).
The optimal solution, which would circumvent all the possible problems that may incur when relying on heterim to maintain bishul Yisroel status with automatic ovens, is to have an observant Jewish worker available to close the oven doors throughout the daily cooking shifts.
*See Halachah #74, Halachah #289, Halachah #461 and Halachah #694 for some of the rules and parameters for this requirement. Note that this halachah applies to Ashkenazim; Sefardim have stricter general guidelines for bishul Yisroel.