It is widely acknowledged that much of the special spirit of Shabbat is due to the three Shabbat meals that are served on the Day of Rest (Friday night dinner, Shabbat lunch and seudah shlishit). The big question, however, is how it is possible for the great cooks of Shabbat meals to make such amazing fare when cooking is one of the 39 m’la’chot (forbidden creative labors on Shabbat).
In halacha, cooking is referred to as bishul, and the first thing one needs to understand regarding bishul is the proper definition of cooking. According to halacha (Jewish law), one performs an act of bishul when heating a substance to a point where it undergoes a physical change (for instance, sauteing vegetables so that they are nice and soft or so that the flavors of spices merge with them). The temperature at which such changes takes place (beyond which one may not heat food) is referred to as yad soledet bo, which literally means when a hand recoils from the intense heat (approximately 110°).
In order to avoid heating a substance beyond the point of yad soledet bo, the food should not be placed on (or very close to) direct heat. Food that had been cooking before Shabbat on a direct heat source* and has reached the point of being cooked, may remain cooking on Shabbat, but once it is officially Shabbat, no uncooked or partially-cooked food may be placed onto the heat.
In order to serve warm food on Shabbat, many people use what is now commonly referred to as a blech, the Yiddish term for a sheet of metal that is placed over the burners/elements on the stove before Shabbat. The general principal of using a blech is that only solid foods that have been fully cooked (even if they have already cooled) may be reheated.
Today’s Treat is a basic overview of the law of bishul on Shabbat and should not be used as a halachic guide. To learn more about proper Shabbat food preparation, please consult a rabbi.
*Please note that a flame or element may not be adjusted or extinguished on Shabbat.