Bishul Akum - The Extent of a Yisroel's Involvement

Q. If a Yisroel begins the cooking, the food is not treated as bishul Akum even though the aino Yehudi finishes the cooking process. To what extent must the Yisroel initially cook the food?

A. The Gemara Shabbos (20a) states in the name of Rebbi Yochanan that once a food is cooked to the level of “maachal ben Drusai,” it is no longer subject to bishul Akum, even if a nochri completes the cooking. (According to Rashi in Shabbos 20a, ben Drussai was a thief who ate partially cooked food, presumably because he was on the run.) Rashi and Rambam dispute what level of cooking constitutes maachal ben Drusai. According to Rashi, maachal ben Drusai means that the food is one third cooked while the Rambam (Hilchos Shabbos 9:5) states it refers to food that is half cooked. Shulchan Aruch (YD 113:8) rules like Rashi that once a Yisroel cooks the food one third, it is permitted even if a nochri finishes the process. The Chazon Ish (Shabbos 37:6) explains that “one third cooked” is a measure of time. One determines how long it takes to cook a food to completion, and one third of that amount of time is maachal ben Drusai. Other poskim, including Rav Shmuel Wosner (Mi’beis Levi, vol. 6 – 5755), maintain that “one third cooked” refers to a level of edibility. Maachal ben Drusai is the first point when the food can be eaten, irrespective of how long it was cooked.

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The Gerald & Karin Feldhamer OU Kosher Halacha Yomis is dedicated to the memory of Rav Yisroel Belsky, zt"l, who served as halachic consultant for OU Kosher for more than 28 years; many of the responses in Halacha Yomis are based on the rulings of Rabbi Belsky. Subscribe to the Halacha Yomis daily email here.