The Eruv Tavshilin, which one prepares before Yom Tov to allow cooking from Yom Tov to Shabbat, must consist of at least one cooked food; customarily, an egg is used for this purpose. Which other cooked foods, besides eggs, may be used for the Eruv Tavshilin?
The Shulchan Aruch (527:4) writes that the food item used for the Eruv Tavshilin must be something that had been cooked and that is normally eaten together with bread. Therefore, canned cooked vegetables, for example, may be used for the Eruv Tavshilin, whereas foods such as rice, pasta and canned corn, which one normally eats without bread, are not valid for the Eruv Tavshilin.
Chacham Bentzion Abba Shaul, in Or Le'tziyon (22:2), rules that the process of pickling qualifies as "cooking" for the purposes of this Halacha, due to the halachic principle of "Kavush Harei Hu Ke'mevushal," which equates pickling with cooking. Therefore, one may use pickles as the cooked food for the Eruv Tavshilin. He adds that pasteurization likewise qualifies as cooking in this respect, and therefore dairy products such as yoghurt, butter and cheeses may be used as the cooked food for one's Eruv Tavshilin. It should be noted that if one indeed chooses to use a dairy product for the Eruv Tavshilin, he must ensure to refrigerate the food so that it does not spoil. Halacha requires that the food used for the Eruv Tavshilin can remain edible until after one completes his Shabbat preparations on Yom Tov, and therefore the yoghurt or cheese used for an Eruv Tavshilin must be refrigerated so that it does not spoil on Yom Tov.
Summary: Although an egg is customarily used for the Eruv Tavshilin, one may use any cooked food that is normally eaten with bread, such as canned cooked vegetables. This also includes foods that have been pickled or pasteurized, and thus one may use pickles, yoghurt, butter or cheese. Foods that are not eaten with bread – such as rice, pasta and canned corn – may not be used. Dairy products used for the Eruv Tavshilin must be refrigerated so that they do not spoil on Yom Tov.
