Study Shabbat folio 140A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
Because it is only made to enhance the color of the food. That does not negate the egg-white as significant food in the sense that it would be considered waste, and therefore, no actual selection is performed.
It is stated: With regard to mustard that one kneaded on Friday, on the following day, Shabbat, Rav said: One may dissolve it in wine or water with a vessel, but not with his hand, as using a vessel diverges from the normal method of preparation.
Shmuel said to him: Why may he not dissolve it with his hand? Is that to say that he dissolves it with his hand every day? If it is prepared in that manner, it is donkey food. Certainly dissolving by hand is not the manner in which mustard is prepared during the week. Therefore, dissolving mustar
It is stated that amora’im from Eretz Yisrael also disputed this issue, as R' Elazar said: Both this and that, dissolving by hand and with a vessel, are prohibited; while R' Yoḥanan said: Both this and that are permitted. Abaye and Rava both said: The halakha is not in accordance with the lenient
Subsequently, R' Yoḥanan stood and adopted the opinion of R' Elazar and prohibited both methods of dissolving. R' Elazar stood and adopted the opinion of Shmuel, who prohibited using a vessel but permitted it by hand. Given these stances, Abaye and Rava both said: The halakha is in accordance with