Coca Cola is Kosher
based on this article by Rav Yehuda Spitz

Rabbi Tuvia (Tobias) Geffen, Chief Rabbi of Atlanta, Georgia for many decades, was one of the select few who actually knew the closely guarded secret ingredient in Coke..
Approached by the company directors, who were seeking Kosher certification for Coke, he agreed to investigate. He concluded it was Kosher, but had some reservations since it contained a minute amount of glycerine, deemed by some to be non-Kosher but even so it was Battel b’shishim [YD 98, Tur, ShA, and commentaries] and therefore insignificant.

“Ain Mevattelin Issur Lechatchila” [ShA YD 99:5] a Rabbinic decree that prohibits adding insignificant amounts of non-Kosher and penalises those who do and those for whom it is done by banning them from partaking of that food, does not apply in this case. R Moshe F explains, there is no decree and certainly no penalty, imposed upon non-Jews, even if they specifically add the non-Kosher for the benefit of Jews, if they do so of their own volition.

However, Rabbi Geffen had two questions. A] Perhaps this situation was prohibited due to “Ain Mevattelin Issur Lechatchila”, and B] even if it is permissible, is it appropriate to give any Hashgacgha and in particular to give his Hashgacha?

The Radbaz [vol. 3:978; old print 547] almost as a lone voice, prohibits foods containing insignificant amounts of non-Kosher even if made by a non-Jew of his own volition, when it is specifically made for a Jew. He argues that the non-Jew must be deemed to be acting under the directions of the Jew which is equivalent to the Jew adding the non-Kosher himself.

This is a delicate analysis. When the non-Jew knows precisely what the Jew wants, and that the Jew is not permitted to instruct him directly, and that he will be appropriately rewarded for taking the initiative; there is almost unanimous agreement that this is tantamount to the Jew instructing the non-Jew to act.

However, there are many shades that are slightly less, and this remains an open debate without much proof one way or the other. See R Moshe F Teshuvah.

The Tashbatz suggests that when this is an ongoing activity, it ought to be prohibited thus suggesting that Coke would be prohibited.

According to Kashrus legend, Rabbi Geffen requested that Coke change their formula and out of respect for him they did. Well, not really, they just substituted glycerine extracted from animal oil with glycerine extracted from vegetable.

Rav Moshe Feinstein zt”l famously wrote, it is an ugly thing, “mechuar hadavar”, to certify foods relying on this argument of BIttul alone.

There were however, Rabbanim that preceded Rav Geffen, who had no compunction providing a Hechsher for Coke, notwithstanding its use of glycerine derived from animal fat. Several Rabbonim had given hashgacha in the late 1920s and early 1930s, as did the Vaadei HaKashrus of Buffalo, Chicago and Rochester. In fact, Coke was advertised as being Kosher in the famed HaPardes Torah Journal. These ads contained a letter from Rav Shmuel Aharon Halevi Pardes, the journal’s editor, that he visited the Coca-Cola factory in Atlanta, and that they ‘revealed to him all of their secrets, including their secret formula’, and he found ‘hamashkeh Coca-Cola kosher lishtoso al pi hadin’.

These Rabbanim included Rav Yaakov ‘JB’ Bienenfeld of New York, Rav Avraham Meir Franklin of Buffalo, and Rav Shmuel Aharon Pardes of Chicago.

They argued that the tiny amount was A] undetectable by taste, and B] had at a stage during processing been significantly altered to the point that it stopped being a food and accordingly the final product that emerged was a food that could not be considered to be Halachically derived from the non-Kosher animal fat it was originally manufactured from. This approach is supported by several Rishonim and Rav Pardes wrote extensively on this topic, including a letter to the Gadol HaDor, Rav Chaim Ozer Grodzensky zt”l, who agreed that it is indeed muttar. 

According to historian Roger Horowitz, in his book ‘Kosher USA: How Coke Became Kosher and Other Tales of Modern Food’, Rabbi Geffen and Rabbi Pardes exchanged halachic responsa on this matter drawing a parallel to the use of animal-based gelatin.