Kosher grocery shopping in 2024. We pull a package of candy off the shelf, glance at it to check it has a kashrus symbol, and casually toss it into our cart.
What we don’t think much about is that somebody had to make sure the unpronounceable additives, preservatives, and colorants in the ingredients list are kosher. And as over the years, food became more high tech, kashrus supervision needed to turn high tech as well. Most of us are unaware that the person who pioneered the kosher certification of all those mysterious chemicals was an unassuming and brilliant woman with a short sheitel, glasses, and a warm smile, named Dr. Judith Leff (née Weisz) a “h”.
A mother of three and grandmother of many, Dr. Judith Leff was nifteres this past November. And while she wasn’t a household name—that’s how she preferred things to be—she’s one of the unsung heroes of the male-dominated kashrus certification industry.
Judith Leff’s life literally took her around the world.
Born in Vienna in 1935 into a family with Hungarian roots and yichus from the Maharam Ash, she was the daughter of an accomplished artist and a seamstress. When the Germans took over Austria during the Anschluss of 1938, Judith’s family fled to Paris, believing they would be safe there.
But a few years later, the Germans invaded France. The French police, in cooperation with the Nazis, began rounding up Jews. Judith’s father was arrested and sent to the French detention camp at Pithiviers in 1940. The last letter the family received from him said he was being transferred to Auschwitz, where he died of tuberculosis. Judith inherited the letter after her mother’s passing and kept it framed in her living room.
In the meantime, the rest of the family—Mrs. Weisz and her five children—connected with a network of Quakers who had made it their mission to rescue Jewish children. The family was separated and placed with different peasant families in the free zone of France, often moving from one place to another. After the war they managed to reunite and went back to live in Paris, where Mrs. Weisz went to court and reclaimed their apartment.
“At one point, when my mother was about twelve, she was sent to an aunt in England for a couple of years,” Judith’s daughter Chana Laks relates. “There, she attended the Hasmonean school and learned English.”
Judith, who had been interested in science from a young age, returned to Paris in 1948 for high school and then enrolled in the Sorbonne, studying toward a doctorate in plant physiology. Attending a secular university could not sway her rock-solid Jewish convictions. “There was an exam for the doctorate that was only held on Shabbos, and in France, there was no flexibility allowed,” Mrs. Laks says. “The only alternative was to repeat the whole year and try again. She refused to show up for the exam.”
So Judith left France to study at
How did Dr. Leff’s work directly impact the kosher certification process for modern food products?
## An Interview About the Pioneer of Kosher Chemistry
**Interviewer:** Today, we’re remembering Dr. Judith Leff, a woman who quietly revolutionized kosher supervision in the modern world. Dr. Leff, who sadly passed away this past November [[1](https://jewishaction.com/food/kashrut/when-science-meets-kashrut-how-one-woman-blazed-a-trail-in-ou-kosher)], left an indelible mark on the way we understand kosher certification, especially when it comes to those complex ingredients lists we see on every packaged food today.
Joining us to discuss her legacy is [ Guest Name & Credentials ]. Welcome!
**Guest:** Thank you for having me.
**Interviewer:** Dr. Leff really flew under the radar, yet her work ensured that so much of what we eat is kosher certified. Can you elaborate on her contributions?
**Guest:** Absolutely. As explained in the article on Jewish Action [[1](https://jewishaction.com/food/kashrut/when-science-meets-kashrut-how-one-woman-blazed-a-trail-in-ou-kosher)], Dr. Leff understood that with advancements in food technology, the requirements for kosher certification became incredibly complex. She became a pioneer in understanding the kosher status of additives, preservatives, and artificial coloring. This was groundbreaking work, and it laid the groundwork for the kosher certification of countless products we find on supermarket shelves today.
**Interviewer:** It’s fascinating to think that behind those seemingly simple symbols on our food is a whole world of scientific investigation and halachic analysis. Dr. Leff’s work really exemplified that connection.
**Guest:** Exactly. She combined a deep understanding of both science and Jewish law. It was a rare combination, especially at the time, and it allowed her to bridge the gap between these two worlds in a truly meaningful way.
**Interviewer:** Did Dr. Leff ever speak publicly about her work?
**Guest:**
She was very humble. As you mentioned, she wasn’t seeking fame. Her greatest reward was knowing she was helping people keep kosher in a complex world. But those who knew her personally, those in the kosher certification world, they knew the tremendous impact she had.
**Interviewer:** It sounds like Dr. Leff was a true pioneer. Thank you for sharing your insights about her remarkable life and contributions.
