Spring 2025

Over the years, I have been invited on multiple occasions to speak at various girls’ high schools in Lakewood about the impact of astronomy on the Jewish calendar and halachic zmanim. The inherent message I have aimed to give over is that one needs a basic understanding of math and science to fully comprehend certain halachic issues.

For example, the earth’s rotation on its axis is the basis of zmanei hayom (halachic times of the day) that are so much a part of our lives with regard to davening times and knowing when Shabbos and Yom Tov begin and end. One needs to know how the moon rotates around the earth to better understand Rosh Chodesh and the Jewish calendar. Indeed, Chazal had keen insights into scientific topics that were discovered hundreds of years later by researchers.

Investigating how a product is manufactured and analyzing the composition of the raw materials used in the process is critical to determining whether a product can be certified kosher. Principles of biology, chemistry, and physics play a fundamental role in food production.

During recent factory inspections, I began to track several examples of how each of these disciplines intersects with kashrus.

Biology

Many food products are produced through fermentation. These include whiskey, in which yeast is used to convert the sugars in grains into ethanol, and which must be carefully tracked to ensure that no grape derivatives were used which could render the product non-kosher[1]; citric acid, an ingredient commonly found in soft drinks; and amino acids, including L‑arginine and L‑methionine, which are staple ingredients in many productions and require the use of kosher certified growth media and other ingredients.

As a STAR-K kashrus administrator, I recently had a unique opportunity to review the production of penicillin in a factory that manufactures thousands of tons of this product each year. Penicillium fungus, better known as mold, was being grown in large fermenters where it was “fed” glucose and lactose. This growth media has important halachic ramifications: one of the sources of the glucose used in this plant is wheat (the other being corn) and lactose (milk sugar) –  rendering the finished product both dairy and, possibly, chometz.

The production process concluded with the introduction of an acid that caused the mold to release penicillin, a self-defense antibiotic chemical, that was then filtered and harvested. This lifesaving, active pharmaceutical ingredient is added to pills, tablets and liquids used by millions to treat a host of infections.[2] From a halachic standpoint, the possible chometz status of the growth media explains why penicillin made at this company is listed as “may contain chometz” in the STAR-K Pesach Guide medicine list, prepared each year by Rav Gershon Bess shlit”a and published in conjunction with Kollel Los Angeles. This is an excellent example of the interplay of biology and kashrus.

Chemistry

Principles of chemistry are the building blocks of the food industry. As many of us learned in high school chemistry class, when two substances are chemically combined, a reaction forms, creating a completely new product.

When a mashgiach goes to inspect a manufacturing facility, he needs to determine which raw materials reacted together, what processing aids were used (even if they were filtered out after the production), and what else was made on the company’s equipment. Safeguards include checking what other products the company is manufacturing at the site, reviewing common steam lines, and identifying ingredients that have both kosher and non-kosher versions and which could be inadvertently swapped in a production.

Some kosher-sensitive ingredients produced through chemical reactions include:

► Triacetin – a plasticizer made by reacting glycerol (derived from animal, vegetable or synthetic sources) with acetic anhydride.

► Polysorbate 80 – known chemically as sorbitan monooleate, is used as an emulsifier (i.e., an additive that helps two liquids such as oil and water mix) in salad dressings and in frozen desserts such as ice cream. Polysorbate 80 is both kosher-sensitive and Pesach-sensitive, because it is made by reacting sorbitol (derived from chometz in Europe) and oleic acid, a fatty acid possibly derived from non-kosher animal derivatives.

Some chemical reactions use chemicals that we would never dream of eating to form ingredients that we consume daily.  For example:

► Propylene oxide – an acutely toxic and extremely flammable chemical, is combined with water to form propylene glycol, which is used to dissolve flavor ingredients in drinks. It also prevents powdered ingredients from caking.

► Carbon monoxide is a well-known poisonous gas. When carbon monoxide reacts with ethylene and water, the result is propionic acid which is also used as a food preservative in bread and other baked goods.

► Isobutene – another highly flammable gas, is used to make polyisobutylene, a chemical that can be transformed into a slightly sticky substance used on the back of sticky-notes. Why does such a product require a hechsher? Because it is also used in the production of chewing gum! Just as a sticky pad requires a weak adhesive so it does not tear the paper it is affixed to, chewing gum should not be “super-glue” sticky or it would never come off one’s teeth.

Physics

Physics involves the study of the interactions between objects and energy in a given environment. This includes what happens when equipment is heated to very high temperatures, which is a regular occurrence in factories, both in the course of kashering a facility as well as during regular productions. I found it most intriguing to have recently seen chemicals reach temperatures of over 700° C (about 1,300° F).

When STAR-K requires special kashering of a factory, a mashgiach must be present to ensure that it adheres to kashrus specifications. The kashering can include kettles, reactors, stainless-steel piping and micronizers (which reduce the diameter of solid particles), among many other types of specialized production equipment at the site.[3] Spray driers that often take up several floors of a factory and convert emulsions into powders require extra attention during the kashering process. This is a complex process that involves a great deal of energy to heat the equipment.

Another application of physics that has important halachic ramifications are induction cooktops. which heat ferrous metals using strong magnetic fields. When a metal pot is placed on the cooktop, the pot begins to heat up; when the pot is removed, the heating process ends. Due to these scientific properties, induction cooktops may not be used on Shabbos or Yom Tov and cannot be Sabbath Mode certified.

Summing Up

Kashrus is greatly impacted by science. For example, a basic knowledge of chemistry can help a kashrus administrator or field representative understand whether certain chemicals are “kosher-sensitive” or if production equipment was compromised through reacting with non-kosher chemicals.

As the world becomes more and more technologically advanced, science becomes even more relevant. The following are contemporary examples where science and kashrus certification intersect:

► Genetically Modified Organisms (GMO’s), first approved for consumer products by the FDA in 1982, have been assessed by poskim and are generally considered kosher (albeit kashrus agencies typically do not address health and ethical issues regarding such items).

► Artificial Intelligence (AI), a much-discussed topic these days, affects many industries – including farming and food production. How AI promotes or hinders kashrus and how agencies adapt to these new realities remains to be seen.

► Bionaphtha, produced from recycled oils, requires a firm understanding of the science behind it to determine its kosher status.

► Food Colors, produced from natural sources that are replacing certain banned artificial colors, likewise need scientific analysis to determine if they are kosher.

► Satellites can now track fields in Israel during the Shemita year.

Incorporating the practical halachic scientific applications into school curricula is a creative way to make the lessons more interesting and to help students retain those lessons even after they have left the classroom. Presenting the material in this way also helps to illustrate to them the niflaos haBorai – and may even serve to inspire the next generation of kashrus professionals. As kashrus continues to evolve within a fascinating world of scientific advancements, STAR-K and all kashrus agencies should have the syata di’Shmaya to continue to serve Klal Yisroel ad bi’as goel tzedek.

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[1] For a detailed explanation, see “Kashrus in High Spirits” by Rabbi Tzvi Rosen at https://www.star-k.org/articles/kashrus-kurrents/1139/kashrus-in-high-spirits/.

[2] Penicillin was discovered in 1928 by Dr. Alexander Fleming when he observed penicillium mold, which can grow on bread, produce a self-defense chemical that could kill bacteria. Rav Moshe Heinemann shlit”a often quotes the Mishna in Pesachim (39b) that says on Pesach one may not chew on wheat and place it on his wound because it becomes chometz. It is fascinating how Chazal understood the therapeutic capabilities of moistened wheat-based products, which were the forerunners of modern-day antibiotics.

[3] Equipment that stores non-kosher liquid (or non-kosher solids in liquid) for 24 hours becomes non-kosher even without heat (see Y.D. 105:1). Such equipment is difficult to kasher because it typically does not have a heating source.