Torah, Science & Kashrus in the Classroom

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 […]

Vinegar: Doing Kashrus Tastefully

Spring 2025

Vinegar has a long and storied history and plays a highly-prized role in every aspect of modern life – whether as a nutrient, flavorant, preservative or household cleanser. The name vinegar is derived from the French “vin aigre, which literally means sour wine. According to legend, its discovery is credited to a neglected barrel of wine that had been left in storage and allowed to ferment and become sour.

We find several references to vinegar in both Tanach and the Gemara. A nazir is forbidden to consume anything derived from grapes, which includes wine vinegar;[1] Dovid Hamelech accuses his tormentors metaphorically of giving him vinegar to quench his thirst;[2] Boaz’s workers dip their bread in vinegar;[3] and Mar Ukva refers to himself as “Chometz ben Yayin” – Vinegar, the son of Wine – when comparing himself to his father’s degree of piety.[4]

Vinegar […]

Tevila Exemption for Appliances with Electronic Components

Spring 2025

For many years, Rav Moshe Heinemann shlit”a instructed STAR-K to advise consumers that electric appliances which require tevila – such as toasters, waffle makers and hot water kettles – can be toveled and left to dry for three days. I have given this advice probably thousands of times and never once had a call back that the appliance was ruined.

There are, however, appliances that have both electric and electronic components. Electric devices convert electrical energy into other forms of energy, while electronic devices control the flow of electrons to perform tasks. Once exposed to water, damage to electronics begins within seconds – and the longer the exposure, the worse the damage.

Printed circuit boards consist of a laminate containing fiberglass and copper-clad epoxy, which forms the circuit’s wiring. This creates the perfect environment for galvanic or two-metal corrosion. Water contains minerals such as calcium, magnesium, potassium and salt, which accelerate […]

The Mitzvah of Tevilas Keilim

Spring 2025

We are an Am Kadosh, a Holy People, who are mandated by Hashem to imbue all aspects of our lives with holiness. We elevate even the mundane activity of eating and vest it with special kedusha (sanctity): the food on our plates must be kosher and the table on which we eat is likened to the holy mizbe’ach. The plates themselves, and all keilim (vessels and utensils) used to prepare our food, must likewise be infused with kedusha.

Just as an aino Yehudi must tovel in a mikvah in order to become Jewish, so too must keilim acquired from an aino Yehudi undergo tevila in a mikvah before being used by a Jew. This is the mitzva of tevilas keilim.

If a kli requires tevila, it may not be used even once before it is toveled. If a kli was used numerous times without tevila, one is still required to immerse […]

Eretz Tzvi: Halachos of Visiting Eretz Yisroel

Kashrus Kurrents Winter 2025 Issue | Updated February 2025

Eretz Yisroel is also called Eretz Tzvi. Chazal explain that, like the skin of a tzvi (a deer), which stretches beyond its natural state, the Land of Israel likewise expands to accommodate its inhabitants.[1] The Talmud states that anyone who walks four amos in Eretz Yisroel merits a place in the World to Come.[2] From here, some poskim derive that one fulfills a mitzvah merely by visiting Eretz Yisroel, even if one intends to stay for just a short while.[3]

Anyone planning a trip should be mindful of several pertinent halachos. We will review some of these below.

Scheduling the Flight

Do not plan to land too close to Shabbos; a flight landing on Friday morning is halachically acceptable.[4]

Try to avoid leaving Israel on a fast day, as the fast will be extended and you will not […]

The Mitzvah of Pidyon Haben: A Brief Overview

Winter 2025

Mazel tov, you are the new parents of a baby boy! If the baby is the bechor of his mother – meaning that he is his mother’s first child – he will need to be redeemed by a kohen. The Torah tells us that Hashem slew every firstborn male in Mitzrayim, passing over the houses of the Bnei Yisrael. As a result, firstborn males acquired a measure of kedusha and must be redeemed by a kohen. The halachos of pidyon haben are somewhat complex and you may not have the time to familiarize yourself with them. Here, then, is a brief primer according to Ashkenazi custom.[1]

When Is a Pidyon Not Required?

If the baby is not his mother’s first child, even if he is his father’s first child

If the father is a kohen or levi, or if the mother is the daughter of a kohen or levi[...] Read More

Destination Simcha: From Meat Board to Surfboard

Winter 2025

Forty years ago, the Lakeshore Hebrew Day School of New Orleans celebrated its 10th Anniversary Dinner in one of the premier hotels in the Vieux Carré, under the supervision of the local Orthodox rabbi. The day school then housed the New Orleans Kollel, of which I was a member. The event was so special that my Rosh Yeshiva, Rav Henoch Leibowitz ztz”l, was brought in as the guest speaker.

Before the event, we met extensively with the hotel chef, the pastry chef, and the food and beverage director to ensure that – even though the hotel was kosher certified – there would be no kashrus hiccups. When the big day arrived, I came with a crew made up of the chevrei hakollel to supervise the cooking for the event. Imagine our alarm when the chef showed us the “kosher” soup kettle – gleaming on the inside but encrusted with crawfish […]

The Perils of Partnering with a Party Planner

Winter 2025

[Sidebar to “Destination Simcha: From Meat Board to Surfboard.”]

For many people, juggling and coordinating all the details involved in planning a simcha – from booking the hall, arranging the décor, designing the invitations, planning the menu, ordering the food, to running random errands – is simply … overwhelming. Enter the party planner. This increasingly popular option has been gaining traction over the last few years, but not without its perils.

Party planners offer concierge services to help alleviate much of the stress involved in planning a simcha. They are typically more affordable than a full-service caterer who is under a hashgacha. Party planners work within your budget to offer any number of services at different tiers: they may handle the décor and design but may leave it to you to bring in your own food, or they can coordinate everything from “soup to nuts.” This is when the problems […]

From Dregs to Riches

Fall 2024

In medieval folklore, alchemists were supposedly able to transform lead into gold. Their craft was the stuff of fantasy. But in contemporary life, through the wonders of kosher food science, we are witness to a veritable world of transformation. An impressive example of chemical transformation that would make an alchemist envious is the production of silica gel.

The Chemical Transformation of Sand

Silica gel is a desiccant. It is a highly versatile industrial product, used to absorb moisture in toothpaste, paint and telephone wires, among a myriad of other uses. Granules of silica gel fill the little white packets marked “do not swallow” in your shoe boxes. Kosher food applications include silica gel in spices as an anti-caking agent or as an absorbent in an oil refinery.

Chemically, the basic raw material for silica gel is sodium silicate. More simply, we know it as sand. When sodium silicate is mixed with sulfuric […]

West Meets East: The Beauty of Sephardi Minhagim

Fall 2024

True to Hashem’s promise, the children of Avraham, Yitzchak and Yaakov are today scattered in countries across the globe, upholding the teachings of the Avot and perpetuating our beautiful mesorah, each according to his own traditions.

A Brief History

Until the 1970s, American Jewry – then comprised mainly of Ashkenazim – was largely unfamiliar with the minhagim of Sephardi Jews[1] and the Bnei Edot Hamizrach.[2] That changed after 1976, when Rabbi Herman Neuberger zt”l embarked on a daring mission to travel to Iran and bring a small group of young Iranian bochurim to Baltimore to learn at Ner Israel. Iranian Jewry in those days had few opportunities to study Torah. This took place during the reign of the westernized, secular leader Shah Mohammad Reza Pahlavi. Rabbi Neuberger’s plan was that once they earned semicha, the newly ordained rabbis would return to Iran to teach.

Hashem had other plans. […]

A Higher Calling: Maintaining Kedushas Kehuna on Land, Air and Sea

Fall 2024

The Torah tells us that Ahron and his sons were appointed by Hashem to serve as the first kohanim. The status of kehuna passes from father to son, in that a son of a male kohen is also a kohen. The kohanim were ordained to serve in the Beis Hamikdash and commanded to fulfill specific mitzvos.[1]

Among these is the obligation for male kohanim to preserve their kedusha and to prohibit becoming tamei meis – that is, becoming defiled through contact or exposure to a dead body.[2] Even though we no longer have a Beis Hamikdash, kohanim in our time are still required to observe all the halachos of tumas meis, both in and outside of Eretz Yisroel.[3] A kohen is restricted from becoming tamei even from an akum meis (the body of a deceased aino Yehudi).[4] At times of significant need, […]

Going Up: All About Shabbos Elevators

Summer 2024

Historians claim that two hundred and twenty-four slaves were needed to operate the pulleys of the elevator system in the Colosseum of Rome. Thankfully, technology has come a long way since then. Modern elevators run on electricity which has necessitated the development of a Sabbath Mode. In Sabbath Mode, an elevator cab moves continuously up and down the elevator shaft, stopping at every floor. However, as will be explained, not all Sabbath Modes are the same.

Physics 101: How Elevators Work

There are two basic types of elevators in common use today: hydraulic and traction.

Hydraulic-Type Elevators

Hydraulics make use of the principle that liquid moved with low force over a large distance can be converted to movement with high force over a short distance. Take, for instance, a simple hydraulic jack (see Fig. 1). If the piston on the right has a surface area ten times that of the piston on […]

Warming Up: Do’s and Don’ts of Slow Cookers and Hot Plates on Shabbos

Summer 2024

Slow cookers and hot plates are the workhorses of many kosher kitchens as they enable the Sabbath-observant hostess to serve piping hot dishes to her family and guests to enhance the Shabbos seuda. In recognition of their importance in a Jewish home, it behooves us to review the halachos involving these appliances about which many users might not be aware.

This article will try to clarify the potential issues and how to address them in a practical way.

Slow Cookers

There are two basic types of electric slow cookers: an insert type (often referred to as a Crockpot®), in which a stoneware vessel sits inside a heated base; and a flatbed type, in which a metal pot sits atop a griddle base. Halachic issues involving their use include hatmana, shehiya and chazara. These will be explained below. (There are some more expensive models equipped with variable thermostats which make their usage on […]

Keeping Your Cool: Using a Refrigerator on Shabbos

Summer 2024 | Updated February 2025

As electricity began to be used as an energy source in the late 1800s and early 1900s, poskim considered how to view electricity from a halachic perspective. The posek hador, Rav Chaim Ozer Grodzinski zt”l, ruled that electric incandescent lighting is considered fire and, to reinforce this psak, he himself would recite Borei Meorei Haesh on an unfrosted incandescent light bulb. While this psak rapidly gained universal acceptance,[1] it only covered incandescent light bulbs, which are very similar to fire in that they generate both light and heat. What about the many other applications of electric power which do not share these characteristics?

Electricity and Halacha

There are two basic approaches to this issue. The Chazon Ish writes that activating any electric device is boneh (building), since the completion of a circuit involves attaching two parts and bringing the electrical device “to life.”[2]

Other […]

For Good Measure: Baking with Gluten-Free Blends, Whole Wheat Flour, Sourdough and at Challah Bakes

Spring 2024

[For a related article on the general laws of hafrashas challah, click here.]

Once upon a time, baking a loaf of bread was simple. Today, when gluten-free blends and processed whole wheat flour are found in many homes, that is no longer the case. Baking with sourdough starters and group baking at “challah bakes” have also become popular. The halachos involved are complex and bear examination.

Let’s begin with a review of the measurements necessary for mitzvos related to regular wheat flour.[1]

Mitzvos Involving Wheat Flour

Separating Challah (hafrashas challah) Without a Bracha – One should separate challah without a bracha when kneading a dough that contains at least 8 ⅔ cups of wheat flour (on average 2.6 lbs.).[2]

Separating Challah With a Bracha – There are differences of opinion as to how much flour is needed to recite a bracha. Some individuals do so when kneading at least 12 ¼ cups of flour (slightly more […]

Producción de Carne Kasher: Shechita Flies South

Spring 2024

From time immemorial, no matter where in the far-flung Diaspora, the presence of a Jewish community has always meant that there was shechita in proximity. The position of community shochet was one of a klei kodesh and the shochtim of a community were subject to the supreme jurisdiction of the local rav and/or Beis Din.  

Here, in the U.S., it was no different. On November 15, 1660, a man named Asser (Asher) Levy acquired a license to serve as the first kosher butcher in the small Dutch-controlled hamlet of Nieuw Amsterdam – now better known as New York City.[1] Ever since, maintaining a reliable supply of kosher beef has been an integral part of Jewish communal life in the U.S. Previous Kashrus Kurrents articles have offered a glimpse into the challenges shechita has faced on these shores and the changes to the way kosher meat is supplied […]

Acids in Digestion

Spring 2024

When my father z”l went to pharmacy school at George Washington University, his course of study had a heavy concentration of chemistry. His background in chemistry proved extremely useful in his forty-year career as an examiner in the U.S. Patent Office. On his workbench, he had shoe boxes with all his pharmacological paraphernalia: Bunsen burners, beakers, and little vials of litmus paper. As a child, I remember my fascination with watching the red litmus paper turn blue when dipped into a base and the blue litmus paper turn red when dipped into an acid. These were literal litmus tests, a term which over time has crept into everyday language to denote a means of determining an outcome.

Although the world of industrial kashrus may not require the deep analysis found in chemistry textbooks, it behooves kashrus administrators and mashgichim to have a working knowledge of chemical compositions and formulations. Solid […]

Yoshon: To Keep or Not to Keep

Winter 2024

The Gemara seems to conclude that the prohibition on the consumption of chodosh applies worldwide.[1] However, many shomrei mitzvos outside Eretz Yisrael do not restrict themselves to eating only yoshon grain.  Various reasons have been proposed:

► The Rema says that people rely on the fact that for any particular product that are two uncertainties. It is possible that there the food was made from a previous year’s wheat crop and is yoshon. It is also possible that this year’s crop took root before 16 Nissan and is yoshon. As there are two areas of doubt – a sfek sfeika – one can be lenient.[2] Others disagree and maintain that there is only one uncertainty here, whether the grain is chodosh or yoshon, and one should be stringent.[3]

► The Bach says that the prohibition does not apply to grain produced in a field owned […]

What’s “New” in Chodosh

Winter 2024

The Torah states[1] that chodosh (new) crops of the five grains may not be eaten until after the second day of Pesach (outside of Israel, not until the third day).[2] Thus, grain harvested in the summer of 2023 would not be allowed until Pesach 2024. On the other hand, yoshon (old) crops, which were harvested in the summer of 2022, became permitted after Pesach 2023. Grain planted at least two weeks or more before Pesach are permitted upon harvest, since they took root before Pesach.[3]

Outside of Israel, there are various customs based on numerous sources as to whether or not one needs to be stringent about using only yoshon products (see Rabbi Mordechai Frankel’s article in this issue). Each person should consult their rav for guidance. In Israel, however, these leniencies do not apply. Therefore, any product from Israel bearing a reliable kosher […]

Controlling Your Temper

Winter 2024

The baalei mussar, our guides in ethical character development, have instructed us that in order to develop and refine one’s behavior, one has to control one’s temper.

Controlling temper in manufacturing is a means to refine and improve the quality of the product in question. When steel is tempered, the resiliency of the steel is improved through the process of heating and cooling. When chocolate is tempered, through a similar process of heating and cooling (albeit at a much lower temperature), the chocolate acquires a lustrous, luxurious sheen, impervious to changes in color.

Likewise, tempering grain for milling improves the grain so that the final product – wheat flour – is rendered white and fluffy. The source of this final product is the humble wheat kernel.

A wheat kernel or berry is the seed of the wheat plant and is comprised of three edible parts: the nutritious bran wrapped protectively around the […]

Toveling Utensils in a Lake or River

Summer 2013

Q: I am traveling, and there is no keilim mikvah in this area. May I tovel new utensils in a lake or river?

A: Metal, glass and glazed ceramic utensils which are purchased from a non-Jew and are used in the preparation and consumption of food require tevila before use.[1] A person may tovel utensils in “spring water” – water that flows naturally from under the ground. If a river has such water as its source, he can tovel his utensils in the river.[2] The river must contain at least forty se’ah of water, which calculates as 175 gallons of water.[3] An ocean or sea is halachically considered to be “spring water.”[4] Therefore, a person may tovel utensils in an ocean, sea, or river which has such water as its source. However, regarding a river which has “spring water” as its source, […]

The Kashrus of Tea—With No Strings Attached!

Summer 2013

Americans generally do not drink as much tea as the rest of the world. This may have something to do with a certain party they had in Boston a while back. That being the case, you might be surprised to learn that tea is second only to water in worldwide beverage consumption. In fact, some estimates place tea consumption in the billions of cups daily. That’s a lot of tea. However, with recent health benefits being ascribed to tea, its popularity in this country is definitely on the rise. In this article we will explore the world of tea vis-a-vis kashrus and halacha. First, a little background is in order.

BACKGROUND

Tea is a processed leaf. It is grown on a tea tree which, if allowed to grow wild, would reach 30 or more feet in height. On tea plantations, the main trunk of the seedlings is cut to produce a […]

The Knead to Know: The Rise of Sourdough

Fall 2023

We are all familiar with the Torah’s directive to rid our homes of chometz in order to prepare for Pesach. The Torah uses two terms when instructing us in the cleaning process: chometz and se’or.

Ask any talmid or talmida: “What is chometz,” and you will get a very erudite response. Ask the next question: “What is se’or,” and seven out of ten will shrug and say, “I dunno,” while the other three might venture, “Sourdough?” When you follow up and ask them to define sourdough, most – if not all – will say, “I dunno!”

Today, more and more homes are seeing sourdough boules find their way into their bread baskets. With its “rise” in popularity, it is only natural that we look into this new trend and ask, “Ma nishtana sourdough bread from its conventional counterpart? Are there halachic and practical differences?”

Wheat and Bread Making Fundamentals

Let’s begin by reviewing […]

Shemita After Shemita: It’s Not Over Yet!

Fall 2023

There are those who think that whatever comes from Israel is kosher and who are not aware of the many issues associated with goods that are produced in Israel, be they concerns of orla, terumos, maasros – or Shemita. And they believe that once the Shemita year ends, Shemita issues are a thing of the past.

The Shemita year ended more than a year ago. To many of us, it already seems like a distant memory, a topic that we will next revisit in roughly five years, when we prepare for Shemita of 5789. But the truth is that Shemita of 5782 is still very relevant. It is important to remember this because our brethren in Chutz La’aretz are less aware of mitzvos hatluyos ba’aretz.[1] Since produce in the Diaspora are not subject to these laws, there is less awareness of Shemita repercussions.

We are currently in a period […]

When It’s “Not Kosher” to Eat Kosher: The Halachos of the Fast Days

Fall 2023

With the impending arrival of Tzom Gedalya and Yom Kippur, now is a good time for a halachic review of the six ta’aneisim that are incorporated into the Jewish calendar.[1] In addition to the aforementioned, we fast on Asara B’Teves, Ta’anis Esther, Shiva Asar B’Tamuz and Tisha B’Av. The halachos apply to males from the age of thirteen and females from the age of twelve.[2]

Timing Is Everything: When the Fasts Begin and End

Yom Kippur[3] and Tisha B’Av[4] begin at sunset. If one wants to eat after the seudas hamafsekes, one should state before the end of the seudah that he wants to do so. Having this in mind before Birchas Hamazon is also enough.

The other fasts begin at alos hashachar (dawn).[5] On those days, if one wants to arise[6] before dawn and eat, he should go to […]

Starbucks, Dunkin’ & Other Coffee Shops: Getting Your Caffeine Boost In-Town and On-the-Road

Summer 2023

The STAR-K Hotline receives no end of calls from coffee heads who dote on their daily cup of joe, whether from a local Starbucks or a Dunkin’ on the road. Recent changes in Starbucks’ company policy vis-à-vis kosher have further elevated the confusion for the kosher coffee connoisseur. Let’s dive in to clear out some of the haze.

Unflavored roasted coffee beans, whole and ground, are considered kosher without a hechsher. Bearing this in mind, buying a cup of unflavored regular or decaf coffee should not present any kashrus issues. Some coffee vendors, however, sell kosher and non-kosher items, like bacon and ham-filled sandwiches. The keilim used for coffee and the treif items are at times washed together, causing blios (absorbed tastes) from the treif utensil to enter the coffee equipment.

For example, at Starbucks, it’s been established that the brew basket that holds the coffee grounds while the coffee is […]

Cool Drinks for a Hot Summer Day: A Review

Summer 2023

Each summer the STAR-K Hotline fields hundreds of questions from concerned kosher consumers, thirsty to know: Is my Slurpee kosher? Do smart waters need a hechsher? What are the concerns with shaved ice and sno-cone stands? We stand ready to quench your thirst for information!

Carbonated Beverages

Carbonated beverages involve two major processes: compounding the flavor bases to create the flavor, and bottling the finished product when the sweetening agents, carbonation and water are added.

Soft drinks are compounded into soda flavor bases at one of three locations: the bottling facility, a separate technical center dedicated to blending soda emulsions, or an outside flavor house. In the latter case, the flavor house will create custom emulsions with specifications laid out by the soft drink company.

Regardless of the location, the most intensive part of kosher soft drink certification entails compounding, since this is when the kashrus of the flavors, colors, oils and blending […]

Insights From the Institute: The Mesorah on Duck Eggs

Summer 2023

Q:        My local farmer’s market sells duck eggs. Can I assume that they are kosher?

A:        Although the Torah lists twenty-four non-kosher species of birds, we no longer know precisely to which species the Torah is referring.[1] The Gemara provides alternative ways to ascertain whether a bird is kosher, but notes an instance in which a mistake in identification transpired.[2] For this reason, Rashi states that we do not rely on the Gemara’s criteria, and we eat only the few species of birds for which we have a mesorah (oral tradition) that attests to their kosher status.[3]

The Baal Ha’maor, one of the Rishonim, maintains that he has a tradition that all birds with wide feet and a wide beak – those more or less resembling a goose – are deemed kosher if they meet the Gemara’s criteria.[4] The Shulchan Aruch […]

Why the “D” in Non-Dairy?

Summer 2023

The Merriam-Webster Dictionary offers the following definitions for the noun dairy: the department of farming or of a farm that is concerned with the production of milk, butter, and cheese; milk from a cow or other domestic animal (such as a goat); and food (such as ice cream, cheese, or yogurt) made primarily of or from milk.

Today, a dairy is far more than a producer of milk products. If we were to explore a modern-day dairy, a far more accurate definition would be: an establishment that processes milk; milk products, such as ice cream, buttermilk and yogurt shakes; non-dairy alternative frozen desserts; non-dairy novelties, such as ices and popsicles; and non-dairy beverages, such as juices, fruit punch and tea.

Unquestionably, liquid milk production is the bread and butter of a successful dairy plant. Juices and teas are suitable side dishes and, of course, the pièce de resistance is ice cream […]

Putting the New in Shehecheyanu

Kashrus Kurrents, Spring 2023

Shehecheyanu is a bracha
that is said on special occasions, which the Gemara defines as something that
only “happens from time to time.”[1] We
say Shehecheyanu not only on religious occasions, such as the Yamim
Tovim, but also to express our appreciation for new experiences and pleasures.
Unlike the obligatory Shehecheyanus said on the zmanim and their mitzvos,[2] these
brachos are voluntary; perhaps that is why people are not always careful to say
them in every situation that would warrant it.[3]

New Fruit

The Shulchan Aruch writes, “One who sees a fruit which grows anew every year says Shehecheyanu, even if he sees it in his friend’s hand, or while still on the tree.”[4] In other words, the primary motivator for the bracha should be the sight of the new fruit. This is indeed how the halacha was originally codified by the Rambam.[5] However, the Mechaber concludes, “The custom is to […]