How is Cheese Made Kosher

Legend has it that cheese was first discovered by accident. Thousands of years ago, an Arabian nomad was carrying milk in a container made from the lining of an animal’s stomach. Upon reaching his destination, the nomad opened the container and noticed that his milk had hardened into something else—something we now call cheese. (The enzymatic properties of the stomach lining must have interacted with the milk to produce cheese.)

Whey to Go: How Cheese Is Made

Technically, cheese is broken down into two distinct categories: acid-set cheese and rennet-set cheese. Acid-set cheese (“soft cheese”) refers to cream cheese, cottage cheese, farmer cheese and other cheeses produced by adding bacterial cultures to milk. This results in the formation of soft cheese curds and whey.

Rennet-set cheese (“hard cheese”) generally refers to cheeses such as cheddar, mozzarella, provolone and hundreds of other types. These cheeses are produced by adding rennet enzymes to milk, whereupon somewhat firm cheese curds form, accompanied by liquid whey.

All cheese production involves gathering the curds together and removing the whey. The curds are then either kept loose or molded tightly. Subsequently, they are processed in a multitude of ways.

In addition to milk, cultures and rennet, various other ingredients are used in most cheese making. Cream (milk fat) and non-fat milk powder are often added to modify the product’s fat ratio; vinegar may be added to adjust the pH of the milk prior to conversion into cheese, and additional cultures and enzymes are commonly added to achieve various flavors as well as to prepare the milk for interacting with the rennet. All of these ingredients help explain how there can be over one thousand varieties of cheese in the world today.

Hard Facts about Hard Cheese

While all hard cheeses include rennet, they vary greatly in how they are manufactured. Parmesan cheese is produced by adding rennet to scalding hot milk and then aging the cheese for over a year until it is quite firm. Mozzarella cheese is cooked and stretched in a large tub after it is formed, resulting in a unique elastic texture, ideal for pizza and lasagna. Mozzarella and many other cheeses are brined, that is, submerged into a salt-water solution to protect the cheese from spoilage. Cheddar cheese is manufactured at cool temperatures and is often aged.

Aside from creating a firm texture, aging provides for a uniquely sharp taste. The more cheese is aged, the more powerful its flavor. (Just compare six-month-old cheddar to its two-year-old counterpart; they are worlds apart in taste.)

Nearly every country in the world has its own varieties of cheese, developed over hundreds, if not thousands, of years. Cheese connoisseurs regard European cheeses as the finest. France boasts Camembert; Switzerland has Swiss cheese (Emmentaler); England gave birth to cheddar, double Gloucester and Cheshire cheeses, and Greece is known for feta cheese. (America has not developed any cheeses of its own. American cheese is not pure cheese; rather it is a blend of already-made cheeses—mostly cheddar—which is melted, hardened and sliced. Think of the hot dog–a collection of various scraps of meat which are mushed together with added spices and molded into a new piece of meat; American cheese is the US dairy industry’s equivalent.)

Most Frequently Asked Questions about Kosher Cheese

How is cheese made kosher?

As with any food, all of the ingredients in the cheese as well as the equipment used during the manufacturing process must be kosher. However, a special rule in Jewish Law makes kosher certification of cheese a bit more challenging: cheese is only deemed kosher when made under continual, onsite rabbinic supervision.

Although various opinions are offered in the Talmud (Jewish Law) for this special stringency, the opinion adopted by the consensus of Jewish legal codes is the concern of cheese being made with non-kosher, animal-derived rennet.

Traditionally, cheese was made with calf rennet – the enzyme that lines the abomasum (fourth stomach section) of ruminants. In order to make cheese, the rennet-rich stomach flesh of a calf would be used to curdle the milk. In some countries, specific types of cheese are still produced from animal rennet, made from milled calf stomachs that are processed into a paste, powder or liquid.

Although most (but far from all) cheeses in our times are made with microbial (synthetic) rennet rather than with calf rennet, the rule that cheese can be deemed kosher only when made under continual, onsite rabbinic supervision still applies.

Why is kosher hard cheese so expensive?

The cost of sending rabbinic field representatives to far-flung places to supervise hard-cheese production for days on end is significant. Kosher cheese manufacturers will naturally need to charge more for their products to cover the costs involved.

Furthermore, nearly all domestic and European hard-cheese plants are non-kosher when not doing special kosher cheese productions. These plants schedule kosher campaigns sporadically in the midst of their normal non-kosher activity. Thus, aside from supervising the cheese manufacturing process, the rabbinic field representatives often need to supervise the kasherization of each plant before every kosher production. This can take days to complete, and it is not simple work.

The kashrut rules for cheese are among the most mysterious to the average kosher consumer. Even otherwise scholarly and erudite members of the kosher community are often “in the dark” as to what makes cheese kosher (and why they pay more for it!). It is hoped that the above discussion sheds light and unravels some of the mystery.

Rabbi Gordimer is a rabbinic coordinator  specializing in the dairy industry, where he manages the kosher certification programs for over 200 plants.

Rabbi Avrohom Gordimer
Rabbi Avrohom Gordimer is a rabbinic coordinator at OU Kosher, where he specializes in the dairy industry. Rabbi Gordimer is the chairman of the OU Dairy Committee, and he manages the OU programs of over 90 certified dairy companies.