(This article originally appeared in Ami Magazine.)

Although people who serve milchige meals on Shavuos may think that they will also incidentally save some money in the process, as dairy food is typically less costly that meat, they often experience sticker shock when they see how expensive the cheese is. Why is this?

An enormous amount of hashgocho work goes into kosher cheese manufacture. The average consumer may not realize it, but cheese is the most kosher-sensitive dairy food, and the kosher supervision costs by definition are factored into the finished product's price (not to mention the cost of cholov Yisroel milk). Think of matzo versus thin regular crackers or flatbreads. While the two items are in fact physically similar, the incredible amount of kashrus hashgocho invested into matzo production from A to Z literally makes all the difference, as reflected by the price.

Whereas foods other than meat, wine, fish, and of course matzo, do not technically require a mashgiach to be present or involved without interruption, cheese is a glaring exception.

What is it about cheese kashrus that is so unusual?

The Gemara in Avodah Zarah (29b, 35a-b) records that Chazal declared that cheese of nochrim  - Gevinas Akum - is non-kosher. Only Gevinas Yisroel, the cheese of a Yisroel, may be eaten. Although the Gemara suggests many different reasons for this gezeirah, this decree, that Gevinas Akum is not kosher, the Rambam (Hilchos Maachalos Asuros 3:13) and the Shulchan Aruch (Yoreh Deah 115:2) adopt the reason of Shmuel in the Gemara, that since cheese is commonly made by incorporating non-kosher stomach meat of a calf (or keivas neveilah) into milk, Chazal forbade all cheese unless a Yisroel was present for the production, in order to assure that non-kosher meat was not used in the cheese's production.

To phrase it in modern terminology: Cheese is produced by dosing milk with the rennet enzyme. This enzyme separates the milk's casein protein and fat from the rest of the milk's components, and the casein protein and fat thereupon form into curd -  semisolid matrixes. Curd is accumulated together, molded and formed into cheese blocks. Rennet is naturally found in the abomasum, the forth stomach (keivah in Hebrew) of suckling animals, and common practice has always been (and still is in many places) to use abomasum flesh to make cheese. Chazal hence forbade cheese unless it meets the requirements of Gevinas Yisroel. Cheese that is not Gevinas Yisroel is wholly non-kosher, and if used with kosher keilim (kitchen utensils), it  renders them non-kosher as well, as does any other non-kosher food. Even in societies which do not normally use animal rennet for cheese-making, the gezeirah of Chazal stands in full force.

What makes cheese Gevinas Yisroel?

If a Yisroel produces his own cheese or has cheese made on his property by his workers, using his own milk, the cheese is Gevinas Yisroel. (Shach on Yoreh Deah ibid. s.k. 20) However, this is obviously very rare, and it is certainly not how the cheeses we buy are manufactured.

For "regular" cases, in which kosher cheese is made in factories belonging to and operated by nochrim (such is the situation for all kosher cheese made outside of Eretz Yisroel), there are more complex solutions.

The Remo and most poskim rule that cheese is considered to be Gevinas Yisroel when there is a mashgiach on-site for the full duration of the cheese-making. This means that hashgocho temidis is necessary for the entirety of every single kosher cheese production. The mashgiach must also conduct a pre-inspection before the cheese-making starts in order to verify that the production equipment has no residue of Gevinas Akum, and he also very often will need to supervise an elaborate kashering of the facility. (Is the kosher cheese cost factor now starting to make a little bit of sense?)

Although this already sounds pretty labor-intensive, this is just the beginning. The Shach, Gro, and many other poskim rule that Gevinas Yisroel is comparable with Bishul Yisroel and Pas Yisroel, meaning that a Yisroel must physically contribute to the production. Just as the mashgiach lights the fire in order for cooked foods and breads to be Bishul Yisroel and Pas Yisroel, so too must the mashgiach help make the cheese! Mere supervision by a Yisroel does not suffice. (V. Shulchan Aruch Yoreh Deah 115:2, Shach ibid. s.k. 20, Bi’ur Ha-Gro ibid. s.k. 14, Pischei Teshiva ibid. s.k. 6, Aruch Ha-Shulchan YD 115:19.)

In order to satisfy this approach, most kosher cheeses are made by the mashgiach climbing up to the cheese vat and pouring in the (kosher, pareve) rennet for every single vat of cheese that is made. This is hard work, but it is all part of standard kosher cheese production.

It must be noted that many modernized cheese factories no longer feature open vats to which the workers (and mashgiach) ascend in order to dose in the rennet. These plants rather have closed systems, meaning that the rennet is injected into the vat via closed pipes that no one can access, and the system is controlled by a computer. In these cases, kosher cheese that is manufactured in accordance with the stricter halachic position, that requires the mashgiach to physically add the rennet, is made by the mashgiach personally activating the rennet feed into the vat. To do this, the mashgiach controls and activates the computerized rennet dosing for every single vat of cheese. Should the mashgiach fail to do this, the kashrus agency can declare the cheese unacceptable.

One may surmise that the cheese production is now over and the mashgiach can return home. Sorry!

The next step, if the cheese is of a stretchy Italian variety (called Pasta Filata cheeses), such as most mozzarella and provolone, is to cook it. In order to endow these cheeses with an elastic texture that makes them ideal for melting, they are cooked in water a hot bath-like vessel called a mixer-molder, where they are pushed and pulled and squeezed and stretched while being heated in water. This activity gives these cheeses their unique texture for melting purposes.

In order to be preserved from rapid spoilage, all cheeses must be salted as soon as they are made. Cheddar cheese curd, before being formed into to cheese blocks, is salted on massive salting tables. The scene sort of resembles Melichah (salting) of meat in large slaughterhouses. Many other cheeses are likewise salted in this manner. In this case, to salt kosher cheese, the salting table is sanitized, the mashgiach examines the salting table for residue of Gevinas Akum, fresh kosher salt is brought out, and let the salting begin!

However (and this is where more kashrus action occurs), most cheeses are salted through the brining process, meaning that the cheeses are submerged in tanks of saltwater solution (brine), where they absorb salt. The problem for kosher production is that cheese factories typically use the same brine for months and never change it, and the brine tanks are also usually made out of fiberglass (hint: cannot be kashered). This poses major problems, as a cheese factory's regular brine is full of absorption of Gevinas Akum, and disposing of the regular, non-kosher brine, is not an option, as brine becomes more valuable and potent as it ages and absorbs more and more cheese flavor, and it is very costly to dispose of, due to its extreme salt content. Cheese factores have been sued by local governments for disposing of brine and other cheese-making substances, as the high salt and fat content are environmental hazards.

It really like we are stuck on this one.

But alas, there are solutions, and kosher brine and kosher as hoc brine tanks are created. Here is what is done:

The cheese factory prepares a new, kosher brine (made of fresh water and salt), and it lines the non-kosher brine tank with thick plastic inserts, into which the kosher brine is poured. The kosher cheeses are submerged in this brine, and after production is over, the brine is poured into another large vessel, which the mashgiach (who is present for this all) will seal and sign, designating it as a secured source of kosher brine for the next kosher cheese production.

We are not done yet:

The cheese then (usually after aging) needs to be cut into wedges, slices or blocks, and the mashgiach or course must be present to first inspect all cutters and to supervise the replacement/cleansing/kashering, as the case may be, of all blades and cutting surfaces. (For aging, the mashgiach must seal each cheese and verify that the aging surfaces are clean and kosher.)

Then, the cheese can finally be packaged. But not so fast - as the packaging machinery, normally used for Gevinas Akum, operates hot and usually uses a recirculating hot water source to produce steam to seal the cheese's packaging! (Yes, another headache...) The mashgiach therefore needs to supervise the emptying and disposal of the regular water, the replenishment of the system with fresh, brand new water, and he may also need to kasher the packaging equipment, depending on its contact with the cheese.

Whew! That was a lot of hashocho work and a lot of work on general. But we are still not done.

There is a major risk of leaving kosher cheese packaging in the factory after the mashgiach departs and the kosher cheese campaign is completed, as what if the factory decides to use the kosher packaging for its regular, non-kosher products? There is normally way too much kosher packaging to take off-site between kosher productions, and we thus have a packaging security scenario to deal with.

In some cases, the mashgiach will seal up all kosher cheese packaging with special tape that he signs; any tampering with the tape in his absence will be readily visible. In other cases, the kosher cheese packaging may be stored in a cage, secured by the mashgiach with special kashrus seals. The OU often resorts to a third option: special security holograms that the mashgiach keeps with him and that are affixed to each package of cheese made under his supervision. The cheese's packaging states that the product is only certified when bearing the special kashrus hologram, and the mashgiach carefully provides these holograms for production, assures that none are left behind, tallies them and retains them with him at all times, thereby ensuring total security. If 150 blocks of cheese are made, the mashgiach provides 150 holograms and observes them being affixed to cheese packaging. He then inventories the number used and left over and keeps them with him as he leaves the facility.

I have personally witnessed the hologram system prevent major cheese kashrus violations.

One final point: Some poskim rule that even cheeses that do not use rennet, such as cottage cheese, cream cheese and farmers cheese, nonetheless need to be Gevinas Yisroel. (V. Chochmas Odom 53:38 and Aruch Ha-Shulchan YD 115:16.) Therefore, aside from regular kashrus supervision, the agencies that follow this stricter position require the mashgiach to add the acid cultures, which create these "soft" cheeses, to the vat of milk, so as to render the cheeses Gevinas Yisroel l'mehadrin. (All cholov Yisroel cheeses are made this way. In fact, in the case of Cholov Yisroel cheeses, the mashgiach always adds all cultures and rennet, no matter what.)

Although kashrus agencies have no control over cheese pricing, they ask you to please think about the massive, incredible amount of hashgocho work that goes into every slice of cheese. Flatbread versus matzo... Gevinas Akum versus Gevinas Yisroel.