Rennet for Making Cheese

I have received countless questions about rennet (also called rennin or chymosin), and am therefore posting a page on it.

First a little background:

HISTORY OF RENNET: Presumably, the first cheese was produced by accident when the ancients stored milk in a bag made from the stomach of a young goat, sheep or cow. They found that the day-old milk would curdle in the bag (stomach), yielding solid chunks (curds) and liquid (whey). Once they discovered that the curd-chunks could be separated out and dried, they had discovered a means by which milk, an extremely perishable food, could be preserved for later use. The addition of salt was found to preserve these dried curds for long periods of time.
At some point, someone discovered that the most active portion of the young animal’s stomach to cause curdling was the abomasum, the last of the four chambers of the stomach of a ruminant animal. (In sequence, the four chambers are rumen, reticulum, omasum and abomasum.) In particular, the abomasum from a suckling kid or calf was especially active. The abomasum was cut it into strips, salted and dried. A small piece would be added to milk in order to turn it into curds and whey. Here is a page about my experiments at making home made rennin. At some point, the Germans began calling this material rennen, meaning to run together, or to coagulate. The technical term for rennin is chymosin. Here is a technical description of its action on the various proteins in milk.

MODERN RENNET: Until 1990, rennet was produced the old fashioned way (from abomasums), from various “vegetable” rennets (some of which, called microbial coagulant, are made from the microorganism Mucor miehei.) These days, at a cost one tenth of that before 1990, chymosin is produced by genetically engineered bacteria into which the gene for this enzyme has been inserted. When the bacteria are grown in large vats,they secrete rennin, and itis then purified for cheese making. Rennet is available commercially in tablet or in liquid form. You will find some cheese makers on the web who prefer liquid rennet and disparage the use of rennet tablets. Perhaps, if you are making hundreds of gallons of milk into cheese, buying bulk liquid would make sense, but for making one to ten gallons of milk into cheese, the tablets make sense. I have never had any problems using rennet tablets in making a wide variety of cheeses, and since it is a principle of mine to try to use materials which are readily available locally, I have used tablets for years.

JUNKET RENNET TABLETS: I use Junket Rennet tablets because they are readily available, inexpensive and they work. They are easily measured out (1 fresh tablet will coalgulate 5 gallons of inoculated milk) and, because they are dehydrated, they are stable at a cool temperature for several years. They can often be found in the pudding section of your supermarket. The front front and back of the package is shown at the top of the page. If you do not find them on the shelf, ask the manager if he or she would please order them. Most managers are willing to do so. (My local Kroger’s Store here in Cincinnati has been very cooperative over the years.) If you have no success at your local store, you can order the tablets through Redco’s web page, by phone at 1-800-556-6674, or directly by snail mail from Redco Foods, Inc., P.O. Box 879, Windsor, CT 06095 (formerly the Salada Foods Division). Be sure to order the plain rennet, not the pudding mixes. “Junket Rennet Tablets” come in a packages of 8 (6.5 g) or (used to be) 12 tablets. Their page on recipes using Junket rennet includes several cheese recipes which I wrote for them. Here is their page on Junket Rennet Tablets.

LIQUID RENNET: One teaspoon of liquid rennet is reported to be equivalent to one Junket Rennet tablet. Thus, you would use one teaspoon to coagulate five gallons of inoculated milk, or 4 drops/gallon of inoculated milk. (I have only used tablet rennet, but am assured that liquid rennet works just as well as the tablets.) Liquid rennet can be ordered from various cheese maker’s suppliers or which New England Cheese Making Supplies is prominent on the web. I have had a number of cheese makers complain that the liquid rennet looses its potency within a year of age, and one must add more and more to acheive the same degree of coagulating.

MICROBIAL RENNET: A rennet of bacterial origin, called microbial coagulant, is made from Mucor miehei. This tableted rennet should pose no problem for vegetarians. I have never used it but here is some information on it , and also a place to order it from a company called Danlac.

USE OF JUNKET TABLETS: They come packaged sealed in foil. One tablet will clabber 5 gallons of inoculated milk. To use it, you dissolve the tablet in a small amount of water (1 tablet in 1/4 cup fresh clean water). The solution will be slightly cloudy . Look for and crush undissolved chunks at the bottom of the glass. The dissolved rennet is then stirred into the inoculated milk .

Feta Cheese

Feta is traditionally made in Greece from ewe’s milk, but I have had success using my goat’s milk. I see no reason why cow’s milk would not work as well. It is a fresh, snow white cheese which is pickled in brine. It is fabulous with kalamata olives and pita bread, as well as in a Greek salad.

By the way, the most popular Turkish cheese called Beyaz Peynir uses essentially the same recipe. We loved it with our breakfasts when we have visited wonderful Turkey. (It may be better not to tell the Turks that it is just like feta, and vice versa… 😉
Thanks to “Lynn” from the Lactobacillus Board for helpful suggestions.


  • 1 gallon fresh goat’s milk (You can use store-bought cow’s milk as well.)
  • 1 Tbl fresh yogurt (I have had most success with Dannon Plain.)
  • ½ tablet rennet, dissolve in 1/4 cup water (I have always used Junket Rennet tablets.)


  • 2 gallon pot with lid (stainless steel with heavy bottom is best, enamel works, but you must stir it!)
  • 1 long bladed knife
  • 2 clean sterile handkerchiefs
  • Strainer
  • Cheese mold: Cut the ends out of a smooth-sided 4 x 5 inch tin can, save one of the cut ends.
  • Table salt


  1.  Warm  1 gallon of fresh milk  in a 1.5 gallon stainless steel pot to 30°C, (86°F)


Troubleshooting a Clean Break, Cheese Making

Greece, Istanbul to Rome: Macedonia Trip

Images of Western Turkey

Rennet, Home Made, Illustrated

Here are the results of an experiment at producing home made rennet.

Rennin is an enzyme which, in an acid environment, digests the water soluble milk protein casein into insoluble products. When these precipitate out of solution, the milk coagulates. The test is the famous “clean break” of cheese making.

Here, the abomasum of a suckling kid was cleaned, salted and dried. A small piece (0.75 gm) of it was suspended in warm water (30 C), and added to 1 gallon of inoculated milk. While a clean break was not achieved in three hours, by the evening (about 7 hours) the milk had formed a very firm coagulant.

This is my first attempt at using home made rennet.  I am sure that the process and conditions can be improved.  Let me know if you have suggestions.

See the bottom of the page for suggestions from Mr. Wolfgang Pachschwöll, of “Hundsbichler company Austria – producer of natural rennet.”

Here are some points of expert advice on making rennet from Wolfgang Pachschwöll of “Hundsbichler company Austria – producer of natural rennet”, sent in response to my initial posting of this page. (Thank you very much Wolfgang!)

1) Do not thoroughly clean out the inside of the abomasum. The “slime” inside contains rennin. Therefore, also no washing nor squeezing.

2) Lightly salt the abomasum, store undried with 30% salt in a closed container to activate the enzyme over three months. (Pepsin, another stomach enzyme, is also secreted in the inactive form (pemsinogen), and activated by acid or enzymatic action.)

3) The traditional way to then dry the abomasum is to inflate it like a balloon and dry by hanging in a cool dark place.

4) Dissolving and activation of rennin occurs best in acid conditions at a cool temperature.


Fresh Mozzarella from a Gallon of Milk

If you are new to cheese making, please read Beginning Cheese Making carefully. Mozzarella is a challenging cheese and should not be attempted as your first cheese. This is a recipe to make a fresh mozzarella which I have developed from a recipe for pasta filata (a type of cheese of which mozzarella is one example) found on an Kenyan Cheesemaking site.

The modified recipe is more straightforward, easier and  dependable than the traditional Italian Fresh Mozzarella I posted on the web in the Summer of 2000. It requires preparation of the curd the night before, allowing the curd to mature in a warm place overnight, and then warmed and molded the next morning.

Stages of Mozzarella

There are six stages to making this mozzarella, many of which follow the general outline of most cheese preparation:

    Bacterial starter is added to slightly acidify the milk so rennet works
    Rennet is added which causes acidified milk protein to coagulate
    Curd is cut to allow the whey (liquid remnant of milk) to be expressed
    Curds are kept warm for 8 hours, allowing bacteria to further acidify
    Acidified curds are stirred with hot water causing them to melt together
    The soft curd mass is kneaded into balls, cooled and placed in brine


Day 1

  • 1 gallon fresh milk
  • 1/4th cup cultured buttermilk
  • ½ tablet rennet

Day 2

  • ½ gallon 85 C water
  • ½ gallon ice water
  • 1/4 cup salt Equipment


Day 1

  • 1 ½ gallon pot with thick heavy bottom and well fitting cover
    sterilized by boiling 1/2 inch water covered, 5 minutes
  • thermometer, 0-110 C (32-230 F)
  • whisk
  • long bladed knife

Day 2

  • 1 gallon bowl
  • ½ gallon jar with lid
  • slotted spoon

Illustrated Stages




Cutting the Curd



Molding and Brining

After completing those steps, be sure to:

  1. Drop the cooled mozzarella balls in the brine, cover and refrigerate.
  2. After 12-24 hours, remove from brine, place balls in zip lock bags until used. (Do not leave too long in the brine, or the surface will soften.)
  3. Use within several days or a week of preparation.  Fresher is better.


Beginning Cheese Making


Troubleshooting a Clean Break, Cheese Making

Mozzarella, Italian

Rennet for Making Cheese

Ricotta Cheese

American Mozzarella, Microwave a la Joyce

I modified this cheese from one I learned from “Joyce of KS” on the old Lactobacillus Board on the web (now It makes an “American mozzarella” similar to what is used on American pizza. It is very elastic, melts well and strings when hot. (It is not, however Italian mozzarella which is more tender at room temperature and possesses a more subtle flavor.) If you would like to make the Italian version,the recipe for making Italian fresh mozzarella which, as you will see is more complex than this one for “American” mozzarella.


  • 1 cup pyrex measuring cup
  • 2 cup pyrex measuring cup
  • 5 quart pot, stainless or enamel, with cover, preferably with a thick heat dispersing bottom
  • Thermometer, -20 to 110C
  • 8 inch strainer
  • 1000 watt microwave oven


  • 1 gallon milk (I used cow’s milk, homogenized, pasteurized, 3.5% butter fat)
  • 1¼ teaspoon citric acid powder (from local pharmacy) dissolved in ½ cup cool water
  • ½ tablet Junket rennet (from local supermarket) suspended in ¼ cup cool water


Italian Mozzarella

Fresh Mozzarella from One Gallon of Milk

Neufchatel Cheese

Beginning Cheese Making

Cheese Making for Beginners

While cheese making is theoretically a science, we also need to appreciate that it is an art.  Often cheese-making instructions appear simple, but there are skills and sensitivities which must be developed for successful cheese making.  Because it is beneficial to engage in projects from easy to challenging, I strongly suggest that you master the following projects in sequence before you progress to more difficult cheeses.

As an avid homesteader, I strive to keep the ingredients for these recipes relatively easily obtained from your local supermarket and to use the equipment commonly found in the kitchen. As you become more skilled and knowledgeable, you may well want to purchase more specific ingredients from the web (etc) to refine your procedures and finished products.

Discussion of Ingredients and Equipment


You can use a wide variety of milks, from commercially purchased pasteurized homogenized cow’s milk, TB certified raw cow’s milk, goat’s milk, sheep or even horse’s milk.  All will make cheese, each with its unique flavor.  Cheese from unpasteurized milk makes the best cheese, but should be cured for 2-4 months if there is any doubt about pathogens in the milk.  If you use pasteurized milk, you may need to add a little calcium chloride to firm up the curd because the heat makes the calcium unavailable.  Calcium is required for a good “clean break.”

Cheese can be made from whole milk (3.5%), 2% or from skimmed milk.  However, remember that the richness of flavor of the cheese is related to the amount of butterfat in the milk.  I do not recommend reconstituted powdered milk. It has not produced either a solid clean break, nor a good flavor of cheese.  Let me know if you do.

You should  get  1 to 1.5 pounds of cheese/gallon of milk.

For store-bought milk, because Pasteurization removes calcium from solution, you may need to add a small amount of calcium chloride to aid coagulation and form curd which does not fall apart when you stir it. The desired concentration of CaCl2 is usually specified as 0.02%. This would mean adding 3.6g CaCl2 to 5 gal of pasteurized milk. My measurements indicate that 3.6g of crystals = ~3/4 tsp. Thus 3/4 tsp crystals/5 gal = ~0.02%. You should completely dissolve the CaCl2 in about 1/4 cup water before adding it to the milk. Add it slowly with thorough stirring.  You should be able to purchase CaCl2 at brewer’s supply house.  Also, it is the non-NaCl deicer that is plant-friendly.  [You might be able to use CaSO4 (plaster of Paris) in a highly diluted state, tho it is much less soluble than CaCl2.]

Reconstituted powdered milk: I have not had good luck using powdered milk, but have heard some say that they have successfully used it.  I suggest you make friends with a local dairy person to get bulk milk.  (You will have better luck getting milk from homesteaders than with commercial operators.  Legally, you must purchase it as “pet milk.”

Ultra pasteurized milk: This is common on the shelves in Europe, but I find it VERY unsatisfying in taste, and, in my opinion, this milk is nearly worthless in making basic cheese. The protein strucure is radically altered, and calcium is chelated so that it is unavailable for coagulation. If you have success with ultrapasterized milk, let us know! (You CAN use it to make yogurt and labneh.)

Bacteria must be added to acidify the milk so that the rennet will work, and to aid in the curing.  Cultured buttermilk can serve as a mesophilic starter (it likes room temperature), and yogurt can serve as a thermophilic starter (it prefers warmer temperatures).  You can also purchase pure cultures from cheese makers supply houses.  Some recipes call for addition of chemical acids to produce acidify the milk.  I prefer the flavor of cheese made from bacterially acidified milk.  Here is a detailed description of bacterial cheese starters from Peter Moller. Be aware that, especially with buttermilk, you should never add too much starter for too long a time such that the milk has even remotely thickened before you add rennet. With even slightly thickened milk, you will never get a “clean break.”

An enzyme rennin converts milk protein (casein) from a soluble to an insoluble material, causing the milk to gel (forming a clean break).  It will only work well in acidified milk.  The gelling process must be undisturbed to get a clean break.  Rennet is commonly available in supermarkets in the pudding section, or you can purchase liquid rennet from a cheese makers supply house. One tablet of Junket rennet is equivalent to 20 drops of fresh liquid rennet.

If you would like to try it, and have the materials available, I have successfully prepared home made rennet from the abomasum of a suckling kid.


Most decently equipped kitchens have the necessary equipment:

Heavy stainless steel pot with lid:  A non-reactive pot is important because the acidifying milk can dissolve aluminum.  Enamel pots would work as well.  A heavy bottom is important to evenly disperse the heat and prevent scorching.  Scorching affects the flavor and is a cleanup hassle.  The size of the pot should be large enough so that you have at least an inch of head space above the milk.  A cover is needed for the steps when the milk must sit for periods of time.  I bought a high quality five gallon pot like this years ago (expensive).  I have never been sorry.

Measuring cups  You may need measuring cups ranging from 1/4 cup to a quart.  Obviously you can improvise, but accurate measurements improve your success rate.  Measuring spoons are occasionally needed.

Thermometer  Very important is an accurate thermometer which reads in the range between freezing and boiling for water (~32-212 F, or 0 to 100 C).  A candy or meat thermometer can work.  There are several reasons that accurate temperature is important: the texture of the cheese depends a great deal on achieving a temperature to within onedegree.  Also, after milk for yogurt is scalded, itmust be cooled to 130 F for optimum bacteria action.

Whisk  Thorough mixing of starter and rennet is important.  A whisk is the obvioius choice for this step.

“Cheese cloth”:  The purpose of “cheese cloth” is to catch the curd and allow the whey to drain out.  What most people think of as “cheese cloth:” the very wide weave flimsy material is often useless for this purpose.  If your curd is fine, it passes through.  Even if it is large curd, the curd can become enmeshed in the coarse weave.  I use either large plain white cotton handkercheifs, or white non-terry cotton dish towels.  I recommend ignoring what is sold as “cheese cloth…”

Cheese press is required for the hard cheeses.  You can purchase them for a handsome price, or fashion one from materials at home.

Waxing your cheese:  This step is important so that your cheese does not dry out during aging, and to prevent mold from growing on the surface (mold needs air to grow).

Cheese Making, Course Syllabus

Setting Up a Home Made Cheese Press

How to Wax Cheese

Rennet for Making Cheese

Rennet, Home Made, Illustrated

Basic Cheese Making, One Gallon Milk

Cheese Making Stages

If this is the first time you are making cheese, check out Beginning Cheese Making.

Otherwise, here are the major stages of cheese making:

Stage 1 Action:
Inoculate, incubate the milk

Bacteria slightly acidify (ferment) the milk so that the rennet will act on the milk

Stage 2 Action:
Add the rennet, achieve a clean break

Rennet (a digestive enzyme) digests casein, causing it to become insoluble in water and coagulate.

Stage 3 Action:
Cut and set the curd

Coagulated milk is cut into cubes and warmed to contract the curds (“curds and whey”)

Stage 4 Action:
Separate and salt the curd

Whey is poured off the “curds and whey,” and the curds are salted to preserve them

Stage 5 Action:
Press the curds

Salted curds are loaded into a press which presses out the whey and gives form to the cheese

Stage 6 Action:
Cure the cheese, wax it

Cheese is dried out and bacteria act on the curds to change their taste and consistency.  It may be waxed to prevent undesirable dehydration and excessive microbial growth.

One gallon of milk yields about one pound of cheese. You may use any kind of milk for this recipe. I primarily use my own fresh goats’ milk, but have made it quite successfully with cow’s milk from the grocery, and even better with raw cow’s milk from a local farmer.

Once you have mastered this one gallon recipe, follow the 5 gallon recipe to make a larger wheel of cheese.


  • One gallon freshest milk (the fewer bacteria present, the more predictable the cheese)
  • 2-3 teaspoonfuls buttermilk (or 1/3rd cup yogurt)
  • 1/4 tablet rennet
  • Salt


  • Thermometer, reading -10 to 110oC (0 to 225oF) (I prefer centigrade, but have included Fahrenheit numbers as well)
  • Wooden mixing spoon, whisk or other stirring device
  • Stainless steel pot1 , 4-6 qt., with lid, with a thick metal bottom (Al or Cu) to spread the heat, sterilized2 .
  • 8″ strainer or colander (A colander does not allow whey to flow through as fast as a strainer.)
  • Large handkerchief, sterilized by boiling
  • Cheese pressing frame (4″ diameter, 5″ tall can, about 20 oz, ends removed, save one end for a follower)


Curing the Cheese:

The next morning, remove from press, remove cloth, rub outside of cheese with salt and rewrap with fresh handkerchief. Place wrapped cheese on a rack in the refrigerator.

Replace the “bandage” daily (as long as it continues to become wet).

When a dry yellowish rind forms (about one to two weeks), dip in melted wax , store in refrigerator for about a month (if you can wait that long) or longer for sharper cheese.

Special Notes:

Avoid aluminum pots, the acid will dissolve them and possibly overload you with aluminum.

Sterilize the pot just before use by pouring ½ inch of water in the bottom, covering, and bring to a rolling boil for at least five minutes. Pour out the water, replace sterile lid, keep sterilized pot covered until you are ready to add the milk.

If the curds float, you have a gas-producing contaminant in your starter or your milk was contaminated. You need to pay closer attention to handling your milk, and/or purchase fresh starter. The bacteria which form bubbles may be a form of Escherichia. However, it does not necessarily ruin the cheese, but does make it iffy.

Many CO2 formers are non-pathogenic. Indeed, you might WANT bubbles in your finished cheese. Think about Swiss cheese… However, to be safe, age your cheese for at least two months because pathogens do not survive this extended aging. In addition, you will have a little more difficulty separating the curds from the whey if the curds float.


Home Made Cheese Press

How to Wax Cheese

Milk Fermenting Bacteria (Milk Fermenters)

Ricotta Cheese Making (Illustrated)

Troubleshooting a Clean Break