By making and preserving your own mother culture (also called a prepared starter); you can effectively inoculate many gallons of cheese, with just a bit of care and know how.
Traditionally, a prepared mother culture was made from the leftover whey from a previous batch of cheese. Through time, starters were propagated from one batch to the next; thereby creating a distinctive strain with a distinctive taste that then became its own style of cheese. Dairies that were making good cheese isolated the strains of culture from their cheese, which are kept pure by the companies we purchase starters from in the present day.
The powdered direct-set starters purchased through cheese supply houses have a frozen lifetime of up to two years, with a refrigerated life of only two months. Your own cheese starter prepared at home can be made and continued by using remnants from the last batch to make the next one, much like a sourdough bread starter. Normally, a prepared starter can be continued in this manner for up to six months with proper attention to sanitation, which is very helpful for those not using a freezer or with limited electricity options. When you make a mother culture, you are exposing a lab-treated strain to an un-sterile environment, and then freezing those cultures. And as with any home-based starters, over time you may begin to develop a distinctive taste which will depend on the airborne bacteria found in your climate. And also like other starters, that doesn’t mean it has “gone bad”; it just gets wilder because of the all-new bacteria found in your environment introducing itself into your starter. And if you like that taste, I would just keep it going until you don’t like the taste. While doing all this can be a very useful skill to propagate your own mother cultures and develop your own cheese profiles, please know that it can be a finicky thing, and if at first you don’t succeed, try, try again.
Not all types of culture you can purchase are good choices for starting your mother culture with. You will have to ask your supplier which one they think would be a good, hardy strain with which to begin your own mother. You can make both Mesophilic and Thermophilic mother cultures. The process of making and storing your mother is much like canning preserves or jelly. You will want to follow the general cleanliness rules which usually apply to any cheesemaking or canning process, for the cleaner you keep things while making your mother and any time you deal with it in the future, the surer you can be that you are going to get the maximum lifetime out of your mother cultures.
Making a Mesophilic Mother Culture:
This recipe will be for one quart of prepared starter, but it can be multiplied however many times you want/need it to be.
1. Sterilize a one-quart canning jar with its band and lid by boiling it in a pot with a lid for 5 minutes.
2. After your sterile jar has cooled a bit, fill it with skim milk to an inch below the rim of the jar. (Skim milk or low-fat milk must be used, for the cultures tend to rise with the cream if it is present in the milk.) Screw the lid on tightly.
3. Place the jar in your water-bath canner, or a large, deep pot. (Your cheese pot might work.) Fill the pot until it covers the jar(s) by about ¼ of an inch. Put the pot on the stove on high heat until it boils. When it begins to boil, start timing it, and let it boil for 30 minutes. After it has done this, turn off the heat.
4. Remove the jar from the pot of water and allow it to cool to 72 degrees F. You can remove the lid and monitor the milk’s temperature with a thermometer, but please take great pains to insure that the environment stays clean during this time to avoid contaminating the milk.
5. Once the milk reaches 72 degrees, inoculate it with ¼ teaspoon of Mesophilic culture. Quickly put the lid on and swirl the jar to incorporate the cultures.
6. Maintain the closed jar of milk at around 72 degrees for 15 to 20 hours for ripening. Check the jar at 16 hours for coagulation, and if it hasn’t fully ripened yet, leave it for another 8 or so. Proper coagulation has been achieved when the milk is the between the consistency of pancake batter and yogurt. It may separate from the sides of the jar and be shiny. When the milk has fully coagulated, taste it. It should be acidic and a little sweet.
7. Once it has properly ripened and passed the taste test, chill the jar(s) immediately. You can keep the starter in the refrigerator for up to three days without using it. But if you don’t plan on using it to make cheese within that time, the best thing to do would be to freeze it.
To Freeze your Mother Culture:
1. Clean and sanitize two or more plastic ice trays. Spoon the culture into the trays with a sterile spoon, or pour it from the jar if you want. Fill all the cube trays with your starter and freeze them solid in the coldest part of your freezer.
2. After they are solid, remove the cubes from the trays (trying your best not to touch them with your hands or anything else that is not scrupulously clean) and put them into airtight freezer bags. Label the bags with the name of the starter and the date it was made. These bags will keep in the freezer for up to one month, after which they are not bad, but their strength will begin to degrade. Each block is about one ounce of starter.
To make Thermophilic Mother Culture:
1. Follow the same directions for making Mesophilic starter until you have allowed the jar(s) of milk to boil for 30 minutes.
2. Remove the jars from the pot and allow the milk to cool to 110 degrees F.
3. Inoculate the milk by adding ¼ teaspoon of starter per quart and quickly replacing the lid. Swirl the jar to incorporate.
4. Keep the milk at 110 degrees for 6 to 8 hours, or until it becomes a yogurt-like consistency.
5. Finish with the rest of the Mesophilic directions.
To make a starter from a previous batch of mother culture, all you have to do is when the directions tell you to add the powdered direct-set culture to the cooled jar of milk, just add 2 ounces of mother culture from the previous batch, and then just continue with the rest of the directions.
Sometimes you might have problems getting your mother to set properly, or it might come out tasting a bit off. Here is a quick list that may help you pinpoint the problem so as to avoid it in the future.
1. If the taste of your starter is slightly acidic, or sharply so, or it has a metallic twang about it, it may be over-ripened. Next time, decrease the ripening temperature by about two degrees, be it Thermophilic or Mesophilic and see if that helps. If it doesn’t, you can also try decreasing the amount of starter you add just slightly.
2. If your mother ever comes out bubbly or carbonated, throw it out immediately. The bubbles are gas produced by yeasts and/or coliform bacteria, which come from poor milk cleanliness or unsanitary equipment.
3. If you have problems getting your prepared starter to coagulate, the cause may be one or a few of the following:
a) The milk you used contained an antibiotic introduced into the cow that produced it, which then transferred to your milk. Some dairies are required to treat their cows with chemical medications; of course this medicates the milk.
b) Bleach or strong detergent was not rinsed properly from your tools.
c) The starter you used was inactive, meaning the live bacteria inside have died.
d) The temperature was not properly maintained during the ripening period, either dropping to low (which is more likely) or getting higher.
Care for your mother culture and attention to the utmost cleanliness when handling or using it is very important. Usually recipes will give you a prepared starter equivalent when specifying how much starter you will need for a cheese, but a good basic ratio is four ounces of a mother starter to one packet direct-set cultures.
This article is one I originally wrote for the Cultures For Health website, and it can be found in it's original form here.