Direct-set powdered cheese starter cultures have a frozen lifetime of a year or more, but once used to make cheese, that starter culture is finished, and a new packet of powdered starter culture is needed for the next batch of cheese.
However, by making and preserving your own mother culture, you can effectively inoculate many gallons of cheese without using a new packet of starter.
Both mesophilic and thermophilic mother cultures can be made using the steps below. Follow the general cleanliness rules that apply to any cheesemaking process or review our article, Sanitization during Cheesemaking.
HOW TO MAKE A CHEESE MOTHER CULTURE
This recipe makes 1 quart of mother culture. Make more than 1 jar at a time, if desired.
Step 1: Sterilize the milk.
- Boil a one-quart canning jar with band and lid in a covered pot for 5 minutes.
- After the 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, as the cultures tend to rise with cream if it is present in the milk.)
- Screw the lid on tightly.
- Place the jar in a large, deep pot. Fill the pot with water until it covers the jar by about ¼ inch. Heat to boiling over high heat. Boil at a full boil for 30 minutes.
- Remove from heat.
Step 2: Cool the sterilized milk.
- Remove the jar from the pot of water.
- Cool the milk: For mesophilic starter, cool to 72°F. For thermophilic starter, cool to 110ºF.
- You may remove the lid to monitor the temperature with a thermometer, but ensure that the environment stays clean, to avoid contaminating the milk.
Step 3: Inoculate the milk.
- Once the milk cools, inoculate it with either 1/4 teaspoon powdered starter culture OR 2 oz mother culture from a previous batch.
- Quickly put the lid on the jar and swirl to incorporate the cultures.
Step 4: Ripen the milk with cultures.
- For mesophilic cultures, ripen at around 72°F for 15-20 hours. Check the jar at 16 hours for coagulation; if not fully ripened, leave up to 8 hours more.
- For thermophilic cultures, ripen at 110°F for 6-8 hours, or until it becomes a yogurt-like consistency.
- Proper coagulation has been achieved when the milk is 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.
Step 5: Chill the mother culture
- Once the milk has properly ripened and passed the taste test, chill the jar immediately.
- Keep the starter in the refrigerator for up to three days for cheesemaking or freeze immediately.
- Makes 1 quart.
FREEZING THE CHEESE MOTHER CULTURE
- Clean and sanitize two or more plastic ice trays. Fill all the cubes with freshly made mother culture.
- Freeze in the coldest part of the freezer until solid.
- After they are solid, remove the cubes from the trays (avoid touching cubes 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 cubes will keep in the freezer for up to one month, after which they may still be viable, but their strength will begin to degrade. Each block is about one ounce of starter.
USING THE CHEESE MOTHER CULTURE
Cheese recipes usually call for a prepared starter equivalent. If not, a good rule of thumb is to use 4 ounces of mother culture in place of one packet powdered direct-set starter culture.
TROUBLESHOOTING THE CHEESE MOTHER CULTURE
Q. My mother culture has an overly sharp or metallic flavor. What do I do?
A. Next time, decrease the ripening temperature by about 2°F. If the sharp flavor persists, decrease the amount of starter slightly on the next batch.
Q. My mother culture is bubbly or has a carbonated taste. Can I use it?
No! Discard it immediately. The bubbles are gas produced by yeasts and/or coliform bacteria, which come from unclean milk or unsanitary equipment. Review Sanitization during Cheesemaking and try again.
Q. My starter did not coagulate. Why?
If the prepared starter does not coagulate properly, the cause may be one or more of the following:
- The milk used contained an antibiotic given to the cow that produced it, which then transferred to the milk.
- Bleach or strong detergent was not rinsed properly from your utensils.
- The starter you used was inactive, meaning the live bacteria in it have died.
- The temperature was not properly maintained during the ripening period, either dropping too low (more likely) or getting too warm.