Troubleshooting a Clean Break, Cheese Making

For beginning cheese makers, I strongly recommend that a series of cheese related projects to be mastered before attempting to make ‘basic cheese.’ With a basic cheese, the step which most often presents difficulties is the ability to achieve a clean break. Test for a clean break by plunging a clean finger into the inoculated & renneted milk and lifting. Properly coagulated milk should break cleanly around the finger, and clear whey should fill the gaps produced:

ACHIEVE A CLEAN BREAK: Test for completed action of rennet ("clean break "): Probe a clean finger into the (hopefully) gelled milk and lift. If the gel is firm enough to break cleanly as the finger is lifted, go to next step.
ACHIEVE A CLEAN BREAK: Test for completed action of rennet (“clean break “): Probe a clean finger into the (hopefully) gelled milk and lift. If the gel is firm enough to break cleanly as the finger is lifted, go to next step.


Ninety nine percent of the time, the failure to achieve a clean break is because one or two of a few critical requirements have not been met. 

Critical Factors in achieving a “Clean Break”

  • Good quality fresh milk (if it has started to turn or has a high bacterial count, it can interfere with lactic bacteria)
  • Active bacterial starter, correct proportions mixed in thoroughly
    Proper incubation with the starter to slightly acidify the milk.
  • NOT over acidified. This would cause it to slightly clabber (thicken). Even slightly clabbered milk will never yield a clean break.
  • Active rennet, correct proportions, mixed in thoroughly
  • Correct time and temp for coagulation, undisturbed.

Note that there are two different approaches to making cheese with regard to timing of inoculation and adding rennet:

  • Add the starter the night before, let sit at room temperature, and add the rennet the next day. Let sit until a clean break, usually 2-3 hours.
  • Add the starter and after a few minutes, add the rennet. Let sit until a clean break, anywhere from 1 to 8 hours depending on proportions.

FAQs for Achieving a Clean Break

Was the milk fresh, and warmed up to room temperature?
If milk has started to “turn,” the wrong bacteria can grow and prevent the starter bacteria from growing properly and acidifying the milk. (If you use store bought, check the expiration date for the freshest.) Also, if the milk is not warmed properly (at several stages), bacteria will not grow, or rennet will not act on the milk.

Was the starter fresh and active (either buttermilk or yogurt)?
The bacteria in the starter must be alive and well. Bacteria may have died in outdated starter. When in doubt, purchase the freshest buttermilk or freshest Dannon plain yogurt which you confirm is not outdated.

Did you add the correct proportions of starter for milk?
If you add too little starter, the milk will not be acid enough for the rennet to work. If you add too much, the milk may get over acidified and curdle. Over acidified milk is recognize the by a slight thickening (clabbering) of the milk. The milk should look exactly like regular milk when the rennet is added. If the milk is even slightly clabbered, you will NEVER get a clean break.

Remember that buttermilk contains mesophilic bacteria which grow well at room temperature while yogurt contains thermophilic bacteria which grow more slowly at room temperature. Buttermilk bacteria are aggressive acidifiers. Therefore, it takes 1/2 to 1/4th as much buttermilk as yogurt to act as starter. (With very active buttermilk, you may only need 2 teaspoons/gallon of milk for proper acidification.)

After adding bacterial starter, did you let the inoculated milk incubate (sit) at room temperature overnight?
Bacteria will not grow if the milk is not warm enough. It should stay close to 68 F (20 C) overnight so that the bacteria can grow and make lactic acid to acidify the milk. This room temperature incubation is mandatory. If it is too warm, the milk may over acidify.

The next morning, did you warm the inoculated and incubated milk up properly before adding the rennet?
Because rennet is an enzyme, it works better at warm temperatures, and hardly at all in cool milk. Also, if the milk is warmed too high, the curd will be tough, and alter the quality of your cheese. The consistency of the milk should not change when warmed.

Was the rennet active, did you use the correct amount?
Rennet is an enzyme, and can deteriorate with time. I have never had problems with Junket Rennet tablets going bad even after a year or two, but I have heard of liquid rennet losing its potency. Obviously weakened or inadequate quantities of rennet will require longer to achieve a clean break, if ever. If you add too much rennet, I have heard that the curd may taste bitter, but I have never experienced this. It will not hurt to add twice the called for rennet if you are in doubt as to its potency.

Did you let the inoculated milk sit UNDISTURBED after you added the rennet?

This is crucial to getting a clean break.

If you disturb the inoculated milk after it has begun to set, even a little, you may never achieve the tight curd required for a clean break. Once you have added the rennet, be careful to place the container in a place where it will not be jostled.

Were you patient enough to wait for a clean break? 
After the specified time (30 minutes to overnight, depending on the cheese), gently lift the lid, slowly plunge your finger into the milk and lift. If it is still liquid, carefully replace the lid and try it again in an hour or so. If it is slightly thickened, let it sit for another 30 minutes without disturbing it. If you have not achieved a clean break in 12 hours, you probably never will.

If you did all these, then you should expect to achieve a clean break within 2-3 hours at the longest.

The Calcium Issue in Formation of Curd…

The one remaining problem relates to use of pasteurized, homogenized milk (as one would get from the store). I am less familiar with it than the fresh raw goat’s milk I use, but the processing alters the protein structure, and may cause problems establishing a firm curd. Some recipes call for purchasing a solution from a cheese making supply house, and adding “1/2 to 1 teaspoons” per gallon (5-10 mL).

But, nobody talks about the concentration of the solution!

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.

If you know more on this subject, please let me know.

This could be critical for folks making cheese from store-bought milk.