Didn't get a clean break.

[artmustel]

Hello, I am a pretty new cheese maker but not a total newbie, I have made several Queso Fresco, 3 Manchegos and 1 Gouda. Today I made a couple of cheeses but on the second one i didn't get a "clean break"; curds were soft and didn't cut well at all. The first cheese I made today was ok, but the second had the problem I described above. Ok, I used same animal rennet for both, the only difference was, on the first one I used Meso and on the second (a Bel Paese), recipe asked for thermo. I followed recipe step by step and i was really shocked that I didn't get a good coagulation. Now, since on this second cheese that failed I used a Thermophillic that I had not used before (and purchased recently) I wanted to ask you guys if a bad, spoiled or outdated culture can cause that problem. If it cannot, then I don't understand where I failed. (Rennet is ok , I used same full cream milk I usually do, I used Calcium Chloride, I use distilled water to dilute the CC and the rennet).

If a bad direct set culture wouldn't cause that, then what else could?

Thanks in anticipation!

[Kern]

Assuming that you used the same milk for both the difference between the two is the culture used.  A meso culture will start reducing the pH at lower temperatures than a thermo.  Rennet works more effectively when there is a pH drop of 0.05 to 0.1 from the initial pH of the milk (6.65 +/- 0.05).  I suspect that is the difference here.  Next time use a combination of meso and thermo at a combined loading level equal to the thermo you used and allow 50% more ripening time.  When you heat the curds to about 103F or above the meso will die and the thermo will kick in.

[artmustel]

Thats very interesting Kern, so I should do that even if recipe doesn't ask for meso?

Thank you!

[awakephd]

It won't hurt anything to use both meso and thermo, and it will give you a faster initial pH drop. You can also just use the thermo, but allow more ripening time. Or more coagulating time. Or both!

That said ... some recipes that I use that call for thermo cultures have a very, very short ripening time, not nearly long enough to get any significant pH drop, and I get a good set. Admittedly, I'm starting with milk that is already a bit low in pH (store bought P&H, unfortunately), so that may make the difference. Note that temperature also has an effect on how quickly the rennet will set.

[artmustel]

This particular recipe asks for thermo only (1/4 tsp to 10 liters of milk). Now if I wanted to use meso too, how much should I ad? And should I let the meso ripen before adding the thermo? I understand this will be all a guess, but since it never happened before and it happens with the first recipe I follow that takes only thermo,

If I understand it right, I will use the meso here just to acidify the milk. (Since as soon as I heat the milk to 42 C, the meso would die). Then tell me if this is correct: I heat milk first to 30 or 32c, add the meso, let it ripen for about 30 minutes, then add the thermo (should I let it ripen too?) and then I heat the milk to the 42c asked on the recipe.

Thanks a lot for your help!

[awakephd]

Just to be clear: after you add the thermo, are you heating to 42°C and then adding the rennet? If so, it is too hot. You need to add the rennet while it is at 30-32, let it coagulate, cut, and then begin to stir and heat up to 42°.

[artmustel]

Wow Andy, then that is what happened. I followed Gavin Webber recipe on youtube and yes, the first thin recipe asks is heating milk to 42C, then adding the culture, then the CC and then the rennet...

[awakephd]

I don't know what the upper range is for when rennet begins to quit working / break down - it's possible that it will work at that high a temperature. But that is considerably higher than the recipes I generally have used. At the least, I'd give it a try at 30-32°, coagulate, cut, and then begin heating - see if that gives you a good set.

[artmustel]

That is exactly what is done with Manchego recipe, it asks for both meso and thermo, first heating milk to 30c. Then adding cultures and cc and a ripen time of 45 minutes, then adding lipase and rennet and waiting for coagulation. Just after coagulation curds are cut and heal for 30 minutes, still at 30c, then temperature is raised to 40c very slowly (about 1 degree every 5 minutes. ) I guess what both you and Kern have contributed make perfect sense. Probably Mr. Webber's recipe works well with raw milk, but in my case it was my first big failure. Next time I try a recipe that takes only Thermo I will add Meso too and follow your suggestions. Thanks! 

[awakephd]

If you try it at the lower temperature, I suspect you could add just the thermo and still come out fine.