Another milk will not coagulate thread..

[Hambone]

For some reason the last batch of milk i obtained from the local dairy would not coagulate. I tried 3 different times using ingredients I had used only a week before which went fine. Initially I was  thinking it might be my rennet, but convinced its definitely the milk.

I'd tried his milk before and it was fine. I was so disappointed, and trying to figure out why it could be so different. I mean no amount of time would make it set (waited 2 hours) and extra rennet did not work in later attempts. I pasteurised what I could store but the rest had to be thrown. Such a waste. 

I did use it raw and not pasteurised.

The only thing I noticed when the farmer was collecting the milk for me was that he took of two or three buckets initially and poured them back into the top of his holding tank which he said he was doing in case the first bucket from the bottom was too thin, I guess thats because the cream tends to float to the top. Needless to say the milk was very creamy, could that be the issue ?

I have also read that if the milk contains the slightest amount of "colustrum" that it will not coagulate.

Any ideas welcome but I am very reluctant to try again ... as its one helluva drive and I bought 25 litres to make the trip worthwhile. Sigh.

[River Bottom Farm]

The rennet is good still for sure? The extra cream should not cause any issues. The bottom of a bulk tank can be very low fat (like skim milk from the store). Did you happen to take a pH reading on the milk before starting and how much starter did you use/ripening time before renneting?

[Hambone]

The rennet is good still for sure? The extra cream should not cause any issues. The bottom of a bulk tank can be very low fat (like skim milk from the store). Did you happen to take a pH reading on the milk before starting and how much starter did you use/ripening time before renneting?

Hi RBF, thanks for the reply.

I just followed the recipe, and did not measure pH (I could have , but instead I trusted in the quantity and times supplied an recipe does not suggest target pH). I doubt rennet can be the issue as am using same bottle that has been successful in the last month and it worked pretty much as expected for my final attempt on this disappointing weekend when I just used store bought milk in desperation.

I had three tries using the farm milk. 2 goes at the camembert recipe in cheesemaking.com (using their ingredients as well I might add!) and a final in desperation with a different starter using a cheddar recipe which had worked just fine before, but again, no coagulation. The fourth try was storebought milk and the camembert recipe. Because the available store milk here is lousy (over pasteurised for shelf life), I didn't get wonderful curds but at least got a product.

I will have a word to the farmer today, see if he'll fess up to antibiotics but I don't hear the world colustrum mentioned much in this forum nor in much of the literature I could find. There is one difference in the process I used this time versus the last batch I used in that I did not pasteurise the milk where as last tim eI did (145 F for 30 mins), but everything I read seems to suggest that pastuerisation in any form can only be detrimental to coagulation, not beneficial.

Really baffling.

[River Bottom Farm]

Not likely to be colostrum related coming from a bulk tank. Most if not all farms will milk out colostrum for two to three days minimum before adding milk from freshened cows to a bulk tank and it's not like a trace amount from a couple cows would effect all the rest of the milk in the tank to the point where it won't coagulate. So unless all the cows where sycronized to calve in the same week I would rule that out.

Antibiotics could be a possibility but that's usually regulated and tested at processing plants so not usually a problem.

Pasturizing isn't necessary as long as you trust the milk and yes it would only kill bacteria that would help acidify and subsequently help coagulate.

[Gregore]

When I first started making cheese I was using raw milk and it seemed to me that at some times of the year it had better buffering capacity for the ph to drop. It would take multiple hours for the ph to start to move down. Then when it did it would move at normal rate or even a little fast .

You might try waiting longer before adding rennet , if you can check ph then maybe try waiting for a full 0.2 or 0.3 drop . 

[Hambone]

Thankyou for the replies.

I did contact the farmer, he told me its possible some colostrum may have gotten into the storage vat because they'd had some recent calving but denied the use of antibiots, but I do take the point on unlikely concentration. I decided to do the milk run again this weekend and try again.

This time I'll make sure my container is rinsed thoroughly (I use Starsan in the recommended concentrations to sanitise most surfaces, which is a no rinse sanitiser, but I always wonder whether its detrimental to starter cultures as well... hmm). I will also use my pH meter and thanks Gregore for the tip ..will correct pH level should be before I add the rennet. I am a newbie so assume its different for different recipes... one q though, should I be looking at a 0.3 to 0.5 or 0.03 to 0.05 drop ? (reading a recipe from OzzieCheese https://cheeseforum.org/forum/index.php/topic,14002.0.html ). tks

[River Bottom Farm]

Star San shouldn't cause any major issues with culture. Might slow it a tad if there is a lot of residue but not enough to notice really. I use it quite often and haven't run into problems with it yet. The pH drop depends on your milk (how much wild flora it has to begin with, how the ph curve usually goes ) as well as your desired make (how fast you want to push the milk into the pressing and bringing etc) I usually look for about .1 on my milk because it buffers for a long time (45 to an hour) before dropping but then drops fairly fast.

I hope you have better luck with the next load of milk.  I usually make fetta if I'm not sure on the rennet amount needed or how the milk will act. Fetta seems to be forgiving enough that even if the floc is off you can still get fetta with a little bit of cheating so you will get a better idea of how much rennet you will need to get the desired floc time.

[Hambone]

Star San shouldn't cause any major issues with culture. Might slow it a tad if there is a lot of residue but not enough to notice really. I use it quite often and haven't run into problems with it yet. The pH drop depends on your milk (how much wild flora it has to begin with, how the ph curve usually goes ) as well as your desired make (how fast you want to push the milk into the pressing and bringing etc) I usually look for about .1 on my milk because it buffers for a long time (45 to an hour) before dropping but then drops fairly fast.

I hope you have better luck with the next load of milk.  I usually make fetta if I'm not sure on the rennet amount needed or how the milk will act. Fetta seems to be forgiving enough that even if the floc is off you can still get fetta with a little bit of cheating so you will get a better idea of how much rennet you will need to get the desired floc time.

Thanks, as a beer brewer I am well aware of the buffering power of a grain mash but never considered it to be a variable in milk but it makes alot of sense.

I continue to explore all options and managed to find a brand of powdered milk that purports to be simply spray dried whole milk only, not UHT prior and no added nonsense like dextrose and vitamins. I just did a small batch to avoid ingredients wastage. Lo and behold I got curds, and stronger ones than over pasteurised store bought milk. Must admit I was pleasantly surprised. I would not say by any means comparable  to the awesome curds I had with the first batch of farm milk, but I'd probably go this route versus storebought milk as a backstop (some rumours afoot that the milk here in Singapore is in fact reconstituted from milk powder depending on the brand. Thats because the most competitive dairy suppliers are in Australia and New Zealand, which is an 8 or 10 hour cargo flight away, so its far more economic to ship in powder and reconstitute... they can still get away with calling it whole milk).

Still, the proof is in the final product and shall see soon whether it does the job!

[Gregore]

Glad to hear it works again .  Just curious at what ph did you add your rennet? And what did it start at?

[Hambone]

Glad to hear it works again .  Just curious at what ph did you add your rennet? And what did it start at?

Hi Gregore, not yet, what I meant was it worked with a powder milk I made up, which shows that my rennet and culture are ok.

Will give the fresh milk a try this weekend. Stay tuned.

[Hambone]

hi guys,

so many threads I read in here where people say they will report back, but never do. but here i am

So I think I figured the issue, but its only a hypothesis.  last weekend I tried 3 batches with raw milk and only one of them coagulated, despite me making sure the pH had fallen by more than .05 before adding rennet. This week, I tried again, and pasteurised the milk (145 F for 30 mins, then rapidly cooling to culture addition temperature). I had three successes, floc time around 10 mins.

I can only figure that the natural bacteria in the raw milk was somehow competing with my added culture preventing it from working the way it is supposed to. It goes against logic but it is what it is....  . Its a bit of a pain and adds and extra hour to the process but if it works that what i gotta do.

[GortKlaatu]

Hambone,
I really don't think the "natural bacteria competing" theory is sound. That shouldn't cause the non-coagulation...if anything it should make it floc/gel/coag even faster....that's why when you use raw milk you always have to decrease the added culture and rennet by 40-50%


Heating the milk for pasteurization not only kills the bacteria, it can denature chemicals that are present. I wonder if the guy you get the raw milk from is giving his animals antibiotics or anti-parasite treatment or some other chemical that is entering the milk and that is what is interfering with flocculation. And when you heated the milk high enough for pasteurization, you also denatured this compounds.


Maybe you should look for a new source for milk??

[River Bottom Farm]

Glad you got it to work for you Hambone!

I also don't think the natural bacteria could be your issue that would only cause fast acid development as Gort said.

What kind of cows does the farmer have? Wondering if the protein content is low or the protein in the milk is of large size maybe? Rennet works on the proteins in the milk and heating the milk will cause some of these proteins to break down into smaller peices giving more surface area for the rennet to work on (might be one explanation)

[Hambone]

Thanks guys.

Fully agreed on the unlikely cause of natural bacteria. I also would have thought raw milk would have coagulated faster. Farmer insists he does not use antibiotics.

I could buy into the complex protein adjustment argument though...

Will find out the breed of cows he has.

[Gregore]

What was the ph when you added rennet ?