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OK, I've now made mozzarella with whole milk, rennet, and citric acid. Wonderful! I'm a real newbie at cheese, but I have decades of experience with breadbaking. A few questions for the experts.

My starting curd was not very solid, and my checkerboard fell apart pretty readily. As a result, the chunks of curd were pretty small. Is this the result of incomplete curdling? I used newly bought vegetable rennet tablets, and I followed the temps pretty carefully with a digital thermometer. Now, that being said, the remaining whey was pretty clear, no "white" left behind. That suggests to me that the curdling was pretty complete. Am I reading this right? How do I get the curds to be more solid?

My final cheese was quite soft. Easily kneaded in the bowl, but couldn't quite pick it up and stretch it. Is that because I didn't drain enough whey?

The stuff is delicious, but I will be putting it on my pizza with a spoon.

Mozzerella, whether the quick method (citric acid) or the traditional way (culture+time), is not the easiest cheese to make.

Yes, when you drained the nearly clear whey, it showed that you had good curd formation because it took the fat portion and the protein portion of the milk and kept it in the curd. This leaves the whey almost clear, yellowish/greenish.

With the quick method, it might not have been hot enough, or cold enough, but in both cases the quick method produces a cheese that does not generally hold it's shape very long and it is a little more mushy than the motz made in the traditional way. When I've made it I put it directly into small containers but it generally flattens out in the containers. This doesn't happen with motz made the traditional way.

Good for you though! I hope it is delicious on your pizza.

Thank you. That's important, that good curd formation leads to almost clear whey. Lots of ideas about what to do if your curd didn't form well, but no one bothers to tell you how you know if your curd didn't form well! So I got everything I could get out of my milk.

Your description of the final product sounds exactly like what I have.

The several videos I've seen doing it exactly this way have the cheese makers lifting the mass, stretching it, and folding it like dough. The checkerboard slots in the curdled milk come out sharp and clean. Can't do that with mine. Do you have any links to doing it the "traditional way"? I was assuming this was the traditional way!

What kind of milk are you using? Pasteurized/homogenized milk for example tends to not form curds well due to the processing the milk goes through that alters the structure of the milk. Homogenized milk is generally not recommended for cheesemaking because of this. If the milk is pasteurized, adding calcium chloride helps to mitigate some of the issues with milk that has gone through processing.

Susan

I agree with SoSeattle calcium choloride would probably fix your issue. Either that or wait a little longer after renneting for the curd to set up a bit more.

Thank you. Yes this was regular store-bought pasteurized/homogenized milk. Not ultra-pasteurized. Next time I was planning to wait longer for the curd to set up. Maybe I'll try some calcium chloride. But I understand that calcium chloride can prevent curds from stretching. How much should I use?

I'm just a little surprised that ALL the online videos of 30-minute mozzarella are very consistent in producing cheese that is firm and stretchable. They never mention pasteurization/homogenization or calcium chloride.

In the end, the consistency was more like cream cheese. Very tasty, and excellent on pizza. I'm pretty happy with it.

In the quick method and the traditional (slow) method, the PH of the curd needs to reach 5.something. You will be advised to get a PH meter. (I still don't use one but I know when the curd is ready by testing a small portion of it in hot water.)

If you are using P&H milk, you will probably need the Calcium Chloride solution, a 30% solution. Shorthand for that is CaCl2.

The traditional method can take hours for the cultures you add to bring the PH into the right range. Too high and it won't stretch, too low and it won't stretch.

Here is a good video and recipe for the traditional method. https://www.youtube.com/watch?v=CluOhy1zu9Q
And if you read threads here on traditional mozzerella you will get a good picture of how it is done.

Some chemistry questions. What exactly does the calcium chloride do? If we're talking pH management, I thought that's what the citric acid was for. I gather it makes for a firmer curd, but how exactly does it do that? What exactly happens in P&H that makes addition of calcium necessary? P&H doesn't remove calcium.

I can't give you the chemistry about the calcium but it is lost during pasteurization and the CaCl2 replaces the stuff lost. The CaCl2 has nothing to do with PH, that I know of. The Citric acid is an acid, that changes the PH to a lower PH, more acid and you bring the solution of milk to the 5.something PH.

Pasteurization may not remove calcium, but it somehow makes it unavailable to making the curd.

Yes, pasteurization is just heating. No amount of heating is going to remove calcium. Calcium can't be volatilized. Heating can change the chemistry, and maybe put the calcium into different molecules, but all the calcium is still all there. But maybe it's in a molecular form that isn't easily accessible to the curd?

Let me add that I've perused a number of semi-scientific explanations on the web. What a hoot! One reference says that pasteurization heating breaks up the calcium phosphate that tends to tie up calcium in older milk. But others say, somewhat mysteriously, that pasteurization "makes calcium unavailable". Duh. How? Best I can gather, it's calcium IONS that are needed, and CaCal2 provides those. But if those ions are bound up in molecules, they are unavailable. No one seems to be able to explain what molecules they get tied up in, and why heating tends to tie them up. CaCl2 sounds like a "magic ingredient", and I don't like magic that much.

But maybe someone can recommend a good reference on chemistry of cheesemaking?

This guy knows what he is talking about and he explains it beautifully. He was explaining a different answer to a question but he also explains your answer to your question.

Quote from: mikekchar on October 07, 2018, 11:27:04 AM
Just to restate the question: why does the milk not set with rennet if you wait too long after adding buttermilk culture?  This is an excellent question and I hope I can explain it well :-)  In case you just want the answer without the explanation: because the milk is too sour to set a curd with rennet.  If you want to understand *why* that matters, then read on.

The thing to understand is that there are *2* mechanisms for making curds in milk.  The one cheese makers are familiar with is by adding rennet.  Rennet is an enzyme.  Enzymes are chemicals that cut other chemicals in pieces (usually proteins or carbohydrates).  You are probably familiar with the protein called casein.  Casein is the main protein that makes cheese curds.  Most people don't realise that on the scale of molecules, casein is pretty big.  You can probably think about it like a big ball of string.  This big ball of string is called a "micelle" (which means nothing other than it's just a whole bunch of stuff stuck together :-) ).  On the outside of the casein micelle (remember -- ball of string) is a whole bunch of "hairy" proteins.  So now our micelle is kind of like a big ball of string with lots of furry hair sticking out.

The hair has a "positive charge".  That might sound complicated, but it's not.  It's just like a magnet.  Remember that in a magnet, there is a positive end and a negative end.  If you hold the positive end next the the negative end, they will stick together (often really hard!).  But if you hold the positive end next to another positive end, then they will *repel* each other -- you can't stick them together, no matter what you do (as a kid I always had fun trying to force magnets together the wrong way around -- yes, I'm *that* kind of person!).  Anyway, same goes for negative to negative -- they won't stick together.

So you've got all these casein micelles (big balls of string) floating around in the milk.  Each one is covered with this positively charged hair -- so each one repels each other!  You can't get the casein micelles to stick together, no matter what you do.  That's why milk is a liquid.  This is where the rennet comes in.  Remember that rennet is an "enzyme" and enzymes cut other chemicals into pieces.  In this case, rennet is a very special enzyme -- it cuts the hair off of the casein micelles!  So now the micelles are no longer positively charged!

Except there is one small problem.  If the hair is positively charged, how is it sticking to the micelle?  If you guessed, "Because the micelle must be negatively charged and it sticks just like a magnet", then you would be exactly right!  Once the rennet "cleaves" (a fancy word for "cuts") the hair off  the micelle it is now negatively charged -- and negatively charged things *also* don't stick together.  But, we have a secret weapon!  Dissolved calcium is positively charged.  If we dissolve some calcium in the milk (say by adding calcium chloride), then we'll have both negatively charged casein micelles and positively charged calcium "ions" (in this context, an ion is just half of some chemical that's dissolved in a liquid -- in our case we dissolved calcium chloride and it broke up into calcium and chloride ions).  As an aside, in unpasteurised milk, you usually don't need to add calcium chloride because there is enough dissolved calcium phosphate to give you the calcium you need.  When you pasteurise the milk, the heat causes the calcium ions and phosphate ions to stick together and literally fall out of the milk, so we have to add extra calcium.

OK, I'm finally getting to the point (I promise!).  We have a "bald" casein micelle which is negatively charged and a calcium ion which is positively charged.  They stick together just like a magnet.  Furthermore, you will get another casein micelle sticking to the other end of the calcium and another calcium ion sticking to the end of that.  It just starts sticking together like magnetic Lego.  And that's when the curd forms.  Rennet set cheese curd is just a gel of "cleaved" casein micelles stuck together with calcium.

That's the first kind of cheese curd (which most cheese makers take advantage of).  There is another kind of milk curd.  It turns out that when a liquid gets very sour, the "charge" on the particles gets weaker.  I actually don't know why it does this and I've been meaning to look it up, but I'm lazy.  In any case, the point at which the charge goes away completely is called the "isoelectric point" (fancy word that literally means "the point at which the electric charges are the same).

When the "isoelectric point" (which I'm going to call the "yogurt point" for ease of typing) is reached, the casein micelles no longer repel each other.  They kind of stick together, but it's not a strong bond -- not like the bond between the casein micelles and calcium.  Remember that the bond with calcium is like a magnet -- it's super strong.  You practically can't pull it apart.  But micelles sticking together because they hit the "yogurt point" are more like sand in a sand castle.  They stick together just because the shape and position happens to be nice.  If you try to move it around (by stirring or something), then it will either flow (like yogurt) or fall to pieces (like ricotta cheese).

Now to answer your question: When milk is sour enough to hit the isoelectric point (yogurt point), there is no electric charge left.  It doesn't matter if you cleave (cut) the hair off the micelles, because it is not positively nor negatively charged.  It won't stick like a magnet to the calcium, no  matter what you do.  And because it won't stick like a magnet, it won't make a curd.  The best it can do is to thicken the milk to make a kind of yogurt.

Note: if you add a strong acid to milk quickly, it will make a stronger curd -- but still nowhere near as strong as rennet formed curds.   The buttermilk is kind of liquidy because the culture is making it sour slowly -- this means that the "sand castle" bits are really, really small.  There is tonnes more to say on this topic, but I've probably outtyped my welcome as it is.  I hope it was interesting for you.

Thank you! That's excellent. So although I thought one web reference said that heat breaks up calcium phosphate, what this person is saying is that heat MAKES calcium phosphate. Maybe I read that one web reference wrong? As I said, what you need is calcium IONS. As in Ca+. If the calcium ions turn into calcium phosphate because of pasteurization, you don't have those Ca+ ions anymore. Calcium chloride dissolves easily in water. When it does, you get Ca+ and the anion Cl- floating around.

Actually, it turns out that the calcium phosphate itself binds to the casein, instead of the calcium ions. And casein with calcium phosphate stuck to it won't bind together. But casein with calcium ions stuck to it can. So the calcium phosphate ruins the stickability of the casein, and what we want is stickable casein.

That's better than magic!

Now, as I said, I had excellent curd formation, but the curds didn't want to stick together well.

Gotta get some calcium chloride. I could pirate some from my DampRid supply, but maybe I'll do it right. DampRid has traces of a few other things that might not be optimal.

You want to use food grade calcium chloride.

Susan

Had a chance to look at the "traditional" mozzarella video. Nice. As I understand, the role of the thermophilic bacteria is primarily in acidifying, and the lipase is mainly for flavor. That being the case, what's the advantage of traditional, versus 30-minute? Citric acid is a convenient instantaneous acidifier. I could always add some lipase to that, for flavor, no? I have to assume that storing the finished cheese in brine just preserves it better, and prevents bacterial degradation.

Yes the thermo is mostly for acid and lipase is for flavor but the traditional is waaay better cheese. If you don't believe me try it. Texture and flavor is much better. Also it's much more consistent as the acidification. Happens over time so you can tweak things along the way if you are using pH measurement