Why isn't the raw milk coagulating properly?

[Cheezie]

Hi Everyone!
I'm new here and new at making homemade mozzarella cheese.
I need your help, you see I can't seem to get past the curd part, the milk isn't coagulating properly, looks like rice and not a block of tofu, so to speak:



It turns to this about 5 minutes after I add the rennet and it doesnt change much to an 60 minutes later. I've tried the liquid rennet and the tablet rennet with exact results.
This is the recipe i'm using for raw milk:
1/2 gallon raw milk
3/4 tsp citric acid
1/8 tsp liquid or tablet rennet
non-chlorinated water

1. dilute citric acid in 1/4c non-chlorinated water
2. place milk in large pot and warm to 22 Celsius
3. add diluted citric acid and gently stir for 30 seconds
4. heat, on medium, milk to 33 Celsius, stirring occasionally
5. once milk reaches 33 Celsius, add rennet to the milk, gently stir 30 seconds
6. turn off heat and let sit covered for 60 minutes

The rest of the recipe I won't include because I'm not making it to that point! 

Thanks in advance for your help and wisdom!
Mike

[Kern]

It should not be coagulating in five minutes. This is coagulation on steroids!  This leads me to believe that it may be either too acidic, too warm and/or you may be using too much rennet (although this seems about right unless you are using a double strength vegetable rennet) .  It could be any one of these things or a combination of them.  Try cutting the citric acid back to 1/2 tsp and the temperature down to 31C and see what happens.  And make sure your rennet is single strength (calf rennet).

[Cheezie]

Hi Kern
Thanks for the suggestions, I will cut back on the citric acid and temperature and report back tomorrow. 

[Cheezie]

On a hunch based on your suggestion, I checked the acidity of raw milk:

"The pH is a measure of the hydrogen ion (H+) activity in aqueous solutions. The most exact measure of pH is obtained electrometrically by means of a pH-meter. The pH in normal fresh milk from healthy cows is 6.6 ± 0.1. Values higher than 6.7 indicate mastitis infections, whereas values below 6.5 indicate the presence of colostrum or bacterial deterioration. Milk with deviating pH should be rejected from the milk powder production, as the heat stability most probably will be inferior."
- http://www.geap.com.au/GPAU/cmsdoc.nsf/webdoc/ndkw74aaj8

Mine measures at 6.0 ph taken from the fridge. Maybe it's too acidic to begin with?

[Kern]

I hate to ask but is your pH meter calibrated using a buffer solution?  Did you also check the rennet strength?

IF you are right about the milk having a pH of 6.0 out of the fridge and then you add the citric acid the pH will likely be in the 5.5+/- range and coagulation will be likety-split at a low pH like this and may not proceed normally.

[Cheezie]

Oh no, I just used a ph strip (paper) for the PH testing. Not sure if this was an accurate test, it's all I had on hand.

[WovenMeadows]

I don't know that you have a problem there. You're using the so-called "30-minute mozzarella" approach, using citric acid instead of cultures. So your milk start off at full acidity, so once you add rennet, it will coagulate very quickly (in 5 minutes). When I used to make this, I would often get that curdled-looking curd too, but it still works if you proceed with the recipe, I think.

[Cheezie]

I saw so many videos on Youtube of folks achieving mozzarella in 30-minutes, I thought it only made sense to try it.
If the milk is raw, then should it not need cultures as they are already in the milk in it's natural form?
And drop the citric acid from the recipe?

[Cheezie]

I don't know that you have a problem there. You're using the so-called "30-minute mozzarella" approach, using citric acid instead of cultures. So your milk start off at full acidity, so once you add rennet, it will coagulate very quickly (in 5 minutes). When I used to make this, I would often get that curdled-looking curd too, but it still works if you proceed with the recipe, I think.

Just realized I didn't respond completely... I have tried it to the end but it doesn't coagulate like one full piece; it just stays in rice-like form. 

[awakephd]

Cheezie, my two attempts to make the 30-min. mozz gave results similar to what your pictures show. After draining the curd, I was (once) able to get it to work as mozzarella, and the other time it just turned into a sort-of-stretchy-ricotta-ish blob. (Still tasted good, though, especially since I had some lipase in that one.)

I think you will be happier using a more traditional recipe, allowing the milk to ripen with added culture(s). (I wouldn't depend only on the cultures already in the milk, but you can cut back the amount of added culture compared to using P&H milk.) This will take longer -- either start it in the morning, and hope the curd is ready to stretch by the afternoon/evening, or start in the evening and put the curd in the fridge overnight.

Your goal is a curd pH of 5.1-5.3 -- which may be very hard to test with pH strips. You can, however, periodically test a small amount of curd in some hot water to see if it is ready to stretch.

[Cheezie]

Hi Awakephd, I think you're right on the money. A traditional recipe is required here. I think there too many Youtube videos of folks claiming to make cheese with "raw" milk when in fact they are using "whole" milk.
The raw milk I'm using is organic, cows are fed hay 12 months of the year, as pure and fresh as can be. Maybe the milk is too pure for these 30-minute recipes.

So thanks for responding, what you're saying makes perfect sense and thanks again!
Cheezie

[Stinky]

If you are going for a mozzarella flavor, it's safer to use cultures. See, raw milk has cultures. These are influenced by what the cows eat and where they are. And then the milk can get cultures from the air. These, too, are geographical. So unless you're in Italy, it's usually a good idea to add cultures if you're going for the certain flavor of a certain cheese. You can make great cheese without cultures, but with great milk, but this helps get you the flavor profile you're aiming for. Or so I understand.

[Ekomilk]

On a hunch based on your suggestion, I checked the acidity of raw milk:

"The pH is a measure of the hydrogen ion (H+) activity in aqueous solutions. The most exact measure of pH is obtained electrometrically by means of a pH-meter. The pH in normal fresh milk from healthy cows is 6.6 ± 0.1. Values higher than 6.7 indicate mastitis infections, whereas values below 6.5 indicate the presence of colostrum or bacterial deterioration. Milk with deviating pH should be rejected from the milk powder production, as the heat stability most probably will be inferior."
- http://www.geap.com.au/GPAU/cmsdoc.nsf/webdoc/ndkw74aaj8

Mine measures at 6.0 ph taken from the fridge. Maybe it's too acidic to begin with?

That's an interesting source about this pH as mastitis indicator, I'll investigate that under which conditions (serious accute clinical cases) it's true that the pH is higher. I'm sure though that milk with an elevated cell count (SCC), which means subclinical mastitis at least, usually has a normal pH value. In other words, pH is not a reliable indicator for cell count nor mastitis. Instead, you could use the reliable cell counters for raw milk which only cost around 0.03$/test. www.ekomilk.eu
In any case, pH value is important for milk processing, 6.0 sounds indeed too acidic.