Author Topic: pH Initial Low, Rapid Drop, Final Too Low  (Read 700 times)

Offline Caseus

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pH Initial Low, Rapid Drop, Final Too Low
« on: May 14, 2012, 11:06:03 PM »
What causes pH to drop quickly during a make?  Is it that I'm adding too much culture?  Or am I doing something else wrong?

Example:

For my most recent make, a Gouda (Pav's recipe) the initial pH of the milk was 6.56. I added 3.5 oz of liquid from boiled mustard seeds.  I didn't measure the pH of the liquid.

A little more than an hour later I hit 87.9 degrees (oops, was targeting 86).  pH measured 6.40 already, and that was before I added any culture.

I added 12 oz of primer culture made from equal amounts of MM100 + Flora Danica.  pH of culture was 4.37. 

Waited 10 minutes, then added CaCl2 and rennet, floc point was 10 minutes, multiplier was 3, so I waited total of 30 minutes, tested for clean break, it was, so I cut the curds.  At the end of cutting curds, pH was 6.31, temp 87.4.   

Let heal for 5 minutes, then stirred for 10 minutes, temp was now 86.5 degrees, pH was 6.26.   Falling like a stone.

Removed whey and added 130+ degree water in three stages over 18 minutes.  Temp was 99.8, so I heated it to 101 degrees.  pH was 6.23.

Let curds settle 5 minutes, drained briefly and mixed in mustard seeds, packed into mold and pressed under whey with 5 lbs weight for 15 minutes.  Removed from whey, flipped and redressed and pressed 6 lbs for 20 minutes.  After 20 minutes, pH of pressed out whey was 5.91.

Flipped and redressed, increased weight to 12 pounds, pressed 30 minutes, pH was 5.71.

Flipped and redressed, increased weight to 25 pounds, pH 5.55.   I should have stopped pressing at this point based on 5.6 pH target in Pav's recipe, but I'd only an hour and 5 minutes of pressing so far counting the 15 minutes under whey, so I was concerned that the cheese might fall apart.  Quite a bit of whey was still coming out of the cheese. I decided to press onward.

I pressed for an hour and flipped, pH of the whey was now 5.39

Flip and press two hours - final pH of the small amount of whey was 5.09, whey below target! 

So needless to say, I'm concerned this cheese won't be very good.  But what I'd like to know is how to slow down the pH drop during the make.  By the whey, the room temperature throughout the make was between 73 and 75 degrees.


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Offline linuxboy

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #1 on: May 14, 2012, 11:16:25 PM »
Raw milk? Your starting pH is a little low... points to possibly having bacteria in the milk already.
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Offline Caseus

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #2 on: May 14, 2012, 11:26:05 PM »
No, sorry.  The milk is low-temperature pasteurized non-homogenized Jersey milk.   Grass fed mostly, organic.  It comes from a local farm that delivers all over the metroplex.

http://texasdailyharvest.deliverybizpro.com/home.php



Offline linuxboy

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #3 on: May 14, 2012, 11:58:04 PM »
I don't think their pasteurization schedule is getting all the psychotrophs and high temp lactobacilli. I would cut back culture amount.

Your cheese should be fine. Not ideal, but acceptable.
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Offline Caseus

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #4 on: May 15, 2012, 11:18:45 AM »
Thank you, Pav.   I hope those psychotrophs and high temp lactobacilli are not pathogenic types. 

I get the milk delivered on Tuesday then keep it in my fridge at about 38°F until Saturday or Sunday.  SInce I only have time to make cheese on weekends, I'd love to have it delivered on Friday, but I don't have a choice on that.  I realize it would be ideal to make cheese as soon as possible after the cows produce the milk.  But they have routes mapped out based on a weekly schedule, and my area happens to fall on their Tuesday route.

Also, I don't know how old the milk is when it is delivered to me. I just have a "use by" date on the jug.  It ranges from 10 to 14 days out, most commonly 14.

I will reduce my culture addition by 25% on my next make and monitor the pH drop, then adjust from there.


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Offline linuxboy

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #5 on: May 15, 2012, 11:54:57 AM »
Yep, Tuesday to Sat with low temp pasteurization would do that in many cases. 25% reduction starter is a good start. See how it goes. Good luck :)
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Offline Hande

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #6 on: May 15, 2012, 04:41:04 PM »
Caseus, you have best milk for cheese making in your hand,
but you need get it way too more fresh  :)
I am concerned about the one day old milk for cheese making.

Hande


« Last Edit: May 15, 2012, 08:07:53 PM by Hande »

Offline Sailor Con Queso

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #7 on: May 15, 2012, 06:32:44 PM »
I use milk that is low temperature pasteurized, and I have no problems with 3 or 4 day old milk. However, I store my milk at 35F and always test the pH before using. The most I have ever seen was a .01 drop over 4 days, and that is statistically insignificant with the margin of error. That is why I would suspect the milk had been warmed before you got it, either before or during delivery. The standard in Kentucky (perhaps nationally) is that the milk can NEVER get warmer than 41F. Milk haulers are required to have plotters that record the time & temperature. Almost all big retail stores here will reject milk deliveries that have gone over 41F even for a short time.

If the milk warms before delivery, it can obviously create an environment that allows bacteria to multiply quickly.

You should always test the pH of the milk before you start making cheese. It should be 6.6 - 6.7. My standard is 6.55. If it's lower than that, I will not use it (or pay for it). That has only happened once, and my farmer/supplier admitted that the milk had sit outside of their cooler for too long prior to loading. They were having mechanical problems and the milk sat on their warehouse floor until the truck was fixed.

And as LB said, their pasteurization schedule may not be hot enough or long enough. I would discuss all of this with your supplier.
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Offline Hande

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #8 on: May 15, 2012, 08:42:42 PM »
Yes, sorry I just thinking about raw milk :o

Hande

Offline Sailor Con Queso

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #9 on: May 16, 2012, 08:18:39 AM »
Hande has pointed out that in a previous post I said that my lower limit was 6.4. Since I made that statement, I have increased my standard to 6.55. A pH even that low shows that there are active bacteria already converting lactose to lactic acid. Milk at 6.55 is still plenty good enough to drink, but generally not good enough for cheese making.
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Offline Caseus

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #10 on: May 16, 2012, 08:54:00 AM »
Sailor, thanks for the pH clarification.  I measured 6.56 on this particular milk, and I have seen 6.6 on a couple of makes. 

I've never seen the delivery vehicle, so I don't know how the milk is transported.  I think it is possible that the milk could be warmed above 41°F after delivery since it is dropped off at local collection points (someone's house) in ice chests.  Then people who are in the delivery group go pick it up.  I can have it delivered directly to me, but it's a little more expensive and I have to meet a minimum order that is more than I generally want to buy.  I might have to go that route anyway, though.

Offline Hande

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Re: pH Initial Low, Rapid Drop, Final Too Low
« Reply #11 on: May 16, 2012, 09:25:32 AM »
Thank you Sailor clarification  :)

Hande