My whey is sour after a day

[colby]

I usually make some ricotta from the whey I save after cheese making.
After separation, the whey is returned to the original milk container and immediately stored in the fridge.
All utensils are vinegar sprayed and rinsed with cool (boiled) water.
Never had a problem doing it this way.

Now, after 24 hours, give or take, it is sour. And I mean sour, non drinkable, whereas before it was sweet for weeks.

I'm at a loss as to why my whey is going sour. Any help would be appreciated.

[bansidhe]

Did you make a different cheese this time, perhaps one that has a lower pH or higher temp?  What did it taste like before you put it in the fridge?  A lactic cheese I believe is not suitable for ricotta because of the pH of the whey, I think.  If the whey was warmer than what you typically do perhaps acid production continued for awhile before it cooled enough.  Ill be interested to read the responses from those more knowledgeable than I.

[colby]

It doesn't matter what cheese I make the whey goes sour.
On the day of make it is nice and sweet and it is placed in the fridge till the next day.
It is then frozen.

[bansidhe]

Im confused.  I thought you said it was never a problem before..  which suggests to me that you have refrigerated whey before and were able to make the ricotta.

But now you are saying the whey always goes sour...

I do know when one makes ricotta it is best to do it immediately after draining the cheese before there is too much acid development.
The bacteria in the whey will continue to work until it is stopped by high heat or adding salt.  If your whey is sour the next day, then your bacteria had a field day and ate up all the lactose in the whey converting it to lactic acid. (I think that's how it works..)

[mikekchar]

If I understand what you are saying, this is a pretty common occurrence with working with natural cultures.  You do something one way for a long time, getting a specific result and then one day it starts doing something else each time.  The reason is that by doing the same thing each time, you are slowly building up the bacteria that can exploit that circumstance.

In fact, it's a bit like Covid (I hope you don't mind me using that example).  Here in Japan, things have been relatively stable since the beginning of the troubles.  People wash their hands a lot, wear masks *all the time*, avoid talking in public, etc, etc.  And so we were gliding along only getting a few hundred cases a day, on average.  If the numbers went up, then we added some extra restrictions and the numbers went down.  A few months ago, the delta variant showed up, but it made very little difference for a long time.  Suddenly, in  a period of a month, we went from between 10K and 20K active cases to 200K active cases.  Adding extra restrictions don't seem to make any difference.  What happened?  We didn't change *anything*.  Things were fine, before.  Why aren't they fine now?

And that's exactly what happens.  You're trucking along with your technique and everything seems totally fine.  But in the background, you are getting a "house infection" that's very, very, very slowly building up.  As soon as it gets to a critical size, it just explodes.  Because your previous technique didn't deal with it earlier, it still doesn't deal with it now.   It's the exponential growth that catches us out.  It has the pattern of nothing, nothing, nothing, basically nothing, still basically nothing, OMFG WTH HAPPENED!!??

My advice is that before you store your whey, bring it up to 63 C to thermise it.  Then store it in the fridge.  If it's going sour in 24 hours in the fridge, then it's a cold loving bacteria, but I'm assuming that if your normal milk in the fridge isn't going off that you're picking it up from outside the fridge.   Just keep changing your technique until it stops happening... and hope that you don't just breed up another super bug ;-)

[bansidhe]

great advice!

[colby]

Thanks for the replies.

Im confused.  I thought you said it was never a problem before..  which suggests to me that you have refrigerated whey before and were able to make the ricotta.

But now you are saying the whey always goes sour...

I do know when one makes ricotta it is best to do it immediately after draining the cheese before there is too much acid development.
The bacteria in the whey will continue to work until it is stopped by high heat or adding salt.  If your whey is sour the next day, then your bacteria had a field day and ate up all the lactose in the whey converting it to lactic acid. (I think that's how it works..)

Sorry for any confusion.
Up until a few months ago, there was never any problem with my whey. I made the cheese and stored it in the fridge. Always did this and never had a problem. Ever.
It has only been recently that I am getting this sour whey problem.
The only change I have made is going to mother cultures. Maybe this has exacerbated the process. I don't know.

The whey is usually taken early in the process when washing the curds. Temps are usually about 38-45 C and pH is usually around 6.5-ish.
I will take pH readings of the whey during various stages after storage in the fridge. It should give me some more data as to what's happening.

Can you recommend a level of salt addition to the whey?

I am meticulous when it comes to sanitizing the work area, utensils and my hands.

I will try mikekchar's suggestion of thermizing the whey to 63 C. It will make for an interesting experiment.

Thanks again for the replies. 

[bansidhe]

oooh do take ph readings for your whey. That would be very interesting!