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Hi

I have noticed that my PH will rise slightly after I introduce culture in my milk.  I check the PH immediately before adding culture and then 10 minutes later and the PH has gone up approx .5.  PH meter is calibrated and is accurate.  Because of the slight rise, it takes me a little longer to get a .1 drop in PH before I can add my rennet.

I only use raw milk.

Has anyone seen this before?

Thanks

What is the milk pH at the start before adding the culture?

Hi

About 6.6 to 6.7

This batch was at 6.63.  Last weeks it was at 6.68.  It does remain constant within each batch

And you measured that after the milk was brought to temperature but before the culture?

That's just where the milk should be.  I take your first post as saying the pH rises about 0.10 after adding the culture.  A pH reading is temperature dependent so a comparison reading should take place at culture adding temperature right before adding the culture and then say 5 minutes after adding (and stirring).  I've not done it this way as I check the milk pH at about 50F and then don't look at it until towards the end of the ripening period when it has dropped only about 0.05-0.10.  Then I add the rennet at the time stated in the recipe, do the floc test, cut the curd and do the heating and stirring and then check the pH of the whey before draining.  Some recipes call for stirring to a certain pH goal and that is the first really important pH check other than the initial milk pH in my mind.

ok.  I will not test so close to the culture addition.

I don't think I have a pathogen problem because the milk does not raise in PH when sitting at room temperature for several hours.  Once the PH begins to drop it drops to all targets I need it to go to.

Now, let's say I have a pathogen?.  How would I know?.  I have not eaten any of the cheese, although I tasted the curds in each batch and I am still alive

Guess I could run a test after pasteurization which I will do for my cream cheese I am starting tonight  

Thanks

Does your wife/mother/daughter/significant other, et al. have a pesky cat you'd like to get rid of?   

lol.  Death by bad cheese.  It will put "the burning bed" to shame

Has anyone else seen what I am describing?

I usually measure the pH when the milk is close to the temp I want for ripening, then add the starter. The only time I have seen it go up, the pH meter needed cleaning from the fat in the milk. So I swished it in warm soapy water, rinsed it well, patted dry and re-checked against my calibration solutions. Then rechecking the ripened milk it was as expected to be, a little lower than my initial pre-ripening measurement.

Mystery solved.  What was causing my PH to appear to go up was my induction stove.  The magnetic coils where throwing my readings off.  I need to remember to turn the stove off when I am reading PH.

I have a PH meter the Extech PH100 which can be used directly in the milk.  Everything is cool.  No pathogens here...lol

Susan, you bring up an interesting point:  Whenever the data doesn't look right check the equipment.  This is a practical application to what is known as Occam's Razor:  Whenever there are competing explanations for some scientific observation the simplest one is most often the correct one.  I saw this yesterday in my large vat Caerphilly (https://cheeseforum.org/forum/index.php/topic,14584.msg110895.html#new).  I calibrated the pH meter at 7.0 and 4.0 set the tip in a little distilled water for about 30 minutes before I checked the milk.  I read the pH three times at 6.49, 6.5 and 6.52.  Milk should come in at about 6.65 to 6.72.  Like you, I washed the tip with some warm water and checked again.  Sure enough 6.69 three times.  My guess is that somewhere between the calibration and the first milk check a little piece of dried cheese swelled up and coated one of the electrodes.   

In johnr's case it was interference with the induction stove.  Who'da guessed?