Acidity decrease after rennet addition

[NimbinValley]

Hi all.

I have recently started measuring acidity during cheesemaking using titration equipment.

I have noticed that the acidity level decreases after I add rennet, then starts the slow increase again as the make progresses.

Does anyone know what accounts for the initial dramatic drop in the acidity level after addition of rennet?

Cheers.  NV.

[linuxboy]

What are the TA numbers?

[NimbinValley]

This morning it started at 19% (pH 6.54) then dropped to 14% (6.57) after 2hrs.

Cow milk - it is 48hrs old. The TA of 19% is a bit higher than usual so I guess this is a reflection of the age.

NV.

[linuxboy]

after addition of rennet?

How much after? Immediate? after gellation? after cutting? Because whey TA is not milk TA. If you're measuring TA of the gel, after it has formed, it will be tough. More so, you're measuring some middle ground between gel and whey, and casein has huge buffering capacity, whereas whey does not.

[NimbinValley]

The initial reading was milk after pasteurisation.

The second reading was about 10mins after cut, after sufficient whey had drained from the curd to take a samlple.

All up about 90mins after addition of the culture and 45mins after renneting.

So I guess that is what I am asking - why is whey TA different to Milk TA?

NV

[linuxboy]

Think about what TA measures. Basically, it is the titratable H+ ions. And what has more of those, the H+ associated with casein (and to a smaller part other proteins), or whey and all its small amounts of salts, proteins, etc? Casein has a ton more. So, when you titrate, the whey will be rather dramatically lower. You can sometimes go .2 at gel cutting, and .12 in whey. Doesn't mean acid development has stopped or changed. You're just measuring different things. It's also why generally pH is easier, though the meters can be a PITA.