Rennet Curd Setting Times: Flocculation Technique

[makkonen]

I'm fascinated and a bit daunted by this flocculation point talk. As someone who is far too laissez-faire with his curd cutting and curd healing times, I'd really love to have a better sense of how this factors into the process.

I assume flocculation and set times (and thus, the multiplier) are determined primarily by pH, and secondarily by rennet strength. Is there anything that goes into this determination that can't be controlled by tightly monitoring pH ranges? I can imagine that further development of the curd before it starts to expel whey leads to changes in texture and moisture content -- I just don't know how, or to what extent.

Cutting the multiplier in half if the wheels can't hold their shape -- this really turns me upside down. OK, working through it, I'm guessing this means that waiting longer to cut leads to less whey expulsion at equivalent pH, and thus a higher moisture, softer curd (which then is more likely to sag and fall apart). Maybe I've answered my own question here. But any other insights would be much appreciated.

[linuxboy]

Hi Mako. I'll try and shed some light on the flocculation question, but it is rather technical. In a sense, you're right that pH and amount of rennet affects it, but that is just part of the story. I'll try to demystify it.

First of all, recall that curds form due to chymosin action in two stages. The first stage is when chymosin (and other enzymes in rennet) cleave the k-casein on the micelles to expose available calcium ions. The second stage is when the calcium ions connect the micelles into large strands to form a lattice which can trap the fat, water, solids, etc.

The point of flocculation is when somewhere around 75% of the micelles have been cleaved through enzymatic action. The key factors that determine cleaving are the same as with other enzymes, specifically: ionic concentrations, pH, and temperature.  That is why it is vital to use a flocculation multiplier. Milk varies through the year based on lactation cycle, time of year, type of feed, stress, etc.

The time you let the curd set based on the multiplier determines several things, most important of which is rate of whey expulsion. Simply put, the lattice that forms after micelles connect retains water, and the longer you wait, the slower the curd will let go of the water from the lattice. The curd size also influences the rate. That's why for brie, you use twice the multiplier as for a hard cheese like cheddar and also cut the curd into very large strips. You did answer your own question

I really love the European method of using flocculation time. Here's one more trick to tell flocculation point. Take an empty bowl that floats, sanitize it, and float it on top of your milk after renneting. Then spin the bowl. At first, it will spin easily. At the flocculation point, it should barely spin or not spin at all because there will be a lattice matrix formed, and in its early stage.

[FRANCOIS]

In simpler terms floculation is the point of surface gelling in the milk.  The spinning bowl is a good method and is how we do it.  Floculation is not necessary related to a cetain pH or rennet amount as other variables effect the floc time.  In most hard/semi-hard recipes floculation occurs in 10-12 minutes unless there is something off in your milk, which does happen if you are using raw milk. 

The longer you wait the more whey is loosly bound in the curd, think chevre/creme fresh/brie etc. which have very long set times between rennet and cut.  It's not quite the same  process becasue you are adding much less rennet to those but the principle is the same. 

Floculation is better method than clean-break for two reasons:
1.  Clean break is imprescise since curd will give a clean break at 1 hr, 2 hr, 3hr....
2. Measuring the floculation time and using a multiplier will help ensure you always have a consistent curd, no matter how your milk changes (within reason).  If somehting is off with the milk, it will show up with this method.

My two cents anyway...

[zenith1]

which brings up the next question, how is everyone determining the point of flocculation?

[linuxboy]

I use the spinning bowl technique. I also keep a log and plot trend lines for flocculation times during various times of the year. Helps me to estimate when flocculation should happen and then confirm visually.

[zenith1]

ok, I'm not familiar with the spinning bowl technique. How is that performed? I have tried the floating toothpick trick, but with little success.

[linuxboy]

Not sure how else to describe it beyond what I already said.

Take an empty bowl that floats, sanitize it, and float it on top of your milk after renneting. Then spin the bowl. At first, it will spin easily. At the flocculation point, it should barely spin or not spin at all because there will be a lattice matrix formed, and in its early stage.

Don't try and spin it at 1,000 RPM or anything, just put the bowl in and nudge the edge to send it in a spin. If you nudge and it doesn't go, then the liquid has thickened. It's easier to understand if you try it a few times; makes more sense when you can see the change between easy spin and no spin.

[DeejayDebi]

I like it! I have never heard of the spinning bowl trick or if I did I forgot. That happens a lot these days. Thanks!

[zenith1]

and I agree with Debi, I now use this method and it works very well,thanks again.

[DeejayDebi]

I tried it tonight it works. Pretty neat! Thanks!

[Sailor Con Queso]

linuxboy taught me to use floc multiplier a couple of weeks ago, and it has REALLY changed my approach to timing. I am finding that some recipes are WAY off on the desired set time.

For example, last weekend I made a Monterey Jack. The reciped called for 30 minutes set time after rennet or a "clean break"... yada, yada, yada. My floc time was 15 minutes. Using a multiplier of 3 added 45 minutes, so the total set time before cutting curds was 60 minutes - TWICE what the recipe called for.

In fairness to the recipe, I am using a little less rennet to avoid bitter tastes, so my floc times are a little longer. Even so, the recipe was way off.

[DeejayDebi]

You'll also notice the floc times differ somewhat with different types of cheese. The multipler will change. I have a chart I look for it tomorrow. I think it's also in the farmstead cheese book.

[FRANCOIS]

The higher the multiplier, the more free moisture is bound and the softer the curd.  For example, romano has a 1x multiplier while brie has a 6x multiplier, generally.  These are just guidelines and can be explored/pushed.

[linuxboy]

One other variable we should keep in mind is the healing time. This is the period of rest from when you cut the curd to when you start heating and stirring it. If you heat right away and stir, syneresis begins earlier and the curd starts letting go of water, fat, and some solids. The end result is a lower fat and lower moisture cheese. On the other hand, if you wait 5-15 mins,  the individual curd pieces have a chance to firm up a bit more, and retain fat a bit better. You can use this in conjunction with the flocculation multiplier to get a cheese profile.

I don't have a good way to measure how long to wait to heal the curd. It seems to depend on the vat size. In general, I use 5-10 mins for smaller batches, and 5-15 mins for doing large vats.

And as Paul Kinstedt writes in American Farmstead Cheese, the size of the curds (1/8"-1") is another variable used with flocculation to create a cheese with a certain profile. The larger the curd, the more moisture it retains. Taking Francois' example, brie uses around 1" curds, or just ladled curd, whereas romano or parmesan is more like 1/8", around the size of a rice grain.

[FRANCOIS]

yup, you are right.  I used to ladle the brie curd.  For romano, I used a giant wisk.  In our plant, we heal 5 min (so the recipes say).  We did a trial vat this morning of a new cheese and I was blown away when the cheesemaker asked me why we were waiting before stirring....ummm healing?  I prefer 15 minutes myself.  Some recipes call for scalding the curd instead of healing.  We do one with a scals, can't recall which one, but it does stand out in my mind as odd.