My third attempt at Mozz (using fresh goat milk), I abandoned the 30 min. recipe and used the Old World Traditional. At last I got Stretch! This batch turned out better, but is still slightly rubbery and squeaky on the teeth. Why is this?
Also, what is the purpose of stretching anyway? To expel milk? The books don't bother to explain quite why and I'm wondering if I'm stretching too much?
Tx in advance!
Quote from: lfrj on January 20, 2011, 08:26:58 AM
Also, what is the purpose of stretching anyway? To expel milk? The books don't bother to explain quite why and I'm wondering if I'm stretching too much?
The increase in acid levels either from adding an acid or working with a culture will make the calcium bonds weaker changing the curd structure. Then with heat the weaker curd will transform in the stretching mass of cheese typical of mozzarella. The stretch is important to develop that unique texture and mouth-feel of mozzarella.
The stretch CAN be overdone and dry the cheese further. The squeak can be caused by cooking at higher temps or longer.
Quotebut is still slightly rubbery and squeaky on the teeth. Why is this?
Like Jim said, it is about the calcium bonds both inside the micelles (casein-casein bonds), and among the micelles (also casein-casein bonds). Acid degrades those bonds, making the curd structure more likely to plasticize. Heat decreases the threshold required for all of those broken bonds to completely let go of their surrounding caseins and reform again with other caseins. When this happens, it orients the strands away from a blob into long, thin "fibers".
The squeakyness, both the sound and the mouthfeel are caused (again) by the calcium bonds. When those calcium bonds are broken, it causes a squeak when the temps exceed about 100F, and if the fat and moisture levels are low enough. If you took two hunks of curd, and one curd had high retained calcium (due to high pH at draining), and a high ph, it would squeak. And of one curd was drained at 6.0, and had a pH of 5.0-5.2, it would not squeak very much.
The cooking longer and at higher temps can contribute, but through very different mechanisms. One, longer, is through fat loss. And higher temps causes protein denaturation, making for a "stiff" kind of curd. This in my experience is less common of a cause than having suboptimal calcium levels.
QuoteAlso, what is the purpose of stretching anyway?
Purpose of heating is to decrease the energy required to break the bonds. Stretching is about orienting the strands.
To get the right mozz, the soft kind that you're looking for, go back and read through the many threads here that talk about tips and tricks. Lots of useful help :)
Quote from: linuxboy on February 28, 2011, 05:43:44 PM
QuotePurpose of heating is to decrease the energy required to break the bonds. Stretching is about orienting the strands.
I am also looking for the holy grail of moist mozzarella. No luck. Still squeaky but I have identfied some of my probs through other posts.
But I still have questions in my mind about this stretching thing. How does 'orienting the strands translate into taste/ texture. My mozzarella tonight was reaaaaaly stretchy. I could stretch 3-4 feet. But maybe that is not good. Temp got to 111F. Maybe I overheated it. But most importantly, how do I know when I'm done stretching? What is my endpoint? I started feeling like I shouldn't be 'working it so much'. I have in my head that when you do that with bread it can get 'tough' and I think I may worry about 'over-working' my cheese too. But I have no basis for this. Or should I keep stretching until it just won't stretch much anymore?
Susan
Someone told me to look for the appearance of the cheese surface to change and that is an indication of when to quit stretching. It is really easy to overstretch .
Minimal is key. You stretch only enough to homogenize the consistency and to be able to shape it in the form you want. This can be done in as little as one stretch to 2-3 feet when the curd temp and acidity are right, and then bringing the mass together to shape it. As soon as the strands orient into long links, the surface will become shiny and smooth.
Got it. I know exactly what you mean. I've had some mozzarella I had to keep stretching to 'get the lumps out' and get it all smooth. Others are smooth almost immediately. I have been over stretching those. Might have to make one tonight the try stretching less.
Susan