Letter to the Editor: On “Why Fresh Cheese Curds Squeak” (Summer issue, 2011)
As seen in our summer 2011 issue:
"In Wisconsin, store-bought cheese curds (a.k.a. “squeaky cheese”) are a beer’s best friend. Locals hardly ever have one without the other. In honor of this regional pairing, just right for summer, here are a few facts about the squeaky specialty:
These fresh-from-the-vat mild cheddar morsels (each about the size of an unshelled peanut) are created immediately after the whey is drained during cheesemaking but before the curds are pressed and aged. Freshness is essential for the oddly shaped chunks of chewy cheese to have an actual squeak when bitten into because the sound is created by air trapped in the curds.
Quality milk, careful handling, and immediate consumption are three essential factors for enjoying top-notch cheese curds. While curds can last for weeks, the squeak and flavor are supreme in the first few days, making squeaky cheese a popular farmers’ market staple (look for them deep fried, too). Or better yet, get them from a creamery, warm from the vat.
After twelve hours or so, curds lose their squeak, even if they’re refrigerated. But curds can be stored in the freezer, and a few seconds in the microwave brings back some of their squeak."
— Tim Newcomb
Before getting to my complaints surrounding the piece "Noisy Noshing, Why Fresh Cheese Curds Squeak” [Summer issue, 2011], I would like to say that I love this magazine and am glad to have had the opportunity to meet, speak, and enjoy Kate Arding's company while working at Jasper Hill 2 years ago.
Not sure where Tim Newcomb sourced his information on "Why Fresh Cheese Curds Squeak", but as a lifelong squeaky cheese eater, and an employee of a Wisconsin creamery that converts over 130,000 lbs of milk a day into a variety of natural and flavored added curds and cheeses, some pretty vital information was missing, or just not accurate.
First, these fresh-from-the-vat mild cheddar morsels are not simply created by draining the vat of it's whey. There are two distinct styles of "Cheddar:" stirred curd and milled curd. If you simply drained the vat of it's whey you would have small to very small pieces of curd, regardless of the style of cheddar you are making. To attain the "size of an unshelled peanut" you would need to ditch the curd and drain the whey. Then proceed to cut the ditched curd mass into slabs and stack them. This process is called "CHEDDARING." After multiple flips, and re-stacking of the curd mass in order to expel inter-granular whey and promote continued acidity development, the slabs are "Milled" into the unshelled peanut shape, and are then salted to enhance flavor and slow the acidity being produced by the lactic acid bacteria.
The squeak affect requires fresh curds, but is not a result of air being trapped inside the curds. I have asked fellow cheesemakers, master cheesemakers, food scienctists at both UW Madison Babcock Institute and Minnesota State University, and the glorious inter-web about the squeakiness of cheese curds, and the only source declaring that the squeak is a result of "air being trapped in the curds" is Wikipedia, where the actual listed source for "air being trapped in curds" was simply a quote taken by Ryon List, reporting for the Ludington Daily News, from a Michigan cheesemaker Judy Hoskins, in 2002.
Not to knock Judy, but if the squeak is a result of air trapped in the curds, how does it escape causing them to "lose" their squeaky qualities? How do you get air to become trapped back inside the curds by microwaving them? Confused by those simple questions as much as I am?
The answer is in the proteins.
All "Curds" are a semisolid network of casein protein and milk fat trapped within a gelatinized protein matrix. Calcium increases the solidity of how the proteins interact and form the gel network. Rennet is an enzymatic protein in ruminate stomachs and some vegetal plants. It binds casein and hydrolyzes, (the chemical reaction in which the splitting of a molecule is divide into parts by addition of a water molecule e.g. whey/water) cleaving the casein into smaller pieces. Essentially rennet removes the negative charge from some proteins leaving the rest of the casein protein to form an amalgam of micelles and form an intricate and long matrix of gelatinized proteins, a coagulum. Once the gelled milk is cut it becomes curds.
This matrix or network of long intricately coagulated proteins is what makes the "squeak" when you eat fresh cheese curds. It is the long protein strands rubbing against the enamel of your teeth. If there was air trapped in the curds, most of it would be released during cheddaring.
The reasons the curds lose this squeakiness after time are: they are salted, hooped, and pressed, (once they have reached the right acidity point) thus expelling additional moisture (whey) and compressing the long protein strands into a more tightly compacted matrix; or if they are left unpressed the inter-granular acidity continues to drop in pH. A low pH begins to denature or break down long proteins into smaller and less stable compounds, causing them to lose their strength and their squeak against your teeth.
The reason microwaving helps reinvigorate some of the squeakiness is that the heat starts to alter the amount of moisture trapped inside the curds and creates another bout of hydrolysis, dropping more negatively charged hydrogen ions from casein proteins while they bind to the internal heating water. If you heat too long you will completely convert and drop all the negative charges, and "melting" occurs. More heat will start a maillard reaction with the remaining milk sugar (lactose), and begin to either caramelize or burn the sugar once the water has evaporated.
I realize that my answer in probably too scientific and over the heads of many folks, but sharing the correct information is necessary, especially when speaking on the thing I have more passion and devotion to than anything else. I will work on altering the Wikipedia, but I could not forgo emailing you about the first real error I've found in the pages of your magazine.
To me Noisy Noshing should have explained how we really get to the curd shape pictured in the article, and the explanation should have followed these lines:
Freshness is essential for the oddly shaped chunks of chewy cheese to have an actual squeak when bitten into, because the sound is created by elongated protein strands rubbing against the enamel of your teeth.
Thanks for your time and you efforts towards AMERICAN CHEESE!
Cheers & Cheese!
Blair C Johnson