Monthly Archives: August 2014

Cheese Notes

book coverAt the beginning of summer, I reviewed a book called The Science of Cheese for American Scientist Magazine. Last week, with summer winding down, the review was published [1] in the midst of a spate of cheese-related activity in my life: I received an invitation to the christening of a local cheese cave [2], I registered for a raw milk cheese tasting class, and my all-time favorite cheese, aged gouda, went on sale.

Reading The Science of Cheese made me consider the range of products that pass for cheese. To some, cheese means a fat quesadilla oozing with melted cheddar jack. To my aunt, cheese is a mail-order box lined with freezer packs from Murray’s in New York City. My cheese history starts with slices of American (which I still love) and progresses to my beloved aged gouda.

cheese-maker at work

Mary Turner, former cheese-maker at Celebrity Dairy in Siler City, NC, pours pasteurized goat milk into the cheese-making vat.

North Carolina has a growing number of cheese-makers. I’ve visited dairy farms and cheese houses, so I know for sure that some cheese is made in small batches and monitored daily by actual people. But there are missing connections. If a cheese comes all the way from France, and it’s sold regularly in the fancy cheese case at my market, surely it’s being produced in bigger batches and sold elsewhere, right? Can good cheese be made in bigger batches? Where are the lines drawn?

So when I picked up The Science of Cheese, I hoped to read about the quaint cheese-making ventures that somehow keep us all well-stocked. I also hoped to learn about massive cheese-making facilities and how they make the dull bricks that pass as cheese in mainstream supermarkets. The book fell open to the back flap; the author looked a lot like my p-chem professor, and his bio described him as “creating new dairy products” and “expanding marketability.”

cheese costume

I actually dressed as cheese one Halloween. The costume had formerly been a book for a Harry Potter release party.

I recoiled in horror; this didn’t sound like my kind of cheese! Then followed an anguished evening of wondering how to reconcile my art half and my science half with thoughts like, “Science is the truth! But I’m swayed by the appealing nature of the phony pastoral setting! I’m a terrible scientist!” and even “Maybe cheese is a metaphor for me: part art and part science….” But anyway, I eventually started reading.

Although The Science of Cheese was informative and entertaining, it didn’t provide the answers I craved. As described in my review, I found a brief description of how tasteless, made-in-America cheese has had its fat and protein replaced with water and its aging time reduced (to save money). But I still lacked a big picture understanding.

Then I went to cheese class.

cheese class

Tyler’s photo of our cheeses at the start of class.

The class was led by Ashley Morton and Tyler Morgan, who recently flew to California to take the American Cheese Society’s Certified Cheese Professional Exam. [3] They had prepared plates for each student with eight wedges of cheese on each, and they described each as we ate it. Here are some of the things I learned:

        • The sources of the microflora that affect raw milk cheese are the milk itself, the added starter culture, and the environment. When milk is pasteurized (heated), the milk microflora are lost.
        • When milk is pasteurized, the proteins denature, which results in a more pliant cheese that is harder to crumble or break. (Tyler used the word plasticky, for lack of a better word, but plastic has a science-y meaning of “the opposite of elastic.”)
        • The properties of a raw milk cheese vary more than those of cheeses made with pasteurized milk. An artisan cheese-maker enjoys this inconsistency and monitors the cheeses daily, but in a larger production facility, consistency is important.
        • The Kinsman Ridge cheese that we tasted had a white color because it was made with milk from April, when the cows (in Jasper Hill, VT) had not been on pasture all winter. The milk from the summertime produces a yellower cheese. This is true of cow’s milk but not of sheep or goat milk because those animals can process the beta carotene that causes the color.
        • The rind that forms on raw milk cheese varies depending on where the cheese is aged because of different microflora in the air. This is an example of terroir, the characteristics brought to cheese by its environment. In The Science of Cheese, the author describes terroir as a disputed concept that some scientists say has only negligible effects; I wondered how they might explain the different rinds.
aged gouda

My beloved aged gouda.

      • There was a question about the crystals sometimes found in cheese. According to the Internet, these crystals can be calcium lactate that crystallizes out of solution as the cheese dries out. They can also be amino acid crystals that form as the casein proteins unravel during aging. (Incidentally, I also discovered that these crystals stimulate stuff that leads to happiness. [4] No wonder I like that aged gouda so much!)
      • Herve Mons is a famous affineur in France who ages 200 types of cheese in cheese caves built inside an abandoned train tunnel. (You can see a slideshow of the tunnel here, and it’s not nearly as dank and creepy as you’d expect. [5]) Some farmers age their own cheeses, but some make the cheese and sell it to an affineur. The farmer makes less money but doesn’t have to spend time on the aging process or take the inherent risks.
      • The blue in blue cheese forms when the cheese is pierced to let in oxygen, which enables the blue mold to grow. The sizes and locations of the blue spots can therefore be controlled.
      • Blue cheeses that are “naturally fused” end up very crumbly, whereas blue cheeses that are pressed end up with more of a creamy texture.

Tyler took a moment to share his thoughts on the FDA’s aggressive stance towards raw milk cheeses. In June, an FDA inspector cited some cheese-makers for aging on wooden boards, saying the boards could not be properly sanitized according to FDA specifications. [6] The cheese-making community responded, and the FDA quickly put out a statement that said (I’m paraphrasing) “Oh, no, no, we didn’t mean that!” [7] Now, the FDA has lowered the acceptable level of E. coli in cheese from 10,000 to 10, in spite of the fact that many strains of E. coli are nonpathogenic and are in fact a healthy part of the microflora of the gut. It seems the FDA is not using actual science to make safety rules.

At this point, I was filled with cheese and beer and was dying to say something about the Cheese Nun, but I couldn’t remember her story well enough. What I remembered was that when traditional cheese-making at a cloister in Connecticut came under fire by government regulators, one of the sisters went to university to receive a doctorate in microbiology so that she could properly defend cheese-making at the cloister. Upon googling, I now remember that she did an experiment for inspectors in which she added E. coli to batches of cheese in wooden and stainless steel vats. (The inspectors had been upset by the use of wood.) The wooden vat ended up with no E. coli, whereas the cheese in the sterile stainless steel vat was filled. The nun, Sister Noella Marcellino, was the subject of a PBS documentary and was included in Michael Pollan’s book Cooked.

Cheese class was wrapping up, and I felt clearer on the whole state of cheese. It’s not an A or B situation but a wide range of possibilities, from farmers who make their own to cheese-makers who buy local milk, to affineurs who age the cheese of others, to larger batches of cheese that are kept consistent, all the way down to Easy Cheese and Cheez Whiz. Tyler not only sent me a photo from class but graciously gave me another book to read: Cheese and Culture by Paul S. Kindstedt, which is sure to lend more insight.

hillsborough cheese

Three stages of a batch of cheese at Hillsborough Cheese Company, Hillsborough, NC.

[1] Buehler, Emily. ”The Cheese Plate Stands Alone,” American Scientist, Sept-Oct 2014.

[2] A slideshow of the construction of the cheese cave at Piemonte Farm in Burlington, NC.

[3] About the ACS CCP exam.

[4] “Why Aged Cheeses Are Crunchy—And Why They Make You Happy.” Savenor’s. March 11, 2013.

[5] Slideshow of Herve Mons’s train tunnel.

[6] I think this is the inspector’s statement; I couldn’t find a version on the FDA website: And this is the code to which she refers, Code of Federal Regulations Title 21, section 110.40(a):

[7] “Clarification on Using Wood Shelving in Artisanal Cheesemaking.” CFSAN Constituent Update. June 11, 2014.

Notes from “The Science of Yeast” Talk

Last April at the Asheville Bread Festival, I heard Dominique Homo from LaSaffre talk on “The Science of Yeast.” I’ve meant to type up my notes ever since, so here they are.

yeast under microscope

Baker’s yeast under a microscope (100× objective, 15× eyepiece; numbered ticks are 11 µm apart). By Bob Blaylock, via Wikimedia Commons.

First off, I was embarrassingly late to the talk because of my own class. I arrived during a description of the yeast budding process, which occurs every 20 minutes under controlled conditions including a temperature of 28° (I assume °C) and regulated pH and air flow. Note that this temperature works well for growing yeast but is too high for dough.

Others points of interest on growing yeast:

  • Traditionally, molasses was used as the platform on which yeast was grown. But the sugar industry has become more developed in America; there is now only about 45% of sugar left in molasses, as opposed to 60% in Cuba. (I don’t know if he meant that 45% of the total sugar remains or that 45% of the molasses is sugar.) Therefore, corn syrup is now used.
  • The yeast-growing process starts with yeast from a yeast bank that is sent frozen by mail. It is grown on pure glucose for three days in a sterile environment. Then it goes into a tank. What starts as less than a gram of yeast becomes about 250 tons in 10 days.
  • Dominique said something interesting about periodically “removing the new yeast” to “control mutations,” but I didn’t catch it. I think he meant that they want as much of the yeast as possible to come from reproduction of the original, pure yeast cells. If a mutation does occur, it will propagate (kind of like when you play Telephone), so removing newer yeast cells reduces the chances of that occurring. This also means a reduction in yeast production, but maybe 250 tons is plenty.

Next, Dominique spoke about the types of yeast. There were a few kinds I had never heard of. Here’s a table:

A table from Dominique's talk


    • Cream yeast. This is 80% water and 20% yeast. It is used by large bakeries (25,000 lbs/week!) and is delivered to the bakeries in tanker trucks. Yikes.
fresh yeast

Fresh yeast. By Hellahulla, via Wikimedia Commons.

    • Crumbled yeast. This is fresh yeast that is crumbled and packaged in 50 lb bags for medium-sized bakeries.
    • Compressed yeast. A.k.a. fresh yeast, this comes in one pound blocks and is used by medium- and small-sized bakeries. It is often two to three weeks old by the time it arrives, so you should only use it if you can use it up quickly.
    • Active dry yeast. This is a dried-out version of yeast that has a much longer shelf-life. Supposedly, it must be activated before use (more on this below). It is used by small bakeries, artisan bakeries, and home bakers. Some of the yeast cells are dead. This can affect dough in ways that some prefer and some don’t; more on this below.
dry yeast

Dry yeast. By Vanderdecken, via Wikimedia Commons.

  • Instant yeast. This is also a dried yeast used by small bakeries, artisan bakeries, and home bakers, but it does not need to be activated before adding to dough. Instant yeast is actually drier than active dry yeast! A different drying process is used that enables it to dry very quickly so that yeast cells are not killed: The yeast is made into very thin noodles with a yeast version of a spaghetti machine. The noodles exit the machine into blowing hot air, which dries them and causes them to break. (If you look closely at the yeast, it has a tubular shape.) The yeast is then vacuum-packed.
  • Deactivated yeast. This is dead yeast. Huh? Why would anyone add that to bread dough? The answer deserves a new paragraph.

Deactivated yeast is made by heating cream yeast on a hot plate until it is dead. It contributes no fermentation to the dough but “enhances the yeasty flavor profile.” It also provides “better machinability” by releasing a molecule (glutathione) that reacts with the protein in the dough. (It is a reducing reaction.) The reaction makes the dough less elastic and more extensible, which means you can mix it less. This yeast is often used in doughs that need to be stretched such as in pizza, croissants (which are folded repeatedly as layers of butter are added—the dead yeast reduces the time needed for the dough to relax between folds), and puff pastry as well as for crackers (it enhances the cheesy flavor). It is also used when consistency is needed in a large number of loaves, for example, 5000 baguettes are being made per hour and each one needs to be 5 inches long, not 4.9. Similar effects are obtained with L-cysteine, but deactivated yeast looks “cleaner” in an ingredient list because it can be called “yeast.”

Some people like active dry yeast because it contains some dead yeast; it can produce a reduced version (ha ha, bad chemistry pun) of the effects of deactivated yeast.

Now we come to activating. Ah, activating! I had just told my class all about why to skip activating, so I cowered lower in my seat as Dominique espoused its necessity. Dominique said that it takes yeast a long time to get going in flour; it needs to rehydrate and dissolve. If the water needed by the recipe is too cold for the yeast, the yeast won’t work, and some of it will die, resulting in a slow fermentation. The yeast needs to be rehydrated with 100 to 110° water (I assume °F).

The reason I don’t like activating, aside from it being a slight pain, is that you need to use some water, which you must subtract from your recipe. With students who aren’t experienced with recipes, this can cause confusion; and if the recipe is not adjusted, the hydration becomes off and the dough is too wet. I always tell students to mix the yeast into their flour, which will protect it if cold water is used. (Incidentally, the way I came to this practice was that I was doing it with “instant yeast” that turned out to be mislabeled active dry yeast, and I never had a problem.)

But I wouldn’t presume to contradict the yeast expert. Now it occurred to me, however, that I always use an autolease when I make bread and teach classes. Maybe this rest period gives the yeast a chance to activate before kneading begins, and this is why I’ve never had a problem.

Dominique compared LeSaffre’s gold and red yeasts. (The names refer to the package colors.) The gold is osmotolerant yeast, which is designed to work with doughs that use more than 5% sugar. Why this works deserves its own blog post, so I’ll get right on that. (Update: Read it here.) Dominique also mentioned that the gold yeast works better with low hydration doughs and produces a more evenly browned crust, whereas the red yeast results in more burn spots on bread. I’m not sure why this happens, but I will post about it if I ever learn more.

Dominique concluded by remarking that people often blame the yeast for problems with their bread-making even while using improper procedures and taking short-cuts. The yeast is rarely at fault! For example, he consulted with a bakery at a grocery store that was not getting good rise and discovered that they were baking everything (not just pastries but breads) at a low temperature of 350° to make it easy on their staff.

Other notes I scribbled down, with no further explanation:

  • You can spike sourdough with up to 0.1% yeast and it won’t affect the flavor.
  • Hard water affects yeast.
  • Chlorine in water slows yeast.
  • Do not use distilled water to make bread.
  • Citric acid is really bad.
yeast sketch

A 1680 sketch of yeast by Anton van Leeuwenhoek, via Wikimedia Commons.