Cultivation of a Cheesemonger

A Blog of Cheese Culture and Cultures


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You Are What You Eat

I was looking up information about probiotic diets one afternoon when I came upon the Wikipedia page for Skin Flora and an image on the page caught my eye.  It was an image of a man and the types of bacteria that grow on skin on different parts of the body.  One of the types of bacteria was familiar — it was the same type we put in the milk to make our washed rind, Tobasi!

Corynebacteriae. It’s in the crevice of your nose, in your groin (inguinal crease), your belly button (umbilicus), and your “toe web space.” It’s also what contributes to the beige-red color (Law, Tamime) of the rind of washed rind or smear-ripened cheeses.

Screen shot 2014-07-28 at 11.26.08 PM

Image from Get Culture

Tobasi

Image by Mia Vergari, Cricket Creek Farm

SkinFlorawArrows

Image by Darryl Leja, NHGRI

 

While in utero, a human fetus is sterile. It is not until the mother’s water breaks and the baby is being pushed through the birth canal that bacteria is introduced to the baby’s skin.  Later, handling and feeding the newborn will contribute to the bacterial population and while we’ve established most of our bacteria in the first 48 hours of our life, our environment will continue to shape us.

Smear-ripened cheese requires a lot of different kinds of microbes for flavor, color, and rind and paste development. (gooey texture? caused by microbes!)  Microbes are purposefully added to the milk during the cheesemaking process and/or colonize the cheese from ambient air.  You may call cheesemakers the mothers of the cheeses we make 🙂

Due to lactic acid in sweat and produced by skin bacteria, superficial layers of the skin are naturally acidic (pH 4-4.5) .  At this pH mutualistic flora such as Staphylococci, Micrococci, Corynebacterium and Propionibacteria grow (Lambers et al.) (Some of you turophiles may find that last one familiar as well). This is about the same pH that we want our Tobasi, our washed-rind cheese, to be when it is ready to be put in the aging room to begin rind development so the rind is hospitable to grow the desired bacteria.

But no, they are not the same bacteria. Same genus, different species.
According to one study done on dogs, (who seem to have similar corynebacteria species as humans) skin harbors Corynebacterium humireducens, Corynebacterium diphtheriae, Corynebacterium pseudotuberculosis and Corynebacterium ulcerans. (Frischmann et al.) and Corynebacterum Casei grows on cheese.  How closely related are they? Check out the phylogenetic tree below —

PhylogeneticTreewAnnotes

(Image by Djossou et al., colored additions by Mia Vergari)

 

When selling cheese people inevitably ask me what the rind is made of and if can they eat it – a valid question and one that I delight in answering.  Upon hearing the answer many people cannot keep from wrinkling up their nose when they hear that the rind is bacteria (or mold).  But it’s all over you too, microbeface!

According to an article that a friend sent me about making cheese from the bacteria on human bodies, scientists found that  “about 25 percent of the fungi and 60 percent of the bacteria found in these microbial cheese communities were not those introduced by the cheesemakers to create the cheese.” – but where did these bacteria come from? (Fessenden)

“Some may have washed in with the salty brine used to age the cheese. Others were present in the milk itself. Still others may have come from the cheesemaker’s hands. Yup, eating “normal” cheese already includes microbes that live on humans.” ~ Christina Agapkis, microbiologist UCLA

It seems that you truly are what you eat!

 

Bibliography

Marissa Fessenden. How to Make Cheese Using the Microbes on your Feet. The Daily Dot. July 22, 2014  Last Accessed: 08/02/2014 http://www.dailydot.com/geek/foot-bacteria-cheese-project/

Kenneth Todar, pHD. The Normal Bacteria Flora of Humans (page 3). Todar’s Online Textbook of Bacteriology. 2008-2012 Last Accessed: 08/02/2014 http://www.textbookofbacteriology.net/normalflora_3.html

Djossou F, Bézian MC, Moynet D, Le Flèche-Matéos A, Malvy D. Corynebacterium mucifaciens in an immunocompetent patient with cavitary pneumonia. BMC Infect. Dis. (2010) Last Accessed: 08/02/2014  http://openi.nlm.nih.gov/detailedresult.php?img=3009641_1471-2334-10-355-3&req=4

Get Culture. Corynebacteria. (2012) Last Accessed: 08/02/2014 https://www.getculture.com/Corynebacteria/

H. Lambers, S. Piessens, A. Bloem, H. Pronk and P. Finkel. Natural skin surface pH is on average below 5, which is beneficial for its resident flora. International Journal of Cosmetic Science. Volume 28, Issue 5, pages 359–370, October 2006. Last Accessed: 08/02/2014 http://onlinelibrary.wiley.com/doi/10.1111/j.1467-2494.2006.00344.x/abstract;jsessionid=53C216F0A3096869D93068A3F8C3263B.f02t03

Darryl Leja. Skin Microbiome. National Human Genome Research Institute. Last Accessed 08/02/2014: http://www.genome.gov/dmd/img.cfm?node=Photos/Graphics&id=85320 

Barry A. Law, A. Y. Tamime eds. Technology of Cheesemaking 2nd ed. Wiley-Blackwell. Last Accessed 08/02/2014 http://books.google.com/books?id=Turm77IMxnUC&pg=RA1-PT156&lpg=RA1-PT156&dq=Corynebacteriae+cheese&source=bl&ots=r6xrF3gyp0&sig=9gfU0WI_lWT9-YzgiKN5GSEC5rE&hl=en&sa=X&ei=dBDUU5KPKZSyyASZv4DYBQ&ved=0CEgQ6AEwBw#v=onepage&q=Corynebacteriae&f=false

Patrick F. Fox, Paul L. H. McSweeney, Timothy M. Cogan, Timothy P. Guinee eds. Cheese: Chemistry, Physics, and Microbiology: General Aspects, 3 ed. Vol. 1. 2004 Elsiver. Last Accessed 08/02/2014: http://books.google.com/books?id=a95C5Nza5_EC&pg=PA197&lpg=PA197&dq=Corynebacteriae+cheese&source=bl&ots=dhTBgImeTz&sig=e34ORx1DYYP6ATlaA5Q6J5DXTl4&hl=en&sa=X&ei=dBDUU5KPKZSyyASZv4DYBQ&ved=0CEoQ6AEwCA#v=onepage&q=Corynebacterium&f=false

Frischmann A, Knoll A, Hilbert F, Zasada AA, Kämpfer P, Busse HJ. Corynebacterium epidermidicanis sp. nov., Isolated from Skin of a Dog. Int J Syst Evol Microbiol. 2012 Sep;62(Pt 9):2194-200. doi: 10.1099/ijs.0.036061-0. Epub 2011 Nov 11. Last Accessed 08/02/2014 http://www.ncbi.nlm.nih.gov/pubmed/22081710


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Food for Thought: Cheese as Model Microbial Ecosystem – The Research of Rachel Dutton

This past Tuesday, I attended a talk by Rachel Dutton, doctor and Bauer Fellow, at Princeton University entitled “Food for Thought: Cheese as Model Microbial Ecosystem.”  I was invited by my friend, Alan, whom I met in Florence this past summer and is attending Princeton for his master’s in synthetic organic chemistry (Hi, Alan!)

Unfortunately, I cannot give a summary of her talk because it was a presentation of data on a project that is not yet complete.  However, she was able to send me some really amazing photos of microbes on cheese.

microflora on Cabot Clothbound Cheddar

microflora on Cabot Clothbound Cheddar

What I can share is the work that Rachel Dutton has done up to now.

THE DUTTON LAB

Rachel’s lab is located at Harvard University, in the FAS Center for Systems Biology.  The goal of her research is to identify the mechanisms and principles through which microbial communities function.  Coming to an understanding of the formation, function, and evolution of microbial ecosystems is seen as one of the most important challenges facing microbiology.

Rachel has observed that  “microbes usually do not exist as individuals in nature, but as part of complex, multi-species communities, however, microbes have traditionally been studied as individuals in the laboratory.”

The Dutton lab “will apply a range of culture-dependent and independent methods to study the microbial diversity in the surface-associated communities that make up the rind, on identifying and characterizing inter-species interactions, and on developing an experimental model system to study microbial ecosystems.” (Bauer Fellows Profile)

In order to fully understand how microbes function within the context of the complex communities in which they exist outside of the laboratory, model systems are needed.  The lab found cheese rinds to serve as that model system.  The lab studies patterns in natural microbial cheese communities and then tests hypotheses in the lab with in vitro models of community formation with a mixture of dried cheese curd powder and agar. (The Dutton Lab Website)

CHEESE AS A MODEL SYSTEM

Microbes…

Determine the Flavors, Smells, and Textures

Rachel Dutton is attracted to cheese because of the simplified, experimentally tractable microbial ecosystems found growing on the surface and cheeses are ideal models to study the behavior of microbes in complex communities.  These communities, and their rich assembly of metabolic capacities, contribute much of the diversity in flavors, smells, and textures of the hundreds of different varieties of cheeses.  Camembert is covered entirely of microscopic organisms that contribute to the creation and consistancy of the paste, the unique flavors, and the familiar bloomy white rind.

Are Able to Communicate

The technical term for this community of organisms is ‘biofilm’ – a web of interconnected microbes that rely on each other to create their own environment.  Interestingly, biofilms are not just a large swath of microbes, but organized masses of organisms that have been proven to have communication capabilities. In a process called quorum sensing, individual cells constantly send out and measure chemical signals.  Through these chemical signals, if a bacterium or fungus can recognize enough of its own kind (or enough other species) in the area, the cells switch from acting as individuals to acting as part of a community of connected organisms.

Protect the cheese

With the addition of  strands of protein and sugars, the microbes weave themselves with these other molecules to become much tougher.  This toughness proves beneficial for cheesemakers in that the biofilm resists the growth of undesirable bacteria and mold, while regulating the flow of gas and moisture into and out of the cheese.

Can Have an Extremely Diverse Community

Industrial cheesemaking techniques ensure that cheeses are inoculated with just one or two key species, so a commercial Brie might be dominated by only a single strain of Penicillium camemberti. While this method does keep cheese production consistent, it doesn’t provide complex, interesting flavors as found on many artisinal cheeses.

Cheesemakers carefully control each element in a cheese’s creation so that the right milk is colonized by the right bacteria and fungi at the right time.  Cheese aging caves are kept at specific temperatures and humidities to cultivate desired species of fungi.  Any slight adjustment in these numbers could cause an explosive bloom of an unwanted microbes.

The students in Rachel Dutton’s undergraduate lab class at Harvard analyzed the rind of Winnimere, a cheese produced at Jasper Hill Farm, VT, and

Winnimere Cheese from Jasper Hill Farm (http://www.cellarsatjasperhill.com/)

found an “exceptionally cosmopolitan” community of microorganisms living there.  The rind of Jasper Hill’s Winnimere is washed in beer brewed from microbes living in the cheese’s aging cave. It was not unexpected that many salt-loving (halophilic) bacteria were discovered on the rind, but what did come as a surprise was the range of other unfamiliar bugs that are also found in places like Etruscan tombs, Tunisian oil wells, or Arctic sea ice.

Culture magazine commented that the discovery of these microbes on cheese is a far cry from the “big three” that dairy scientists generally focus on: the Lactococcus bacterial strains that produce the cheese paste, the Penicillium fungi that produce blue and bloomy rinds, and the Brevibacterium that supply the pungent pieds-de-Dieu aroma of washed rinds.

While the exact role of each of the oddball microbes found in Winnimere isn’t known, it is understood that without this specific mix living on the rind, Winnimere wouldn’t have its unique flavor. The Dutton lab is working hard to figure out the purpose of each microbe, and their interaction within the larger cheese rind community.

An article in The New York Times about Rachel Dutton’s lab states that “…as word about the lab’s work spread, first among microbiologists, then among cheesemakers, Ms. Dutton’s in-box filled with requests from nonscientists, including chefs, bakers and even a pickle maker in Berkeley, Calif. Packages started showing up at her office, containing food samples for her to analyze. …Chefs are looking for a signature taste, something that is completely unique to their location. “What makes terroir is the microbes. It’s literally what’s in the air.”

“There really is no one else doing what she is doing,” said Mr. McGee, a contributor to The New York Times Dining section. “Academic microbiologists have not taken an interest in small-scale fermentation, focusing on food safety rather than food quality. There is really only one person at the moment.”  And Vince Razionale, the cheese buyer for Cambridge-based Formaggio Kitchen has said that “her work was described as “groundbreaking.”

In the bigger picture, beyond developing cheese textures and flavors, Dr. Dutton sees cheese as a model for how all kinds of microbial systems work. Helping researchers better understand microbial communities could mean that cheese could act as a proxy for the biofilm of an oil-slicked wetland or the distressed lung of a cystic fibrosis sufferer.

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REFERENCES

A majority of this post is a summarization of the article Microbe Managing – The Lifesaving Potential of Cheese Bacteria written by Will Fertman for Culture magazine.

Will Fertman. Microbe Managing – The Lifesaving Potential of Cheese Bacteria. Culture magazine, Fall 2012
http://www.culturecheesemag.com/autumn_talk_microbes

Peter Andrew Smith. For Gastronomists, a Go-To Microbiologist. New York Times, September 17, 2012
http://www.nytimes.com/2012/09/19/dining/for-gastronomists-a-go-to-microbiologist.html?_r=0

FAS Center for Systems Biology Bauer Fellows Program Profile page
http://sysbio.harvard.edu/csb/research/dutton.html

The Dutton Lab website
https://sites.google.com/site/theduttonlab/


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You sell raw milk cheese? Is that true?

cheeses at the shop where I work

Customer: “The card on this cheese says that it is made from raw milk… is that true? I didn’t think they were allowed to sell raw milk cheese…”

Me:  “It is raw milk, but it’s been aged for at least 60 days…as per the USFDA regulations”

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This question has come up more than once.  And so, it got me to thinking, what is the story behind this 60-day rule?

While doing research for the answer to this question, I came across many other topics that may help give you, the reader, a better and more comprehensive understanding of raw and pasteurized milk and milk products in the United States. And so, I realized that in order to properly tell this story I’ll have to let it unfold in multiple parts.  First, I’ll give a brief background on what raw milk is, the ways milk can become contaminated, and the pasteurization of milk as per the regulations of the U.S. Food and Drug Administration.  Next, I’ll go ahead and look into the story of how the regulation developed throughout history, and perhaps address various states’ regulations regarding raw milk sales and European regulations regarding the manufacture and sales of raw milk and fresh cheese as well as a discussion of the flavor of pasteurized versus unpasteurized cheeses.  For now, let us begin with the basics:

What is Raw Milk?

Raw milk is un pasteurized milk from cows, goats, sheep, or other animals.  It is thought, but not known exactly, that less than 1% of milk sold to consumers in the United States has not been pasteurized.

What Contaminates Could Be Found In Raw Milk?

According to the Center for Disease Control (CDC), raw milk can carry harmful bacteria and other germs that can make you very sick or kill you.  A wide variety of bacteria (e.g.,  Brucella, Campylobacter, Listeria, Mycobacterium bovis (a cause of tuberculosis),Salmonella, Shiga toxin-producing Escherichia coli [e.g., E. coli O157], Shigella, Yersinia), viruses (e.g., norovirus), and parasites (e.g., Giardia) that can make people sick or on few occasions, be fatal are sometimes found in raw milk.  The CDC also states that while it is possible to get foodborne illnesses from many different foods, raw milk is one of the riskiest of all.

These bacteria, viruses, and parasites may introduce themselves to milk through many different routes, such as:

• Cow feces coming into direct contact with the milk
• Infection of the cow’s udder (mastitis)
• Cow diseases (e.g., bovine tuberculosis)
• Bacteria that live on the skin of cows
• Environment (e.g., feces, dirt, processing equipment)
• Insects, rodents, and other animal vectors
• Humans, for example, by cross-contamination from soiled clothing and boots

What Is Pasteurization?

Pasteurization is the process of heating milk to a high enough temperature for a long enough time to kill illness-causing bacteria contained in the milk and is the only way to kill many of the bacteria in milk that can make people very sick.

According to Code of Federal Regulations Title 21, Volume 8, Section 1240.61 (Revised as of April 1, 2012), the terms “pasteurization,” “pasteurized,” and similar terms shall mean the process of heating every particle of milk and milk product in properly designed and operated equipment to one of the temperatures given in the following table and held continuously at or above that temperature for at least the corresponding specified time:

Milk Pasteurization Regulations According to 21CFR1240.61

Is Pasteurization 100% Effective?

Pasteurized milk products have occasionally caused illnesses and outbreak because of germs introduced in the dairy after the pasteurization process. However, pasteurized milk that is correctly handled in the dairy, bottled, sealed, and refrigerated after pasteurization, and that is properly handled by the consumer, is very unlikely to contain illness-causing bacteria. Considering the amount of pasteurized milk consumed in the United States, illness from it is exceedingly rare.

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References

(1) Raw Milk Questions and Answers, Center For Disease Control and Prevention Website

http://www.cdc.gov/foodsafety/rawmilk/raw-milk-questions-and-answers.html#rawmilk  Last Accessed: November 4, 2012

(2) 21CFR1240.61

http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=1240.61  Last Accessed: November 4, 2012