Cultivation of a Cheesemonger

A Blog of Cheese Culture and Cultures


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Mother Noella Marcellino: Geotrichum Diversity in France

Mother Noella Marcellino is a Benedictine nun of the Abbey of Regina Laudis in Bethlehem, CT (She earned the title “mother” in 1985).  Walled off from outsiders, the abbey encompasses a 360 acre farm complete with bees, cows and hogs, a garden with herbs to make tea, a pottery studio, and a smith shop making the cloistered nuns practically self-sustaining.  Mother Noella enrolled at Sarah Lawrence in 1969 and became a cloistered nun a couple years later.  After many years of milking the abbey’s cows,  she was asked to make the abbey’s cheese in 1977.  Mother Noella’s first attempts at cheese were unsuccessful and many of these batches were thrown to the pigs.  However, one fortuitous day, at the invitation of the abbess, Lydia Zawislak, a third-generation cheesemaker came from Auvergne and showed Mother Noella a traditional way of making cheese in a wooden barrel.

SisterNoella_cheesemakingfacility

Cheesemaker brother David Aeschliman, apprentice Stephanie Cassidy, and Mother Noella Marcellino

The wooden barrel method was working very well and the F.D.A. was turning a blind eye to the nuns’ method of cheese production until 1985, when 29 fatalities were caused from a Listeria monocytogenes outbreak in Southern California from an unaged raw milk.  After the outbreak, Mother Noella was told that she needed to get rid of her wooden cheese barrel and start using a stainless-steel vat.  The abbey went above and beyond to comply with the regulation enforcement and four nuns enrolled n a nearby University and received doctorates in key disciplines: microbiology, animal science, plant science, and agronomy.  Mother Noella went to the University of Connecticut for microbiology.  In 1994, she earned a Fulbright Scholarship to France and a subsequent three year fellowship from the Institut National de la Recherche Agronomique (INRA) to pursue her research.  She received her doctorate in Microbiology in the Department of Molecular and Cell Biology at the University of Connecticut in 2003.

Her original objective came from an observation she had made from her own cheese aging facility – Mother Noella wanted to study the history and ecology of French cheese caves.  This topic proved too vast so she narrowed it down to study only one strain of mold – Geotrichum candidum – in French cheese caves.  Her new and functional thesis was “The diversity of French fungus-ripened cheeses is due partly to the succession of fungi that colonize the cheese during ripening.”  Mother Noella wondered how much the mold varied from one cave to another.  She isolated and collected 180 samples from milk, curd, and cheese from farms that produce 11 types of soft and semihard cheese in Normandie, Lorraine, Champagne–Ardenne, Bourgogne, Franche-Comte’, Haute Savoie, and Auvergne (Fig. 1.) Samples were frozen until processed in the laboratory – where Mother Noella spent the next two years at the bench characterizing the molds with genetic and biochemical tests.

Sister Noella at the lab

Sister Noella at a pop-up lab

After two years of analysis, the results were that each individual strain found on cheese (only a few popular strains are well researched) “has it’s own appetites, it’s own ecology, it’s own bio-chemical effects. And each mold produces a different cheese.”

SisterNoella_fig1_2

Fig. 1

Geotrichum candidum is a fungus that colonizes nearly all fungal surface-ripened cheese during the early stages of ripening  and Mother Noella’s study revealed that there is an enormous diversity of Geotrichum candidum. Of the 180 samples, sixty-four Geotrichum candidum isolates were characterized.  High genetic diversity of G. candidum was found even within the same cheesemaking regions and strains did not group according to region.

On soft cheeses, such as Camembert, and semihard cheeses, such as St. Nectaire and Reblochon, the biochemical attributes of G. candidum impact the course of cheese ripening.  Yeast-like colony morphology predominated in Reblochon, while all of the strains isolated from St. Nectaire were filamentous. On some cheeses, like St. Marcellin, it is responsible for the appearance of the cheese, imparting a uniform, white, velvety coat to the surface (Marcellino).

After colonizing a cheese, lipases and proteases of G. candidum release fatty acids and peptides that can be metabolized by ensuing microbial populations and that contribute to the development of distinctive flavors and other qualities (Marcellino).

SisterNoella_filamentous

Filamentous Geotrichum candidum

“[Each strain of Geotrichum candidum] has it’s own appetites, it’s own ecology, it’s own bio-chemical effects. And each mold produces a different cheese.”

Mother Noella’s study continues on to say that considerable morphological variation occurs between strains within the taxon.  These basic morphologies have been described:

  • strains with yeast-like colonies that produce abundant arthrospores and have generally low proteolytic activity,
  • strains whose colonies are white and resemble filamentous fungi with a predominance of hyphae and high proteolytic activity
  • and those strains that fall in between (strains of G. candidum that predominates on a cheese rind helps to determine the texture, cohesiveness, and thickness of the rind.)

However, not all strains are beneficial for cheese – Some less desireable strains create unstable rinds that disintegrate when the young cheeses are flipped during aging.  Other strains can lead to irregular growth of fungal populations or may provide the opportunity for contamination by blue molds or Mucor spp..  However, some strains of G. candidum can inhibit the growth and/or sporulation of Mucor spp. (Noella).

The population density of strains also has an effect on covering gas exchange facilities across the surface of the cheese.

Samples of cheese were gathered for mold strain analysis, and some cheese were collected from the same batch after 1 week and again at the end of the ripening period.  Observations were as follows:

1. Some strain groups were found within the same cheesemaking facility at different times during ripening.

Four closely related strains (GC63, GC59, GC64, and GC60 – at the top of Fig. 3) were isolated from two 35-day-old Reblochon cheeses and two 7-day-old Tomme de Savoie cheeses produced and ripened in the same facility in Annecy, Haute Savoie.  A similarly diverse set of five strains was isolated from a farm that was located 19km from Annecy and that also produced Reblochon.

2. Similar diversity was found among strains isolated from milk and curd of the same facilities showed 90% or greater similarity and had similar morphology and carbon assimilation profiles.

For example, GC84 and GC82 from Epoisses and GC45 and GC43 from Mont d’Or were isolated from the milk and curd, respectively, of the same facility. According to Fig. 3, these strains couples are highly related but the sets are rather far removed. However,  this observation suggests that a strain can be followed during the cheesemaking process.

The results  from Mother Noella’s research team suggest that cheesemaking techniques play a role in strain selection and that French cheesemakers have optimized production techniques to select empirically for native strains of microorganisms that produce the best cheeses.  Interestingly, centuries-old cheesemaking methods are not based on a thorough knowledge microbiology, yet much of the flavor development associated with cheese ripening is due to microbial activity which causes the diversity of various cheeses and their aromas, textures, and flavors. Many microbial populations that have developed in primitive cheesemaking environments remain largely uncharacterized.

SisterNoella_dendogram2

Fig. 3 GC = Geotrichum candidum
The colored lines correspond to the colored text (strains mentioned) within the blog.

A documentary film about this journey, The Cheese Nun: Sister Noella’s Voyage of Discovery, produced by the Paris American Television Company, has been shown in film festivals and aired nationally on PBS Television in 2006.  Sister Noella was honored with the reception of the International Academy of Gastronomy’s Grand Prix de la Science de Alimentation in 2005, and the French Food Spirit Award in Scientific Advancement, given in the French Senate, Paris, in 2003.  She was a scholar-in-residence at the 2011 American Cheese Society Conference in Montreal.

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BIBLIOGRAPHY

Marcellino, N. et al., Diversity of Geotrichum candidum Strains Isolated in Traditional Cheesemaking Fabrications in France. Applied and Environmental Microbiology. Oct. 2001 p. 4752-4759.  http://web.uconn.edu/mcbstaff/benson/BensonHome/AEM01Marcellino.pdfBibliography

‘Cheese Nun’ leads abbey in production of the traditional gourmet food. Kathryn Boughton. New Haven Register. February 27, 2013 http://www.nhregister.com/articles/2013/02/27/news/doc512e5188f3e2d416400350.txt

Raw Faith. Burkhard Bilger. The New Yorker. August 19, 2oo2.http://www.newyorker.com/archive/2002/08/19/020819fa_fact_bilger

Photo Credits

Madame Fromage Blog. “Who’s at ACS?” August 5, 2011.http://madamefromage.blogspot.com/2011/08/whos-who-at-acs.html

http://abbeyofreginalaudis.org/

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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/