The Science of Artisan Cheese – A Recap

Kate Arding, co-founder of Culture Magazine, ACS Board member, and Chair of the ACS Regulatory & Academic Committee, traveled to England in August 2012 for “The Science of Artisan Cheese” — a two-day conference held by the Specialist Cheese Makers Association. The goal of the conference was to develop discourse between scientists, public health policy makers, and cheesemakers.

Kate and Gianaclis Caldwell of Pholia Farms have provided a summary of the sessions they attended at the conference for the benefit of ACS members, below.

Raw Milk Biodiversity and its Influences
Dr. Marie-Christine Montel, INRA Clermont-Ferrand, France

This amazing session focused on the barrier effect that a biodiverse, “functional  group” of bacteria, yeasts, and molds can have in the control and elimination of pathogens in cheese through the following technologies: Decrease of pH, production of H202, acids, and peptides, and the production of bacteriocins.  While the elimination of pathogens at the milk production level was still emphasized, Dr. Montel also stipulated that “farms and cheese plants are not [nor should be] hospitals”. Her discussion included several fascinating examples of the relative index (RI) of five functional groups – lactic acid bacteria, gram +bacteria,  gram – bacteria, yeasts, and molds in milk and cheese and how this RI influenced ripening and cheese safety.  She indicated that quite likely the total plate count (SPC or APC) of bacterial colonies in milk is not the best indicator of milk’s suitability for cheesemaking, but that rather the development of RI parameters, along with the reduction and/or elimination of pathogens at milk collection, might be more indicative of milk’s suitability for cheesemaking. She also emphasized that changes in practices(such as the cessation of post dipping and the decreased use of sanitizers on the teat surface – which is the main reservoir for the functional groups) that would encourage the inclusion of higher levels of functional groups can take several months and should not be attempted without concurrent assessments of milk such as lactofermentation and laboratory profiles to document the RI of the milk.

Microbial Diversity and Interactions
Dr. Rachel Dutton and Dr. Ben Wolfe, Harvard University, USA

In this fascinating presentation, Drs Dutton and Wolfe shared the latest (and still emerging) results of their microbiological studies of over approx. 170 cheese rind samples – including bloomy, washed, and naturally rinded products. Their data showed that in all cases an incredibly diverse population of some surprising microbes (including bacteria, yeasts and molds) were present at the conclusion of aging in all cheeses.   An especially interesting discovery is that most of these microbes have little relation to any ripening or starter cultures that might have been added at the beginning or during the process (including brevabacterium on washed rinds). Cheeses from all three groups (bloomy, washed, and natural rind) were shown to have a familiar footprint of organism with very few exceptions.  Amongst the many surprising discoveries was the fact that Staphlococus proved as able to deacidify cheese rinds as yeasts. Their studies also found zero pathogens competing with the rind flora.

Achieving Control of Listeria During Artisan Cheese Production
Dr. Catherine Donnelly, Vermont Institute for Artisan Cheese (VIAC)
Dr. Kiernan Jordan, Moorepark Food Research Centre, Ireland

Dr Donnelly presented a thorough and pertinent update on the status of the FDA’s inspection of farmstead and artisan cheese plants in the US, as well as the impact of the USA’s Food Safety Modernization Act on cheesemakers exporting products to the US.  She pointed out that the consumer profile in the US and many European countries continues to increase in the percentage of consumers considered “high risk” (due to age and other immunosuppressant factors).  She also noted the decrease in food borne illnesses (in the US) due to listeria over the past several years.

As an illustration of how the scientific and academic community can be proactive in the support of improving the quality and safety of cheese, Dr Donnelly cited programs offered through VIAC that assist artisan and farmstead producers with the improvement of manufacturing practices and food safety plans.  She emphasized that confidentiality is maintained through these programs.

In the second part of the session, Dr. Jordan gave suggestions for environmental sampling and cleaning protocols.  He shared a unique and disturbing case in which a single cow in a dairy herd  was traced (through an extensive process of elimination and testing) as the source of the contamination of the entire bulk milk supply by Listeria monocytogenes. The cow in question had a single quarter infected with LM (without showing any abnormal milk qualities). He also shared that some of the younger strains of LM have shown resistance to sanitizers such as quaternary ammonium, indicating that future resistance to other sanitizers and antibiotics is likely to be a crisis that the producer could be facing in near future.

Influence of Yeasts on Blue Cheese Aroma Production in Stilton and Stichelton Blue Cheese
Dr. Christine Dodd and Dewi Yunita, University of Nottingham

In their studies of these two blue cheeses, the cheese was physically separated into its three main components of rind, white paste, and blue veins.  Each of these components was then analyzed.  The results showed great differences in aromatic and volatile compounds between each of the three end products. Amongst the differences, the crust contained 80% ketones, the blue veins were 40% ketones and 15% aldehydes and alcohols, and the white core was 40% aldehydes and alcohols.  All yeasts present in the cheeses were shown to be both proteolytic and lipolytic. Trichosporum was found to likely be the cause of “blue fading”, a problem in some cases where Penicilium roqueforti is added, but no blue molds appear.

Quality and Control
Ivan Larcher, Larcher Consulting, France
Randolph Hodgson, Neal’s Yard Dairy, UK
Mateo Kehler, Jasper Hill Farm, USA

This session pointed out the many layers of hygiene present during the production of cheeses and the importance of viewing the steps in the production of different types of cheese as opportunities to producing safe products. As an example Banon, a traditional French cheese with a 5 day milk ripening period, was used to point out how different production technologies bring different challenges to the cheesemaker and must be understood and addressed during the process in order to attain the desired outcome. He especially emphasized that “knowledge of the milk” is key to deciding what type of cheese can be successfully made – particularly from a microbiological standpoint.

Randolph reminded the group that for some producers the knowledge of the details of the science may not be as important as understanding how to achieve their cheesemaking goals. He emphasized the need for dialog and a balanced relationship between the producer and scientists that would bring greater understanding of the full spectrum and equation of the cheesemaking process.

Mateo’s presentation used Jasper Hill’s Winnimere – a raw milk washed rind cheese (considered high risk according to the US regulatory officials) as an example of using process control and technology hygiene to consistently produce a pathogen free product.   He said that in his view, the best way to see what is in the milk is to take samples from the milk filter itself as testing from one area of the bulk tank can produce random results.

As far as Staph., within the Jasper Hill herd they maintain a policy of “2 strikes” in that the first time a cow presents, she is treated.  The second time, she’s sold.


New Tools for Cheese Producers
Dr. Mansel Griffiths, University of Guelph, Canada
Dr. Maria Pais, Fytzomius Biotech, Portugal

This session presented several ideas for the use of new ingredients as well as their health and marketing benefits to the cheesemaker. While a couple of these where genetically engineered products (such as lactic acid bacteria designed to produce Omega 3 fatty acids) of most interest to the artisan were the bioactive molecules produced by probiotics (specifically lactobacillus acidopholus) in the direct inhibition, competitive exclusion, and alteration of the barrier function of the gut (through the immune system) to provide resistance to E coli 0157:H7. Dr Griffiths shared the scientific research showing these effects in mice. Not only did the prophylactic use of probiotics protect the mice from infection by 0157, but there was significant therapeutic effect when given post infection. Similar results were demonstrated in pigs infected with salmonella. The question was raise whether probiotic use in cattle might cause the prevention of shedding of EHEC strains of E. coli.

The talk also included the use of phage to kill pathogens with an emphasis on its use in packaging materials. (currently being explored).

Dr. Pais gave a presentation on the history of plant derived coagulants and her work on the development of standardized extracts of cardoon thistle. (Also known as thistle rennet). She talked about the use of traditional thistle rennet, including problems faced by the cheesemaker of inconsistency in coagulating properties, limited, seasonal production, and concern over contaminants such as herbicides. The development of the cardoon protease cyprosin through genetic engineering was discussed, including its high cost and unfavorable reception by the majority of the potential market.  Tests done using other coagulants, such as recombinant chymosin and traditional animal source rennet alongside cyprosin, show a softer curd set, softer final texture of the cheese, and unique flavor profile possibly giving an advantage to the cheesemaker searching for a different product.

Molecular Methods for Cheese and Milk Testing
Matthew Ranieri, Cornell University, USA
Dr. Cathy Rees, University of Nottingham, UK

The main spoilage microorganisms were discussed (coliforms, pseudomonas, yeasts and molds) along with Matt’s research in identifying these organisms through various methods including gene sequencing and pulsed field gel electrophoresis (PFGE). Prevention of contamination of milk and product was explored and the importance of recognizing zones of priority (from direct food contact surfaces down to those remote from product) and cleaning regimens based on these zones was discussed.

Dr. Rees shared her research into the detection of mycobacterium, including the four types of concern to the dairy industry (bovis, tuberculosis, leprea, and avium paratuberculosis- MAP) All were shown to be have long survival, latent time and be exceedingly slow growers on culture (from 8-18 weeks) making them particularly difficult for detection by traditional culturing methods. MAP, the cause of Johnes disease in ruminants and possibly linked to Cohn’s disease in humans, was of particular interest. Dr. Rees said that preliminary studies show that MAP is killed during cheesemaking. Through her research utilizing microphage specific for mycopbacterium, a method has been developed that can provide results within 48 hours.

Risk Perception and Categorization
Professor Art Hill, University of Guelph, Canada
Professor Heather Paxson, Massachusetts Institute of Technology, USA

Professor Hill shared a presentation on a program in which Canadian food inspectors were trained to interview cheese workers and managers regarding their perceptions of food safety and risk management.

Professor Paxson’s presentation on the categorization of cheeses pointed out the challenge that faces cheesemakers, retailers, and consumers when attempting to describe an accurate category in which to place cheeses – including how these categories might be perceived in regards to risk

Concluding Session – Building a Working Relationship Between Scientists and Cheesemakers
Bronwen Percival, Neals Yard Dairy, UK

The closing remarks summarized the general consensus that opportunities for scientists to work with cheesemakers and retailers on an international scale, through shared information, is vast and untapped.

The point that “research is driven by professional needs and therefor that industry can drive research” was explored and options for initiating such opportunities discussed.

There was universal agreement with regard to the need for further collaboration not just between dairy scientists and cheesemakers but also between countries in order to facilitate greater and more intelligent regulation as well as education for all parties involved.