Microbial strains versus species —why small differences matter in fermented foods
By Megan Biango-Daniels with editing assistance from Megan Martin
Many cheesemakers credit strains of microbes that are specific to their caves with providing terroir, flavors, or appearances that cannot be replicated. This so-called microbial terroir is the unique taste imparted by microbes that make these foods. But what are microbial strains and how do they differ from species? [click to view the full story]
The curious case of the purple cheese rind
When you buy an aged cheese at the store, you expect it to have a specific appearance. Camembert should be white and fuzzy. Limburger should be orange and sticky. Cheese makers work hard to manage aesthetics, but sometimes unplanned colors or textures cause cheese defects. In the past few years, cheese rinds around the world have started turning an unusual purple color. In this Science Digested, I’ll explain how my lab discovered the microbial cause of this purple rind defect.
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Get to know your sourdough yeast
As a part of the Sourdough citizen science project, we have sequenced the DNA of sourdough starters from around the world to better characterize sourdough microbial biodiversity. As we sift through data from that project, many participants want to know more about the yeasts identified in their starter. Here we provide profiles of research conducted on some of the most abundant sourdough yeasts. [click to view the full story]
A Visual Guide to the Microbiology of Natural Rind Cheese
Ever wonder what is living in that undulating crust on your favorite blue cheese or clothbound Cheddar? Our new visual guide provides an overview of the microbial diversity of natural rind cheeses. Print it out. Hang it up. Impress your friends with your new cheese microbiology knowledge.
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What causes cheese to turn pink?
Various attributes of a cheese, including both flavor and appearance, contribute to the final quality of the product. During the production of some cheeses, microbial processes can cause strange quality defects, often with colorful outcomes. Researchers in University College in Cork, Ireland identified the microbial culprit behind a notorious pink cheese defect. In this Science Digested, Adam Shutes from the Boston Cheese Cellar explains what they found.
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Cheese mites, gophers of cheese rinds
Next time you buy a piece of cheese with a mottled natural rind, such as a clothbound Cheddar or Tomme de Savoie, take a close look at the rind with a magnifying glass. If you look long enough, you will see tiny pieces of the rind are moving! These specks are microscopic arachnids known as cheese mites. Gophers of the cheese world, these tiny mites can both impart flavors as well as cause headaches for cheese producers.
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Geotrichum candidum: A yeast holding on to its moldy past
Have you ever noticed those goat’s milk cheeses with the wrinkly surface at the cheese shop? They look like a fuzzy white brain or a dusty grey coral and they smell like sweet, buttery flatulence. Those aesthetics and aromas come from the growth of the fungus Geotrichum candidum. Using in-depth genomic sequencing, French scientists recently unlocked the evolutionary history of this important cheese microbe and revealed a fungus with an identity crisis.
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Profile: Arielle Johnson – Head of Research, MAD
Arielle Johnson manages the research program for MAD in Copenhagen, Denmark. MAD is a non-profit organization founded by chef Rene Redzepi, devoted to improving both the practical and theoretical understanding of food. Arielle entered the food industry with a PhD in flavor chemistry and perception, but her interests and work are wide-ranging, encompassing new techniques for the kitchen and, of course, fermentation management. In her own words, “My role within the organization is to sort through the existing body of scientific knowledge and find things that we can apply to make the creative process more creative.” [click to view the full story]
Organic and conventional flours produce different sourdough fermentations
It’s difficult to connect the dots throughout our complex food system. Although it is rarely demonstrated scientifically, we generally accept that what happens on farms impacts the quality of our food. For microbial foods, the raw materials we use in fermentation can introduce different microbes depending on how those materials were produced. A recent study in Italy of sourdough fermentation demonstrated that organic vs. conventional farming can affect the quality of sourdough bread. This exciting new research highlights the role that microbes play in shaping food quality as it moves along the path from farm to fork.
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Microbe guide: Chrysosporium sulfureum
If you’ve ever spotted yellow fluff on the surface of a cheese rind, you were probably looking at the mold Chrysosporium sulfureum. Considered a typical fungal species on the rinds of many classic French cheeses including Tomme de Savoie and Saint-Nectaire, this cave-loving fungus is widespread, but enigmatic. Here’s a summary of the little that we do know about this cheese fungus.
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Microbe Guide: Yarrowia lipolytica
From biofuels to fish food to gold nanoparticles, Yarrowia lipolytica is all the rage these days as a powerful workhorse for biotechnology. But this yeast also has important roles in the flavor development and appearance of some traditional fermented foods. Here’s all you need to know about this versatile and beautiful yeast. [click to view the full story]
The Microbiology of Raw Milk – Microflores du lait cru
This groundbreaking practical guide to raw milk microbiology was written by a group of French scientists. In 2015 we used a Kickstarter campaign to fund and publish an English translation.
Within its pages, the authors show how protecting the natural diversity of carefully produced raw milk is not only crucial for maintaining the identity and flavour of cheese, but also promotes a barrier effect that can help to protect against the growth of pathogens. Rather than subverting modern food safety targets, this approach may actually help cheese producers to achieve them. [click to view the full story]
Lactobacilli no more—a key genus is broken down
In March of 2020, a paper written by a multinational group of scientists was published that rewrites the book on the genus Lactobacillus, amongst the most beloved organisms of fermented food producers. What had been a massive single genus containing over 250 species has now officially been broken down into 25 new, smaller genera. Bronwen Percival spoke with one of the lead authors of the paper, Professor Sarah Lebeer of the University of Antwerp in Belgium, about the project, her work on the role of lactobacilli in human and other microbiomes, including those of food, and how this knowledge might ultimately be applied. [click to view the full story]
Experimental design for fermented food producers
When a fermented food product is not meeting quality standards, a producer will want to quickly identify the potential causes of poor quality. If microbes are playing a role, it might be helpful to conduct controlled experiments to determine how to control a fermented food microbiome to improve quality.
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Profile: Cecilia Garmendia – Scientist and Cheesemaker
Artisanal cheesemaking and science may appear to have little in common. “Not so!” according to Cecilia Garmendia who has translated her Ph.D. to cheesemaking and business ownership.
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Book Profile: Reinventing the Wheel: Milk, Microbes, and the Fight for Real Cheese
Reinventing the Wheel: Milk, Microbes, and the Fight for Real Cheese is a book that, like MicrobialFoods.org itself, was directly inspired by time spent collaborating with Benjamin Wolfe at the Dutton Lab in early 2014. Returning to London with a new appreciation for the power of microbial communities in shaping the flavors of the food that we eat, I was eager to start a conversation within the cheese industry. I wanted to see more cheesemakers enhance the flavor of their cheeses by encouraging healthy microbial communities native to their farms to play an active role in the cheesemaking process. [click to view the full story]