The microbes that make buffalo mozzarella revealed

Scientists in Italy have been looking at the microbiota of buffalo mozzarella, hoping it reveals the secrets of the taste of what many people consider a delicacy.

The science is fascinating, but for me, savouring a tasty morsel of buffalo mozzarella, even better accompanied with a slice of prosciutto, cherry tomato, and sprig of fresh basil, is one of the great pleasures in life.

Buffalo mozzarella originates from the Campania region of Italy, where my family is from. So, naturally when I read about new research into the microbes involved in making it, I wanted to know more.

In a fairly limited study scientists used genetic sequencing to give a detailed picture of what microbes are present and in what proportions, at different points of the mozzarella-making process.

In doing so, they discovered the dominant role of microbes from the Lactobacillus and Streptococcus genera, and showed how they differ between traditional and modern processes of production.

“This study sheds light on the intricate interactions of microorganisms throughout the manufacturing process and fosters a deeper understanding of the craftsmanship behind this esteemed Italian cheese,” says Dr Alessia Levante of the University of Parma, lead author of the new study in Frontiers in Microbiology.

“Mozzarella di bufala Campana” has been recognised as protected designation of origin (PDO) product under EU law since 1996. In order to qualify for this PDO status, buffalo mozzarella must be made according to a very specific recipe and in select locations only in Italy.

Two workers wearing all white make mozzarella cheese
Workers while making mozzarella, Campania, Italy. Credit: tanukiphoto/Getty Images

It’s made from the raw or pasteurised Italian water buffalo milk as well as rennet – enzymes produced in the stomachs of ruminant mammals – and natural whey starter. The starter is made up of undefined bacterial communities of the previous mozzarella-making round from the leftover whey – the liquid remaining after milk has been curdled and strained.

It is also processed using fresh water and brine.

The researchers wanted to investigate the role of bacteria in making mozzarella, and whether this varied between just two dairies in Campania – one larger and using more modern technology and a smaller one using more traditional processes.

Taking samples of the milk, natural whey starter, cheese curd, brine, and mozzarella, they performed 16S rRNA amplicon gene sequencing to identify the microbes present and their proportions.

“Subtle variations, such as temperature and duration of process influenced the cheese’s microbial composition and potentially impacted organoleptic properties,” says Levante.

That’s another way of saying it potentially changes the taste, sight, smell, and texture of the mozzarella.

Specifically, they found that pasteurised milk used by the modern dairy added fewer microbes and species of microbes to the process than the thermised milk used by the more traditional dairy. Thermisation is the mildest heat treatment given to milk, involving heating it to 57-68°C for 5-20 seconds.

A worker uses his hands to mould the mozzarella balls
Shaping the mozzarella. Credit: jcmanfredi/Getty Images

During the curdling process, they found that a small number of Lactobacillus and Streptococcus species begin to dominate. Some species within each genus were specific to each dairy.

Then, after curdling, Lactobacillus increased and Streptococcus dropped.

The brine also inoculates the external layer of the cheese with new microbes as it touches the cheese surface. But not all microbes in the brine also appear in the cheese, possibly because they’re not suited to living there or they develop later in the cheese’s shelf-life, after these samples were taken.

Ultimately, the researchers found that despite the large number of microbial species in the milk and the brine, they came to the conclusion that the microbial make-up of mozzarella is most influenced by the natural whey starter.

“We are planning a larger project to investigate more deeply the role of raw buffalo’s milk in defining the microbiota,” says Levante.

“This study’s scope was limited to two dairies and a specific sampling size. To provide more comprehensive insights into the microbial intricacies of traditional food production, future research aims to encompass a larger number of producers and manufacturing days.”

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