Page 18 - IAV Digital Magazine #433

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Scientists Discover Chemical Mysteries of Cheese
By Rachel Clun
Cheese has been made around the globe for cen- turies, but research is shed- ding light on the chemicals that make cheese hap- pen.
Associate Professor Mark Turner, of the University of Queensland’s School of Agriculture and Food Sciences, said one of the molecules they worked was dis- covered just seven years ago.
“At the moment it's fairly fundamental research: so we know that the bac- teria grow in milk, and cheesemaking has been happen- ing for thousands of years, but it's about better understanding how enzymes like these are con- trolled,” he said.
The researchers were looking at an enzyme in lacto- coccus, the main starter bacterium used in the cheesemaking
process in Australia and over- seas.
“The bacterium lactococcus is used to acidify milk and it’s the first step in the cheesemaking process,” Dr Turner said.
In that bacterium is an enzyme - pyruvate carboxy- lase - which the researchers found played an impor- tant role in the milk.
“It's also used to produce amino acids inside the cells so it can make new cells and grow,” the associate profes- sor said.
“One of those
amino acids is called the aspar- tate, and this enzyme is essen- tial for producing that amino acid so it can grow and produce high lev- els of acid in the milk.”
In joint research with Columbia University and the University of Washington, he said the researchers also found a newly dis- covered molecule affected the impor- tant enzyme.
“We did find that there was a sort of unique controlling mechanism of how this other little mol- ecule comes and binds to that enzyme and actu- ally inhibits its
activity,” Dr Turner said.
While the team did not make any edi- ble cheese - their test matter was not allowed to leave the lab - Dr Turner said their experiments using milk gave them some interesting findings.
“We basically put them (the bacteria) in milk and com- pared the different strains, one was the wild type and one which pro- duced lots of acid, and then we had the mutant which was missing that enzyme,” he said.
“Then we were able to show that (bacterium) wasn't able to produce as
much acid as the one that had the enzyme.”
He said the research was important because it could help the dairy industry in the future.
“Australia pro- duces over $1 bil- lion worth of cheese every year and exports $700 million, so it’s a big economy and pret- ty much all cheese is made from a starter culture like this bacteria.”
While their research was exciting, Dr Turner said the next step was to look at what was impor- tant for good acid production in milk, and what genes and enzymes were involved.
“Eventually maybe we can look at try- ing to develop ways to control those enzymes better, to modify the process, make it more efficient or more reproducible or faster.”
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