Does Swiss cheese come from Swiss cows? How about blue cheese? Professor of animal science at McGill's Macdonald campus K.F. Ng-Kwai-Hang has the answer to these questions. He has spent the last 25 years studying the genetics of cows and how this affects quality and type of cheese.
"There are more than 100 different breeds of cows. However, the best milk producers are Holsteins," says Ng-Kwai-Hang. "Within a specific breed, the milk these cows produce is not the same - it differs in its fat, protein and lactose (a type of sugar found only in milk) content. Consequently, the cheese made from this milk will also differ in its composition and the taste will be affected. Basically, cheddar cheese can be made from all milk, but the taste and quality will be different from breed to breed and also within a breed.
"By looking at the genetic profile of cows, we are able to predict which one will produce the best cheese."
Ng has identified the role of specific milk protein genes that affect cheese yield, composition and quality. He and his research team have found that small changes or mutations in the DNA of certain genes lead to changes in the protein which results in dramatic changes in the cheese. Their findings show that a mutation in the particular protein, the kappa-casein, is associated with a higher yield of cheese and one which is better quality.
According to Ng, in addition to the two genetic variants for kappa casein mentioned above, there are about 50 known milk protein gene variants and they have diverse effects on dairy product production. These findings have generated a great interest in the dairy industry. Attempts are underway in some countries to breed for specific genetic variants.
"Because the genetic variants are inherited according to simple Mendelian rules, it is possible to breed for specific variants," says Ng. "We are seeing this already where breeding programs are in place to increase the frequency of the B type of kappa-casein in cow populations in order to improve the milk quality and its cheese making characteristics. We are at the forefront of what is possible and can look forward to more efficient cheese production and better quality cheese."
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