Spruce becomes yeast, and the yeast becomes part of the concentrate. Martine Andrea Olsen has in her PhD work at NMBU and Foods of Norway studied how the locally produced feed affects the cheese quality.
It is not often that researchers can answer as clearly as Olsen does to the question of whether feed with yeast is good enough for both the cow and the cheese factories: “The main purpose was to see if we can replace soy with yeast. And we can,” she says.
To produce milk and cheese of good quality, the cow needs proteins in the diet. If imported soy in the concentrate feed can be replaced with Norwegian raw materials, it is good for both sustainability and self-sufficiency.
Martine Andrea Olsen's specialty is the cheese, not the feed or the cows.
“The feed must be developed and produced. Then the cow must be happy with the feed, and then I am the one who can see how it affects the production of the cheese. It doesn't help to have feed that is sustainable and can be produced in Norway if it doesn't produce milk and cheese of good quality,” she explains.
Sugar becomes yeast
That is why she has tested what happens to milk and cheese when the cow has been fed with three different protein sources. Soy is one. Norwegian barley is the other, but due to its low protein content the cow gives less milk.
“The third is a novel protein source that we can be produced from Norwegian spruce trees,” she says. The process is a bit more complicated. You break down the cellulose in the tree so that it turns into sugar. This sugar is used to grow yeast cells, and it is this yeast that contains proteins.
“The yeast we use when we bake bread at home, by comparison, contains 43 per cent protein,” says Olsen.
The result is therefore promising:
“Considering the production and quality of cheese, we can replace soy with yeast,” she states.
“The cow did not react differently to the feed either: - It tastes the same, and we noticed no differences when examining the health of the cows,” she says.
Thus, it is the economy that decides when the concentrate can become fully Norwegian. One of the partners in the project, Borregaard, even has a plant that can be used to produce sugar. Another partner, Lallemand, has used this sugar to produce larger quantities of yeast for feed.
Is it worth it?
It is still expensive to produce yeast this way. But the researchers continue to work on using such ingredients in the feed. They are also looking at ways to make production cheaper.
The consumers, who are going to drink milk and eat cheese, do not notice the difference between yeast and soy in the feed, and neither does the cow. At the cheese factory, it is the protein content that affects the cheese-making efficiency, and there is not much of a difference between yeast and soy in the feed. The end product – the cheese – will be the same anyway.