Guest Columns

Dairy Research

What is milk?

John Lucey

John Lucey, director of the Wisconsin Center for Dairy Research at the University of Wisconsin-Madison, contributes this column for Cheese Market News®.

In recent years, groups within the dairy industry have raised concerns that plant-based drinks are using the term “milk” on their labels instead of “beverage.” These are valid concerns, since the federal definition of milk is the lacteal secretion from mammals, which cannot apply to oats, almonds or any other plant-based source.

These beverages do state on the label they are made from plants, so it’s unlikely consumers think they are drinking cow’s milk.

However, there remains a consumer protection or responsibility issue in labeling. In the case of dairy milk and plant-based beverages, it is important that consumers are aware each type varies widely in its components both structurally and nutritionally.

We now have an emerging situation where startups are trying to manufacture cow’s milk, or, more accurately, make some components of milk, without the cow. There are several different technologies or possible approaches these startups are attempting to utilize.

One of these options is to use a precision fermentation approach where the gene for an individual milk component, like a protein, is put into a genetically modified bacteria or yeast. This microbe is grown in a fermenter producing that protein, which is then extracted and concentrated/dried. This type of fermentation process has been used to produce rennets for the dairy industry since around 1990.

However, using this process for making a milk protein raises many questions. Can I really call this new protein a milk protein since it was not produced by a cow? Is this protein safe (e.g., more/less allergic) as the bacteria or yeast may not make a truly identical protein compared to the cow? While rennets are a very minor ingredient in cheeses, a fermentation-derived casein would be present at very high levels, raising valid safety concerns for its consumption. Some of these startups like to suggest that since their new proteins are similar to the proteins produced from cows, and we have consumed milk for millennia, that their new proteins are also safe. Is that a valid assumption?

There are other questions and issues with using precision fermentation to produce milk proteins. For instance, what process steps have been used to remove all impurities from the fermentation media, like genetic materials and enzymes from the bacteria/yeast? Will these fermentation-derived proteins have similar functionality to milk proteins? For the caseins, the functionality answer is not likely as they do not have the high calcium binding ability that is so important for the structure and performance of caseins in products like cheese.

We have already seen plant-based “cheeses” do not meet the traditional requirements (i.e., federal definitions) stating that cheese must be made from milk that needs to be coagulated and have a whey removal step. For these fermentation-derived proteins, it is likely they will follow a similar plant-based route to produce a gelled-like ultra-processed product, much like in imitation cheeses.

So, could this fermentation approach be used to replicate milk itself? The answer comes down to what we expect milk to be. If we are satisfied with mixing a couple of proteins, a little sugar and a few fats to make it look white, then the chances are high that we will have someone claim to have successfully replicated milk.
However, real milk from cows contains thousands of components and nutrients needed to sustain health that are naturally assembled by the cow into unique complex structures like casein micelles and fat globules.

There is growing awareness by nutritionists that these complex structures, or dairy matrices, are necessary for optimum digestion and health. Yeast/bacteria do not have the means to replicate the specific enzymes and delicate processes that are found in the mammary gland necessary to create these structures.

There are other startups that want to produce milk proteins in genetically modified plants like soya beans. It is not clear how consumers might react to the use of genetically modified organisms to make milk proteins in a plant.

Lastly, a different approach is being attempted by startups to use isolated mammary cells and culture them in a bioreactor to produce milk in the lab (they are starting with human milk). This type of process would be very complex and very expensive but could, in theory, produce identical milk components to the cow/human.

I’d like to wrap up this column with a couple of points. First of all, I think that the dairy industry could use some of these technologies to advance the industry. As I mentioned, the dairy industry already uses precision fermentation to make rennets due to global shortages with the supplies of traditional calf rennet. I think that precision fermentation is a great technique to make value-added ingredients that can cover the costs of this complex and expensive process. For instance, precision fermentation could use modified microbes to ferment cheese whey and permeate into value-added chemicals like bioplastics.

Second of all, startups attempting to make non-cow milk are funded by venture capital with the selling point or claim that their approach is more sustainable than producing milk from cows. There are no peer-reviewed studies to support such claims, and, from what limited information is shown on company websites, it appears that producing milk proteins by the fermentation route has a higher carbon footprint than an equivalent milk production naturally performed by the cow. It appears that protein yields are low from these fermentation processes, so significant processing would be required to produce a purified dried protein powder. We should also appreciate the massive volume and enormous scale of fermenters and bioreactors that would be needed to replace all the milk currently obtained from cows. Wisconsin alone produces over 30 billion pounds of milk per year.

For me, all these topics make me stop and wonder again at the amazingly complex components and structures that are naturally produced in milk providing us with outstanding nutrition and tasty dairy products like cheese. Don’t forget the cow uses her own bacterial fermentation process (rumen) to break down grass and produce high-quality proteins and nutrients 24 hours a day, seven days a week for most of the year. It’s truly amazing what nature can create.


The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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