Grassmilk: An Amateur Flavoromics Investigation

I bought some half & half from Organic Valley made by cows on a diet of grass instead of grain.

To begin with, this grassy stuff looks a bit different than what I am used to. Instead of being white, it appears off white. Just a tad. It also definitely tastes different from my usual half & half courtesy of the cows at Sassy Cow. I'm not sure how to describe the flavor. I think it tastes more like butter and...a bit floral, perhaps? I cannot discern any green type of flavor - it doesn't taste like it would if you pull up some blades from your lawn and pop them in your mouth. The best analogy I can think of is that your common milk is like white chicken meat and the stuff from grass-fed cows is like lamb. More aromatic, more pungent.

I live in America's Dairyland. Within 10 miles of my house is the University of Wisconsin-Madison, home of Stephen Babcock, the man who figured out how to accurately measure the amount of butterfat in milk 130 years ago. Surely today it is home to the world's leading dairy scientists, at least one of whom can give me the 411 on the taste of milk from grass-fed cows.

...

I posed the question of what makes milk from grass-fed cows taste different to Jimena Laporta, Assistant Professor Lactation Physiology, here in town at the esteemed Department of Animal & Dairy Sciences at the University of Wisconsin-Madison.

She begins:

I am not sure I have a well rounded answer to your question, my understanding is that increasing the inclusion of grass in the diet of dairy cows changes the fatty acid composition of the milk (higher omega 3 lower omega 6 in grass fed cows according to the literature).

I wonder if this fatty acid composition accounts for the buttery flavor I tasted. She continues:

The gut microbes will work differently to digest grass compared to grain and legume based diets and that changes the profile of precursors and intermediates reaching the mammary gland.  Also, in organic milks there is a different processing after milk is harvested leading to (possibly) crystallization of the sugars (mainly lactose) and denaturation of primary milk proteins.

This whole milk production thing is more complicated than I thought.

I found this paper called "The Flavor of Dairy Products from Grass-Fed Cows" and, though most of it was way above my head, three things stood out.

The first is that the science addressing this question is somewhat lacking. "...there is sufficient evidence of the presence of a distinctive aroma in milk from grass-fed cows, but the connection with specific aroma-active compounds is still in progress," the authors say. "...several molecules have been identified as potential key-flavor compounds of grass-based milk and dairy products, but their real sensory impacts still need to be defined in detail," they admit.

"Further work is still needed to answer the question," we are told. "...but the increasing application of a flavoromics approach to the studies should rapidly bring about a decisive contribution to the knowledge."

Woo hoo!

We should have an answer in my lifetime.

Secondly, the paper explained the off white color I noticed:

"Under the sensory point of view, the yellow color and the smoother texture of derived butter and cheese is the most evident effect of grass feeding: these features are connected to the higher concentrations of β-carotene and unsaturated fatty acids with respect to non-grass-based products."

The final thing that stood out for me was this:

"Other potentially flavor-active compounds in milk from grass-based farming systems are indole and skatole (presenting flowery of fecal odor, depending on the concentration)."

Now there is an aroma descriptor I have never used when writing about food going in, just coming out.

I think more research is needed in this area to close our diary knowledge gap.