Scientists Fed Cows Sunflower Seeds And Made A Fascinating Discovery

No, brown cows don't produce chocolate milk. However, it's true that the diet of an animal affects the flavor of its milk. The effect has even been observed in human breast milk. In 2008, researchers from the University of Copenhagen in Denmark gave mothers different flavor concentrates in capsules, and the flavors were noticeable in the mothers' breast milk a few hours later. That raises the question: Can we change the flavor of cow's milk by changing the diets of dairy cows? The answer is unequivocally yes, but it's not a straightforward, black-and-white process. In the 1980s, researchers from Australia's Commonwealth Scientific and Industrial Research Organisation (CSIRO) discovered that feeding cows a mixture of oats and sunflower seeds could give their milk an entirely unexpected flavor: raspberry.

Certain plants can produce unintended, sometimes unappetizing flavors in cows' milk. When fed to dairy cows, cruciferous vegetables, such as broccoli and cauliflower, give milk an "off-taste" that has sometimes been described as akin to that of raw turnips. Such observations have been documented since at least 1829, when William Harley, writing for the London dairy industry, investigated the compositional effects of diet on the quality of cows' milk. Since then, the industry has developed a stronger understanding of the complex chemical relationship between feed and flavor.

The CSIRO team likely wasn't even expecting a raspberry flavor at all. Lactose is the primary reason milk tastes sweet — even before it's actually broken down into simpler, digestible sugars by lactase enzymes. However, the actual flavor profile of milk comes from combinations of other chemical compounds. Those chemical compounds can combine in virtually countless ways to produce entirely unexpected outcomes. When the team gave its dairy cows sunflower seeds and oats, a two-step pathway to raspberry flavor emerged.

Much of the research connecting sunflower seeds and raspberry-flavored milk emerged from the 1970s, 1980s, and 1990s and was never digitized for public access. Consequently, contemporary literature on the topic is mostly restricted to second-hand sources referencing the original findings. Fortunately, a 1990 paper by Gerda Urbach from CSIRO titled "Effect of Feed on Flavor in Dairy Foods" was digitized and published by The Journal of Dairy Science in 2010, and it clearly points to a particular compound responsible for giving milk a raspberry flavor: γ-dodec-cis-6-enolactone.

The chemical compound γ-dodec-cis-6-enolactone is a gamma-lactone. Unlike simpler lipids that make up the majority of fat content in cow's milk, such as triglycerides and phospholipids, lactones can produce drastically different flavor profiles depending on small molecular differences. Gamma-lactones are particularly stable, which is why food chemists must go through great measures to synthesize them for artificial flavorings. In laboratory settings, food chemists manipulate special yeasts to produce a variety of different lactones, producing flavors that include wood, coumarin, cream, hay, peach, butter, and, according to Urbach's findings, raspberry.

But producing specific lactones in a cow's gut isn't the same as producing them in a laboratory. Cows possess four separate stomachs, each with unique enzymes like rennin and rennet, to help convert grass into nutrient-dense milk. That's why the pathway to raspberry-flavored milk requires a delicate balance of oats and sunflower seeds. The CSIRO researchers observed that the oats encouraged specific bacterial blooms within the cows' guts. After devouring the oats, the excess bacteria then consumed the sunflower seed oil, leaving behind γ-dodec-cis-6-enolactone as a byproduct, which finally made its way into the cows' milk. The chemical process was complex, but the result was simple: sweet, fruity milk that tasted like raspberries.