Those LED Lights in Supermarket Dairy Cases are Making Milk Go Bad

But light, even the highest-end of LED lights, can have ill effects on grocery items, according to a new study from Cornell University.

It’s been known for decades that light can negatively affect milk’s flavor, bacterial decay, and even color – really, decades! That, along with weight and durability, is one of the reasons milk is no longer as commonly stored in transparent glass bottles. But this new study shows that despite all this knowledge, milk is still being degraded right in the supermarket.

Light can trigger a few unwanted chemical reactions in milk. Paramount in that list is that riboflavin, an essential nutrient, is destroyed incredibly quickly upon being exposed to light. That degradation triggers all kinds of other reactions: fats and proteins are oxidized, creating unpleasant flavors sometimes described as “metallic” or “cardboard-y.”

The study is a comparison of consumer preference; it measured how much testers liked milk that was kept under typical LED light exposure for different amounts of time. The results are pretty crazy: It found that testers greatly preferred milk that was kept well away from sources of light. They even preferred two-week-old milk that was kept in the dark to fresh milk that had been exposed to normal amounts of LED lighting for a mere few hours.

The researchers suggest that light may have a greater impact on the freshness of milk than when the milk was bottled – that, basically, how well-lit the display is can tell you more about the freshness of milk than the expiration date. But will supermarkets risk de-lighting their dairy aisles if that makes the milk look less enticing?