Grocers “might unwittingly sabotage the product they are trying to sell” by installing energy-saving LEDs in the dairy case, says Cornell. In taste tests, consumers—who prefer fresh and high-quality milk—gave lower scores to milk exposed to LED light for four hours than to milk that was days or even weeks older.
“This study shows that light exposure is a much greater factor explaining deteriorating milk quality than even age,” said Nicole Martin, lead author of the study. Co-author Martin Wiedmann said the study “provides new information that can be used to further improve the quality of milk, for example, through light-shielding packaging.”
LED lighting produces a different wavelength pattern than the florescent lights often used to illuminate refrigerator cases. The peak in LED light is near the light band where riboflavin absorbs light, which the Cornell researchers surmised could damage the nutrients and lower the perceived quality of the milk. “The light exposure effects were so powerfully negative that the ‘near code/near expiration date’ sample was preferred in every case to the fresh sample regardless of microbial defects,” said a Cornell release.