10 Jan 2017 The science of better-tasting milk
A new study finds that fluorescent light can degrade the flavour of milk in supermarkets—and offers some solutions.
There’s no use crying over spilt milk, but you might well shed a tear or two over the taste of milk in the era of plastic cartons.
Scientists at Virginia Tech in the US report that, in blind tastings, the flavour of milk stored in a standard supermarket-style dairy cooler is significantly degraded by fluorescent light passing through translucent plastic containers.
But when LED bulbs were used instead, tasters rated the milk about the same as when it was packaged in a lightproof container—which is to say, a lot better.
Americans drink less milk just about every year. According to data from the USDA, per-capita consumption is off by more than a third since 1975—which, says Dr Susan Duncan, one of the Virginia Tech scientists, is around the time that plastic milk cartons went mainstream.
Of course, health experts and public officials were also warning against animal fat. But cheese and yoghurt consumption increased considerably over the same period, and even butter saw an uptick, suggesting that cholesterol warnings were not much of a deterrent.
On the other hand, says Duncan, the widespread adoption of translucent plastic containers almost certainly changed the flavour of milk for the worse. By now, she says, consumers mistakenly believe that this is how milk is supposed to taste.
In blind tastings, two panels of more than 150 volunteers each were given milk and asked to rate their experience of it using a nine-point scale (in which 1 means “dislike extremely” and 9 means “like extremely”).
Milk that had been exposed to fluorescent light had far more ratings in the “dislike region” of four or lower. Volunteers described the fluorescent-exposed milk as tasting like “cardboard” or seeming “stale” or “painty”.
“Changes occurred in milk that affected flavour and quality after as little as four hours of light exposure, which were noticeable to untrained consumer panelists,” the scientists write.
Fluorescent lighting has been named as a culprit in milk degradation before. But Duncan says that her study is the first to use regular retail dairy coolers, thereby simulating real-world milk storage conditions, and that it bolsters the case for LEDs in milk-storage cases.
(LED stands for light emitting diode. Bulbs made with this technology are rapidly gaining market share thanks to falling prices, long life, low energy consumption and the pleasing quality of their light.)
How does fluorescent lighting affect milk?
Scientists say that its higher ultraviolet energy, among other characteristics, triggers a process of oxidation that damages essential nutrients, especially riboflavin, resulting in inferior flavour as well as a less healthful beverage.
Over longer time periods, LEDs can degrade milk flavour as well, though not as much. Notably, neither kind of light makes milk go sour any sooner.
Duncan says that she is working with the dairy industry (which partly funds her work) to encourage costlier packaging that blocks light and to suggest that retailers switch away from fluorescent bulbs.
Meanwhile, she advises, consumers might want to buy milk in cardboard cartons. If you are buying by the gallon (which usually comes in plastic packaging), Duncan suggests looking for jugs stored on lower shelves or pushed way to the back, as far as possible from any fluorescent lighting source.
“Retail lighting and packaging influence consumer acceptance of fluid milk,”
Hayley Potts, Kemia Amin and Susan Duncan, Journal of Dairy Science (Nov 16)