Since they use only a fifth of the electricity required by a comparable incandescent bulb, light emitting diodes (LEDs) are currently among the most energy-efficient light sources in the world. Although, the LEDs are still more expensive than the conventional bulbs, the “green” image makes them very attractive for many businesses and consumers alike. Recently it was observed that many retailers are starting to replace the fluorescent lights with the LED lighting in their stores. 
According to statista.com, by 2020 the LED lighting will occupy 61% of the global lighting market.
It is well know that milk sensory quality and nutritional content are affected by the exposure to sun light. Milk exposed to sunlight develops a “light oxidized” odor and flavor, which is typically described as “plasticky, burnt protein/feathers, or medicinal” odor/flavor (Clark et al., editors, 2009. The Sensory Evaluation of Dairy Products). Light also degrades riboflavin (Vitamin B2), an essential nutrient.
For the past 100 years, it has been discussed how to produce milk in packaging that is protected from sunlight (Hammer and Cordes, 1920). It is also known that any light, not just sunlight, has potential to induce off-flavors in milk. As any light, the LED lighting has a potential to damage the perceived quality of milk. The light exposure is dependent upon the wavelengths of the stimulus. The pattern of wavelengths produced by the LED lighting differs from that of the fluorescent lighting. LEDs typically emit in the blue spectrum around 460 nm (Heffernan et al., 2007; Narukawa et al., 2010) in a broader emission peak than the fluorescents. This lies adjacent to the 450 nm which is found to promote the most riboflavin degradation (Choe et al., 2005). As any light, the LED lighting has potential to damage the perceived quality of milk.
Little is known about the effects the change in lighting (conversion to LED vs fluorescent) has on the sensory properties and perceptions of quality of the food products that are stored and sold under these conditions.
A recent study by Cornell University compared the sensory qualities and consumer perceptions of 2% and skim milks that were exposed to LED lighting versus unexposed/”light-shielded” products, over their shelf-life. (Note: This research did not compare the effects of the LED lighting compared to the fluorescent lighting exposure.)
Overall, the data suggests that consumer preference of skim and 2% milk is more profoundly influenced by exposure to light (LED lighting) than by the storage time. On a 9-point hedonic scale, 
consumers rated light-exposed fresh samples almost one point lower than non-light-exposed fresh samples (6.8 vs. 5.9). The initial 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, when considering only the light exposed samples. This is presumably due to the freshly light-exposed samples have no time for off aromas to disperse.
The consumer liking of 2% milk samples was significantly higher than for the skim milk samples. Similar to skim milk, consumers liked 2% milk samples that were not exposed to light more than those that were light exposed. Interestingly, consumers were somewhat more forgiving and penalizing 2% milk less severely than skim for light exposure. This is possibly due to inherent higher degree of liking for the product or for its innate white, thick, creamy appearance.
Although this research did not compare the effects of the LED and fluorescent lighting “head to head”, the data clearly showed that LED light exposure for a relatively short period of time (4 hours) will readily induce light-oxidized flavor, reducing consumer liking to a similar level noted in previous studies of fluorescent lighting.
All current popular milk packaging allows for certain light exposure to occur. Therefore, these types of packaging have potential to compromise the highest quality milks by allowing the off-flavors to develop, which we know lead to lower consumer liking of milk. The Dairy Industry should start thinking about investing more in the fields of Material Sciences and Package Engineering for possible affordable and effective solutions to this problem. Its success depends on the delivery of the highest quality of milk to consumers.
Meanwhile, the next time you’re buying milk in the store, don’t just to look at the “expiration date” on the package, but reach deep into the display case and get the least light exposed milk package from the back of the cooler.
For the full article, click on the link below:
http://www.sciencedirect.com/science/article/pii/S002203021630131X
May 2016 Update:
This article, “Exposure of fluid milk to LED light negatively affects consumer perception and alters underlying sensory properties”, has been selected as an Editor’s Choice for the Journal of Dairy Science, with authors Nicole Martin, Nancy Carey, Steven Murphy, David Kent, Jae Bang, Tim Stubbs, Martin Wiedmann, and Robin Dando. Congratulations to all the authors!!!
References:
Choe, E., R. Huang, and D.B. Min. 2005. Chemical reactions and stability of riboflavin in foods. J. Food Sci. 70:R28-R36.
Clark, S., M. Costello, M. Drake, F. Bodyfelt, editors. 2009. The Sensory Evaluation of Dairy Products. 2nd Edition.
Hammer, B.W., and W.A.Cordes. 1920. A study of bown glass milk bottles with special reference to their use in preventing abnormal flavors due to light. Iowa Agric. Expt. Stat. Res. Bull (Sun Chiwawitthaya Thang Thale Phuket) 64:246
Heffernan, W.J. B., L.P. Frater, and N.R. Watson. 2007. LED Replacement for Fluorescent Tube Lighting. Power Engineering Conference, AUPEC2007, Australasian Universities, Pert, WA. p.4
Martin, N., N. Carey, S. Murphy, D. Kent, J. Bang, T. Stubbs, M. Wiedmann, and R. Dando. 2016. Exposure of fuild milk to light-emitting diode light negatively affects consumer perceptions and alters underlying sensory properties. J. Dairy Sci. 99:1-16
Narukawa, Y., M. Ichikawa, D. Sanga, M. Sano, and T. Mukai. 2010. White light emitting diodes with super-high luminous efficacy. J. Phys. D Appl. Phys. 43:1-6
