The study, published in the Journal of Dairy Science, noted that light exposure can damage the sensory properties of milk, leading to adverse consumer responses.
This begins with riboflavin, porphyrins, chlorins, and other photosensitive components that, once activated, produce singlet oxygen that can react with proteins, vitamins, and lipids, leading to sensory defects in the milk.
Light-emitting diode (LED) light usage in retail stores is increasing, but some disagreement is present about the details of the sensory effects of LED on milk.
LED lighting is assumed to be less damaging to milk; however, the authors argued previous research shows consumers have mixed reactions to LED-exposed milk, dependent on the amount of exposure, and type of milk.
The purpose of this study was to determine the minimum duration of exposure to fluorescent and LED light in fat-free milk, and to evaluate the efficacy of antioxidant enrichment; to compare the flavor profile via descriptive sensory of fat-free milk exposed to LED and fluorescent light, as well as determine the effectiveness of protective measures in milk exposed to LED; and to characterize consumer acceptance for all these conditions.
For the investigation, fat-free milk was exposed to LED and fluorescent light at 2,000 lx.
The sensory threshold from LED exposure was no longer than from fluorescence, whereas with antioxidants (tocopherols and ascorbic acid), the majority of panelists failed to discriminate milk exposed to LED light even after 48 hours of exposure.
The trained panelists described light-exposed milk as significantly higher in cardboard, old oil, and plastic, with LED exposure resulting in a marginally more ‘plastic’ aroma, and fluorescent marginally more ‘cardboard.’
Consumers reported higher liking for fluorescent-exposed samples versus those exposed to LED. The antioxidant-supplemented samples, and those exposed to LED light engineered to eliminate wavelengths below 480 nm (thus most of riboflavin's absorption peaks), resulted in significantly higher old oil aroma; however, the former received higher liking scores than LED-exposed samples.
Protective packaging materials, light wavelength tailoring, and antioxidant supplementation have been studied as possible interventions to prevent milk off-flavors from developing during light exposure.
Light-protective packaging offered near-complete protection from LED exposure, with a similar flavor profile as unexposed milk, and the best liking scores of any treatment.
The authors noted that consumer liking of the appearance of the container was not in agreement with consumer response to the milk's flavor. In fact, consumers rated this package as less liked than any other treatment, flavor notwithstanding.
The majority of criticisms of the packaging were related to unfamiliarity, and that it might not sell well.
The authors argue that an appearance that better resembles current packaging options needs to be found, or some degree of consumer education may be necessary for such a strategy to succeed.
However, as the issue relates primarily to unfamiliarity, they noted the problem would become less important with time, as such packaging became progressively more familiar.
Exposure to light-emitting diodes may be more damaging to the sensory properties of fat-free milk than exposure to fluorescent light
Source: Journal of Dairy Science
Authors: Ana C. Chang, Robin Dando