Packaging may protect sensory properties of milk

A study published in the Journal of Dairy Science suggests that packaging is key in protecting milk from the damaging effects of light exposure. In addition, the study shows that light-emitting diode (LED) lighting causes nearly as much damage as fluorescent lighting. The damage to milk’s sensory properties is presumed to occur through the action of photosensitive compounds such as riboflavin, present in milk and capable of releasing energy when irradiated, leading to damage of proteins and fats in the milk.

The researchers exposed fat-free milk to LED and fluorescent light at 2,000 lx (light intensity) to compare the sensory thresholds of exposure, the flavor profile of milk produced by these exposures, and resultant consumer acceptance of the samples. Additionally, they tested the effectiveness of light-protective packaging and supplementation with antioxidants.

The researchers found that the sensory threshold for detecting differences in fluorescent light-exposed milk was 12 hr. In contrast, the threshold for detecting differences in LED-exposed milk was 9 hr, meaning that LED offered no significant improvement in the exposure time required for untrained panelists to detect off-flavors in light-exposed milk. The addition of antioxidants resulted in significantly fewer panelists discriminating the LED-exposed sample from controls, with the group sensory threshold over the maximum 48-hr time point.

Trained panelists described the 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 nanometers (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.

The researchers found that 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. Nevertheless, consumers disliked its appearance, due to unfamiliarity, suggesting some consumer education may be needed if this were to be an efficient protective strategy.

Study