Milk cartons reduce freshness and flavor, find researchers

30 Jan 2023 --- Study authors explain that the flavor of milk has changed over time due, in part, to changes in the packaging used to transport milk to the consumer. Light oxidation from transparent containers, as well as scalping and migration from different packaging types, “affect the flavor of milk and have led to consumer dissatisfaction,” it explains. 

Dr. MaryAnne Drake of the North Carolina State University Department of Food, Bioprocessing and Nutrition Sciences, US, explains that “milk is more susceptible to packaging-related off-flavors than many other beverages because of its mild, delicate taste.”

Besides light oxidation, “milk’s taste can be impacted by the exchange of the packaging’s compounds into the milk and by the packaging absorbing food flavors and aromas from the surrounding refrigeration environment.”

Glass is the optimal packaging type for preserving milk, shows the study.The study, published in the Journal of Dairy Science, shows that skim milk is more susceptible to flavor impacts than whole milk. Of different packaging types, paperboard cartons and the plastic bag preserved milk freshness the least due to the paperboard’s absorption of milk flavor and the transfer of paperboard flavor into the milk.

Fiber-based frenzy
Carton box-based milk packs are traditional in most parts of the world. Packagers are increasingly turning away from plastic alternatives wherever possible, as highlighted by Innova Market Insights’ 2021 Top Ten Trend “Fiber-based Frenzy,” which examined the rush industry players are making to avoid plastics as global legislation and public sentiment tightens. 

However, Dr. Drake and her team hypothesized that fiber-based containers such as cartons would have an adverse effect on the taste of milk when compared to glass or plastics.

To quantify flavor impacts, the researchers examined pasteurized whole and skim milk stored in six half-pint containers: paperboard cartons, three plastic jugs (made from PET, HDPE, or LDPE), a plastic bag, and glass as a control. The milk was stored in total darkness to control for light oxidation and kept cold at 4°C (39°F).

The samples were tested on the first processing day, then again at five, ten, and 15 days after. A trained panel examined the sensory properties of each sample, and the research team conducted a volatile compound analysis to understand how the packaging was intermingling with the milk. 

Finally, the samples underwent a blind consumer taste test on day ten to see whether tasters could tell any difference between milk stored in the paperboard carton or the plastic jug compared with milk packaged in glass.

Results
The results showed that package type does influence milk flavor, and skim milk is more susceptible to flavor impacts than whole milk. 

Milk packaged in paperboard cartons, in fact, showed distinct off-flavors as well as the presence of compounds from the paperboard. 

The final results show that, while glass remains an ideal container for preserving milk flavor, plastic containers provide additional benefits while also maintaining freshness in the absence of light exposure.

Paperboard cartons are the most widely used packaging type for school meal programs in the US, so these findings are especially relevant for considering how young children consume and enjoy milk.

“These findings suggest that industry and policymakers might want to seek new package alternatives for milk served during school meals,” says Drake. “Over time, the consequences of using milk packaging that contributes significant off-flavors may affect how young children perceive milk in both childhood and adulthood.” 

Edited by Louis Gore-Langton

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