02-15 Milk carton

[Image above] Paperboard cartons are widely used in school meal programs, but a new study shows they do not preserve milk freshness as well as other containers. Credit: angela larose, Flickr (CC BY-NC-ND 2.0)


You may have had your fair share of chocolate yesterday—or today if you waited for post-Valentine’s sales. Either way, what better way to wash down the sugary treats than with a tall glass of cold milk?

Depending on how that milk was stored, there may indeed be better ways. In a recent open-access paper, researchers from North Carolina State University and Clemson University investigated the role that packaging material has on the flavor of milk.

Though glass bottles are the classic milk packaging choice, anyone who attended U.S. public school since the 1950s likely remember school lunches consisting of paperboard milk cartons served alongside a giant rectangular pizza slice featuring a “vegetable serving” worth of tomato paste. In grocery stores today, plastic jugs or bags are a common way milk is sold.

Credit: PBS Origins, YouTube

While it is well known that packaging material can affect the flavor of food, “The role of flavors from packaging (scalping or migration) on the sensory quality of fluid milks have not been fully investigated,” the researchers of the open-access paper write.

To investigate this role, the researchers packaged whole and skim milk in six different types of packages: amber glass, paperboard carton, and the plastics low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyethylene terephthalate (PET), and linear low-density polyethylene (LLDPE).

Sensory properties and volatile compound analysis were conducted on the day of first processing and then again on days 5, 10, and 15. Consumer difference testing was conducted on day 10 for milk packaged in HDPE versus glass, PET versus glass, and paperboard carton versus glass. The entire experiment was repeated three times.

The milk had no light exposure during the experiment because it “allows control of the study parameters such that the actual role of package material on migration or scalping, or both, can be clearly identified and sourced,” the researchers explain.

Testing confirmed that package type did influence milk flavor, with skim milk more susceptible to flavor impacts than whole milk. These off-flavors, which were detected by sensory analysis, correlated with increased specific migration of volatile compounds.

Milks packaged in paperboard cartons and LLDPE had the highest intensities of off-flavors, with off-flavors present almost immediately in skim milk. In contrast, milks packaged in HDPE, PET, and glass had no discernable sensory differences even after 10 days.

“These findings suggest that industry and policymakers might want to consider seeking new package alternatives for milk served during school meals [because it may affect how young children perceive milk in both childhood and adulthood],” says senior author MaryAnne Drake, William Neal Reynolds Distinguished Professor of Food Science at North Carolina State University, in an Elsevier press release.

The open-access paper, published in Journal of Dairy Science, is “The role of packaging on the flavor of fluid milk” (DOI: 10.3168/jds.2022-22060).

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