USA- Scientists from the North Carolina State University carried out a test analysis that offers insights into how some packaging materials impact the sensory and chemical properties of milk, which was published in the Journal of Dairy Science.
Research led by MaryAnne Drake a director of the Southeast Dairy Foods Research Centre was carried out where the team poured samples of pasteurized whole milk and skimmed milk into six different types of packaging.
The varieties of packages were glass, LDPE (low-density polyethylene), HDPE (high-density polyethylene), PET (polyethylene terephthalate), LLDPE (linear low-density polyethylene) and paperboard carton.
The researchers then conducted sensory and volatile compound analysis first at the time of the initial processing and again on days 5,10 and 15.
All the samples were stored at 4℃ in total darkness and on the test days consumers were asked to taste and test the samples and record the differences they observed.
According to the study report, glass bottles are the most advisable package as they retain the milk flavour, are more environmentally friendly and are considered more hygienic.
Plastics, on the other hand, have other desirable properties like recyclability, and how they provide strong barriers between the milk and the packaging.
Cardboard containers are mostly used to block light from penetrating into the milk to protect the photosensitive milk components like riboflavin.
Paperboard-packaged milk reported to have a stronger ‘paper taste’
From the trial, different distinct flavours were observed across the different packaging types for both skimmed and whole milk however skimmed milk was more found to be susceptible to off-flavours.
Milk packaged in paperboard cartons and LLDPE packages was found to have ‘lower cooked and sweet aromatic flavours with storage time and distinct stale flavours’ compared to milk stored in PET, HDPE and LDPE containers.
The paperboard-packaged milk was also reported to have a stronger ‘paper taste’ within hours of storage.
As for chemical transfer, milk packaged in paperboard and plastic bags also had higher amounts of chemical compounds after days of storage.
Volatile packaging compounds found in carton milk
This is attributed to paperboard and LLPDE barriers being more permeable than the rest as their milk was reported to contain higher concentrations of volatile packaging compounds such as styrene, as compared to the milk packaged in glass, PET, HDPE and LDPE.
These compounds migrated into the milk the longer it stayed in refrigeration and the longer the milk interacted with the packaging materials.
The respondents generally detected differences between milk packaged in cartons and milk packaged in glass but could not detect the differences between milk in PET and glass or HDPE and glass.
Implications for the dairy industry
According to the USDA, HDPE and PET make up more than 85% of fluid milk packaging in the united states, while paperboard cartons make up 14%.
Cartons are mostly used as packaging in school meal programs and the study, therefore, recommends that new packaging types be employed to mitigate the potentially negative effects of milk packaged into cartons among children.
“Our findings suggest that industry and policymakers should seek new package alternatives for school meal fluid milk,” noted the authors of the report.
“The consequences of using fluid milk packaging that contributes significant off-flavours, over time, may affect how young children and those children as adults perceive fluid milk.”
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