Writing in the International Dairy Journal, scientists at the Fonterra Research Centre explored the sources and causes of an undesirable musty smell in drinks containing calcium caseinate from New Zealand.
Samples of finished beverages and calcium caseinate affected by the musty smell were collected off-shore and returned to New Zealand for analysis.
In an examination of the samples the Fonterra scientists traced the intense musty/leather smell to chemical tainting by 2,4,6-tribromophenol (TBP) and 2,4,6-tribromoanisole (TBA).
In samples of finished beverages TBA was found at concentrations of between 0.5 and 0.9 μg kg-1; substantially above the sensory threshold (0.02 μg kg-1 in a 10 per cent calcium caseinate solution). TBA concentrations were even higher in the calcium caseinate samples (20 to 560 μg kg-1).
Because TBP and TBA are highly unusual compounds to be found in dairy products and were not found in retention samples, it was concluded that contamination must have occurred in the supply chain, after manufacture.
Knowing that shipping containers are commonly associated with tainting, the Fonterra researchers turned their investigation in this direction.
Origin of TBA and TBP taint
In the search for the origin of the TBP and TBA taint, the scientists identified timber shipping container floors and slipsheets constructed from recycled plastics as the two likely sources.
TBP was found in both timber samples and recycled slipsheets - TBA was not identified but TBP readily converts to TBA by environmental fungi in the general environment. Both could therefore be considered sources of TBP and TBA.
Despite identifying these potential sources, the scientists found that even materials that contained significant amounts of TBP still did not contain enough to fully account for the amount of tainting in the retail beverages.
However, no other potential sources were found so it was concluded that this may be due to samples not being representative or poor extraction of the samples. Acting on the conclusions, Fonterra now ships using slipsheets made from virgin plastic resins free from BFRs (the suspected cause of TBP contamination in slipsheets made from recycled plastic). No significant levels of TBP or TBA have been detected in products that ship on these slipsheets.
Source: International Dairy Journal
A musty flavour defect in calcium caseinate due to chemical tainting by 2,4,6-tribromophenol and 2,4,6-tribromoanisole
Authors: Paul Andrewes, Justin G. Bendall, Graham Davey, Rebecca Shingleton