Other Potential Migrants from PLA

Conn et al. [8] made a detailed discussion about the average daily intake of lactic acid from food sources that was estimated as 924 mg/day for those 2 years of age and older. In addition, 377 mg/day for calcium lactate was estimated for the same group. Regarding infants consumption of lactic acid, breast milk contains 60 mg/L of L-lactic acid with an estimated daily intake as high as 10 mg/kg. From a different perspective, a breast-fed infant weighing 4 kg would consume about 36 mg of L-lactic acid/day from both, human and formula milk. 

Regarding the consumer exposure to D-lactic acid, in 1995 Conn et al. [8] took the dietary concentration of 0.018 mg/kg of lactic acid as indirect food additive from all purpose uses of PLA and considering that PLA would never have more than 50% of D-lactic acid (usually 0-10% at that time), a maximum dietary concentration of 0.009 mg/kg value was estimated for this isomer for which intake is controlled for infants. From these estimations. Conn et al. [8] confirmed that PLA was safe and GRAS for being used in fabricating articles intended to be in contact with food. At present, a commercial racemic PLA (50 50 L-lactic acid D-lactic acid) is used for high-temperature applications [25], which was already considered by Conn et al. s [8] estimations in 1995, as the worst-case scenario. At present and in order to update the dietary exposure to lactic acid, a new CF that considers 

The plastics industry has been introducing new formulations of PLA with additives intended to improve the properties of the final article. Plasticizers, stabilizers, and other substances are now integrated in the articles that will be in contact with food. 

Other additives used in PLA formulations are slip additives (natural waxes) [26], impact modifiers (sodium alkyl sulfonate) [26], melt strength modifiers (epoxy-functional styrene/acrylic oligomer) [30], and so on. Although the companies that produce these resins or masterbatches claim to have been approved in materials in contact with food, there are no reports of migration to food or food simulants to show that they comply with the legislation. 

New additives for PLA and their impurities should be tested for migration into food or food simulants in order to confirm their safety before they are used for food packaging. 

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