Distribution of spiked drugs between milk fat, skim milk, whey, curd, and milk protein fractions: Expansion of partitioning models

Authors: Lupton, Sara; Shappell, Nancy; Shelver, Weilin; Hakk, Heldur

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2017
Publication Date: 1/10/2018
Publication URL: https://handle.nal.usda.gov/10113/6042277
Citation: Lupton, S.J., Shappell, N.W., Shelver, W.L., Hakk, H. 2018. Distribution of spiked drugs between milk fat, skim milk, whey, curd, and milk protein fractions: Expansion of partitioning models. Journal of Agricultural and Food Chemistry. 66(1):306-314. https://doi.org/10.1021/acs.jafc.7b04463.
DOI: https://doi.org/10.1021/acs.jafc.7b04463

Interpretive Summary: Animal health drugs are sometimes secreted into milk after administration to dairy cattle. The fate of such chemicals during the processing of milk into products such as cream, skim milk, cheese, and whey is largely unknown. We measured the relationships among certain chemical properties (fat and water solubility) of 15 animal drugs and their distributions into skim milk, milk fat, curd (used to make cheese), whey, and whey protein. We then used the data to construct mathematical prediction models. The models generally provided good predictions of drug distribution into cow milk products based on the drug’s chemical properties. Data-based prediction models are valuable to risk assessors when evaluating the potential for human exposures to drug residues after the inadvertent consumption of drug residues in milk products.

Technical Abstract: The distributions of 8 drugs (acetaminophen, acetylsalicylic acid/salicylic acid, ciprofloxacin, clarithromycin, flunixin, phenylbutazone, praziquantel, and thiamphenicol) were determined in milk products (skim milk, milk fat, curd, whey, and whey protein) and used to expand a previous model (from 7 drugs to 15 drugs) for predicting drug distribution. Phenylbutazone and praziquantel were found to distribute with the lipid and curd phases (=50%). Flunixin distribution was lower, but similar in direction (12 % in milk fat, 39% in curd). Acetaminophen, ciprofloxacin, and praziquantel preferentially associated with casein proteins, whereas thiamphenicol and clarithromycin associated preferentially to whey proteins. Regression analyses for log of [milk fat]/[skim milk] and log of [curd]/[whey] had r2 values of 0.63 and 0.67, respectively, with p of <0.001 for 15 drugs (7 previously tested and 8 currently tested). The robustness of the distribution model was enhanced by doubling the number of drugs originally tested.