Differences in milk total oxylipins between unthawed samples and samples with previous freeze–thaw cycles. Samples were collected as part of a case–control study of low milk supply. In this study, unthawed samples were not available for all subjects, so we tested for differences with previous freeze–thaw cycles. Total oxylipin (esterified + non-esterified) concentrations were higher with previous thawing for (A) 9-hydroxy octadecadienoic acid (9-HODE), (B) 13-HODE, (C) 9(10)-epoxy octadecamonoenoic acid (9(10)-EpOME), (D) 12(13)-EpOME, (E) 9(10)-dihydroxy octadecamonoenoic acid (9(10)-DiHOME), (F) 12(13)-DiHOME, and (G) Total Oxylipins, although the difference was not statistically significant for DiHOMEs. In contrast, (H) 9-hydroxy eicosatetraenoic acid (9-HETE), a marker of autoxidation, was not different from previous thawing. Unthawed, n = 36; Previously thawed, n = 10. Differences assessed by t-test. Data graphed as mean ± SEM.