Mature breast milk samples were collected from volunteer healthy mothers (n = 6; between 32 and 36 years old and between 3 and 26 months from parturition) from Maire Association (Association of Breastfeeding support of Badajoz, Spain) in July 2012. Each mother donated between 100 and 200 mL of milk that was collected during the previous day of the assay. Milk was kept in the refrigerator until the experiments were carried out during the next morning.