1. Chemistry Department, The Royal Veterinary and Agricultural University, Copenhagen, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark, Department of Dairy and Food Sciences, The Royal Veterinary and Agricultural University, Copenhagen, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark, and Novo Nordisk A/S, Novo Allé, DK-2880 Bagsvaerd, Denmark