1. University of Turku, Department of Biochemistry and Food Chemistry, FIN-20014 Turku, Finland.
2. Corresponding author. Email: anja.lapvetelainen@uku.fi Fax: +358-17-163 903. Phone: +358-17-163 931.
3. Melia Ltd., PO Box 101, FIN-21201 Raisio, Finland.
4. University of Turku, Department of Statistics, FIN-20014 Turku, Finland.