Effects of 1 year long-term freezing with different preservatives on milk cholesterol, progesterone and lactoferrin determination

This study was performed to determine the effects of long-term freezing on milk composition and to evaluate the possible effects on analysis of four preservative substances (Azidiol, Kathon CG, NaOH and Thiomersal) on the determination of milk cholesterol, progesterone and lactoferrin concentration. Collected milk was separated in aliquots, stored at 20 °C in 10mL plastic vials and analysed after 1, 6 and 12 months. It could be shown that the preservatives are not equally appropriate for all analysing methods used in this experiment. Preservatives and storage conditions for milk samples have to be carefully selected during the study design depending on the parameters to be measured.