Impact of Dehydration on Lysine Loss in a Model Dairy Formulation

The essential amino acid lysine can be damaged due to exposure to elevated temperatures and due to dehydration during drying of dairy products. In this study, the impact of dehydration on the loss of available lysine was elaborated using vacuum dehydration at moderate temperatures at timescales that allow recording the degradation kinetics. The content of available lysine decreased during dehydration. The drying rate as well as the thermal conditions during drying had no significant impact on the loss of available lysine above a water content of 10%. A sharp increase in lysine loss was observed at water contents below 10% when thermal stresses become important. In conclusion, the dynamics during water removal seem to provoke lysine losses during drying.