Modeling the effect on skim milk during ultra-high pressure homogenization using front-face fluorescence

This study provides a rapid method to evaluate and control quality changes in skim milk, using front-face fluorescence during ultra-high pressure homogenization (UHPH), for potential inline usage. Tryptophan, dityrosine and Maillard compounds were selected as indicators for their intrinsic fluorescence. The homogenization pressure was from 100 to 300 MPa and inlet temperature was from 23 to 83 °C, both distributed on a central composite design. The selected fluorophores showed good fit to the models as functions of pressure and inlet temperature. However, there was little formation of dityrosine and Maillard compounds when inlet temperature was below 50 °C. Tryptophan and dityrosine fluorescence could provide information on milk protein changes, such as denaturation, reformation and aggregation, while generation of Maillard compounds indicated thermal effects between sugars and amino acids. This work shows a promising potential to monitor and predict structural and functional changes in milk during UHPH processing and decide on its appropriate usage for further dairy production.