Challenges in developing a Process Analytical Technology (PAT)-based verification of UV-C treatment of milk

Ultraviolet radiation (UV-C) is building a strong reputation as a non-thermal processing method in the food industry which inactivates spoilage and pathogenic microbes through DNA damage. Approved under Regulation (EC) No 258/97, UV-treated milk is deemed safe, with EFSA approving a dose of 1045 J/L post-pasteurisation, increasing vitamin D3 content and shelf life to 21 days. However, current verification relies solely on reactor process conditions, which may fail. Therefore, a verification method, akin to pasteurisation's alkaline phosphatase test, is essential. A process analytical technology sensor, analysing photooxidation-induced spectral changes, could ensure treatment efficacy. However, developing such sensors faces challenges from milk's optical properties (low UV transmission) and natural variability. Developing such sensor could pave the way for standalone UV-C treatment as a future environmentally friendly alternative. The objective of this study is to systematically document the challenges encountered to date in the investigation of this novel verification methodology.