Potential use of DBD based 222 nm exciplex light source for milk sterilization and its comparative analysis with 253 nm UV-light and conventional pasteurization

KrCl* excilamp treatment has emerged as a potential method to replace conventional 254 nm low-pressure mercury UV-C lamps to ensure the microbiological safety of food items. In this study, we demonstrated a dielectric barrier discharge (DBD) based mercury-free 222 nm exciplex source to investigate the microbial and physicochemical properties of raw milk and compared it with 253 nm and pasteurization methods. The UV dose delivered to the milk samples was estimated using the chemical actinometry method and found to be 10.9 J/ml. The methylene blue reduction test (MBRT) of milk was increased for more than 5 h, with just 2.5 min of far UV-C (222 nm) treatment. Approximately 2.58 log and 2.11 log decrease in the E. coli and S. aureus were achieved after 2.5 min of 222 nm treatment of whole milk. We inferred that 222 nm UV light is more efficacious vis-à-vis 253 nm and pasteurization in increasing milk quality without altering its physicochemical properties, indicating its potential use as a more efficient UV source for enhancing milk safety, quality, and shelf life. This widens the scope for the use of mercury-free far UV-C irradiation as a viable and non-thermal technology in the dairy industry, food sector, and overall sterilization applications.