Ultraviolet-C light inactivation of Escherichia coli and Salmonella typhimurium in coconut (Cocos nucifera L.) milk

• Coconut milk UV-C light treated to inactivate E. coli and S. typhimurium.
• First order kinetics and Weibull models fitted the microbial inactivation well.
• Phenolics were significantly reduced as the dosage of UV-C light increased.
• Coconut milk treated at 1.026 kJ/m2 was similarly sensory accepted as control.
• 4-log reductions of E. coli and S. typhimurium were achieved after 30 min treatment.

Coconut milk was inoculated with Escherichia coli and Salmonella typhimurium to evaluate their inactivation using a double tube type UV-C light system at different flow rates (0–30.33 mL/s) and times (0–30 min). Non inoculated coconut milk was UV-C light processed at 30.33 mL/s for selected dosages (0.342–1.026 kJ/m2) to evaluate some physicochemical (total soluble solids, pH, titratable acidity, and color), bioactive (phenolic compounds and antioxidant activity), microbial, and sensory characteristics. Untreated and heat treated coconut milk were used as controls. The maximum log reduction for both E. coli and S. typhimurium was 4.1 ± 0.1 after 30 min of UV-C light treatment at 30.33 mL/s. UV-C light affected color parameters of coconut milk. Phenolic compounds decreased and antioxidant activity barely changed by the UV-C light treatment. At 1.026 kJ/m2 of UV-C light dosage the reductions of mesophiles and molds plus yeasts were 2.0 and 1.3 log cycles, respectively.Industrial relevanceCoconut is a fruit of the tropical regions of the world. Today, water of coconut and coconut milk are being produced due to their natural benefits. Thermal processing is used to treat these products, however, flavors and change in color may occur as well as the inactivation of antioxidants and vitamins. The UV-C light processing is a promising non-thermal technology for “cold pasteurization” of coconut milk to avoid sensorial and nutritional changes and deliver a nutritious and microbiological safe food product to consumers.