Use of Dean Flow Ultraviolet (UV) Reactors for the Cold Pasteurization of Tender Coconut Water

Introduction: The natural water inside the green coconuts is regarded as a healthy drink due to the elements of nutritional and therapeutic value. Since there is chance of contamination of tender coconut water (TCW) during extraction from its hard shell with psychrophilic microbes if they are stored at 4°C, thermal pasteurization is currently practiced. However, the thermal treatment of TCW causes rise in off flavors and loss of the vital nutrients. To solve this problem, a non-thermal pasteurization technology is desirable.

Purpose:  The goal of this research was to assess the antimicrobial effectiveness of Ultraviolet light (UVc) as cold pasteurization of TCW and evaluation of physico-chemical and sensory quality of the treated TCW in comparison to the fresh TCW.

Methods: A dean flow ultraviolet reactor with wavelength of 200-280 nm at the residence time of 14.2 seconds was used. The independent variables were 3 Reynold numbers (Re) and 2 diameters of transparent PFA tubes (1/8” and 1/16”).  The antimicrobial effect was evaluated with E. coli W1485 as a model organism for cold pasteurization. Physico-chemical and sensory quality of TCW were tested and analyzed throughout the storage period of 4 weeks.

Results: UVc treatment was significantly effective to inactivate E.coli W1485 (P <0.05) in both the tube sizes. Also, the diameter of tubes and Reynold numbers significantly  affected CFUs of E.coli in treated TCW as lesser diameter (1/16”) tube was more effective (3.1, 4.2 and 5.3 log reduction) than 1/8” tube (1.9, 2.4 and 3.09 log CFU reduction) and higher the Re values better the inactivation observed for 47, 95 and 142 Reynold numbers. The physico-chemical and sensorial changes of cold pasteurized TCW was not significantly different compared to the fresh TCW.

Significance: Dean flow UVc reactor offers a potential cold pasteurization technology for tender coconut water.