Inactivation of Bacillus and Clostridium Spores in Coconut Water by Ultraviolet Light

Abstract

Bacterial spores are generally more resistant than vegetative bacteria to ultraviolet (UV) inactivation. The UV sensitivity of these spores must be known for implementing UV disinfection of low acid liquid foods. UV inactivation kinetics of bacterial spores in coconut water (CW) and distilled sterile water was studied. Populations of Bacillus cereus and Clostridium sporogenes dormant spores were reduced by more than 5.5 log₁₀ at the UV-C photon fluence of 1142 μE·m^-2 and 1919 μE·m^-2 respectively. C. sporogenes spores showed higher UV-C resistance than B. cereus, with the photon fluence 300 μE·m^-2 required for one log inactivation (D₁₀) and 194 μE·m^-2, respectively. No significant difference was observed in D₁₀ values of spores suspended in the two fluid types (p > 0.05). The inactivation kinetics of microorganisms were described by log linear models with low root mean square error and high coefficient of determination (R² > 0.98). This study clearly demonstrated that high levels of inactivation of bacterial spores can be achieved in CW. The baseline data generated from this study will be used to conduct spore inactivation studies in continuous flow UV systems. Further proliferation of the technology will include conducting extensive pilot studies.