Ultraviolet inactivation of bacteria and model viruses in coconut water using a collimated beam system

Abstract

This study investigated the effect of ultraviolet-C irradiation on the inactivation of microorganisms in coconut water, a highly opaque liquid food (1.01 ± 0.018 absorption coefficient). Ultraviolet-C inactivation kinetics of two bacteriophages (MS2, T1UV) and three surrogate bacteria ( Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes) in 0.1% (w/v) peptone and coconut water were investigated. Ultraviolet-C irradiation at 254 nm was applied to stirred samples, using a collimated beam device. A series of known ultraviolet-C doses (0–40 mJ cm−2) were applied for ultraviolet-C treatment except for MS2 where higher doses were delivered (100 mJ cm−2). Inactivation levels of all organisms were proportional to ultraviolet-C dose. At the highest dose of 40 mJ cm−2, three surrogates of pathogenic bacteria were inactivated by more than 5-log10 (p < 0.05) in 0.1% (w/v) peptone and coconut water. Results showed that ultraviolet-C irradiation effectively inactivated bacteriophage and surrogate bacteria in highly opaque coconut water. The log reduction kinetics of microorganisms followed log-linear and exponential models with higher R2 (>0.95) and low root mean square error values. The D10 values of 3, 5.48, and 4.58 mJ cm−2 were obtained from the inactivation of E. coli, S. Typhimurium, and L. monocytogenes, respectively. Models for predicting log reduction as a function of ultraviolet-C irradiation dose were found to be significant (p < 0.05). Fluid optics were the key controlling parameters for efficient microbial inactivation. Therefore, the ultraviolet-C dose must be calculated not only from the incident ultraviolet-C intensity but must also consider the attenuation in the samples. The results from this study imply that adequate log reduction of vegetative cells and model viruses is achievable in coconut water and suggested significant potential for ultraviolet-C treatment of other liquid foods.

Genomic Modeling as an Approach to Identify Surrogates for Use in Experimental Validation of SARS-CoV-2 and HuNoV Inactivation by UV-C Treatment

“…UV inactivates a broad spectrum of microorganisms by damaging the DNA or RNA and thereby prevents and/or alters cellular functions and replication ( Patras et al, 2020 ). UV-C inactivation of various microorganisms such as pathogenic bacteria, spores, protozoa, algae and viruses has been reported ( Malayeri et al, 2016 ; Bhullar et al, 2019 ; Gopisetty et al, 2019 ; Pendyala et al, 2019 , 2020 ; Patras et al, 2020 ). Because UV inactivation studies with SARS-CoV-2 requires specifically trained and skilled personnel working under biosafety level 3 (BSL-3) laboratory containment conditions, the use of surrogate coronaviruses has the potential to cross these hurdles for experimental validation of designed UV systems.…”

Effect of UV-C irradiation on the inactivation kinetics of oxidative enzymes, essential amino acids and sensory properties of coconut water

“…Since the dean muber, which denotes secondary dynamic instability of dean vorices (De [ 75) to fully turbulent flow conditions (De [ 400) (Ligrani 1994). Validation of UV-C fluence delivery and uniformity of the treatment at similar experimental flow conditions was performed by using biodosimetry (Bhullar et al 2019). A linear relationship between flow rate and reduction equivalent fluence (REF) was observed with R 2 [ 0.99, which confirm uniform distribution of UV fluence throughout the reactor (Bhullar et al 2019).…”

Evaluation of UV‐C LEDs efficacy for microbial inactivation in tender coconut water

“…The D 10 value of E. coli is slightly higher than the values reported in other studies where the D 10 value of E. coli ranges from 0.1 to 3.5 mJ/cm 2 (Bhullar et al, 2018;Sommer et al, 2000;Tosa & Hirata, 1999;Yaun et al, 2003) with UV-C mercury lamp. Bhullar et al (2019) reported the tailing effect during the inactivation of E.…”

“…Whereas with UV mercury lamp collimated beam system, the log inactivation for S. enterica was 5.14 log at a UV dose of 30 mJ/cm 2 . The dose-response curve followed the log-linear model with the UV-C mercury lamp (Bhullar et al, 2019).…”

“…Several studies have been reported on the inactivation of E. coli in coconut water using UV mercuryLamp (Augusto et al, 2015;Gautam et al, 2017;Ochoa-Velasco et al, 2014) Bhullar et al (2019). highlighted the application of UV-C in treating coconut water with a low-pressure mercury lamp collimated beam system, and reported that E. coli ATCC 25922 inactivation of 5.58 log CFU/ml in coconut water was achieved with a maximum UV-C dose of 40 mJ/cm 2 and a D 10 value of approximately 3 mJ/cm 2 at 254 nm.…”