Evaluation of UV-C Irradiation Treatments on Microbial Safety, Ascorbic Acid, and Volatile Aromatics Content of Watermelon Beverage

Ultraviolet irradiation as alternative non-thermal cold pasteurization to improve quality and microbiological parameters of mango juice during cold storage

The objectives of this research were to study the effect of UV irradiation on quality characteristics of mango juice during cold storage. Mango juice exposed to UV radiation was also used to determine zero-order and first-order kinetic models of microbial (total plate count, yeast and mold count, and Escherichia coli) reduction. According to the microbiological results, UV light at 120 J/cm2 caused a 5.19 log reduction. It was found that microbial inactivation of all tested microorganisms followed first-order kinetic model. The treatments did not differ significantly in terms of the quality metrics. L*, b*, pH, total soluble solid, total phenolic compound, total flavonoid content, and antioxidant activity as measured by the DPPH and FRAP assay all tended to decline during storage at 4 °C, whereas a*, ∆E, titratable acidity, total plate count, yeast and mold count, as well as the total plate count, had an increasing trend. During storage at 4 °C, UV irradiation increased the shelf life of mango juice by about 14 days compared to the control sample. In conclusion, this study demonstrated the potential of UV treatment as an alternative to thermal pasteurization for preserving mango juice quality and safety while also prolonging shelf life.

Modeling and validation of delivered fluence of a continuous Dean flow pilot scale UV system: monitoring fluence by biodosimetry approach

The inactivation of pathogenic microorganisms in water and high transmittance liquid foods has been studied extensively. The efficiency of the process is relatively low for treating opaque liquid foods using traditional UV systems. This study evaluated the ability of UV-C light to inactivate foodborne pathogens in a simulated opaque fluid (6.5 to 17 cm^-1) at commercial relevant flow rates (31.70, 63.40, 95.10 gph) using a pilot-scale Dean Flow UV system. In this study, a mathematical model for the prediction of delivered fluence was developed by the biodosimetry method. The results revealed that increased Reduction equivalent fluence (REF) rates were observed with increased flow rates due to additional turbulence. The experimental and calculated REF were well correlated with the UV-C absorption coefficient range of 6.5 to 17 cm^-1 indicating efficient mixing in the reactor. REF scaled up linearly at experimental conditions as an inverse function of flow rate and absorption coefficient, and a linear mathematical model (R² > 0.99, p < 0.05) to predict delivered REF was developed. The model was tested and validated against independent experiments using Salmonella Typhimurium and Bacillus cereus endospores. The predicted and experimental REF values were in close agreement (p > 0.05). It is demonstrated that the developed model can predict the REF, thus microbial inactivation of microbial suspensions in simulated fluid with the absorption coefficient of 6.5-17 cm^-1 and flow rates of 31.70-95.10 gph. The pilot system will be field-tested against microorganisms in highly absorbing and scattering fluids.

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

Severe Acute Respiratory Syndrome coronavirus-2 (SARS-CoV-2) is responsible for the COVID-19 pandemic that continues to pose significant public health concerns. While research to deliver vaccines and antivirals are being pursued, various effective technologies to control its environmental spread are also being targeted. Ultraviolet light (UV-C) technologies are effective against a broad spectrum of microorganisms when used even on large surface areas. In this study, we developed a pyrimidine dinucleotide frequency based genomic model to predict the sensitivity of select enveloped and non-enveloped viruses to UV-C treatments in order to identify potential SARS-CoV-2 and human norovirus surrogates. The results revealed that this model was best fitted using linear regression with r ² = 0.90. The predicted UV-C sensitivity (D ₉₀ - dose for 90% inactivation) for SARS-CoV-2 and MERS-CoV was found to be 21.5 and 28 J/m², respectively (with an estimated 18 J/m² obtained from published experimental data for SARS-CoV-1), suggesting that coronaviruses are highly sensitive to UV-C light compared to other ssRNA viruses used in this modeling study. Murine hepatitis virus (MHV) A59 strain with a D ₉₀ of 21 J/m² close to that of SARS-CoV-2 was identified as a suitable surrogate to validate SARS-CoV-2 inactivation by UV-C treatment. Furthermore, the non-enveloped human noroviruses (HuNoVs), had predicted D ₉₀ values of 69.1, 89, and 77.6 J/m² for genogroups GI, GII, and GIV, respectively. Murine norovirus (MNV-1) of GV with a D ₉₀ = 100 J/m² was identified as a potential conservative surrogate for UV-C inactivation of these HuNoVs. This study provides useful insights for the identification of potential non-pathogenic (to humans) surrogates to understand inactivation kinetics and their use in experimental validation of UV-C disinfection systems. This approach can be used to narrow the number of surrogates used in testing UV-C inactivation of other human and animal ssRNA viral pathogens for experimental validation that can save cost, labor and time.

Performance of a UV-A LED system for degradation of aflatoxins B1 and M1 in pure water: kinetics and cytotoxicity study

The efficacy of a UV-A light emitting diode system (LED) to reduce the concentrations of aflatoxin B₁, aflatoxin M₁ (AFB₁, AFM₁) in pure water was studied. This work investigates and reveals the kinetics and main mechanism(s) responsible for the destruction of aflatoxins in pure water and assesses the cytotoxicity in liver hepatocellular cells. Irradiation experiments were conducted using an LED system operating at 365 nm (monochromatic wave-length). Known concentrations of aflatoxins were spiked in water and irradiated at UV-A doses ranging from 0 to 1,200 mJ/cm². The concentration of AFB₁ and AFM₁ was determined by HPLC with fluorescence detection. LC–MS/MS product ion scans were used to identify and semi-quantify degraded products of AFB₁ and AFM₁. It was observed that UV-A irradiation significantly reduced aflatoxins in pure water. In comparison to control, at dose of 1,200 mJ/cm² UV-A irradiation reduced AFB₁ and AFM₁ concentrations by 70 ± 0.27 and 84 ± 1.95%, respectively. We hypothesize that the formation of reactive species initiated by UV-A light may have caused photolysis of AFB₁ and AFM₁ molecules in water. In cell culture studies, our results demonstrated that the increase of UV-A dosage decreased the aflatoxins-induced cytotoxicity in HepG2 cells, and no significant aflatoxin-induced cytotoxicity was observed at UV-A dose of 1,200 mJ/cm². Further results from this study will be used to compare aflatoxins detoxification kinetics and mechanisms involved in liquid foods such as milk and vegetable oils.