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Recent advancements in ultraviolet light-emitting diodes (UV-LEDs) have allowed for their successful integration into continuous disinfection reactors including small-scale systems designed for low UV transmission (UVT) applications. This study characterized the performance of the first commercially available benchtop continuous-flow multiple-wavelength UV-LED system used for the treatment of juices and beverages in thin film. Three beverages (coconut water, blue lemonade, and pink lemonade), two juices (green juice blend and beet juice blend), and saline solution were inoculated with a non-pathogenic Escherichia coli indicator organism and treated at 281 nm. The volume averaged fluence delivered to the samples per pass ranged between 1.6 and 11.6 mJ cm−2 and was dependent on their absorption coefficients which ranged from 0.67 to 26.9 cm−1. Microbial inactivation ranging from 4.2 to 7.2 log10 was achieved within a reasonable number of passes or treatment time in pink and blue lemonade, coconut water, and saline solution which corresponded to an absorption coefficient below 6 cm−1 (UVT = 0.3%). Other than in beet juice blend, which had the highest absorption coefficient, a 1-log10 reduction fluence value in the range of other E. coli strains (previously reported in water) was reported (1.9–5.8 mJ cm−2). These results also suggest that the continuous-flow UV-LED system can be used to investigate inactivation kinetics and effects on nutritional and quality parameters at multiple wavelengths following treatment of low UVT water samples and high UVT juices and beverages with absorption coefficients up to 10–12 cm−1 (4.6e−3 to 6.3e−6% UVT).

Tiger nut milk is a low-acid health beverage that is marketed with the claims of being high in protein, monounsaturated fatty acid (oleic acid), fiber, starch, and minerals, in addition to...

This study compared the inactivation efficacy and performance of UV-LEDs emitting at 259, 268, 275, 289, and 370 nm against a low pressure mercury lamp at 253.7 nm for the foodborne pathogens, E. coli, Listeria and Salmonella. Action spectra were determined for three pathogenic and three non-pathogenic strains and compared with UV absorbance of their bacterial DNA. The lethality of UV wavelengths correlated with bacterial DNA absorbance. At an equivalent UV dose (7 mJ·cm−2), UV-LEDs emitting at 259 and 268 nm achieved the highest log count reductions out of the tested wavelengths. Refrigeration (4 °C) increased irradiance of the 268 nm UV-LEDs while not affecting reduction of Listeria compared to 25°C. Combining 259 and 289 nm UV-LED wavelengths at an equivalent UV dose had a synergistic effect on reduction of E. coli and Listeria, yielding a 1.2 and 0.6 log higher reduction, respectively, than the expected additive effect. Industrial relevance UV-LED treatment at 259, 268, and 275 nm can either equal or, in most cases, surpass the inactivation efficacy of traditional LPM lamps at 253.7 nm. Further, the determined action spectra can be used to identify the optimum inactivation wavelength for common foodborne pathogens and hence increase processing efficiency. In some cases, inactivation efficacy can be improved by combining UV wavelengths in order to achieve a synergistic effect. The effectiveness of UV-LED treatment at refrigeration temperatures validates their use in cold environments. Overall, UV-LEDs have strong potential within the food industry due to their advantages and possibilities for incorporation into a wide variety of treatment systems.

Ultraviolet light (UV, UVC) disinfection is a well-established technology for air, water, and surfaces treatments. In the last decade, UV technology found more applications in food production chain because this is economic, effective, and versatile dry processing technology that can potentially improve safety and preservation quality of different categories of foods. Traditional way of generating UVC light is using high-voltage arc-discharge mercury or amalgam lamps that can generate photons solely at 253.7 nm. Light-emitting diodes or LEDs are semiconductor devices that can also emit UVC light, but depending on the material properties of the diodes, they can emit photons at multiple wavelengths in the UV range between 255 and 365 nm. The germicidal effects of UV LEDs against bacteria, viruses, and fungi already have been demonstrated and reported along with the first applications for disinfection of air, water, and surfaces made for the “point of use” integration. Despite the fact that there are no commercial applications in food production yet, the UV LEDs are the next wave in the LED revolution that can bring numerous advantages for food processing, safety, and plants facilities disinfection. This chapter will present the introduction in basics of LEDs technology and will discuss the unique advantages of this technology for food safety applications. Also, economical, energy saving, and sustainability aspects of UV LED applications are introduced.

At present, there are a few techniques based on the unique properties of light to treat a variety of foods and food-related microflora that are explored for preservation operations and can result in improved quality, nutrition, and desired functionality. This includes continuous ultraviolet (UV)-C lamps and light-emitting diodes, pulsed UV (PUV) light, and pulsed light (PL). Each light-based technology is characterized by specific emission spectra, inactivation mechanisms, and unique advantages and disadvantages that lead to applications differences. This chapter will summarize the basics of generation and emission of PL and PUV, mechanisms of microbial inactivation, effects on quality and nutrition, and existing applications with emphasis on nutritional and other quality effects. Available light sources and commercial equipment, the pros and cons of the PL and PUV for preservation and improving quality and functionality of food and beverages are presented.

The quality, nutritional and organoleptic parameters of cold-pressed lemonade, citrus and green juice were assessed following commercial HPP (600 MPa/3 min), UV-C light (253.7 nm/1000 L h−1/411.4 mJ cm−2) and thermal treatment (75 °C/90 s) using processing regimes currently accepted in the beverage industry. Although the treatments did not affect pH, soluble solids and viscosity, they affected colour with the most pronounced change occurring in the green juice following thermal treatment. Overall, the treatments resulted in good retention ( 90% reduction of ascorbic acid in lemonade). HPP treatment had a neutral or positive effect on consumer acceptance of all juices, whereas thermal and overdosed UV-C treatments caused undesirable sensory changes to green and citrus juices, respectively. Overall, thermal treatment and UV-C light induced chemical changes that differentiated treated juice from the raw sample. Industrial relevance This study verified that the currently accepted processing regimes for commercial scale HPP, UV-C light and thermal treatment affected colour, nutritional, chemical and/or sensory properties depending on the beverage matrix, suggesting that an individual product treatment approach is required for each juice. In the case of UV-C light, the effectiveness of the treatment was influenced by juice composition and UV transmission as well as the fluence level. Overdosed UV-C treatment was shown to cause undesirable effects on juice nutritional parameters. Hence, further optimization of commercial processing regimes and studies evaluating the suitability of each technology on a case by case basis should be considered.

The inactivation efficacies of low pressure mercury (LPM) lamps (253.7 nm) and UVC LEDs (277 nm) were compared for Escherichia coli O157:H7 on lettuce leaves and Listeria monocytogenes on apple skin. Reductions ranging from 1.19 ± 0.59 to 1.58 ± 0.27 log CFU per sample at 4 and 25 °C were achieved. At 4 °C, UVC LEDs increased in fluence rate, while achieving log reductions similar to those at 25 °C. The effect of wavelength on lettuce quality was also evaluated. Treatment (500 mJ·cm−2) from either light source increased browning of romaine lettuce, while mesophilic counts, chlorophyll content and spoilage enzyme activity were not affected significantly over a storage period of up to 21 days. Finally, the adjusted germicidal power (AGP) as a means of comparing inactivation performance between UV wavelengths was evaluated. It was found that AGPs generated in a water-based model system did not adequately predict efficacy on solid food matrices. Industrial relevance The use of ultraviolet-C (UVC) light for disinfection represents a possible dry means to augment or replace existing batch-wash disinfection systems for fresh produce. In this study we have shown that UVC LEDs at 277 nm have comparable germicidal efficacy to LPM lamps against the foodborne pathogens E. coli O157:H7 and Listeria monocytogenes on lettuce leaves and apple skin, respectively, while both light sources achieve log reductions similar to an aqueous sodium hypochlorite wash. Overall these results indicate that UVC LEDs (and UVC light in general) is an alternative effective and sustainable method of disinfecting apples and lettuce in an industrial setting, reducing or eliminating the dependence on aqueous sanitizers.

The ultraviolet (UVC) light irradiation has been recently studied as a novel non-thermal treatment method for milk. However, the potential reactivation of microorganisms following exposure to UVC light in milk medium was not studied yet. Therefore, the present study was conducted to determine the inactivation and reactivation of pathogenic Escherichia coli O157:H7 following exposure to UV light at three monochromatic wavelengths (222, 254 and 282 nm) in bovine milk. The results showed that inactivation of E. coli O157:H7 following exposure to the UV light at 254 nm was higher (P0.05) than that following exposure at 222 and 282 nm at the same UV fluence of 5, 10 and 20 mJ/cm(2). The reactivation of E. coli O157:H7 was increased as the incubation time and temperature increased regardless of the UV light sources under dark incubation phases. The evaluated reactivation ratios of E. coli O157:H7 following exposure to the UV light at 254 nm in milk were lower (P0.05) than that following exposure at 222 nm after 1 to 6, 2 to 5 and 5-6 h incubation at 4, 20 and 37 °C, respectively. Furthermore, at most incubation time points, the reactivation ratio of E. coli O157:H7 following exposure to these three UV light sources were lower (P0.05) than that of non-UV treated cells regardless of the incubation temperature. The lowest reactivation ratios of E. coli O157:H7 were observed after milk exposure to the UV light at 254 nm at 4 °C incubation when compared to that following exposure to the UV light at 222 and 282 nm.

Nonthermal technologies are being investigated as viable alternatives to, or supplemental utilization, with thermal pasteurization in the food-processing industry. In this study, the effect of ultraviolet (UV)-C light on the inactivation of seven milkborne pathogens (Listeria monocytogenes, Serratia marcescens, Salmonella Senftenberg, Yersinia enterocolitica, Aeromonas hydrophila, Escherichia coli, and Staphylococcus aureus) was evaluated. The pathogens were suspended in ultra-high-temperature whole milk and treated at UV doses between 0 and 5000 J/L at a flow rate of 4300 L/h in a thin-film turbulent flow-through pilot system. Of the seven milkborne pathogens tested, L. monocytogenes was the most UV resistant, requiring 2000 J/L of UV-C exposure to reach a 5-log reduction. The most sensitive bacterium was S. aureus, requiring only 1450 J/L to reach a 5-log reduction. This study demonstrated that the survival curves were nonlinear. Sigmoidal inactivation curves were observed for all tested bacterial strains. Nonlinear modeling of the inactivation data was a better fit than the traditional log-linear approach. Results obtained from this study indicate that UV illumination has the potential to be used as a nonthermal method to reduce microorganism populations in milk.

Ultraviolet (UV) light irradiation at 254 nm is considered as a novel non-thermal method for decontamination of foodborne pathogenic bacteria. However, lower penetration depth of UV light at 254 nm in apple juice resulted in higher UV dose consumption during apple juice decontamination. In addition, no studies are available on the reactivation of pathogens following exposure to UV light in drinks and beverages. Two novel monochromatic UV light sources (λ = 222 and 282 nm) have been developed for bacterial disinfection. However, the inactivation of pathogenic Escherichia coli O157:H7 following exposure to these UV wavelengths is still unclear. Therefore, the present study was conducted to determine the inactivation and reactivation potential of pathogenic E. coli O157:H7 in apple juice following exposure to UV light at three monochromatic wavelengths: Far UV (λ = 222 nm), Far UV+ (λ = 282 nm) and UVC light (λ = 254 nm). The results showed that E. coli O157:H7 is acid-resistant, and up to 99.50% of cells survived in apple juice when incubated at 20 °C for 24 h. Inactivation of E. coli O157:H7 following exposure to Far UV light (2.81 Log reduction) was higher (P < 0.05) than the inactivation caused by UVC light (1.95 Log reduction) and Far UV+ light (1.83 Log reduction) at the similar levels of UV fluence of 75 mJ/cm(2). No any reactivation potential was observed for E. coli O157:H7 in dark incubation phases after exposure to UV light as determined by the regular plating method. In addition, the exposure to Far UV light at 222 nm followed by incubating at 37 °C significantly decreased (P < 0.05) the survival of E. coli O157:H7 during dark incubation phase compared to that of UVC and Far UV+ light.

Seven non-pathogenic Escherichia coli strains: ATCC 25253, ATCC 25922, ATCC 11775, ATCC 8739, ATCC 11229, NAR and O157 Dm3Na were tested as potential candidates for the surrogate of pathogenic O157:H7 and non-O157 STEC strains (O111:NM, O26:H11, O145:NM and O103:H2) in apple juice treated by UV-C light. The survival studies in apple juice (pH 3.5) revealed that all non-O157 pathogens exhibit acid resistance similar to O157:H7. Subsequently the acid tolerant bacteria, i.e.: all STEC strains, ATCC 11229, ATCC 11775, ATCC 8739 and O157 Dm3Na, were exposed to three UV-C sources emitting light at the wavelengths of 222 nm, 254 nm and 282 nm. The inactivation studies of the nine most UV resistant strains indicated that ATCC 11229 strain can be recommended as a potential surrogate organism for UV treatments of non-O157 STEC strains at 222 nm. In the case of UV-C at 254 nm and 282 nm E. coli ATCC 8739 strain met the criteria for the surrogate organism for O157:H7 and non-O157 STEC strains. The manuscript presents the systematic procedure for the selection and verification of the potential surrogate organisms that can be recommended for validation of UV light processing of high acid juices and beverages.

The aim of the study was to quantify microbiological, biochemical and sensory changes in full cream raw milk (RM) processed with high temperature short time (HTST) pasteurisation (P), ultraviolet light treatment (UV) and a combination of UV light treatment and HTST pasteurisation (UVP) in commercial scale production of Cheddar cheese. The three treatments have been compared at a similar level of microbial efficacy. No significant differences were reported on the macro-nutrient composition, however a 35% and 18% reduction in cholesterol in the UV and UVP treatments were observed. HTST treatment (UVP and P) reduced riboflavin and Vitamin B12 in milk by ~ 31% and ~ 18% respectively, with no reduction in riboflavin and Vitamin B12 observed after the UV treatment alone. Lipid oxidation and lipolysis results indicated a significant difference between raw and UVP treated milk (p Industrial relevance UV light has been proposed as a non-thermal alternative or adjunct to traditional heat treatment for the reduction of micro-organisms in fluids. UV technology presents numerous benefits over traditional preservation, such as use of heat treatment, for example: low cost of installation and maintenance, lower production cost and the reduction of carbon emissions when compared to traditional thermal pasteurisation systems. Furthermore UV technology also offers alternative processing technology in developing countries where production of milk and cheese are done on a small scale. Known limitation for the efficacy of UV as a processing option was its low penetration depth into turbid liquids, such as milk, and the possible negative impact on organic compounds when over-exposed to UV light. New optimised reactor design features of the swirl tube Surepure Turbulator™, could potentially negate these negative effects associated with UV treatment due to improved uniformity of treatment. This technology would provide and affordable and accessible processing solution to not only enhance the safety and extend shelf-life of the milk being produced, but will also increase final product quality of secondary dairy products such as Cheddar cheese produced from UV treated milk. These advantages could positively impact on the safety, profitability and sustainability of the agro-industrial sector within such regions.

The pilot-scale Taylor–Couette UV unit was tested at turbulent vortices (TV), transitional (TRA) and Couette–Poisuille (CP) flow conditions to treat apple cider (pH 3.65, α = 17.41 cm −1 ), carrot juice (pH 6.31, α = 52.69 cm −1 ) and soy milk (pH 7.04, α = 162.01 cm −1 ) for inactivation of Escherichia coli ATCC 8739. The germicidal effectiveness of Taylor–Couette unit was dependent on Taylor and Reynolds numbers and flow regimes formed in the annulus. From all studied flow regimes the CP flow resulted in the lowest microbial inactivation. For instance at the flow rate of 1500 ml/min and rotation of 0 rpm the UV decimal reduction dose in apple cider was of 13.15 ± 0.45 mJ/cm 2 . On the contrary the superior E. coli inactivation was achieved at the TV flow (1500 mL/min, 200 rpm,), characterised by the least UV decimal reduction dose of 4.57 ± 0.35 mJ/cm 2 . Obtained results indicate that Taylor–Couette UV unit provided efficient mixing conditions capable of overcoming the low penetration of UV photons in opaque liquids.

Application of continuous and pulsed ultraviolet (UV-C) and pulsed light technologies for disinfection of food contact services and food surfaces is discussed as a novel nonthermal purely physical method. The features and efficiency of commercially available sources of continuous and pulsed light, such as mercury lamps, light-emitting diodes and pulsed UV-C, and light sources, are reviewed. The factors affecting the UV disinfection efficiency on the food and contact surfaces are presented along with the principles of light-based disinfection process design.

Performance of three innovative high-intensity pulsed (HIP) ultraviolet (UV) sources characterized by different emission spectra, energy per pulse, and frequency (HIP-1: 31 J/pulse, 8 Hz; HIP-2: 344 J/pulse, 0.75 Hz; HIP-3: 644 J/pulse, 0.5 Hz) was evaluated at UV fluence of 5 mJ/cm2 by measuring the effects on quality parameters of 30% (w/v) fructose solution, apple juice and milk. The results were compared with the continuous monochromatic low pressure (LPM) and medium pressure polychromatic (MPM) mercury lamps at the UV fluence of 10 mJ/cm2 that was determined based on 5-log microbial reduction requirement. The effects of HIP-1 and HIP-3 pulsed lamps on color, pH, and vitamin C, were comparable with the LPM lamp. For example, pH of fructose decreased by 1.94% for the LPM lamp and by 0.78% and 4.31% for HIP-1 and HIP-3, respectively. Treatment with the LPM lamp reduced the vitamin C content by 1.30% in apple juice and 35.13% in milk. In the case of pulsed lamps the reduction of vitamin C was 0.85% for HIP-1 and 1.78% for HIP-3 in apple juice, 12.31% (HIP-1) and 21.66% (HIP-3) in milk. HIP-2 and MPM lamps caused the most significant deterioration of the quality parameters in all tested liquids. The HIP-2 lamp decreased vitamin C by 8.52% in apple juice and 35.80% in milk, and also reduced pH of fructose solution by 5.29%. These results indicate that UV treatment with pulsed HIP-1 and HIP-3 sources could represent a promising alternative for the treatment of low UV transparent and opaque liquid foods.

The objectives of the study were to measure the effect of water activity (a w) and to quantitatively evaluate the effect of the selected humectants under high-pressure processing (HPP) in combination with processing parameters such as treatment time, temperature, and pressure on the inactivation of Escherichia coli K12 in solid and liquid model systems. Glycerol was used in liquid and solid models to vary a w at 0.90, 0.95, and 0.99 levels. The model systems samples and transmitting media were preconditioned to initial temperatures of 4 and 20 °C to compensate for adiabatic heating upon compression to ensure that HPP treatments at 400 and 600 MPa were performed at final temperatures not higher than 40 °C. Decrease of a w from 0.99 to 0.90 in glycerol-based models caused considerably less inactivation of E. coli K12 at tested pressures and temperatures. Effect of different humectants at a w 0.95 and 0.99 on the inactivation of E. coli K12 was studied comparing glycerol, fructose, sodium chloride, and sorbitol. Among four types of solutes tested in the study, sodium chloride appeared the least protective, with glycerol and fructose being approximately equal, and sorbitol showed the most protective effects on inactivation of E. coli K12. The obtained data of E. coli K12 inactivation by HPP at varied a w levels in different solutes demonstrated similar effects of a w on microbial inactivation by thermal treatments. The results must be taken into account when HP preservation process and foods are developed.

The objective of this study was to validate the performance of a coiled ultraviolet (UV) module with 24 lamps for fresh juice pasteurization. Escherichia coli K12 at an inoculation level of 106 cfu mL–1 was chosen as a target microorganism for biodosimetry. All tested fruit juices highly absorbed UV light, with absorption coefficients ranging from 11 cm–1 to 78 cm–1 for lillikoi and pineapple juice, respectively. Of the juices examined, pineapple juice appeared to be the worst case scenario in terms of UV absorptivity and high viscosity. A caramel model solution was developed to mimic juice absorption properties and was used for inoculation studies. The 5-log10 reduction standard under turbulent flow required by the FDA was achievable in Newtonian liquids with absorption coefficient less than 15 cm–1 after one pass. Turbulent flow was not developed in more viscous orange and pineapple juices at the flow rates tested. A biodosimetry technique that utilizes E. coli as a tracer showed no distribution of UV dose in liquids with absorption coefficient lower than 26 cm–1. The proposed technique may assist in validating the performance of UV reactors and improve efficiency of UV pasteurization. Key words: coiled ultraviolet module, fruit juices, caramel model, E. coli K12, biodosimetry.

National and international health agencies have recommended a significant reduction in daily intake of sodium by reducing the amount of NaCl in foods, specifically processed meats. However, sodium reduction could increase the risk of survival and growth of spoilage and pathogenic microorganisms on these products. Therefore, alternate processing technologies to improve safety of sodium reduced foods are necessary. This study examined the effects of three different salt types and concentrations on high-pressure inactivation of Listeria monocytogenes in pre-blended ground chicken formulations. Ground chicken formulated with three salt types (NaCl, KCl, CaCl2), at three concentrations (0, 1.5, 2.5%) and inoculated with a four strain cocktail of L. monocytogenes (10(8) CFU g(-1)) were subjected to four pressure treatments (0, 100, 300, 600 MPa) and two durations (60, 180 s) in an experiment with factorial design. Surviving cells were enumerated by plating on Oxford agar and analysed by factorial ANOVA. Pressure treatments at 100 or 300 MPa did not significantly (P=0.19-050) reduce L. monocytogenes populations. Neither salt type nor concentration had a significant effect on L. monocytogenes populations at these pressure levels. At 600 MPa, salt types, concentrations and duration of pressure treatment all had a significant effect on L. monocytogenes populations. Formulations with increasing concentrations of NaCl or KCl showed significantly lower reduction in L. monocytogenes, while increase in CaCl2 concentration resulted in a significantly higher L. monocytogenes reduction. For instance, increase in NaCl concentration from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 2.49 and 1.29, respectively, when exposed to 600 MPa for 60s. In the case of CaCl2, increase from 0 to 1.5 or 2.5% resulted in a log reduction of 6.16, 7.28 and 7.47, respectively. These results demonstrate that high-pressure processing is a viable process to improve microbial safety of sodium reduced poultry products.

Individual physical and chemical factors were examined in a model fluid for their effects on the efficacy of UV light on the destruction of Escherichia coli K-12 bacteria using laminar and turbulent flow treatment systems. Factors unique to juice, such as Brix and pH, did not exhibit a large effect over the range tested when examined individually. The single factor found to consistently affect the efficacy of UV light inactivation in juice was absorbance. Particulate material resulted in apparent increased rates of UV killing when solutions of equal absorption coefficients were compared. The flow rates and mixing in the turbulent flow also affected microbial inactivation: the higher the flow rates the higher inactivation rates in turbulent flow UV reactor. Regression equations were developed to describe the relationship between the rate of reduction of E. coli K-12 and absorption coefficient in a thin film reactor and for turbulent flow UV reactor. Running biodosimetry test with minimum and maximum flow rates is recommended to ascertain safe UV disinfection.

Publisher Summary This chapter provides an overview of the fundamental principles of continuous and pulsed ultraviolet (UV) light applications in low-UV transmittance (UVT) liquid foods. It discusses the available designs and operation of UV systems. Furthermore, it describes the process and control parameters of UV processing of fluid foods. It also sheds light on the mechanisms and efficacy of UV light microbial inactivation, illustrating examples of applications and effects on fluid food nutritional and quality parameters. UV light is the part of the electromagnetic spectrum with wavelengths between 100 and 400 nm. It has broad antimicrobial action, providing effective inactivation of viruses, vegetative bacteria, bacterial spores, yeasts, conidia, and parasites. The use of UV light in fluid foods was originally limited to highly transparent liquids; however, development of new reactors with optimized hydraulics and thin-film design now allows delivery and exposure of target microorganisms to UV light in low-UVT fluids. The success of UV technology for low-UVT liquids depends on the correct alignment of the UV source parameters to the specific demands of the UV application. Low-pressure mercury lamps are currently the dominant sources for UV treatment of liquid foods and beverages. Special technology lamps, for example, pulsed UV lamps, are promising due to the lack of mercury in the lamp, but more research is needed to establish their suitability for fluid food applications.