Utility of UV-C radiation as anti-Salmonella decontamination treatment for desiccated coconut flakes

This study established the ultraviolet-C (UV-C)-mediated reduction of a cocktail of Salmonella enterica serovars, artificially inoculated onto desiccated coconut flakes. Inoculated cells exhibited biphasic inactivation behavior, characterized by an initial, log-linear population reduction, followed by a slower log-linear population decline where sublethal injury accumulated. Decimal reduction times in the faster inactivation phase (D_fast) ranged from 0.65 to 0.82 min, equivalent to UV-C energy dose of 86.58–109.22 mJ/cm². The D_slow values ranged from 21.19 to 24.21 min, equivalent to energy dose of 2822.51–3224.78 mJ/cm². A total of 3-log cycles reduction in inoculated Salmonella were observed after 40 min exposure of desiccated coconut to UV-C. Further, this 40-min process resulted in changes in the Hunter L*, a* and b* color parameter values, but were not detected by a test consumer panel as evident in the non-significant difference in the color acceptability of UV-C treated and untreated coconut flakes. The UV-C process also did not affect the general acceptability of baked coconut macaroons made from UV-C treated coconut flakes. The results obtained in this work may serve as baseline information in the development of an in- or post-process integration of a UV-C radiation step against Salmonella spp. in the desiccated coconut production process flow.     

Suboptimal growth conditions induce heterologous ultraviolet-C adaptation in Salmonella enterica in orange juice

This study was conducted to determine the effects of single and simultaneous physicochemical stress exposures on the subsequent resistance of Salmonella spp. to ultraviolet-C (UV–C) in orange juice (pH 3.1, 11.5 °Brix, 0.63% citric acid). Seven strains of the test bacterium were individually subjected to suboptimal growth conditions (24 h), including gradual acidification (final pH 4.5), abrupt desiccation (a_w 0.96), heat stress by incubation at high temperature (40 °C), and combinations of acid + desiccation (pH 4.5, a_w 0.96), acid + heat (pH 4.5, 40 °C), and desiccation + heat (a_w 0.96, 40 °C). Cocktail of the different strains previously exposed to specific stress were then subjected to UV–C inactivation. The UV–C resistance of Salmonella enterica was expressed in terms of D and D_UV–C values, which correspond to the unit time of exposure and UV–C energy necessary to reduce the population by 1 log cycle (90%), respectively. Results showed that in all treatments, S. enterica exhibited logarithmic linear or first-order UV inactivation kinetics, indicating that the cells had homogenous responses towards the environmental stresses and the eventual kill step. Except for heat, all prior stress exposures resulted in cells more resistant to UV–C than the control (D = 12.7 s, D_UV–C = 63.56 mJ/cm²). Cells previously exposed to desiccation were most resistant to UV–C with a D and D_UV–C values of 16.6 s and 83.20 mJ/cm², respectively. Combining desiccation with acid (D = 16.2 s, D_UV–C = 80.88 mJ/cm²) and heat (D = 15.0 s, D_UV–C = 75.16 mJ/cm²) also resulted in relatively more resistant cells, with D and D_UV–C values greater than those exposed to acid (D = 14.9 s, D_UV–C = 74.56 mJ/cm²), acid + heat (D = 14.4 s, D_UV–C = 72.00 mJ/cm²), and heat stresses (D = 11.9 s, D_UV–C = 59.67 mJ/cm²). All (D ratio = D stress/D control >1.0) but those previously exposed to heat stress (D ratio <1.0) exhibited heterologous adaptation against UV–C in orange juice. These results provide additional evidences of the induction of heterologous UV–C tolerance response in S. enterica from environmental stresses commonly encountered by cells in food and food processing ecologies.     

Combined sustainable sanitising treatments to reduce Escherichia coli and Salmonella Enteritidis growth on fresh-cut kailan-hybrid broccoli

The effects of peroxyacetic acid (PA), neutral electrolysed water (NEW), ultraviolet C light (UV-C) and superatmospheric O₂ packaging (HO), single or combined, on the growth rate of Escherichia coli and S. Enteritidis inoculated onto fresh-cut kailan-hybrid broccoli were studied throughout 14 days of shelf life at 5 and 10 °C. As controls, unwashed, water-washed and NaClO-washed were used. PA and NEW showed a better sanitising effect than NaClO against both E. coli/S. Enteritidis with reductions of 2.2/2.7 and 2.6/2.6 log CFU g⁻¹, respectively. UV-C attained E. coli/S. Enteritidis decreases of 1.3–1.4/2.1–2.2 log CFU g⁻¹ compared to unwashed samples. The bacteriostatic effects of PA or NEW were improved when they were combined with UV-C, decreasing E. coli and S. Enteritidis counts by about 3 log CFU g⁻¹. After 14 days, PA and NEW-treated samples attained E. coli/S. Enteritidis reductions at 5 °C of 2.3/1.4 and about 1 log CFU g⁻¹, respectively. Storage of those samples at 10 °C masked that sanitising effect. At both storage temperatures, UV-C-treated samples registered lower E. coli and S. Enteritidis reductions (or higher increases for S. Enteritidis at 10 °C) regarding conventional NaClO-sanitized samples or other single treatments. However, PA, NEW or UV-C-treated samples under HO at both storage temperatures showed better bacterial control than individual treatments with the greatest effectiveness for UV-C + HO. Triple combination did not imply an enhanced benefit over double combinations. Conclusively, PA, NEW and UV-C seems to be effective emergent alternatives to NaClO to reduce initial E. coli and S. Enteritidis populations in fresh-cut kailan-hybrid broccoli. Storage at 5 or 10 °C under HO greatly controlled microbial growth.     

Growth of Escherichia coli,Salmonella enterica and Listeria spp., and their inactivation using ultraviolet energy and electrolyzed water,on ‘Rocha’ fresh-cut pears

The present study aimed at evaluating the growth of Escherichia coli, Salmonella enterica, and Listeria spp. and studying the efficacy of Ultraviolet-C (UV-C) irradiation, acidic electrolyzed (AEW) and neutral electrolyzed (NEW) waters in the reduction of these bacteria on ‘Rocha’ pear. Fresh-cut pieces were inoculated and incubated at 4–20 °C for 8 days. Inoculated pears were treated with UV-C (2.5–10 kJ/m²), AEW, NEW and sodium hypochlorite (SH) and microbiological and quality parameters were evaluated. The three bacteria, inoculated at 6.1–6.2 log cfu/g, grew on the pear at high growth rates at 12 and 20 °C reaching populations of 8.1–8.6 log cfu/g, in 24 h. At 8 °C the microorganisms increased their populations by at least 1 log cfu/g in three days. At 4 °C adaptation phases of less than 24 h for Listeria spp. were measured before exponential growth occurred and the enterobacteria did not grow despite having survived for 8 days. AEW and NEW caused microbial reductions similar to SH, of approximately 1 log cfu/g, while the best UV-C dose (7.5 kJ/m²) of at least 2.4 log cfu/g. Fresh-cut pears were a good substrate for foodborne bacteria emphasizing the importance of preventing contaminations and cross contaminations. The UV-C was more effective than the chemical decontaminations, as it provided superior microbial reductions without greatly affecting the quality of pears.     

Effects of UV-C on physicochemical quality attributes and Salmonella enteritidis inactivation in liquid egg products

The perspectives of UV-C radiation as a non-thermal treatment for liquid egg products were evaluated from the point of view of the effects on egg quality attributes and the decontamination efficiency against the main egg contaminant Salmonella enterica subsp. enterica Ser. Enteritidis. UV-C treated egg fractions (egg yolk, egg white and whole egg) were analyzed for changes in pH, color, temperature-dependent viscosity and TBARS index, and were inoculated with S. enteritidis (ATCC 13076). Contrary to heat treatments, UV-C was not affecting viscosity and pH. Browning due to Maillard was perceptible in egg yolk and whole egg at low UV-C doses, but the corresponding browning indexes were always lower than in heat pasteurized egg fractions. Major changes were only due to lipid oxidation. TBARS values at the highest UV-C doses were larger than in pasteurized egg yolk and whole egg; under dynamic conditions and 0.61 J cm^?2, results were not significantly different to natural untreated samples. And UV-C was effective to inactivate S. enteritidis. In egg white, a load reduction up to 5.3 log₁₀ was achieved under dynamic conditions (9.22 J cm^?2, 39 min), while 3.3 log₁₀ and 3.8 log₁₀ reductions were recorded in egg yolk and whole egg. Static treatments were less efficient, but still, load reductions between 1.7 and 2.8 log₁₀ were obtained. At 3.94 mW cm^?2, time necessary to achieve a 4D reduction of Salmonella cells was estimated to be around 7.4 min in egg white.     

Effect of combination of ultraviolet light and hydrogen peroxide on inactivation of Escherichia coli O157:H7, native microbial loads,and quality of button mushrooms

Mushrooms are prone to microbial spoilage and browning during growing and processing. Ultraviolet light (254 nm, UV-C) has been used as an alternative technology to chemical sanitizersfor food products. Hydrogen peroxide (H₂O₂) is classified as generally recognized as safe for use in foods as a bleaching and antimicrobial agent, and could control the bacterial blotch and browning of mushrooms. This study investigated the effects of water wash (control), 3% H₂O₂ wash, 0.45 kJ m⁻² UV-C, and combination of H₂O₂ and UV-C (H₂O₂ + UV) on microbial loads and product quality of mushrooms during storage for 14 days at 4 °C. Additionally, the inactivation of Escherichia coli O157:H7 inoculated on mushrooms was determined. Results showed that water wash, H₂O₂, UV-C and H₂O₂ + UV resulted in 0.44, 0.77, 0.85, and 0.87 logs CFU g⁻¹ reduction of E. coli O157:H7, respectively. Hydrogen peroxide, UV-C and the combination reduced total aerobic plate counts on the surface of mushrooms by 0.2–1.4 logs CFU g⁻¹ compared to the control, while there was no significant difference among the three treatments during storage. After storage, UV-C treated mushrooms had similar L* and a* values as the control while H₂O₂ and H₂O₂ + UV-C treated mushrooms had higher L* (lighter) and lower a* (less brown) values than the control. Compared to water wash, all the treatments inhibited lesion development on the mushroom surface on day 14. The combination of H₂O₂ and UV achieved the best overall dual control of lesion and browning. There was no significant difference in ascorbic acid and total phenolic content among the treatments. Overall our results suggested that H₂O₂ + UV reduced microbial loads, and extended storage life by reducing lesion development without causing deterioration in nutritional quality of button mushrooms. Therefore, when properly utilized, H₂O₂ + UV could potentially be used for maintaining postharvest quality while marginally reducing populations of E. coli O157:H7 and background microflora.     

Effectiveness of UV light as a means to reduce Salmonella contamination on tomatoes and food contact surfaces

The effectiveness of ultraviolet light at a wavelength of 254 nm to reduce Salmonella contamination on tomatoes and food contact surfaces was evaluated. Inoculated tomatoes were exposed to UV-C light at doses ranging from 0 to 223.1 mJ/cm². All UV treatments significantly reduced Salmonella populations (p < 0.05). The effectiveness of UV-C light in reducing Salmonella contamination on different locations on tomato surfaces under various UV doses (0–117.2 mJ/cm²) was also explored. Results indicated that regardless of the locations, UV treatment was shown to be effective in decreasing Salmonella populations. Subsequent studies evaluated possible photoreactivation or dark repair of injured Salmonella post-UV treatment. Following UV light exposure at doses of 0, 22.3, 44.6, and 89.2 mJ/cm², tomatoes were either exposed to visible light for 0, 3, and 5 h or stored in the dark for the same amount of time. Photoreactivation was not detected, nor was dark repair. UV light was also evaluated for its effectiveness to reduce Salmonella contamination on food contact surfaces (stainless steel, HDPE, waxed cardboard and PVC). Contaminated coupons were exposed to UV-C light at 0, 3.3, and 19.7 mJ/cm². Significant differences were observed between coupons treated with UV light and the controls (p < 0.05). Coupons exposed for longer time had greater Salmonella population reductions, except for waxed cardboard coupons. Application of UV-C light to reduce Salmonella contamination in tomato handling facilities is feasible.     

Determination of thermal inactivation kinetics of Listeria monocytogenes in chicken meats by isothermal and dynamic methods

The objective of this research is to determine the thermal inactivation kinetics of Listeria monocytogenes in chicken breast meat under both isothermal and dynamic conditions. A four-strain cocktail of L. monocytogenes was inoculated to chicken breast meat. Isothermal studies were performed by submerging samples under hot water maintained at constant temperatures ranging from 54 to 66 °C. The D values at each temperature were determined and used to calculate the z value, using log(D) = log(D₀) − T/z. Dynamic studies were conducted by submerging samples in a water bath with its temperature programmed to increase linearly from 30 to 65 °C at 1.25 °C/min or 1.73 °C/min. A method was developed to determine the kinetic parameters from linear heating temperature profiles.The thermal inactivation of L. monocytogenes in chicken breast meat followed the first-order kinetics. The z value determined from the isothermal studies was 4.95 °C, which is very close to the values reported in the literature. The dynamic method can also be used to determine the thermal inactivation kinetics of L. monocytogenes. The average z value (4.10 °C) determined by the dynamic method was slightly lower than that determined by the isothermal method. However, the parameters (D₀ and z) determined from both isothermal and dynamic methods can be used to estimate the survival of L. monocytogenes exposed to linear heating temperature profiles, with statistically equal accuracies.The dynamic method explored in this study can be used to determine the D₀ and z values of microorganisms that exhibit first-order kinetics and are exposed to linear heating temperature profiles. Compared to the isothermal method, the dynamic method requires few data points and is equally accurate.     

Inactivation of foodborne pathogens in powdered red pepper (Capsicum annuum L.) using combined UV-C irradiation and mild heat treatment

This study was performed to investigate the effectiveness of combined ultraviolet (UV-C) irradiation and mild heating as an alternative to conventional inactivation of foodborne pathogens, including Escherichia coli O157:H7 and Salmonella Typhimurium on powdered red pepper. A cocktail of three strains of E. coli O157:H7 ATCC 35150, ATCC 43889, ATCC 43890) and S. Typhimurium (ATCC 19585, ATCC 43971, DT 104) was inoculated onto powdered red pepper and then treated with UV-C irradiation and mild heat. A constant UV intensity (3.40 mW/cm²) of the emitting lamps was applied to samples for 5, and 10 min at 25, 35, 45, 55, and 65 °C, respectively. Also, quality change of powdered red pepper was measured in order to identify the efficiency of combined treatment. The reduction levels of E. coli O157:H7 and S. Typhimurium on powdered red pepper when treated with UV-C irradiation alone at 20.4 kJ/m² for 10 min was 0.22 and 0.29 log CFU/g, respectively. While, combined treatment with mild heating at 65 °C reduced the surviving numbers of each pathogens by 2.88 and 3.06 log CFU/g, respectively. Although the inactivation efficiency was influenced less by the UV-C radiation dose, the synergistic effect was observed with increasing temperature and UV-C radiation dose. CIE color value and extractable color value were not significantly (P > 0.05) different between non-treated and combination treated samples. The moisture and capsaicinoids contents showed significant (P < 0.05) differences when treated at 65 °C because of sample drying during heat treatment. Therefore, these results suggest that UV-C irradiation combined with mild heating can be utilized by the food industry in order to effectively inactivate E. coli O157:H7 and S. Typhimurium without incurring quality deterioration of powdered red pepper.     

Combined treatment with chlorine dioxide gas,fumaric acid,and ultraviolet-C light for inactivating Escherichia coli O157:H7 and Listeria monocytogenes inoculated on plums

Combined non-thermal treatment with chlorine dioxide (ClO₂) gas, ultraviolet-C (UV-C) light, and fumaric acid was performed to inactivate Listeria monocytogenes and Escherichia coli O157:H7 inoculated on plums. Plums were treated with ClO₂ gas (15 and 30 ppmv), fumaric acid (0.1, 0.3, and 0.5%), and by UV-C irradiation (3, 5, and 10 kJ/m²). The single treatments with 15 or 30 ppmv ClO₂ gas, 0.5% fumaric acid, and 10 kJ/m² UV-C decreased the population of L. monocytogenes by 1.78, 2.00, 1.65, and 1.62 log CFU/g, respectively, and the population of E. coli O157:H7 by 1.73, 1.81, 1.34, and 2.07 log CFU/g, respectively. In addition, combined treatments reduced the populations of the pathogenic bacteria more than each treatment alone. In particular, the combined treatment with ClO₂ gas (30 ppmv) for 20 min, fumaric acid (0.5%), and UV-C (10 kJ/m²) decreased the populations of L. monocytogenes and E. coli O157:H7 by 6.26 and 5.48 log CFU/g, respectively. These results suggest that combined treatment with ClO₂ gas, UV-C light, and fumaric acid may be a useful hurdle technology to enhance the microbiological safety of plums.     

Effects of integrated treatment of nonthermal UV-C light and different antimicrobial wash on Salmonella enterica on plum tomatoes

The aim of this study was to evaluate inactivation of inoculated Salmonella enterica on whole tomato surface exploiting integration of nonthermal ultraviolet light (UV-C) treatment with antimicrobial wash. The effect of combined treatment on background microflora (aerobic mesophilic, and yeast and mold), during storage at ambient temperature (22 °C) for 21 days was also determined. A bacterial cocktail containing three serotypes of S. enterica (S. Newport H1275, S. Stanley H0558, and S. Montevideo G4639) was used based on their association with produce-related outbreaks. Tomatoes were spot inoculated using approximately 100 μL of inocula to achieve cell population of about 10⁷ CFU/tomato. An inoculated tomato was initially treated with a low (0.6 kJ/m²) dose of UV-C light (253.7 nm) followed by immersion in selected sanitizing solution (700 ml) to wash under mild agitation (ca. 250 rpm) for 2 min at room temperature (22 °C). Inactivation efficacy of combined treatments varied widely depending on the sanitizer property. Combined UV-C plus aqueous ozone (1 ppm) provided 3.13 ± 0.47 log CFU/fruit Salmonella reduction which was significantly lower (p < 0.05) compared to the rest of the combination treatments; whereas the treatment of UV-C followed by immersion in a novel antimicrobial preparation ‘HEN’, formulated mixing hydrogen peroxide, EDTA and nisin provided the best log reduction (4.71 ± 0.25 log CFU/fruit). Organic acids (1%) or their binary mixtures, hydrogen peroxide (3%), and HEN provided greater than 4.0 log reductions for UV-C treated tomatoes. Treatments were effective in controlling native microbial loads as the total aerobic mesophilic organisms and the population of yeast and mold remained significantly (p < 0.05) low during storage compared to control. Findings from this study provide safe and effective post harvest intervention strategies for produce industry as an alternative to current chlorine based wash. These results may also help researchers design future decontamination studies.     

Thermal inactivation of Salmonella Typhimurium on dressed chicken skin previously exposed to acidified sodium chlorite or carvacrol

Salmonella is a leading cause of foodborne illness and live poultry is a main reservoir of this pathogen, worldwide. Cross-contamination and transportation of contaminated poultry meat act as an important vehicle of Salmonella infections in humans. In this study, we assessed the effect of two antimicrobials; acidified sodium chlorite (ASC) and carvacrol followed by thermal treatment to inactivate Salmonella Typhimurium on dressed chicken skin. D-values (time in min for the pathogen to decrease by 90%) of Salmonella Typhimurium at 56, 60 and 64 °C on dressed chicken skin in the control samples, determined by linear regression, were 6.17, 3.16, 1.32 min, respectively. Two D-values calculated using a logistic model, ranged from 6.28 (D_1, major population, plus T_L) and 11.66 (D_2, heat-resistant subpopulation, plus T_L) min at 56 °C to 1.08 (D₁ plus T_L), and 2.07 (D₂ plus T_L) min at 64 °C. Pre-dipping in 100–300 ppm ASC or 0.02–0.06% carvacrol rendered the pathogen more sensitive to the lethal effect of heat. Thus, combination of antimicrobials with thermal inactivation was more effective in reducing heat resistance of the pathogen on dressed chicken surface. The model developed will assist poultry processors in estimating the time required for specific log reductions of Salmonella Typhimurium on chicken skin and thus, will contribute in designing acceptance limits at critical control points for chicken skins at lower times and temperatures for cooking.     

Influence of vacuum and modified atmosphere packaging in combination with UV-C radiation on the shelf life of rainbow trout (Oncorhynchus mykiss) fillets

The effects of UV-C radiation, modified atmosphere packaging (MAP) and their combination on rainbow trout (Oncorhynchus mykiss) fillets quality were examined during a period of 22 days. The samples were submitted to five packaging conditions: (AP) aerobic packaging; (VP) vacuum packaging; (VP + UV-C) vacuum packaging + UV-C radiation; (MAP) modified atmosphere packaging (80% CO₂/20% N₂) and (MAP + UV-C) modified atmosphere packaging + UV-C radiation (80% CO₂/20% N_2; 106.32 mJ/cm²) and storaged at 4 °C. The samples were analyzed daily for microbiological (mesophilic, psychrotrophic and Enterobacteriaceae counts) and chemical (pH, TMA-N, TBV-N, lipid oxidation, ammonia and biogenic amines) parameters. Overall, UV-C radiation promoted lag phase formation in mesophilic and psychrotrophic groups. Mesophilic and psychrotrophic groups presented significant lower (P < 0.05) growth rate and colony forming units in the stationary phase in the samples submitted to MAP. MAP significantly reduced (P < 0.05) total mesophilic count and MAP + UV-C total mesophilic and psychrotrophic counts. Values of pH decreased at all packaging conditions except in the case of aerobic packaging. TBARS value increased faster in samples subject to MAP and MAP + UV-C whereas TMA-N, TVB-N and ammonia values increased slowly. Lower production of putrescine and cadaverine was observed in MAP and VP samples. MAP reduced total production of ammonia, TVB-N and putrescine, whereas MAP + UV-C reduced total production of TVB-N and cadaverine during entire the storage time. Results of the current study suggest that MAP retarded microbial growth and delayed chemical changes enhancing the shelf life of rainbow trout fillets at least twice.     

Effects of UV-C treatment on inactivation of Salmonella enterica and Escherichia coli O157:H7 on grape tomato surface and stem scars,microbial loads,and quality

The purpose of this study was to investigate the effectiveness of ultraviolet-C (UV-C) light inactivation as affected by the location of pathogens on the surface and at stem scars of whole grape tomatoes. A mixed bacterial cocktail containing a three strain mixture of Escherichia coli O157:H7 (C9490, E02128 and F00475) and a three serotype mixture of Salmonella enterica (S. Montevideo G4639, S. Newport H1275, and S. Stanley H0558) were used. Tomatoes were spot inoculated using approximately 100 μL of inocula to achieve a population of about 10^7±1 CFU/tomato. Additionally, the effects of treatment on color, texture, lycopene content, and background microbial loads during post UV-C storage at 4 °C for 21 days were determined. Results showed that UV-C doses of 0.60–6.0 kJ/m² resulted in 2.3–3.5 log CFU per fruit reduction of E. coli O157:H7 compared to 2.15–3.1 log CFU per fruit reduction for Salmonella on the surfaces. Under the same conditions, log reductions achieved at stem scar were 1.7–3.2 logs CFU for E. coli O157:H7 and 1.9–2.8 logs CFU for Salmonella. The treatment was effective in controlling native microbial loads during storage at 4 °C as the total aerobic mesophilic organisms (PCA) and anaerobic lactic acid bacteria (LAB) counts of treated tomatoes were significantly (p < 0.05) lower during storage compared to the control group and the yeast and mold populations were reduced significantly below the detection limit. Furthermore, the firmness of tomato and its color was not affected by the UV-C doses during storage. UV-C radiation could potentially be used for sanitizing fresh tomatoes and extending shelf-life. The results of this study indicate that the specific location of pathogens on the produce influences the effectiveness of UV-C treatment, which should be taken into consideration for the design of UV-C systems for produce sanitization.     

Minimization of water consumption in fresh-cut salad washing by UV-C light

The decontamination effect of UV-C light at increasing fluence up to 1.2 kJ/m² was studied with reference to natural microflora and inoculated pathogens in lamb's lettuce wash water. UV-C light dose of 0.4 kJ/m² allowed to inactivate most of the native microflora and to achieve more than 5- Log-reductions in inoculated microorganisms (Salmonella enterica, Listeria monocytogenes and Escherichia coli). In multiple washing cycles up to 5, UV-C light treatment allowed to obtain more than 3-log reductions in native microflora in wash water. Spectral properties indicated that, independently on the number of recycling cycles, a considerable amount of UV-C light can penetrate wash water if its thickness is lower than circa 1 cm.     

Combinations of selected physical and chemical hurdles to inactivate Escherichia coli O157:H7 in apple and orange juices

This study evaluated the individual and combined efficacies of physical processing techniques such as heating, Dynashock multi-frequency ultrasound waves, ultraviolet-C (UV-C), and additives such as sodium benzoate, potassium sorbate, α- and β-Pinene for pasteurization of orange and apple juices against acid-adapted Escherichia coli O157:H7. In heated apple juice, log-linear inactivation of the test organism resulted in D values which were used to calculate for the recommended 5-log reduction process schedules (t_5D) at 45, 50, 52, 55, and 60 °C equal to 481.5, 103.6, 45.0, 22.4, and 10.54 min, respectively. E. coli O157:H7 exhibited biphasic inactivation composed of a slow inactivation lag, followed by log-linear inactivation in ultrasound-treated juice. t_5D schedules were similarly calculated at 54.7 and 77.5 min for orange and apple juice, respectively. Lethal rate analyses in the ultrasound-treated apple juice revealed that 85% of the reduction in E. coli population was due to the heat liberated by cavitation. Combined ultrasound and UV-C treatment resulted in greater inactivation rates in both juices, with greater efficacy in apple juice. Supplementation of all tested additives, whether singly or in combination, similarly resulted in significantly shorter t_5D schedules in both juices.     

Inactivation of a non-pathogenic strain of E. coli by ionising radiation

Ionising radiation is an effective method to reduce pathogenic E. coli O157:H7 in meat and poultry products. Radiation sensitivity of bacteria, however, depends on several factors. After applying an irradiation dose of 1 kGy to cultures of the non-pathogenic strain of E. coli, DSM 498, grown and irradiated in nutrient broth, reductions of 3–4 decimal units were achieved (D₁₀ = 0.27 kGy). If grown on minced turkey meat, however, reduction rates were lower (D₁₀ = 0.47 kGy). Even lower reduction rates were obtained during irradiation of frozen meat (D₁₀ = 0.72 kGy) compared to treatments at cooling temperatures (D₁₀ = 0.48 kGy). For data evaluation, both, first order reduction kinetics and the Weibull model were compared. The results emphasise the necessity to determine inactivation kinetics in food matrices of target extrinsic factors (e.g. temperature).     

Application of ultraviolet-C light on oranges for the inactivation of postharvest wound pathogens

Germicidal effects of ultraviolet-C (UV-C) light on the postharvest wound pathogens of citrus fruits namely Penicillium digitatum and Penicillium italicum were investigated. P. digitatum and P. italicum spores were inoculated (4.00–4.50 log cfu/orange) onto Washington navel oranges (Citrus sinensis L. Osbeck cv Washington navel) by using wound and spot inoculation methods and subjected to eight different UV-C doses in the range of 0.26–15.84 kJ/m². Maximum reductions of 2.75 and 3.33 log cfu/orange of P. digitatum were obtained at the UV-C dose of 3.17 kJ/m² for spot and wound inoculation methods, respectively. P. italicum was more resistant than P. digitatum to UV-C treatments. The results suggest that UV-C treatments designed to reduce P. italicum spores will provide an adequate degree of protection against P. digitatum spores. UV-C light could be an alternative technique for the use of synthetic chemicals to reduce the development of postharvest pathogens of oranges.     

Removal of Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157:H7 biofilms on stainless steel using scallop shell powder

Biofilms on steel surfaces containing Listeria monocytogenes, Staphylococcus aureus and Escherichia coli O157:H7 continue to threaten dairy and meat processors. In this study, the ability of scallop shell powder (SSP) to remove biofilms formed by these three pathogens on stainless steel plates was examined. Whey powder solution (WPS) and bench wash water (BWW) provided by dairy and meat factories, respectively, were inoculated with L. monocytogenes, S. aureus or E. coli O157:H7 (9 log₁₀ CFU/ml). Stainless steel plates (10 cm²) were placed in the inoculated fluids and incubated at 20 °C at 48 h to form biofilms. After drying and washing in sterile water, the plates were treated with 0.0, 0.25, or 0.50% (w/v) SSP slurries for 1, 5, or 10 min and then quantitatively examined for the three pathogens. Both 0.25 and 0.50% SSP reduced L. monocytogenes on the plates by 4 log CFU/cm² with a 1 min exposure to 0.50% SSP decreasing S. aureus by 5 logs CFU/cm². After 1 min in 0.25 and 0.50% SSP, E. coli O157:H7 populations in WPS and BWW biofilms decreased 4 and 6 log CFU/cm² and 3 and 5 log CFU/cm², respectively. Increasing the concentration of SSP led to significantly increased efficacy against the tested pathogens (P < 0.05). In conclusion, this study showed that SSP slurries could significantly reduce the numbers of L. monocytogenes, S. aureus and E. coli O157:H7 in biofilms on stainless steel surfaces.     

Effect of UV-C irradiation on the inactivation of inoculated pathogens and quality of chicken breasts during storage

In this study, we evaluated the inactivation of foodborne pathogens inoculated on chicken breasts by UV-C treatment. Chicken breasts were inoculated with Campylobacter jejuni, Listeria monocytogenes, and Salmonella enterica serovar Typhimurium at 6–7 log CFU/g. The inoculated chicken breasts were then irradiated with UV-C light of dose 0, 0.5, 1, 3, and 5 kJ/m². Microbiological data indicated that the populations of the foodborne pathogens decreased significantly (p < 0.05) with increasing UV-C irradiation. In particular, UV-C irradiation at 5 kJ/m² reduced the initial populations of C. jejuni, L. monocytogenes, and S. typhimurium by 1.26, 1.29, and 1.19 log CFU/g, respectively. After UV-C irradiation, the samples were individually packed using polyethylene terephthalate containers and stored at 4 ± 1 °C for 6 d. The pH of the control increased more than the samples irradiated at 0.5, 1, 3, and 5 kJ/m², while TBARS values increased during storage regardless of UV-C irradiation. UV-C irradiation caused negligible changes in Hunter L, a, and b values. These results suggest that UV-C irradiation can be useful in improving the microbial safety of chicken breasts during storage, without impairing quality.