Search results for: log inactivation

Authors: Z. Herceg, V. Stulic, T. Vukusic, A. Rezek Jambrak

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High voltage electrical discharge plasmas are new nonthermal developing techniques used for water decontamination. To the full understanding of cell inactivation mechanisms, this study brings inactivation, recovery and cellular leakage of L. innocua cells before and after the treatment. Bacterial solution (200 mL) of L. innocua was treated in a glass reactor with a point-to-plate electrode configuration (high voltage electrode-titanium wire, was in the gas phase and grounded electrode was in the liquid phase). Argon was injected into the headspace of the reactor at the gas flow of 5 L/min. Frequency of 60, 90 and 120 Hz, time of 5 and 10 min, positive polarity and conductivity of media of 100 µS/cm were chosen to define listed parameters. With a longer treatment time inactivation was higher as well as the increase in cellular leakage. Despite total inactivation recovery of cells occurred probably because of a high leakage of proteins, compared to lower leakage of nucleic acids (DNA and RNA). In order to define mechanisms of inactivation further research is needed.

Keywords: Listeria innocua ATCC 33092, inactivation, gas phase plasma, cellular leakage, recovery of cells

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Authors: Zoran Herceg, Višnja Stulić, Anet Režek Jambrak, Tomislava Vukušić

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Electrical discharge plasma is a new non-thermal processing technique which is used for the inactivation of contaminating and hazardous microbes in liquids. Plasma is a source of different antimicrobial species including UV photons, charged particles, and reactive species such as superoxide, hydroxyl radicals, nitric oxide and ozone. Escherichia coli was studied as foodborne pathogen. The aim of this work was to examine inactivation effects of electrical discharge plasma treatment on the Escherichia coli MG 1655 in pure culture. Two types of plasma configuration and polarity were used. First configuration was with titanium wire as high voltage needle and another with medical stainless steel needle used to form bubbles in treated volume and titanium wire as high voltage needle. Model solution samples were inoculated with Escerichia coli MG 1655 and treated by electrical discharge plasma at treatment time of 5 and 10 min, and frequency of 60, 90 and 120 Hz. With the first configuration after 5 minutes of treatment at frequency of 120 Hz the inactivation rate was 1.3 log₁₀ reduction and after 10 minutes of treatment the inactivation rate was 3.0 log₁₀ reduction. At the frequency of 90 Hz after 10 minutes inactivation rate was 1.3 log₁₀ reduction. With the second configuration after 5 minutes of treatment at frequency of 120 Hz the inactivation rate was 1.2 log₁₀ reduction and after 10 minutes of treatment the inactivation rate was also 3.0 log₁₀ reduction. In this work it was also examined the formation of biofilm, nucleotide and protein leakage at 260/280 nm, before and after treatment and recuperation of treated samples. Further optimization of method is needed to understand mechanism of inactivation.

Keywords: electrical discharge plasma, escherichia coli MG 1655, inactivation, point-to-plate electrode configuration

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Authors: H. Shokouhmand, H. Sobhani, B. Sajadi, M. Degheh

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In recent years, experimental and numerical investigation of water UV reactors has increased significantly. The main drawback of experimental methods is confined and expensive survey of UV reactors features. In this study, a CFD model utilizing the eulerian-lagrangian framework is applied to analysis the disinfection performance of a closed conduit reactor which contains four UV lamps perpendicular to the flow. A discrete ordinates (DO) model was employed to evaluate the UV irradiance field. To investigate the importance of each of lamps on the inactivation performance, in addition to the reference model (with 4 bright lamps), several models with one or two bright lamps in various arrangements were considered. All results were reported in three inactivation kinetics. The results showed that the log inactivation of the two central bright lamps model was between 88-99 percent, close to the reference model results. Also, whatever the lamps are closer to the main flow region, they have more effect on microbial inactivation. The effect of some operational parameters such as water flow rate, inlet water temperature, and lamps power were also studied.

Keywords: Eulerian-Lagrangian framework, inactivation kinetics, log inactivation, water UV reactor

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Authors: Sanam Pudasaini, A. T. K. Perera, Ahmed Syed Shaheer Uddin, Sum Huan Ng, Chun Yang

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Development of high-efficiency and environment friendly bacterial inactivation methods is of great importance for preventing waterborne diseases which are one of the leading causes of death in the world. Traditional bacterial inactivation methods (e.g., ultraviolet radiation and chlorination) have several limitations such as longer treatment time, formation of toxic byproducts, bacterial regrowth, etc. Recently, an electroporation-based inactivation method was introduced as a substitute. Here, an electroporation-based continuous flow microfluidic device equipped with an array of micropillars is developed, and the device achieved high bacterial inactivation performance ( > 99.9%) within a short exposure time ( < 1 s). More than 99.9% reduction of Escherichia coli bacteria was obtained for the flow rate of 1 mL/hr, and no regrowth of bacteria was observed. Images from scanning electron microscope confirmed the formation of electroporation-induced nano-pore within the cell membrane. Through numerical simulation, it has been shown that sufficiently large electric field strength (3 kV/cm), required for bacterial electroporation, were generated using PDMS micropillars for an applied voltage of 300 V. Further, in this method of inactivation, there is no involvement of chemicals and the formation of harmful by-products is also minimum.

Keywords: electroporation, high-efficiency, inactivation, microfluidics, micropillar

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Authors: Golnoosh Torabian, P. Valtchev, F. Dehghani

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The need for efficient nutraceutical products has been dramatically changing the approach of the industrial processes. The development of novel mild processes is highly demanded for the production of such products; especially when both quality and safety need to be guaranteed during their long shelf life. Within this research, for the first time, we investigated the effect of supercritical carbon dioxide treatment for the inactivation of microbes and enzymes in a berry juice possessing therapeutic effect. We demonstrated that a complete inactivation of microbes can be achieved at optimized conditions of treatment. However, the bottle neck of the process was represented by the unpromising inactivation of the degradative enzyme by supercritical carbon dioxide treatment. However, complete enzyme inactivation was achieved by applying two strategies: the first was optimizing juicing method by adding a mechanical step and the second strategy was addition of natural inhibitors to the juice. Overall these results demonstrate that our hybrid process has a significant effect on the inactivation of microorganism and enzymes in the fresh juice. The developed process opens the possibility for the evolution of new products with optimal nutritional and sensorial characteristics, as well as offering a competitive cost and an environmentally friendly alternative for pasteurization and extension of shelf life in a wide range of natural therapeutic products.

Keywords: hybrid method, berry juice, pasteurization, enzymes inactivation

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Authors: Ozan Kahraman, Hao Feng

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Several models such as Weibull, Modified Gompertz, Biphasic linear, and Log-logistic models have been proposed in order to describe non-linear inactivation kinetics and used to fit non-linear inactivation data of several microorganisms for inactivation by heat, high pressure processing or pulsed electric field. First-order kinetic parameters (D-values and z-values) have often been used in order to identify microbial inactivation by non-thermal processing methods such as ultrasound. Most ultrasonic inactivation studies employed first-order kinetic parameters (D-values and z-values) in order to describe the reduction on microbial survival count. This study was conducted to analyze the E. coli O157:H7 inactivation data by using five microbial survival models (First-order, Weibull, Modified Gompertz, Biphasic linear and Log-logistic). First-order, Weibull, Modified Gompertz, Biphasic linear and Log-logistic kinetic models were used for fitting inactivation curves of Escherichia coli O157:H7. The residual sum of squares and the total sum of squares criteria were used to evaluate the models. The statistical indices of the kinetic models were used to fit inactivation data for E. coli O157:H7 by MTS at three temperatures (40, 50, and 60 0C) and three pressures (100, 200, and 300 kPa). Based on the statistical indices and visual observations, the Weibull and Biphasic models were best fitting of the data for MTS treatment as shown by high R2 values. The non-linear kinetic models, including the Modified Gompertz, First-order, and Log-logistic models did not provide any better fit to data from MTS compared the Weibull and Biphasic models. It was observed that the data found in this study did not follow the first-order kinetics. It is possibly because of the cells which are sensitive to ultrasound treatment were inactivated first, resulting in a fast inactivation period, while those resistant to ultrasound were killed slowly. The Weibull and biphasic models were found as more flexible in order to determine the survival curves of E. coli O157:H7 treated by MTS on apple-carrot juice.

Keywords: Weibull, Biphasic, MTS, kinetic models, E.coli O157:H7

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Authors: Zoran Herceg, Višnja Stulić, Tomislava Vukušić, Anet Režek Jambrak

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High voltage electrical discharge is a new technology used for inactivation of pathogen microorganisms. Pathogen yeasts can cause diseases in humans if they are ingested. Nowadays new technologies have become the focus of researching all over the world. Rhodotorula is known as yeast that can cause diseases in humans. The aim of this study was to examine whether the high voltage electrical discharge treatment generated in gas phase has an influence on yeast reduction and recovery of Rhodotorula spp 74 in pure culture. Rhodotorula spp. 74 was treated in 200 mL of model solution. Treatment time (5 and 10 min), frequency (60 and 90 Hz) and injected gas (air or argon 99,99%) were changed. Titanium high voltage needle was used as high voltage electrode (positive polarity) through which air or argon was injected at the gas flow of 0.6 L/min. Experimental design and statistical analyses were obtained by Statgraphics Centurion software (StatPoint Technologies, Inc., VA, USA). The best inactivation rate 1.7 log10 reduction was observed after the 10 min of treatment, frequency of 90 Hz and injected air. Also with a longer treatment time inactivation rate was higher. After the 24 h recovery of treated samples was observed. Therefore the further optimization of method is needed to understand the mechanism of yeasts inactivation and cells recovery after the treatment. Acknowledgements: The authors would like to acknowledge the support by Croatian Science Foundation and research project ‘Application of electrical discharge plasma for preservation of liquid foods’.

Keywords: rhodotorula spp. 74, electrical discharge plasma, inactivation, stress response

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Authors: Ruby Siwach, Manish Kumar, Raman Seth

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Extent of inactivation of pectin methylesterase (PME) in mosambi juice during thermal and thermosonication treatments was studied to obtain a minimally processed product. Effect of both treatments on cloud value, pH, titratable acidity, oBrix, and sensory attributes (flavour and taste) was studied. Thermal treatments (HT) were carried out at three temperatures 60, 70, and 80°C in a serological water bath for 5, 10, 15, and 20 min at each temperature. Thermosonication treatments (TS) were also given for same time-temperature combinations in water bath of a thermosonicator. Treated samples were stored in a deep freezer at 18°C for PME assay. PME activity of untreated sample was also assayed and residual PME activity and % loss in PME activity was calculated at each time-temperature combination. The extent of inactivation of PME increased with increase in treatment temperature and duration. Thermosonication treatments were found far more effective than thermal treatments of same time temperature combination in PME inactivation and retention of sensory attributes.

Keywords: pectin methylesterase, heat inactivation kinetics, thermosonication, thermal treatment

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Authors: Adrian Garrido Sanchis, Richard Pashley

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The MS2 (ATCC15597-B1) virus was used as a surrogate to estimate the inactivation rates for enteric viruses when using a hot air bubble column evaporator (HBCE) system in the treatment of household wastewater. In this study, we have combined MS2 virus surface charging properties with thermal inactivation rates, using an improved double layer plaque assay technique, in order to assess the efficiency of the HBCE process for virus removal in water. When bubbling a continuous flow of dry air, at 200°C, only heats the aqueous solution in the bubble column to about 50°C. Viruses are not inactivated by this solution temperature, as confirmed separately from water bath heating experiments. Hence, the efficiency of the HBCE process for virus removal in water appeared to be caused entirely by collisions between the hot air bubbles and the virus organisms. This new energy efficient treatment for water reuse applications can reduce the thermal energy required to only 25% (about 113.7 kJ/L) of that required for boiling (about 450 kJ/L).

Keywords: MS2 virus inactivation, water reuse, hot bubble column evaporator, water treatment

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Authors: Nikolai Nosik, Vladislav Podmasterjev, Nina Kondrashina, Marina Chataeva, Olga Lobach, Dmitry Noosik, Sergei Razumovskii

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Virucidal activity of ozone is well known: dissolved in water it kill viruses very fast. The virucidal capacity of ozone in ozone-air mixture is less known. The goal of the study was to investigate the virucidal potentials of the ozone–air mixture and kinetics of virus inactivation. Materials and methods. Ozone (O3 ) was generated from oxygen with ozonizer ( 1.0 – 75.0 mg\l). The ozone concentration was determined by the spectrophotometric methods. Virus contaminated samples were placed into the flowing reactor. Viruses: poliovirus type 1, vaccine strain (Sabin) and adenovirus, type 5, were obtained from the State virus collection. Titrations of viruses were carried out in appropriate cell cultures. CxT value ( mg\l x min) was calculated. Results. Metallic, polycarbonic and fiber “Kevlar” samples were contaminated with virus, dried and treated with ozone-air mixture in the flowing reactor. Kinetics of poliovirus inactivation: in 15 min at 5.0 mg\l -2.0 lg TCID50 inhibition , in 15 min at 10 mg\l – 2.5 lg TCID50 , 4.0 lg TCID50 inactivation of poliovirus was achieved after 75min at ozone concentration 20.0mg\l (99.99%). ( CxT = 75, 150 and 1500 mg\l x min on all three types of surfaces). It was found that the inactivation of poliovirus was more effective when the virus contaminated samples were wet (in 15 min at 20mg\l inhibition of virus in dry samples was 2.0 TCID50 , in wet samples – 4.0 TCID50). Adenovirus was less resistant to ozone treatment then poliovirus: 4.0 lg TCID50 inhibition was observed after 30 min of the treatment with ozone at 20mg\l ( CxT mg\l x min = 300 for adenovirus as for poliovirus it was 1500). Conclusion. It was found that ozone-air mixture inactivates viruses at rather high concentrations (compared to the reported effect of ozone dissolved in water). Despite of that there is a difference in the resistance to ozone action between viruses – poliovirus is more resistant then adenovirus-ozone-air mixture can be used for disinfection of large rooms. The maintaining of the virus-contaminated surfaces in wet condition allow to decrease the ozone load for virus inactivation.

Keywords: adenovirus, disinfection, ozone, poliovirus

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Authors: Z. Herceg, V. Stulic, T. Vukusic, A. Rezek Jambrak

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Gas phase plasma treatment is a new nonthermal technology used for food and water decontamination. In this study, we have investigated influence of the gas phase plasma treatment on yeast cells of S. cerevisiae. Sample was composed of 10 mL of yeast suspension and 190 mL of 0.01 M NaNO₃ with a medium conductivity of 100 µS/cm. Samples were treated in a glass reactor with a point- to-plate electrode configuration (high voltage electrode-titanium wire in the gas phase and grounded electrode in the liquid phase). Air or argon were injected into the headspace of the reactor at the gas flow of 5 L/min. Frequency of 60, 90 and 120 Hz, time of 5 and 10 min and positive polarity were defined parameters. Inactivation was higher with the applied higher frequency, longer treatment time and injected argon. Inactivation was not complete which resulted in complete recovery. Cellular leakage (260 nm and 280 nm) was higher with a longer treatment time and higher frequency. Leakage at 280 nm which defines a leakage of proteins was higher than leakage at 260 nm which defines a leakage of nucleic acids. The authors would like to acknowledge the support by Croatian Science Foundation and research project 'Application of electrical discharge plasma for preservation of liquid foods'.

Keywords: Saccharomyces cerevisiae, inactivation, gas-phase plasma treatment, cellular leakage

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Authors: Zohreh Rashmei

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Introduction: Plasma inactivation is one of the emerging technologies in biomedical field and has been applied to the inactivation of microorganisms in water. The inactivation effect has been attributed to the presence of active plasma species, i.e. OH, O, O3, H2O2, UV and electric fields, generated by the discharge of plasma. Material and Method: To evaluate germicidal effects of plasma, the electric spark discharge device was used. After the effect of the plasma samples were collected for culture medium agar plate count. In addition to biological experiments, the concentration of hydrogen peroxide was also measured. Results: The results showed that Plasma is able to inactivate a high concentration of E. coli. After a short period of plasma radiation on the surface of water, the amount log8 reduced the microbial load. Starting plasma radiation on the surface of the water, the measurements show of production and increasing the amount of hydrogen peroxide in water. So that at the end of the experiment, the concentration of hydrogen peroxide to about 100 mg / l increased. Conclusion: Increasing the concentration of hydrogen peroxide is directly related to the reduction of microbial load. The results of E. coli culture in media containing certain concentrations of H2O2 showed that E. coli can not to grow in a medium containing more than 2/5 mg/l of H2O2. Surely we can say that the main cause of killing bacteria is a molecule of H2O2.

Keywords: plasma, hydrogen peroxide, disinfection, E. coli

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Authors: Nickolay Nosik, Dmitry Nosik, Marina Bochkova, Nina Kondrashina, Olga Lobach

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The bactericidal effect of UV radiation is known for long time and widely used for inactivation of pathogens but for viruses it is not so uniform. Due to a wide variety of viruses their sensitivity to UV radiation is quite different and not quite predictable. The goal of the study was to determine the inactivation kinetics of UV radiation ( 254 nm) of the viruses of social importance (HIV), as well as test-viruses (poliovirus, adenovirus) used for the evaluation of the viral inactivation efficacy of germicides. Methods: DNA viruses- adenovirus, type 5; Herpes simplex virus (HSV), type 1, and RNA viruses–human immunodeficiency virus (HIV), type 1 and poliovirus, type 1 (Sabin strain) were obtained from State collection of viruses ( The D.I. Ivanovsky Institute of Virology). The source of UV radiation was a 15-watt low-pressure mercury vapor lamp (over 60% 254nm). The samples of 5cm2 were placed direct under the UV lamp flow (h-0.3m). Log reduction value was used as a marker for the rate of virus inactivation. Results: The data obtained indicate that poliovirus (one of the viruses most resistant to chemical germicides) and HSV are rather sensitive to UV radiation ( D90 =250-311 J/m2). Adenovirus is much more resistant to UV radiation (750 J/m2 ). The kinetics of adenovirus inactivation : 0 min- 5.0 lg TCID50, 10 min - 5,0, 15 min -4,0, 30 min – 3.5, 60 min – 1,0, 75 min -0,5 lg TCID50, 90 min –virus not detectable. HIV is most resistant to UV radiation among the studied viruses. It takes more than 4 hrs to inactivate the virus on the surface. D90 = 2000 J/m2 Conclusion: The results of the study show that there is no direct dependence between sensitivity to UV light and the size of the virion or presence\absence of the envelope of the virus. Poliovirus and adenovirus are small viruses (20-30nm poliovirus and 70-90nm adenovirus) and both are non-enveloped viruses but adenovirus 3-fold more resistant to UV radiation than poliovirus. It can be expected that viruses with more complicate structure, like Herpes virus (200nm) or HIV (80-100 nm), would be more sensitive to UV light. However, the very high resistance of HIV to UV radiation needs further investigation. The diverse resistance of the different viruses to UV radiation should be taken into the account when UV light is used to inactivate infectious viruses in hospitals and other public environments.

Keywords: HIV, HSV, inhibition of viruses, UV radiation

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Authors: I. A. Landa-Fernandez, I. Monje-Ramirez, M. T. Orta-Ledesma

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Every year plant-parasitic nematodes diminish the yield of high-value crops worldwide causing important economic losses. Currently, Meloidogyne enterolobii has increased its importance due to its high aggressiveness, increasing geographical distribution and host range. Root-knot nematodes inhabit the rhizosphere soil around plant roots. However, they can come into contact with irrigation water. Thus, plant-parasitic nematodes can be transported by water, as eggs or juveniles. Due to their high resistance, common water disinfection methods are not effective for inactivating these parasites. Ozone is the most effective disinfectant for microbial inactivation. The objective of this study is to demonstrate that ozone treatment is an alternative method control in irrigation water of the root-knot nematode M. enterolobii. It has been shown that ozonation is an effective treatment for the inactivation of protozoan cysts and oocysts (Giardia and Cryptosporidium) and for other species of the genus Meloidogyne (M. incognita), but not for the enterolobii specie. In this study, the strain of M. enterolobii was isolated from tomatoes roots. For the tests, eggs were used and were inoculated in water with similar characteristics of irrigation water. Subsequently, the disinfection process was carried out in an ozonation unit. The performance of the treatments was evaluated through the egg's viability by assessing its structure by optical microscopy. As a result of exposure to ozone, the viability of the nematode eggs was reduced practically in its entirety; with dissolved ozone levels in water close to the standard concentration (equal to 0.4 mgO₃/L), but with high contact times (greater than 4 min): 0.2 mgO₃/L for 15 minutes or 0.55 mgO₃/L for 10 minutes. Additionally, the effect of temperature, alkalinity and organic matter of the water was evaluated. Ozonation is effective and a promising alternative for the inactivation of nematodes in irrigation water, which could contribute to diminish the agricultural losses caused by these organisms.

Keywords: inactivation process, irrigation water treatment, ozonation, plant-parasite nematodes

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Authors: Zoran Herceg, Tomislava Vukušić, Anet Režek Jambrak, Višnja Stulić

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Today one of the greatest challenges are directed to the safety of food supply. If food pathogens are ingested they can cause human illnesses. Because of that new technologies that are effective in microbial reduction are developing to be used in food industries. One of such technology is cold gas phase plasma. Salmonella enterica was studied as one of the pathogenes that can be found in food. The aim of this work was to examine the inactivation rate and stress response of plasma treated cells of Salmonella enterica inoculated in apple juice. After the treatment cellular leakage, phenotypic changes in plasma treated cells-biofilm formation and degree of recovery were conducted. Sample volume was inoculated with 5 mL of pure culture of Salmonella enterica and 15 mL of apple juice. Statgraphics Centurion software (StatPoint Technologies, Inc., VA, USA) was used for experimental design and statistical analyses. Treatment time (1, 3, 5 min) and gas flow (40, 60, 80 L/min) were changed. Complete inactivation and 0 % of recovery after the 48 h was observed at these experimental treatments: 3 min; 40 L/min, 3 min; 80 L/min, 5 min; 40 L/min. Biofilm reduction was observed at all treated samples. Also, there was an increase in cellular leakage with a longer plasma treatment. Although there were a significant reduction and 0 % of recovery after the plasma treatments further investigation of the method is needed to clarify whether there are sensorial, physical and chemical changes in juices after the plasma treatment. Acknowledgments: The authors would like to acknowledge the support by Croatian Science Foundation and research project 'Application of electrical discharge plasma for the preservation of liquid foods'.

Keywords: salmonella enterica serotype typhimurium lt21, gas-phase plasma treatment, inactivation, stress response

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Authors: O. Baghriche, A. Zertal, C. Pulgarin, J. Kiwi, R. Sanjines

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High-Power Impulse Magnetron Sputtering (HIPIMS) is a technology that belongs to the field of Ionized PVD of thin films. This study shows the first complete report on ultrathin TiO2/Ag nano-particulate films sputtered by highly ionized pulsed plasma magnetron sputtering (HIPIMS) leading to fast bacterial loss of viability. The Ag and the TiO2/Ag sputtered films induced complete Escherichia coli inactivation in the dark, which was not observed in the case of TiO2. When Ag was present, the bacterial inactivation was accelerated under low intensity solar simulated light and this has implications for a potential for a practical technology. The design, preparation, testing and surface characterization of these innovative films are described in this study. The HIPIMS sputtered composite films present an appreciable savings in metals compared to films obtained by conventional sputtering methods. HIPIMS sputtering induces a strong interaction with the rugous polyester 3-D structure due to the higher fraction of the Ag-ions (M+) attained in the magnetron chamber. The immiscibility of Ag and TiO2 in the TiO2/Ag films is shown by High Angular Dark Field (HAADF) microscopy. The ionization degree of the film forming species is significantly increased and film growth is assisted by an intense ion flux. Reports have revealed the significant enhancement of the film properties as the HIPIMS technology is used. However, a decrease of the deposition rate, as compared to the conventional DC magnetron sputtering Pulsed (DCMSP) process is commonly observed during HIPIMS.

Keywords: E. coli, HIPIMS, inactivation bacterial, sputtering

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Authors: Catherine Joke Adeseko

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Enzymatic browning is an economically important disorder that degrades organoleptic properties and prevent the consumer from purchasing fresh fruit and vegetables. Prevention and control of enzymatic browning in fruit and its product is imperative. Therefore, this study sought to investigate the catalytic effect of polyphenol oxidase (PPO) in the adverse browning of African bush mango (Irvingia gabonensis) fruit peel and pulp. PPO was isolated and purified, and its physicochemical properties, such as the effect of pH with SDS, temperature, and thermodynamic studies, which invariably led to thermal inactivation of purified PPO at 80 °C, were evaluated. The pH and temperature optima of PPO were found at 7.0 and 50, respectively. There was a gradual increase in the activity of PPO as the pH increases. However, the enzyme exhibited a higher activity at neutral pH 7.0, while enzymatic inhibition was observed at acidic region, pH 2.0. The presence of SDS at pH 5.0 downward was found to inhibit the activity of PPO from the peel and pulp of I. gabonensis. The average value of enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) obtained at 20 min of incubation and temperature 30 – 80 °C were respectively 39.93 kJ.mol-1, 431.57 J.mol-1 .K-1 and -107.99 kJ.mol-1 for peel PPO, and 37.92 kJ.mol-1, -442.51J.mol-1.K-1, and -107.22 kJ.mol-1 for pulp PPO. Thermal inactivation of PPO from I. gabonensis exhibited a reduction in catalytic activity as the temperature and duration of heat inactivation increases using catechol, reflected by an increment in k value. The half-life of PPO (t1/2) decreases as the incubation temperature increases due to the instability of the enzyme at high temperatures and was higher in pulp than peel. Both D and Z values decrease with increase in temperature. The information from this study suggests processing parameters for controlling PPO in the potential industrial application of I. gabonensis fruit in order to prolong the shelf-life of this fruit for maximum utilization.

Keywords: enzymatic, browning, characterization, activity

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Authors: Kubra Dogan, Fatih Tornuk

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Due to increasing consumer demand for the high-quality food products and awareness regarding the health benefits of different nutrients in food minimal processing becomes more popular in modern food preservation. To date, heat treatment is often used for inactivation of spoilage microorganisms in foods. However, it may cause significant changes in the quality and nutritional properties of food. In order to overcome the detrimental effects of heat treatment, several alternatives of non-thermal microbial inactivation processes have been investigated. Ultraviolet (UV) inactivation is a promising and feasible method for better quality and longer shelf life as an alternative to heat treatment, which aims to inhibit spoilage and pathogenic microorganisms and to inactivate the enzymes in vegetable juice production. UV-C is a sub-class of UV treatment which shows the highest microcidal effect between 250-270 nm. The wavelength of 254 nm is used for the surface disinfection of certain liquid food products such as vegetable juice. Effects of UV-C treatment on microbiological load and quality parameter of vegetable juice which is a mix of celery, carrot, lemon and orange was investigated. Our results showed that storing of UV-C applied vegetable juice for three months, reduced the count of TMAB by 3.5 log cfu/g and yeast-mold by 2 log cfu/g compared to control sample. Total phenolic content was found to be 514.3 ± 0.6 mg gallic acid equivalent/L, and there wasn’t a significant difference compared to control. The present work suggests that UV-C treatment is an alternative method for disinfection of vegetable juice since it enables adequate microbial inactivation, longer shelf life and has minimal effect on degradation of quality parameters of vegetable juice.

Keywords: heat treatment, phenolic content, shelf life, ultraviolet (UV-C), vegetable juice

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Authors: M. T. Amina, A. A. Alazba, U. Manzoor

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Solar disinfection (SODIS) is a viable method for household water treatment and is recommended by the World Health Organization as cost effective approach that can be used without special skills. The efficiency of both SODIS and solar collector disinfection (SOCODIS) system was evaluated using four different sources of water including stored rainwater, storm water, ground water and treated sewage. Samples with naturally occurring microorganisms were exposed to sunlight for about 8-9 hours in 2-L polyethylene terephthalate bottles under similar experimental conditions. Total coliform (TC), Escherichia coli (E. coli) and heterotrophic plate counts (HPC) were used as microbial water quality indicators for evaluating the disinfection efficiency at different sunlight intensities categorized as weak, mild and strong weathers. Heterotrophic bacteria showed lower inactivation rates compared to E. coli and TC in both SODIS and SOCODIS system. The SOCODIS system at strong weather was the strongest disinfection system in this study and the complete inactivation of HPC was observed after 8-9 hours of exposure with SODIS being ineffective for HPC. At moderate weathers, however, the SOCODIS system did not show complete inactivation of HPC due to very high concentrations (up to 5x10^7 CFU/ml) in both storm water and treated sewage. SODIS even remained ineffective for the complete inactivation of E. coli due to its high concentrations of about 2.5x10^5 in treated sewage compared with other waters even after 8-9 hours of exposure. At weak weather, SODIS was not effective at all while SOCODIS system, though incomplete, showed good disinfection efficiency except for HPC and to some extent for high E. coli concentrations in storm water. Largest reduction of >5 log occurred for TC when used stored rainwater even after 6 hours of exposure in the case of SOCODIS system at strong weather. The lowest E. coli and HPC reduction of ~2 log was observed in SODIS system at weak weather. Further tests with varying pH and turbidity are required to understand the effects of reaction parameters that could be a step forward towards maximizing the disinfection efficiency of such systems for the complete inactivation of naturally occurring E. coli or HPC at moderate or even at weak weathers.

Keywords: efficiency, microbial, SODIS, SOCODIS, weathers

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Authors: Jihane Saad, Thomas Lendormi, Caroline Le Marechal, Anne-marie Pourcher, Céline Druilhe, Jean-louis Lanoiselle

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Agricultural anaerobic digestion consists in the conversion of animal slurry and manure into biogas and digestate. They need, however, to be treated at 70 ºC during 60 min before anaerobic digestion according to the European regulation (EC n°1069/2009 & EU n°142/2011). The impact of such heat treatment on the outcome of bacteria has been poorly studied up to now. Moreover, a recent study¹ has shown that enterococci and clostridia are still detected despite the application of such thermal treatment, questioning the relevance of this approach for the hygienisation of digestate. The aim of this study is to establish the heat inactivation kinetics of two species of enterococci (Enterococcus faecalis and Enterococcus faecium) and two species of clostridia (Clostridioides difficile and Clostridium novyi as a non-toxic model for Clostridium botulinum of group III). A pure culture of each strain was prepared in a specific sterile medium at concentration of 10⁴ – 10⁷ MPN / mL (Most Probable number), depending on the bacterial species. Bacterial suspensions were then filled in sterilized capillary tubes and placed in a water or oil bath at desired temperature for a specific period of time. Each bacterial suspension was enumerated using a MPN approach, and tests were repeated three times for each temperature/time couple. The inactivation kinetics of the four indicator bacteria is described using the Weibull model and the classical Bigelow model of first-order kinetics. The Weibull model takes biological variation, with respect to thermal inactivation, into account and is basically a statistical model of distribution of inactivation times as the classical first-order approach is a special case of the Weibull model. The heat treatment at 70 ºC / 60 min contributes to a reduction greater than 5 log10 for E. faecium and E. faecalis. However, it results only in a reduction of about 0.7 log10 for C. difficile and an increase of 0.5 log10 for C. novyi. Application of treatments at higher temperatures is required to reach a reduction greater or equal to 3 log10 for C. novyi (such as 30 min / 100 ºC, 13 min / 105 ºC, 3 min / 110 ºC, and 1 min / 115 ºC), raising the question of the relevance of the application of heat treatment at 70 ºC / 60 min for these spore-forming bacteria. To conclude, the heat treatment (70 ºC / 60 min) defined by the European regulation is sufficient to inactivate non-sporulating bacteria. Higher temperatures (> 100 ºC) are required as far as spore-forming bacteria concerns to reach a 3 log10 reduction (sporicidal activity).

Keywords: heat treatment, enterococci, clostridia, inactivation kinetics

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Authors: Miao Zhang, Limin Liu, Feng Zhi, Panpan Niu, Mengya Yang, Xuemei Zhu, Ying Diao, Jun Wang, Ying Zhao

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Background and Aims: Clinical studies have demonstrated that serum semicarbazide-sensitive amine oxidase (SSAO) activities positively correlate with the progression of atherosclerosis. The aim of the present study is to investigate the effect of SSAO inactivation on the development of atherosclerosis. Methods: Female LDLr knockout (KO) mice were given the Western-type diet for 6 and 9 weeks to induce the formation of early and advanced lesions, and semicarbazide (SCZ, 0.125%) was added into the drinking water to inactivate SSAO in vivo. Results: Despite no impact on plasma total cholesterol levels, abrogation of SSAO by SCZ not only resulted in the enlargement of both early (1.5-fold, p=0.0043) and advanced (1.8-fold, p=0.0013) atherosclerotic lesions, but also led to reduced/increased lesion contents of macrophages/smooth muscle cells (SMCs) (macrophage: ~0.74-fold, p=0.0002(early)/0.0016(advanced); SMC: ~1.55-fold, p=0.0003(early) /0.0001(advanced)), respectively. Moreover, SSAO inactivation inhibited the migration of circulating monocytes into peripheral tissues and reduced the amount of circulating Ly6Chigh monocytes (0.7-fold, p=0.0001), which may account for the reduced macrophage content in lesions. In contrast, the increased number of SMCs in lesions of SCZ-treated mice is attributed to an augmented synthetic vascular SMC phenotype switch as evidenced by the increased proliferation of SMCs and accumulation of collagens in vivo. Conclusion: SSAO inactivation by SCZ promotes the phenotypic switch of SMCs and the development of atherosclerosis. The enzymatic activity of SSAO may thus represent a potential target in the prevention and/or treatment of atherosclerosis.

Keywords: atherosclerosis, phenotype switch of smooth muscle cells, SSAO/VAP-1, semicarbazide

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Authors: Tanmaya Pradhan, K. Midhun, M. Joy Thomas

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Increasing the shelf life and improving the quality are important objectives for the success of packaged liquid food industry. One of the methods by which this can be achieved is by deactivating the micro-organisms present in the liquid food through pasteurization. Pasteurization is done by heating, but some serious disadvantages such as the reduction in food quality, flavour, taste, colour, etc. were observed because of heat treatment, which leads to the development of newer methods instead of pasteurization such as treatment using UV radiation, high pressure, nuclear irradiation, pulsed electric field, etc. In recent years the use of the pulsed electric field (PEF) for inactivation of the microbial content in the food is gaining popularity. PEF uses a very high electric field for a short time for the inactivation of microorganisms, for which we require a high voltage pulsed power source. Pulsed power sources used for PEF treatments are usually in the range of 5kV to 50kV. Different pulse shapes are used, such as exponentially decaying and square wave pulses. Exponentially decaying pulses are generated by high power switches with only turn-on capacity and, therefore, discharge the total energy stored in the capacitor bank. These pulses have a sudden onset and, therefore, a high rate of rising but have a very slow decay, which yields extra heat, which is ineffective in microbial inactivation. Square pulses can be produced by an incomplete discharge of a capacitor with the help of a switch having both on/off control or by using a pulse forming network. In this work, a pulsed power-based system is designed with the help of high voltage capacitors and solid-state switches (IGBT) for the inactivation of pathogenic micro-organism in liquid food such as fruit juices. The high voltage generator is based on the Marx generator topology, which can produce variable amplitude, frequency, and pulse width according to the requirements. Liquid food is treated in a chamber where pulsed electric field is produced between stainless steel electrodes using the pulsed output voltage of the supply. Preliminary bacterial inactivation tests were performed by subjecting orange juice inoculated with Escherichia Coli bacteria. With the help of the developed pulsed power source and the chamber, the inoculated orange has been PEF treated. The voltage was varied to get a peak electric field up to 15kV/cm. For a total treatment time of 200µs, a 30% reduction in the bacterial count has been observed. The detailed results and analysis will be presented in the final paper.

Keywords: Escherichia coli bacteria, high voltage generator, microbial inactivation, pulsed electric field, pulsed forming line, solid-state switch

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Authors: Rimzhim Gupta, Bhanupriya Boruah, Jayant M. Modak, Giridhar Madras

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Microbial contamination is one of the major concerns in the field of water treatment. AOP (advanced oxidation processes) is well-established method to resolve the issue of removal of contaminants in water. A Z-scheme composite g-C₃N₄/CuWO₄ was synthesized by sol-gel method for the photocatalytic inactivation of a mixed population of Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli). The photoinactivation was observed for different types of bacteria in the same medium together and individually in the absence of the nutrients. The lattice structures and phase purities were determined by X-ray diffraction. For morphological and topographical features, scanning electron microscopy and transmission electron microscopy analyses were carried out. The band edges of the semiconductor (valence band and conduction band) were determined by ultraviolet photoelectron microscopy. The lifetime of the charge carriers and band gap of the semiconductors were determined by time resolved florescence spectroscopy and diffused reflectance spectroscopy, respectively. The effect of weight ratio of C₃N₄ and CuWO₄ was observed by performing photocatalytic experiments. To investigate the exact mechanism and major responsible radicals for photocatalysis, scavenger studies were performed. The rate constants and order of the inactivation reactions were obtained by power law kinetics. For E. coli and S. aureus, the order of reaction and rate constants are 1.15, 0.9 and 1.39 ± 0.03 (CFU/mL)⁻⁰.¹⁵ h⁻¹, 47.95 ± 1.2 (CFU/mL)⁰.¹ h⁻¹, respectively.

Keywords: z-scheme, E. coli, S. aureus, sol-gel

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Authors: Noor Akhmazillah Fauzi, Mohammed Mehdi Farid, Filipa V. Silva

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The aim of this paper is to investigate if different concentration of Manuka honey (as a model food) has a major influence on the inactivation of Saccharomyces cerevisiae (as the testing microorganism) after subjecting it to HPP. Honey samples with different sugar concentrations (20, 30, 40, 50, 60 and 70 °Brix) were prepared aseptically using sterilized distilled water. No dilution of honey was made for the 80 °Brix sample. For the 0 °Brix sample (control), sterilized distilled water was used. Thermal treatment at 55 °C for 10 min (conventionally applied in honey pasteurisation in industry) was carried out for comparison purpose. S. cerevisiae cell numbers in honey samples were established before and after each HPP and thermal treatment. The number of surviving cells was determined after a proper dilution of the untreated and treated samples by the viable plate count method. S. cerevisiae cells, in different honey concentrations (0 to 80 °Brix), subjected to 600 MPa (at ambient temperature) showed an increasing resistance to inactivation with °Brix. A significant correlation (p < 0.05) between cell reduction and °Brix was found. Cell reduction in high pressure-treated samples varied linearly with °Brix (R2 > 0.9), confirming that the baroprotective effect of the food is due to sugar content. This study has practical implications in establishing efficient process design for commercial manufacturing of high sugar food products and on the potential use of HPP for such products.

Keywords: high pressure processing, honey, Saccharomyces cerevisiae, °Brix

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Authors: Arash Dara, Mahsa Mokhtari, Nafiseh Zamindar

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The aim of this study was to determine the effect of thermal resistance, temperature, voltage, and pH changes in an ohmic heating system on reducing the logarithmic number of Byssochlamys fulva species (PTCC 5062) in tomato juice water and to investigate the quantitative properties of tomato juice in the ohmic heating pasteurization system. The percentage of thermal degradation by ohmic heating was determined in tomato juice for the kinetics of Byssochlamys fulva in ohmic chamber at the temperatures of 88, 93, and 98°C, with two voltages of 30 and 40 volts and two pH levels of 3.5 and 4.5; this was done using Weibull frequency distribution model. Three different parameters (pH = 3.5, two voltages of 30 and 40, at three temperatures 88, 93, and 98) and (pH = 4.5, two voltages 30 and 40, at three temperatures 88, 93, and 98) in three replications were considered in the ohmic system. Heating time for the temperature of 88°C was 20 minutes once every 2 minutes, while for the temperature of 93°C, it was 10 minutes once every 1 minute. At the temperature of 98°C, the first time was 0.5 minutes, and for other times, sampling was done every 1 minute. In each condition, the qualitative characteristics, including acidity, Brix, and pH, were measured before and after the ohmic process in the tomato juice. This study demonstrates that the differences in pH and voltage due to different temperatures in the ohmic process can greatly affect the inactivation of Byssochlamys fulva fungus and the qualitative characteristics of the tomato juice. This is the first study using the Weibull frequency method to model the inactivation of Byssochlamys fulva in tomato juice. Variation in parameters such as temperature, voltage, and pH can prevent the presence of Byssochlamys fulva in the pasteurized juices.

Keywords: pasteurization, ohmic heating process, Byssochlamys fulva, tomato juice, heat resistance, voltage, pH

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Authors: Muhammad Arifur Rahman, Talukdar M. Waliullah, Takashi Ushimaru

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Nucleophagy selectively degrades nuclear materials, especially nucleolus after nutrient starvation or inactivation of TORC1 kinase in budding yeast. Budding yeast phosphatidate (PA) phosphatase Pah1 that converts PA to diacylglycerol is essential for partitioning of lipid precursors between membrane and storage that is crucial for many aspects of cell growth and development. Pah1 is required for nuclear/ER membrane biogenesis and vacuole function, but whether Pah1 and its activator Nem1/Spo7 protein phosphatase complex are involved in autophagy is largely unknown. Loss of Pah1 causes expansion of the nucleus and fragmentation of the vacuole. Here we show that Pah1 is required for bulk autophagy and nucleophagy after TORC1 inactivation. Loss of Pah1 impaired nucleophagy severely and bulk autophagy to a lesser extent. Loss of the Pah1 activator Nem1-Spo7 protein phosphatase exhibited similar features.

Keywords: autophagy, Nem1/Spo7 phosphatase, Pah1, nucleophagy, TORC1

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Authors: Helan Satish, M. Ramasubba Reddy

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The simulation of an endocardial cell for gene mutation in the cardiac sodium ion channel NaV1.5, encoded by SCN5A gene, is discussed. The characterization of Brugada Syndrome by loss of function effect on SCN5A mutation due to L812Q mutant present in the DII-S4 transmembrane region of the NaV1.5 channel protein and its effect in an endocardial cell is studied. Ten Tusscher model of human ventricular action potential is modified to incorporate the changes contributed by L812Q mutant in the endocardial cells. Results show that BrS-associated SCN5A mutation causes reduction in the inward sodium current by modifications in the channel gating dynamics such as delayed activation, enhanced inactivation, and slowed recovery from inactivation in the endocardial cell. A decrease in the inward sodium current was also observed, which affects depolarization phase (Phase 0) that leads to reduction in the spike amplitude of the cardiac action potential.

Keywords: SCN5A gene mutation, sodium channel, Brugada syndrome, cardiac arrhythmia, action potential

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Authors: Hamed Ahari, Sepideh Farokhi, Mohamad Reza Abedini

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This paper focuses on inactivation of the growth of the bacterial mixture, Salmonella enteritidis, Staphylococcus aureus, Bacillus cereus and Escherichia coli, experimentally subjected to the chicken eggshell by two types of nano particle-Ag, composite film and colloidal spray carried out at concentrations of 500, 1000 and 2000 ppm over 28 days. The GLM, Repeated Measurement-ANOVA procedure was used to analyze the effect of time and concentration of nano groups on inactivation of bacteria, simultaneously. The maximum reduction of the bacterial growth was respected to the group “spray 2000 ppm” for which the value of the bacteria reached the minimum (0.93±0.42) on day 7, calculated to be 0.0 on days14 and 28 and followed by the group “spray 1000 ppm”. It was obviously concluded that increasing the dilution of nano coating in spray and film created a significant decrease in the number of bacteria colonies on the eggshells but the effect of packaging in different concentrations of nanocomposite was not statistically significant in different days of the study.

Keywords: nano particle, composite film, eggshell, bacteria

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Authors: M. Peña Aguilar Juan, E. Nava Galván Claudia, Pastrana Palma Alberto

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In this work was developed and implemented a thermal fogging disinfection system to counteract pathogens from poultry feces in agribusiness farms, to reduce mortality rates and increase biosafety in them. The control system consists of two phases for the conditioning of the farm during the sanitary break. In the first phase, viral and bacterial inactivation was performed by treating the stool dry cleaning, along with the development of a specialized product that foster the generation of temperatures above 55 °C in less than 24 hr, for virus inactivation. In the second phase, a process for disinfection by fogging was implemented, along with the development of a specialized disinfectant that guarantee no risk for the operators’ health or birds. As a result of this process, it was possible to minimize the level of mortality of chickens on farms from 12% to 5.49%, representing a reduction of 6.51% in the death rate, through the formula applied to the treatment of poultry litter based on oxidising agents used as antiseptics, hydrogen peroxide solutions, glacial acetic acid and EDTA in order to act on bacteria, viruses, micro bacteria and spores.

Keywords: innovation, triple helix, poultry farms, biosecurity

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Authors: Mohsen Padervand

Abstract:

Functionalized magnetic core-zeolitic shell nanostructures were prepared by the hydrothermal and coprecipitation methods. The products were characterized by Vibrating Sample Magnetometer (VSM), X-ray powder diffraction (XRD), Fourier Transform Infrared spectra (FTIR), nitrogen adsorption-desorption isotherms (BET) and Transmission Electron Microscopy (TEM). The growth of mordenite nanoparticles on the surface of silica coated nickel ferrite nanoparticles at the presence of organic templates was well approved. The antibacterial activity of prepared samples was investigated by the inactivation of E.coli as a gram negative bacterium. A new mechanism was proposed to inactivate the bacterium over the prepared samples. Minimum Inhibitory Concentration (MIC) and reuse ability were studied too. TEM images of the destroyed microorganism after the treatment time were applied to illustrate the inactivation mechanism. The interaction of the noble metals with organic components on the surface of nanostructures studied theoretically and the results were used to interpret the experimental results.

Keywords: nickel ferrite nanoparticles, magnetic core-zeolitic shell, antibacterial activity, E. coli

Procedia PDF Downloads 331