Inaktivierung von bakteriellen Endosporen durch die Anwendung gepulster elektrischer Felder in Kombination mit thermischer Energie

Die Anwendung von gepulsten elektrischen Feldern (PEF) ist im Bereich Inaktivierung vegetativer Mikroorganismen zur schonenden Haltbarmachung von hitzeempfindlichen Produkten wissenschaftlich validiert. Eine deutlich intensivere Behandlung ist bei Produkten, die mit bakteriellen Endosporen kontaminiert sind, nötig. Das Ziel dieser Studie ist eine Inaktivierung von bakteriellen Endosporen mit geringerer thermischer Produktbelastung durch den Einsatz von PEF in Kombination mit thermischer Energie zu erreichen. Der Einfluss von verschiedenen Prozess (elektrische Feldstärke, Temperatur und spezifischer Energieeintrag) und Produkt (pH, Zucker-, Ionen- und Fettkon-zentration) Parametern auf die Inaktivierung von B. subtilis, A. acidoterrestris und G. stearothermophilus Sporen wurde untersucht. Es wurde ein mathematisches Modell basierend auf einer Schulterformation mit anschließendem linearen Inaktivierungsverlauf angewendet, um den Einfluss der PEF Bedingungen und Produktparameter bewerten zu können. Im Bereich Prozessparameter zeigte die Eingangstemperatur den größten Einfluss auf die zur Inaktivierung benötigte Energie. Die Zucker- und Fettgehalte von maximal 10 °Bx bzw. 10 % Fett zeigten keinen Effekt auf die Inaktivierung. Geringere Energieeinträge konnten bei geringen Salzkonzentrationen (1 mS/cm, pH 4) eingesetzt werden. Der Einfluss der Temperatur auf die Inaktivierung wurde durch eine Kombination aus sporenspezifischen thermischen Inaktivierungskinetiken und des Temperatur Zeit Profils des PEF Prozesses modelliert. Das Modell ermöglichte die Trennung der Gesamtinaktivierung in thermische und PEF induzierte Inaktivierung. Es zeigte sich ein Anteil thermische Inaktivierung von B. subtilis und A. acidoterrestris Sporen, jedoch hatte die PEF induzierte Inaktivierung den größeren Anteil. Aufgrund der hohen thermischen Resistenz der G. stearothermophilus Sporen, ist die Gesamtinaktivierung größtenteils durch PEF induziert. Der Wirkmechanismus der PEF induzierten Inaktivierung konnte nicht eindeutig geklärt werden. Mikroskopische Aufnahmen und DPA Messungen nach der PEF Behandlung zeigten einen sich zur thermischen Behandlung unterscheidenden Mechanismus. Durch den schnellen Temperaturanstieg und das elektrische Feld wurden Strukturveränderungen induziert, welche ein Auslaufen der Sporen bewirken könnten. Die Validierung des entwickelten PEF Prozesses wurde durch Fallstudien analysiert. Der Karottensaft und das Hefeextrakt zeigten eine nach einer thermischen Behandlung vergleichbare Haltbarkeit mit höherer Produktqualität. Die Ergebnisse dieser Studie zeigen die Anwendung von PEF zur Inaktivierung bakterieller Endosporen bei geringeren Temperaturen. Somit können qualitativ hochwertige und mikrobiologisch sichere Produkte hergestellt werden.Pulsed Electric Fields (PEF) technology is widely studied in literature for the inactivation of vegetative microorganisms and offers a gentle preservation for heat sensitive products. Some products might be contaminated with bacterial endospores and require a more severe treatment for inactivation. The objective of this study was the inactivation of bacterial endospores by application of PEF with a lower heat load compared to thermal sterilization. Therefore, the PEF process was combined with thermal energy. The influence of different process (electric field strength, temperature and specific energy) and product (pH, sugar-, ion- and fat concentration) parameters on the inactivation of B. subtilis, A. acidoterrestris and G. stearothermophilus spores were analyzed. From experimental data, a model based on shoulder followed by linear distribution was applied. This model was used for evaluating the effect of PEF conditions and product parameters on the resistance of spores. As a result, the inlet temperature was identified as the most influencing process parameter. No effect of sugar and fat on the energy required for inactivation was obtained in the studied range from a maximum of 10 °Bx and 10 % fat. Low specific energy values were obtained at low salt concentrations (1 mS/cm) and pH 4. The impact of temperature on the inactivation by the developed process was modeled by combination of thermal inactivation kinetics of each spore type and the related temperature time profile of the PEF process. The model allowed a separation of total inactivation in thermal and PEF induced inactivation. The separation indicated a thermal inactivation rate for B. subtilis and A. acidoterrestris spores, but the PEF induced inactivation had a higher part. Based on the high thermal resistance of G. stearothermophilus spores, the obtained total inactivation was mainly based on PEF. The PEF induced inactivation of spores cannot be clearly explained as the mechanism of action is unclear. Microscopic studies and measurements of DPA after PEF treatment demonstrate a different mechanism compared to thermal inactivation. Due to the fast temperature increase and the electric field, changes in structure were induced, which might cause a leakage of spore content. The validation of the developed PEF process was analyzed by performance of case studies. Therefore, yeast extract and carrot juice were PEF treated and the microbial safety as well as quality were studied over shelf life. In both cases, the obtained shelf life was comparable to the thermally treated product, but a higher quality could be achieved. The presented data in this study demonstrates the possibility of inactivation of bacterial endo-spores at lower temperature than thermal sterilization. Therefore, the developed process can be used to produce products with a higher quality and ensure microbial safety

The influence of Pulsed Electric Fields (PEF) on the peeling ability of different fruits and vegetables

The impact of Pulsed Electric Fields (PEF) on the peeling ability of different fruits and vegetables in particular tomatoes, peaches, peppers, and oranges were investigated. Samples were exposed to a fixed electric field strength of 2.15 kV/cm. The specific energy ranged from 0.6 kJ/kg to 50.3 kJ/kg. The treated raw materials were analysed regarding to the peeling ability, skin size and weight and firmness. The best result for tomatoes at a specific energy of 1.2 kJ/kg induced a high score of peeling ability that led to less product loss and could therefore increase the yield by 33.84%–41.53% compared to untreated samples. Moreover, an increased skin size by a factor of 3.7 was observed. However, PEF had no significant impact on peeling ability of oranges, peppers, and peaches. Although oranges showed an improvement in peeling ability by up to 32%, this cannot be traced back to the PEF treatment. The different properties and structures of the raw materials were discussed and provided indications about the limitation of PEF

Affecting Casein Micelles by Pulsed Electrical Field (PEF) for Inclusion of Lipophilic Organic Compounds

The increased consumption of reduced-fat or non-fat products leads to a reduced intake of fat-soluble bioactive substances, such as fat-soluble vitamins. Due to their natural role as transport systems for hydrophobic substances, casein micelles (CM) might depict a viable system. The structure of CM is characterized by a lipophilic core stabilized by an electric double layer-like structure. Modification allows accessibility of the core and, therefore, the inclusion of fat-soluble bioactive substances. Well-known modifications are pH reduction and use of rennet enzyme. A completely new procedure to modify CM structure is offered by pulsed electrical fields (PEF). The principle behind PEF is called electroporation and affects the electric double layer of CM so that it is interrupted. In this way, lipophilic substances can be incorporated into CM. In this work, we evaluated integration of β-carotene into native CM by an industry-compatible process to overcome disadvantages associated with the use of Na-caseinate and avoid great technical effort, e.g., due to treatment with high hydrostatic pressure. Our research has shown that PEF can be used for disintegration of CM and that significant amounts of β-carotene can be incorporated in CM. Furthermore, after disintegration using PEF, a combination of another PEF and thermal treatment was applied to restructure CM and trap significant amounts of β-carotene, permanently, ending up with an encapsulation efficiency of 78%

Pulsed electric field assisted extraction of soluble proteins from nettle leaves (Urtica dioica L.) : kinetics and optimization using temperature and specific energy

Plant-based proteins are rapidly emerging, while novel technologies are explored to offer more efficient extraction processes. The current study aimed to evaluate the effects of pulsed electric fields (PEFs) and temperature on the extraction of soluble proteins from nettle leaves (Urtica dioica L.) and identify an optimal operational range for the highest yield of soluble proteins. Extractions and kinetic modeling were conducted with whole and ground dried leaves at different temperatures (30–70 °C) and specific energy of PEF (0–30 kJ kg−1) with extraction times of up to 60 min. The influence of temperature and specific energy on the soluble protein extraction yields was investigated and modeled using composite central design and response surface methodology. The experimental results were fitted to Peleg's kinetic model, which satisfactorily described the extraction process (R2 > 0.902), and PEF treated samples resulted in a higher soluble protein yield and shortened processing time. Response surface methodology showed that the linear effect of temperature and quadratic effect of PEF (p < 0.01) were highly significant for protein yield. In the optimized PEF-extraction region (specific energy between 10 and 24 kJ kg−1, and 70–78 °C), soluble protein yield was higher than 60% after 5 minutes of extraction. The achieved results are relevant for developing processes for PEF assisted extraction of soluble proteins from leaves. Understanding the effects of PEFs and process parameters is crucial to obtain high protein yields, while requiring low energy and short processing time

Повышение эффективности снятия покровной ткани с плодов томата импульсным электрическим полем

Electrophysical technologies are a global trend of sustainable agriculture and food industry. Peeling is an energy-intensive procedure of fruit and vegetable processing. The research featured the effect of pulsed electric field (PEF) treatment on tomato peeling effectiveness. The assessment included such factors as specific effort, energy costs, and product losses in comparison with thermal and electrophysical methods. Tomatoes of Aurora variety underwent a PEF treatment at 1 kV/cm. The expended specific energy was 1, 5, and 10 kJ/kg. The tomatoes were visually evaluated with optical microscopy before and after processing. The peeling effectiveness and mass loss were measured with a texture analyzer and digital scales. The PEF treatment decreased the specific force of mechanical peel removal by 10% (P < 0.05). The mass loss decreased by 4% (P < 0.05) at 1 kJ/kg. The PEF method resulted in cell electroporation, which activated the internal mass transfer of moisture from the endocarp region between the mesocarp and the integumentary tissue. The hydrostatic pressure produced a layer of liquid, which facilitated the peeling. In comparison with thermal treatment (blanching), ohmic heating, and ultrasonic processing, the PEF technology had the lowest production losses and energy costs. The research proves the prospects of the PEF treatment in commercial tomato processing

Pulsed Electric Field Treatment Application to Improve Product Yield and Efficiency of Bioactive Compounds through Extraction from Peels in Kiwifruit Processing

The kiwifruit processing industry is focused on product yield maximization and keeping energy costs and waste effluents to a minimum while maintaining high product quality. In our study, pulsed electric field (PEF) pretreatment enhanced kiwifruit processing to facilitate peelability and specific peeling process and enhanced valorization of kiwifruit waste. PEF optimization was applied to obtain the best treatment parameters. A 32 factorial design of response surface methodology was applied to find the effect of time elapsed after PEF treatment and the PEF-specific energy input on specific peeling force and kiwifruit firmness as response criteria. Under the optimized condition, the specific peeling force decreased by 100, and peelability increased by 2 times. The phenolic content and antioxidant capacity of PEF-treated kiwifruit bagasse were 5.1% and 260% richer than the control sample. Overall, the optimized PEF pretreatments incorporated into kiwifruit processing led to decreased energy demand and increased productivity

Clinical manifestations and outcome of SARS-CoV-2 infections in children and adolescents with rheumatic musculoskeletal diseases: data from the National Paediatric Rheumatology Database in Germany

Objectives This study aimed to investigate the clinical manifestations, course and outcome of SARS-CoV-2 infection among children and adolescents with rheumatic and musculoskeletal diseases (RMD). Due to their underlying disease as well due to therapeutic immunosuppression, these patients may be at risk for a severe course of COVID-19 or for a flare of the underlying disease triggered by SARS-CoV-2 infection. Methods Demographic, clinical and treatment data from juvenile patients with RMD as well as data about SARS-CoV-2 infection like test date and method, clinical characteristics, disease course, outcome and impact on the disease activity of the RMD were documented on a specific SARS-CoV-2 questionnaire implemented in the National Paediatric Rheumatology Database (NPRD) in Germany. The survey data were analysed descriptively. Results From 17 April 2020 to 16 February 2021, data were collected from 76 patients (52% female) with RMD and laboratory-proven SARS-CoV-2 infection with median age of 14 years, diagnosed with juvenile idiopathic arthritis (58%), autoinflammatory (24%) and connective tissue disease (8%). Fifty-eight patients (76%) received disease-modifying antirheumatic drugs (DMARDs), 41% biological DMARDs and 11% systemic glucocorticoids. Fifty-eight (76%) had symptoms of COVID-19. Disease course of SARS-CoV-2 infection (classified as asymptomatic, mild, moderate, severe, life-threatening) was mild and outcome of COVID-19 (classified as recovered, not yet recovered, permanent damage or deceased) was good (recovered) in the majority of patients. Two patients were hospitalised, one of whom required intensive care and died of cardiorespiratory failure. In 84% of SARS-CoV-2-positive patients, no relevant increase in disease activity of the RMD was observed. Conclusions In our cohort, SARS-CoV-2 infection in juvenile patients with RMD under various medications was mild with good outcome in the majority of cases and does not appear to have a relevant impact on disease activity of the underlying condition