Application of Novel Thermal Technology in Foods Processing

Advanced and novel thermal technologies, such as ohmic heating, dielectric heating (e.g., microwave heating and radio frequency heating), and inductive heating, have been developed to improve the effectiveness of heat processing whilst guaranteeing food safety and eliminating undesirable impacts on the organoleptic and nutritional properties of foods. Novel thermal technologies rely on heat generation directly inside foods, which has implications for improving the overall energy efficiency of the heating process itself. The use of novel thermal technologies is dependent on the complexity and inherent properties of the food materials of interest (e.g., thermal conductivity, electrical resistance, water content, pH, rheological properties, food porosity, and presence of particulates). Moreover, there is a need to address the combined use of thermal processing with emerging technologies such as pulsed electric fields, high hydrostatic pressure, and ultrasound to complement the conventional thermal processing of fluid or solid foods. This Special Issue provides readers with an overview of the latest applications of various novel technologies in food processing. A total of eight cutting-edge original research papers and one comprehensive review paper discussing novel processing technologies from the perspectives of food safety, sustainability, process engineering, (bio)chemical changes, health, nutrition, sensory issues, and consumers are covered in this Special Issue

Annual Report 2013 / Institute for Pulsed Power and Microwave Technology = Jahresbericht 2013 / Institut für Hochleistungsimpuls- und Mikrowellentechnik. (KIT Scientific Reports ; 7666)

The Institute for Pulsed Power and Microwave Technology (Institut für Hochleistungsimpuls- und Mikrowellentechnik - IHM) is doing research in the areas of pulsed power and high power microwave technologies. Both, research and development of high power sources as well as related applications are in the focus. Applications for pulsed power technologies are ranging from material processing to bioelectrics. Microwave technologies are focusing on RF sources for electron cyclotron resonance heating and on applications for material processing at microwave frequencies

Variability in the response of salmonella and listeria strains to different strategies for inactivation

[ENG] The last EFSA report, notified a total of 5146 food outbreaks in the European Union in 2018. The food industry plays an important role in the food chain and has to adapt and reinvent itself when consumers place certain demands on products. Food safety is the first issue to take into account. There is already a large variety of microbiological species that are capable of developing in food and the safety of food makes it questionable whether or not the product is suitable for consumption. Listeria monocytogenes and Salmonella spp. are characterised by being two ubiquitous microbial species capable of living in borderline conditions of pH, water activity and sodium chloride concentrations. Another circumstance of these two microorganisms is the variability between their different strains and the capacity they have to recover from the different stresses to which they are subjected. For these reasons, it is of utmost importance to know their response to stress in order to control their inactivation and/or development in any situation. This knowledge will enable to efficiently apply technologies and treatments that are capable of inactivating or inhibiting growth of microorganisms, so to prevent or, at least, reduce food contamination. So, in this thesis, the main objective was to study the application of different strategies for the inactivation of L monocytogenes and Salmonella that could reduce the intensity of the treatments, while ensuring food safety. In this thesis, the effect that different inactivation strategies have on L. monocytogenes and Salmonella spp. has been studied. Firstly, the heat resistance of four L. monocytogenes strains -Scott A, CECT 4031, CECT 4032 and 12MOB052- in three different matrices -buffered peptone water (BPW), pH 7 Mcllvaine phosphate citrate buffer and a last one of food origin; semi- skimmed milk- was studied. Under isothermal conditions, there was no between-strains and between-media variability in the resistance. However, when this experiment was carried out under dynamic conditions, some strains were able to develop acclimation to stress, leading to important differences in resistance. Between-strains, the CECT 4031 increased its D-value by 10, with CECT 4032 being the least acclimated and between-media, peptone water buffer and semi- skimmed milk were the mediums where most acclimation was found. These results are of great importance, as they highlight that some mechanisms of heat resistance may not be detected when conditions, such as acclimation.Another part of the research was carried out to evaluate the response to heat when Salmonella Senftenberg and S. Enteritidis - the treatment applied is under isothermal conditions, but they show up under dynamic heating were exposed to a previous acid shock. Both serovars of Salmonella were grown at pH 4.5 and subsequently exposed to heat treatment under isothermal conditions at four different temperatures. The heating medium used was peptone water at pH 4.5 and 7.0. The results showed that both serovars had a different response to a heat treatment after the exposure to acid. On the one hand, S. Senftenberg reduced its heat resistance when subjected to a previous acid shock, while in S. Enteritidis its heat resistance increased. Again, these results bring out the inherent variability in microorganisms, in this case related to a stress response mechanisms. Finally, the effectiveness of the combination of applying electrical pulses (PEF) and oregano essential oil to L. monocytogenes was determined. The medium used was a Mcllvaine buffer at pH 7 with a conductivity of 6 μS/cm. On the one hand, the efficiency of the electric field was evaluated between 5 and 20 kV/cm and it was found that after 60 pulses at 20 kV/cm field strength, 1 Hz frequency and 20 μs pulse width, an inactivation of 2.01 log10 cycles was achieved, while to achieve a similar level of inactivation at 15 kV/cm, 300 pulses were required. Then, PEF treatments were then applied (20 kV/cm field strength, 60 pulses, 1 Hz frequency and 20 μs pulse width) after having exposed the cells to the minimum inhibitory concentration (MIC) of the oregano essential oil (2000 ppm) and these results showed no significant differences (p>0.05) with respect to the PEF treatments applied alone. However, when the same PEF treatment as above was applied first and then the surviving microorganisms were resuspended on the MIC of oregano essential oil, significant differences (p0,05) con respecto a los tratamientos PEAV aplicados solos. Sin embargo, cuando se aplicó primero el mismo tratamiento PEAV que el anterior y luego se resuspendió a los microorganismos sobrevivientes en la CIM del aceite esencial de orégano, se encontraron diferencias significativas (p<0,05) con respecto al FEM aplicado solo y al PEAV después del orégano. También se encontró que al reducir a 1/16 la CIM (125 ppm) el efecto fue el mismo que si aplicáramos la CIM. Para concluir, esta tesis ha investigado cómo pueden combinarse diferentes estrategias de inactivación microbiana para conseguir un alimento seguro con un tratamiento más suave, que en un solo tratamiento convencional. También ha ayudado a abordar las predicciones para futuros estudios y como contribución a la industria alimentaria mejorará la cuantificación de la evaluación de riesgos microbiológicos.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado de Técnicas avanzadas en investigación y desarrollo agrario y alimentari

Annual Report 2017 / Institute for Pulsed Power and Microwave Technology / Institut für Hochleistungsimpuls- und Mikrowellentechnik. (KIT Scientific Reports ; 7754)

Das Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM) forscht auf den Gebieten der gepulsten Leistung und der Hochleistungsmikrowellentechnologie. Sowohl die Forschung und Entwicklung von Hochleistungsquellen als auch verwandte Anwendungen stehen im Fokus. Die Anwendungen für Impulsstromtechnologien reichen von der Materialbearbeitung bis zur Bioelektrik. Hochleistungsmikrowellentechnologien konzentrieren sich auf HF-Quellen (Gyrotrons) für die Elektronenzyklotronresonanzheizung von magnetisch eingeschlossenen Plasmen und auf Anwendungen für die Materialbearbeitung bei Mikrowellenfrequenzen

Annual Report 2015 / Institute for Pulsed Power and Microwave Technology = Jahresbericht 2015 / Institut für Hochleistungsimpuls- und Mikrowellentechnik. (KIT Scientific Reports ; 7722)

Das Institut für Hochleistungsimpuls- und Mikrowellentechnik (IHM) arbeitet auf dem Gebiet der Hochleistungsimpuls- und Hochleistungsmikrowellentechnologie. Sowohl die Forschung und Entwicklung von Hochleistungsquellen als auch die damit verbundenen Anwendungen stehen im Fokus

Renewable Energy

This book discusses renewable energy resources and systems as well as energy efficiency. It contains twenty-three chapters over six sections that address a multitude of renewable energy types, including solar and photovoltaic, biomass, hydroelectric, and geothermal. The information presented herein is a scientific contribution to energy and environmental regulations, quality and efficiency of energy services, energy supply security, energy market-based approaches, government interventions, and the spread of technological innovation

Biological response of Chlorella vulgaris to pulsed electric field treatment for improvement of protein extraction

Angesichts des Klimawandels und einer stetig wachsenden Weltbevölkerung können Mikroalgen eine wichtige Rolle als nachhaltige Energie- und Nahrungsquelle der Zukunft spielen. Zur Extraktion wertvoller Inhalts- und Nährstoffe ist ein Zellaufschluss notwendig. Die Elektroimpulsbehandlung (EIB) bietet eine energieeffiziente und schonende Alternative im Vergleich zu mechanischen Zellaufschlussmethoden. Jedoch sind die biologischen Prozesse und zellulären Mechanismen hinter dem Zelltod nach EIB noch wenig untersucht. Aus diesem Grund wurden die einzellige grüne Mikroalge Chlorella vulgaris und das Cyanobakterium Spirulina als Modellorganismen verwendet, um die Wirkung von EIB auf biologische Zellen zu untersuchen. Dafür wurde eine Methode zur Überwachung der Viabilität nach EIB unter Verwendung von Fluoresceindiacetat (FDA) in C. vulgaris etabliert. Im Anschluss wurden die experimentellen EIB-Parameter so eingestellt, dass ein fixes Verhältnis von Zellen nach der Behandlung abstirbt, während der andere Teil überlebt. Mit diesen Werkzeugen war eine quantitative Analyse des Zelltodes nach EIB möglich. Basierend auf den Analyseergebnissen wurde die EIB-Extraktion von Proteinen und dem wertvollen blauen Farbstoff Phycocyanin aus Spirulina unter verschiedenen post-EIB Inkubationsbedingungen untersucht. Zur Optimierung der Elektroextraktionseffizienz in Spirulina wurden die Einflüsse des pH des externen Mediums, der Biomassekonzentration, der Zellaggregation sowie der Energiereduktion untersucht. Das optimierte Elektroextraktionsprotokoll mit höherer Biomassekonzentration und geringerer Behandlungsenergie erfordert eine post-EIB-Inkubation unter kontrollierten Bedingungen (Raumtemperatur, pH 6 oder 8, homogene Suspension), die für die Freisetzung und Stabilität von Phycocyanin entscheidend sind. Mit diesem Wissen besteht eine mögliche biotechnologische Anwendung darin, schonende EIB mit niedrigstem Energieeintrag durchzuführen, was zu einer effizienten Protein- und Phycocyanin-Gewinnung führt. An C. vulgaris konnte gezeigt werden, dass EIB mit niedrigem Energieeintrag auch als abiotisches Stresssignal wirken kann. Dies wurde sichtbar in Form einer gestörten Redox-Homöostase, bei der sowohl die Freisetzung von Wasserstoffperoxid als auch Lipidoxidation gemessen werden konnten. Die Hemmung von Prozessen, die mit dem programmierten Zelltod (PCD) zusammenhängen, zeigten, dass höchstwahrscheinlich Ca-Signalwege, Aktindynamik und Membranversteifung keine notwendige Rolle beim EIB-induzierten Zelltod spielen. Die Freisetzung von Cytochrom f konnte nur im Hochdruckhomogenisations (HPH) Extrakt und nicht nach EIB nachgewiesen werden. Zellsuspensionen mit hoher Zelldichte, die an der Überlebensschwelle gepulst wurden, zeigten nur eine langsame Manifestation des Zelltods. Dies führte zur Entdeckung eines Zelltod-induzierenden Faktors (CDIF). Es konnte nachgewiesen werden, dass durch EIB und HPH-Behandlung der CDIF aus C. vulgaris extrahiert werden kann. Wasserlöslicher Extrakt, der diesen CDIF enthielt, führte zum Absterben von unbehandelten Mikroalgen (insbesondere nur bei C. vulgaris). Weitere Experimente zeigten die Entstehung des CDIF in der stationären Wachstumsphase, Hitzelabilität und Dosisabhängigkeit. Ebenso wie die Empfindlichkeit gegenüber direkter EIB hing die Empfindlichkeit der Empfängerzellen gegenüber dem CDIF vom Zellzyklusstadium ab. Untersuchungen zur Extraktionseffizienz von Proteinen aus C. vulgaris führten zu dem Ergebnis, dass die erforderliche spezifische Energie für maximalen Ertrag der zuvor bestimmten Behandlungsenergie an der Überlebensschwelle entspricht. Alle experimentellen Ergebnisse weisen darauf hin, dass der EIB-induzierte Zelltod und die damit verbundene hohe Extraktionseffizienz nicht nur auf rein physikalische Phänomene zurückzuführen sind, sondern einen biologischen Prozess beinhalten müssen. Das Arbeitsmodell bezüglich des CDIF beinhaltet, dass der Faktor aus zellwandabbauenden Enzymen wie Chitinasen besteht. EIB bei sehr geringem Energieeintrag wirkt als abiotisches Stresssignal. In Kombination mit einer beschädigten Zellintegrität aufgrund von Poren in der Zellmembran führen PCD-Prozesse zu einer enzymatischen Autolyse, bei der der CDIF (Chitinasen) freigesetzt wird. Die Zellwand wird durch den CDIF geschwächt. Wird der CDIF-haltige Extrakt unbehandelten Empfängerzellen zugesetzt, zeigt er zunächst über den Zellwandabbau eine äußere Wirkung. Nach Internalisierung kann der CDIF als internes Signal fungieren, das PCD auslöst

Effect of processing on muscle structure and protein digestibility in vitro : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand

Figures 2-1, 2-2, 2-3, 2-4 and Table 2-2 are re-used with publishers' permission.The objective of this thesis was to investigate the effect of processing on meat protein properties, muscle structure and in vitro protein digestibility of beef. Meat processing techniques including pulsed electric field (PEF), shockwave (SW) processing, exogenous enzyme (actinidin) treatment, and sous vide (SV) cooking were explored, either alone or in combination, in this project. This thesis also aimed to study the diffusion of enzymes (actinidin from kiwifruit and pepsin in the gastric juice) into the meat. The first experiment investigated the effect of PEF processing alone on the ultrastructure and in vitro protein digestibility of bovine Longissimus thoracis, a tender meat cut (Chapter 3). It was observed that the moisture content of the PEF-treated samples (specific energy of 48 ± 5 kJ/kg and 178 ± 11 kJ/kg) was significantly lower (p < 0.05) by 1.3 to 4.6 %, compared to the untreated samples. The pH, colour, and protein thermal profile of the PEF-treated muscles remained unchanged. Pulsed electric field treatment caused the weakening of the Z-disk and I-band junctions and sarcomere elongation (25 to 38 % longer) of the muscles. The treatment improved in vitro meat protein digestibility by at least 18 %. In this thesis, the protein digestibility was determined in terms of the ninhydrin-reactive amino nitrogen released during simulated oral-gastro-small intestinal digestion. An enhanced proteolysis of the PEF-treated meat proteins (such as α-actinin and β-actinin subunit) during simulated digestion was also observed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The improvement in protein digestibility of the PEF-treated meat was supported by more severe disruption of Z-disks and I-bands observed in PEF-treated samples, at the end of simulated digestion. In the second experiment, PEF treatment (specific energy of 99 ± 5 kJ/kg) was applied to bovine Deep and Superficial pectoral muscles in conjunction with SV cooking (60 ℃ for 24 h) (Chapter 4). This muscle cut was tested as it is a tough cut and requires slow cooking. There was no significant difference detected in the specific activities of the sarcoplasmic cathepsins present in the cytosol between the control and PEF-treated samples, both before and after cooking. In addition, similar micro- and ultrastructures were observed between the control SV-cooked and PEF-treated SV-cooked pectoral muscles. The combined PEF-SV treatment increased the in vitro protein digestibility of the pectoral muscles by approximately 29 %. An improvement in proteolysis of the treated meat proteins (e.g. myosin heavy chains and C-protein) during simulated digestion was also observed using SDS-PAGE. More damaged muscle micro- and ultrastructures were detected in PEF-treated SV-cooked muscles at the end of in vitro oral-gastro-small intestinal digestion, showing its enhanced proteolysis compared to the control cooked meat. Next, the effect of SW processing and subsequent SV cooking on meat protein properties, muscle structure and in vitro protein digestibility of bovine Deep and Superficial pectoral muscles were investigated (Chapter 5 and 6). Shockwave processing (11 kJ/pulse) alone decreased the enthalpy and thermal denaturation temperature of the collagen (p < 0.05) when compared to the raw control, studied using a differential scanning calorimeter. The purge loss, pH, colour, and the protein gel electrophoresis profile of the SW-treated raw muscles remained unaffected. Shockwave processing led to the disorganisation of the sarcomere structure and also modified the protein secondary structure of the myofibres. After subsequent SV cooking (60 ℃ for 12 h), more severe muscle fibre coagulation and denaturation were observed in the SW-treated cooked meat compared to the cooked control. An increase in cook loss and a decrease in the Warner-Bratzler shear force were detected in the SW-treated SV-cooked meat compared to the control cooked meat (p < 0.05). The in vitro protein digestibility of the SW-treated SV-cooked meat was improved by approximately 22 %, with an enhanced proteolysis observed via SDS-PAGE, compared to the control SV-cooked meat. These results were supported by the observation of more destruction of the micro- and ultrastructures of SW-treated cooked muscles, observed at the end of the simulated digestion. The effect of the kiwifruit enzyme actinidin on muscle microstructure was studied using Picro-Sirius Red staining (Chapter 7). Meat samples were subjected to two different conditions, simulating meat marination (pH 5.6) and gastric digestion in humans (pH 3). Actinidin was found to have a greater proteolytic effect on the myofibrillar proteins than the connective tissue under both conditions. When compared with pepsin under simulated gastric conditions, actinidin had a weaker proteolytic effect on the connective tissue of cooked meats. Nevertheless, incubating the cooked meat in a solution containing both actinidin and pepsin resulted in more severe muscle structure degradation, when compared to muscles incubated in a single enzyme system. Thus, the co-ingestion of kiwifruit and meat could promote protein digestion of meat in the stomach. In addition, both actinidin and pepsin were successfully located at the edges of the muscle cells and in the endomysium using immunohistofluorescence imaging. The observations suggest that the incubation solutions penetrate into the muscle through the extracellular matrix to the intracellular matrix, enabling the proteases to access their substrates. Overall, the present work demonstrated that there were strong interactions between processing, muscle protein properties and structure, and in vitro protein digestibility of the meat. Processing induces changes in meat protein properties and muscle structure, which in turn affects the digestion characteristics of muscle-based foods