Impact of different water activities (aw) adjusted by solutes on high pressure high temperature inactivation of Bacillus amyloliquefaciens spores

Much research has been conducted to comprehend the mechanisms of high pressure (HP) inactivation of spores in aqueous systems but for food model systems these information are scarce. In these systems spores can interact with ingredients which then could possibly lead to retarded or reduced inactivation, which can cause a problem for the sterilization process. The protective mechanism of a reduced aw-value is still unclear. HP processing might prove valuable to overcome protective effects of solutes and achieve shorter process times for sterilization under HP. To gain insight into the underlying mechanisms five aw-values (0.9, 0.92, 0.94, 0.96, 1) were adjusted with two different solutes (NaCl, sucrose). Solutions were inoculated with spores of Bacillus amyloliquefaciens and treated at 105, 110, and 115°C at 600 MPa. Further a thermal inactivation was conducted at the same temperatures for a comparison with the HP data. Afterward, the influence of HP high temperature treatment on the inactivation, the dipicolinic acid (DPA)-release and membrane constitution was assessed by plate count, HPLC and flow cytometry (FCM). The results show that during HP treatments sucrose and salt both have a protective effect, in which the influence of sucrose on the retarded inactivation is higher. The threshold water activities (aw), which is 0.94, here salt and sucrose have a significant influence on the inactivation. The comparison of thermal (105–115°C) and HP and high temperature (600 MPa, 105–115°C) treated samples showed that the time needed to achieve a 4–5 log10 inactivation is reduced from 45 (aw = 1) to 75 (aw = 0.9) min at 105°C to 3 (aw = 1) to 15 (aw = 0.9) minutes at 600 MPa and 105°C. The release of DPA is the rate limiting step of the inactivation and therefore monitoring the release is of great interest. The DPA-release is slowed down in high concentrated solutions (e.g., sucrose, salt) in comparison to aw 1. Since there is a difference in the way the solutes protect the spore it could be seen as an inner spore membrane effect. Maybe as shown for vegetative microorganism the solutes can interact with membranes, e.g., the inner spore membrane. Flow cytometry (FCM) measurement data show a similar trend

Inactivation of Brettanomyces bruxellensis by High Hydrostatic Pressure technology

Póster presentado en el XXV Congreso de la Sociedad Española de Microbiología (SEM), celebrado en Logroño del 7 al 10 de julio de 2015.Peer Reviewe

Aspects of high hydrostatic pressure food processing: Perspectives on technology and food safety

The last two decades saw a steady increase of high hydrostatic pressure (HHP) used for treatment of foods. Although the science of biomaterials exposed to high pressure started more than a century ago, there still seem to be a number of unanswered questions regarding safety of foods processed using HHP. This review gives an overview on historical development and fundamental aspects of HHP, as well as on potential risks associated with HHP food applications based on available literature. Beside the combination of pressure and temperature, as major factors impacting inactivation of vegetative bacterial cells, bacterial endospores, viruses, and parasites, factors, such as food matrix, water content, presence of dissolved substances, and pH value, also have significant influence on their inactivation by pressure. As a result, pressure treatment of foods should be considered for specific food groups and in accordance with their specific chemical and physical properties. The pressure necessary for inactivation of viruses is in many instances slightly lower than that for vegetative bacterial cells; however, data for food relevant human virus types are missing due to the lack of methods for determining their infectivity. Parasites can be inactivated by comparatively lower pressure than vegetative bacterial cells. The degrees to which chemical reactions progress under pressure treatments are different to those of conventional thermal processes, for example, HHP leads to lower amounts of acrylamide and furan. Additionally, the formation of new unknown or unexpected substances has not yet been observed. To date, no safety-relevant chemical changes have been described for foods treated by HHP. Based on existing sensitization to non-HHP-treated food, the allergenic potential of HHP-treated food is more likely to be equivalent to untreated food. Initial findings on changes in packaging materials under HHP have not yet been adequately supported by scientific data

Hochdruckbehandlung bei moderaten und erhöhten Temperaturen und deren Einfluss auf Lebensmittelprozesskontaminanten, pathogene Mikroorganismen und bakterielle Sporen in Model- und echten Lebensmittelsystemen

Hochdruck bei 600 MPa in Kombination mit milden Temperaturen macht es möglich sichere und qualitativ hochwertige Lebensmittel herzustellen. In den letzten Jahren gab es grundlegende Arbeiten zum Verständnis des Inaktivierungsmechanismus von Sporen (Bacillus subtilis etc.) und vegetativen Mikroorganismen, wie Escherischia coli und Lacotbacillus subsp., die zum größeren Verständnis der Wirkungsweise dieser Technologie beitrugen. Ein weiteres Anwendungsgebiete der Hochdrucktechnologie ist die schonende Dekontamination von Lebensmitteln, die mit resistenten pathogenen Keimen, wie dem Escherichia coli (EHEC) Stamm O104:H4, der für den Infektionsausbruch in Deutschland 2011 verantwortlich war, verunreinigt sind. Die Kombination von Drücken zwischen 100-400 MPa und Temperaturen zwischen 40-70°C führten zu einer schnelleren Inaktivierung im Vergleich zur thermischen Behandlung. Um eine Haltbarkeit von Lebensmitteln bei Raumtemperatur zu gewährleisten, wird das Lebensmittel mittels Hitze sterilisiert. Dieser Prozess ist sehr intensiv und birgt eine hohe thermische Belastung des Produktes, wodurch zwar Sporen abgetötet werden, aber es zur Bildung von unerwünschten Prozess-Kontaminanten und dem Verlust von wertgebenden Inhaltsstoffen kommen kann. Deshalb soll im Rahmen dieser Arbeit die Hochdrucksterilisation als Alternative zur thermischen Sterilisation hinsichtlich der Inaktivierung von Sporen und Reduzierung der Prozesskontaminanten getestet werden. Es gibt bis heute jedoch keinen festgelegten Leitkeim für die Hochdrucksterilisation und Wissen über das Verhalten möglicher Leitkeime, wie Clostridium sporogenes, Bacillus amyloliquefaciens oder Geobacillus stearothermophlius, in lebensmittelnahen oder echten Lebensmittelsystemen ist gering. In den letzten Jahren gab es grundlegende Arbeiten zum Verständnis des Inaktivierungsmechanismus von Sporen (Bacillus subtilis etc.) aber diese wurde hauptsächlich in Puffersystemen durchgeführt. Deshalb wurden die vorhergenannten Sporenbildner in einem breiten Druck-Temperatur Spektrum getestet, um ihre Resistenz zu bestimmen. Die Inaktivierung unterschiedlicher Sporen (Clostridium sporogenes, Bacillus amyloliquefaciens und Geobacillus stearothermophlius) in einem breiten Druck- (100-600 MPa) und Temperaturbereich (40-100°C) in ACES-Puffer zeigte, dass unter diesen getesteten Bedingungen die Bacillus amyloliquefaciens Sporen die mit der höchsten Resistenz waren und könnte somit als Leitkeim für die Hochdrucksterilisation in Frage kommen. Zum besseren Verständnis der Inaktivierung in komplexeren Systemen und dem möglichen Schutzeffekt von gelösten Stoffen wurden Bacillus amyloliquefaciens Sporen in unterschiedliche Zucker-und Salzkonzentration (0.83-1.7 mol/l bzw. 1.2-2.7 mol/l) mit variierenden aw-Werten (0.9-1) inokuliert und hinsichtlich Inaktivierung, Dipicolinsäure (DPA)-Ausschleusung und Veränderung an der Membranstruktur mittels FCM, in einem Temperaturbereich von 105-115°C bei 600 MPa untersucht. Je höher die Konzentration der gelösten Stoffe desto schlechter die Inaktivierung und dementsprechend die DPA-Ausschleusung. Wobei Zucker einen höheren Schutzeffekt auf die Sporen hatte als Salz. Für beide Stoffe zeigte sich ein ausgeprägter schützender Effekt bei einem aw von ≤ 0.94. Ab einer Temperatur von 115°C verschwindet der schützende Effekt und es existieren kaum Unterscheide hinsichtlich der Inaktivierung oder der DPA-Ausschleusung. Die FCM-Analyse zeigte, dass diese für Systeme, die eine hohe Konzentration an gelösten Stoffen enthalten hinsichtlich der Färbung noch optimiert werden muss. Allerdings zeigten die Ergebnisse Tendenzen, die auf einen Einfluss der gelösten Stoffe auf die innere Sporenmembran schließen lassen. Noch komplexer sind echte Lebensmittelsysteme und deren Einfluss auf die Sporeninaktivierung und mögliche chemische Reaktionen während der Behandlung, die zur Bildung von von Prozesskontaminanten führen können. In den letzten Jahren die Reduzierung der krebserregenden Food process contaminants (FPCs), wie Furan oder Monochlorpropandiol (MCPD)-ester, in Lebensmitteln diskutiert und Alternativen, wie die Hochdrucksterilisation, zur herkömmlichen Prozessierung nach ihrem Potential diesbezüglich gilt es ebenfalls zu untersuchen. Deshalb wurde Bacillus amyloliquefaciens in ausgewählte Lebensmittelsysteme (Babynahrung auf Gemüsebasis und Rohprodukte für Fischkonserven) inokuliert, um das Potential der Hochdrucksterilisation auf die Inaktivierung von Sporen und die Reduzierung von FPCs zu untersuchen. Es zeigte sich, dass eine Inaktivierung von Bacillus amyloliquefaciens Sporen in den Lebensmittelsystem und Modelllebensmittelsystemen im Bereich 90-110°C stark von der Zusammensetzung/Konzentration der Inhaltsstoffe abhängig war. Ab 115°C existierten nur marginale Unterschiede zwischen den Systemen, da hier die treibende Kraft der Inaktivierung die Temperatur war. Die gewonnen Inaktivierungskinetiken für Babynahrung auf Gemüsebasis und Rohprodukte für Fischkonserven, konnten zur Modellierung einer extrapolierten 12 log10 Inaktivierung, mittels eines nten –Ordnung Ansatzes verwendet werden und ein Scale up vom Labormaßstab (4 ml) auf Pilotmaßstab (55 L) durchgeführt werden. Die durchgeführten Lagerversuche zeigten, dass ein sicheres Produkt in einem Temperaturbereich von 110-115°C und einer Haltezeit zwischen 6.5 – 28 min bei 600 MPa gewährleistet werden kann. Die Furananalyse zeigte, dass die Bildung von Furan nur in Lebensmittelsystemen auftritt, die Vorläufer (sog. Precursor wie Zucker, mehrfachungesättigte Fettsäuren und Aminosäuren) enthalten. Bei den Produkten Sardine in Olivenöl und Babynahrung auf Basis von Gemüse konnte eine Reduzierung im Vergleich zur thermischen Sterilisierung (F0=7) von 72-97 % (ausgehend von 57.88 µg kg-1) bzw. 81-96 % (ausgehend von 30 µg kg-1) in einem Temperaturbereich von 90-121°C bei 600 MPa erzielt werden. Bei den MCPD-estern erfolgte keine Bildung während der thermischen oder der hochdruck-hochtemperatur Behandlung in den getesteten Systemen. Nur in Thunfisch in Sonnenblumenöl wurden größere Mengen an MCPD-estern gefunden, diese sind allerdings auf die Verwendung von raffiniertem Sonnenblumenöl zurückzuführen. Die Daten dieser Arbeit können dazu beitragen, diese vielversprechende Technologie zu kommerzialisieren und somit die Lebensmittelsicherheit und Lebensmittelqualität zu erhöhenHigh pressure pasteurization, high pressure at 600 MPa in combination with mild temperatures, makes it possible to produce safe and high quality foods. In the last few years groundbreaking research was conducted to understand the inactivation mechanisms of vegetative microorganism such as, Escherischia coli and Lacotbacillus subsp., under high pressure conditions, which lead to a better understanding of this technological the working principle. Another application field of the high pressure technology is the mild decontamination of foods, which are contaminated, with resistant pathogen bacteria such as the Escherichia coli (EHEC) strain O104:H4, responsible for an outbreak of HUS in Germany in 2011. The combination of pressures between 100-400 MPa and temperatures between 40-70°C showed an accelerated inactivation as in comparison to the thermal treatment. The kinetic data from this study and the suggested mechanisms can aid in optimizing this promising sterilization technology and will increase food safety and food quality. To obtain long storage periods for foods at ambient temperatures, sterilization by heat is one of the main technologies used in the food industry. The process is quite intense with a huge thermal load applied to the product, leading not only to the inactivation of spores but also to the formation of other unhealthy compounds such as food processing contaminants (FPCs) and a loss of nutrients. This is why the use of the high pressure thermal sterilization is tested as an alternative for the thermal retorting of spore inactivation in real and model food systems and the mitigation of FPCs. To this day there is no indicator microorganism for the high pressure thermal sterilization and knowledge about the behavior of possible target microorganisms, such as Clostridium sporogenes, Bacillus amyloliquefaciens or Geobacillus stearothermophilus, in food model systems or real food system is scarce. In the last few years groundbreaking research was conducted to understand the inactivation mechanisms of spores (Bacillus subtilis etc.) but mainly in buffer systems. Therefore the aforementioned spore strains need to be tested in a broad pressure temperature range to evaluate their resistance. The inactivation of different spore strains (Clostridium sporogenes, Bacillus amyloliquefaciens and Geobacillus stearothermophilus) in a wide pressure (200-600 MPa) and temperature (40-100°C) domain in ACES-buffer showed that the most resistant one under these conditions is the Bacillus amyloliquefaciens. Therefore this spore strain could be used a possible indicator microorganism for the high pressure thermal sterilization. To gain a better understanding of the inactivation of spores and possible baroprotective effects of solutes in complex food systems Bacillus amyloliquefaciens spores were inoculated in different sucrose and NaCl solutions (0.83-1.7 mol/l respectively 1.2-2.7 mol/l) with aw-values ranging from 0.9-1. Investigated were inactivation, DPA-release and possible inner membrane changes via FCM in a temperature range of 105-115°C at 600 MPa. The higher the solute concentration the more pronounced was the impact on a retarded inactivation and DPA-release. The impact of sucrose as a baroprotective solute was stronger than NaCl. Both solutes showed their potential as a baroprotective solute at aw ≤ 0.94. At temperatures of 115°C and higher the baroportective effect of the solutes diminishes and the differences in inactivation and DPA-release are nominal for all aw. The FCM-analyses needs to be optimized for high concentrated solutions since the dying of all spores was not always possible. Although the results showed tendencies that the solutes had an impact on the inner spore membrane and therefore led to a retarded inactivation and DPA-release. Even more complex are real food systems and their influence on the inactivation of spores and possible chemical reactions during the processing which can lead to the formation of FPCs. Therefore Bacillus amyloliquefaciens was inoculated in selected food system baby food on the basis of vegetables and raw products for fish cans and tested at lab scale level concerning the inactivation and the formation of FPCs, such as furan and MCPD-ester under high pressure thermal sterilization conditions. The treatment was conducted in a temperature range of 80-121°C at 600 MPa with dwell times up to 40 minutes. It showed that the inactivation in food of Bacillus amlyoliquefaciens at 600 MPa 90-110°C and food model systems is strongly dependent on the composition/concentration of the ingredients. At 115 °C and 600 MPa the difference in terms of inactivation was nominal since the driving force of inactivation was the temperature. The collected inactivation data, for the baby food puree and the raw products for fish cans, was used to model with an nth-order approach extrapolated optimal treatment conditions for a 12 log inactivation. Based on these calculations from lab scale (4 ml) a scale up approach for a 55 L vessel was conducted. The storage trials revealed that in a temperature range of 110-115°C and dwell times between 6.5-28 min a safe product can be guaranteed. The analyses of furan showed that the formation of furan was only present in those foods (baby food puree and sardine in olive oil), which contained precursors of furan, such as amino acids, sugar and poly unsaturated fatty acids. For the products sardine in olive oil and baby food puree a reduction of furan in comparison to the initial content in the thermal treated sample was possible. The reduction was between 72-97 % (based on 57.88 µg kg-1) respectively 81-96% (based on 30 µg kg-1) in a temperature range of 90-121°C at 600 MPa. No MCPD-esters were formed either under thermal or under high pressure high temperature treatment. Only high amounts of MCPD-esters were found in tuna in sunflower oil which is due to the use of refined sunflower oil. The kinetic data from this study and the suggested mechanisms aid in optimizing this promising sterilization technology and will increase food safety and food quality

Fatty acids profile in canned tuna and sardine after retort sterilization and high pressure thermal sterilization treatment

8 páginas, 4 tablasFatty acid composition was asssessed for yellowfin tuna (Thunnus albacares) and sardine (Sardina pilchardus) canned in three different ways (brine, sunflower oil, olive oil) and subjected to two different sterilization treatments: retorting (as conventional treatment) and high pressure thermal sterilization (HPTS) (as alternative treatment). Impact of treatments on the fatty acid profile of the whole product was evaluated, particularly on the polyunsaturated fatty acids (PUFA) fraction since it is more susceptible to oxidation. Treatments were applied at pilot scale and the threshold for the sterilization factor was 7 min. HPTS treatment did not significantly affect the fatty acid profile of both canned tuna in brine and tuna in sunflower oil as compared with retorting. However, significant differences (p < 0.05) were observed in sardine in olive oil, where total PUFA content and the sum of eicosapentanoic acid and docosahexaenoic acid were nearly half in samples treated by HPTS. This work provides novel information on the impact of the combination of thermal treatment and high pressure as compared with classical retorting. Nevertheless, further investigation focused on the role of the prooxidants and antioxidants balance is necessary to confirm the oxidative effect of HPTS on PUFA content in oily fish species.This research was funded by EU-FP7-265558 PROMETHEUS project.Peer reviewe

Inactivation of Brettanomyces bruxellensis by High Hydrostatic Pressure technology

© 2015. High Hydrostatic Pressure (HHP) technology was tested on two strains of Brettanomyces bruxellensis isolated from Rioja red wines for analyzing the microbial inactivation reached in different oenological conditions. With this purpose, these strains were inoculated in synthetic wine with different pH and ethanol content. The inactivations reached with 100MPa, 200MPa and 300MPa applied from one to seven minutes were tested just after the treatment and after a week.Current consumers demand quality, free-additive wines. This has made oenological industry search alternative non-thermal technologies. The present results supported that high pH and high ethanol wines shortly treated at 100MPa made B.bruxellensis undetectable. Moreover, low pH and low ethanol wines content should be at least treated at 200MPa, and wines with intermediate ethanol content should be carefully analyzed in terms of strain composition before applying HHP. Finally, treatments at 300MPa managed a complete inactivation regardless of oenological conditions.This work has been supported by funding and pre-doctoral grant (B.O.E. 12th May, 2012) of the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria project RTA2011-00070-00-00 and FEDER of the European Community.Peer Reviewe

The effect of high pressure on Bacillus licheniformis spore germination and inactivation

publishedVersio

Inactivation de Brettanomyces Bruxellensis par les technologies non thermiques

Trabajo presentado en el 39th World Congress of Vine and Wine (Vitiviniculture: Technological advances to market challenges, OIV 2016), celebrado en Bento Gonçalves (Brasil) del 24 al 28 de octubre de 2016.[EN] Winemaking is a step in which several and complex microbiological and physicochemical conversions occur. The alcoholic fermentation is mainly conducted by Saccharomyces yeast species, although some non-Saccharomyces yeast could contribute to the final quality of wines with their presence during the elaboration. Some of them can produce wine spoilage developing during vinification even staying during ageing. The Brettanomyces genus is one of the most dangerous microorganisms for wine quality. The anamorphic species Brettanomyces bruxellensis has the ability of developing in wines, surviving into the natural wood pores of barrels during the ageing. It is considered a potentially spoiler microorganism when generate undesirable phenolic volatile compounds. The most employed tool for ensuring the wine microbial stability is the sulphur dioxide addition. This traditional task is usually aimed to prevent wine oxidation and to ensure the inactivation of most of the wine-borne spoilage microorganisms. Actually, the sulphur dioxide is added to must, after alcoholic fermentation, after malolactic fermentation and during the ageing. Specifically, the ageing of wine in wood barrels is the most complex stage because the solid sulphur dioxide has to be burnt inside the barrel, generating an inadequate and non-safe atmosphere for winery workers. Although very useful, the sulphur dioxide can cause allergic reactions so the maximal legal dose to be added is going to be probably reduced in a near future. Current consumers demand quality, free-additive wines, so alternative and new technologies should be investigated, in order to both reduce the sulphur dioxide addition and avoid the wine spoilage by this yeast. This has made oenological industry search for alternative non-thermal technologies as pulsed electric field (PEF) and high hydrostatic pressure (HHP). Two different PEF treatments were tested in a continuous-flow system for inactivating B. bruxellensis yeast in a red wine. Overall, the reached inactivations were moderated and varied from 1,97 log units with a treatment of 21 KV/cm to 2,34 log units with a treatment of 23 KV/cm but in any case were significant differences. Curiously, the application of higher specific energy did not provide significant declination of this yeast population. On another note, different treatments of HHP technology were also tested on populations of B. bruxellensis with different pH and ethanol conditions in synthetic wine. The results supported that high pH and ethanol wines shortly treated at 100 MPa made B. bruxellensis undetectable (8 log units); low pH and ethanol wines should be at least treated at 200 MPa; and treatments at 300 MPa managed a complete inactivation regardless of oenological conditions. Based on the results, the inactivation of B. bruxellensis was mainly dependent on the applied technique, PEF or HHP, and for this latter one on the characteristics of the treatment applied. The diversity in PEF and HHP resistance of this yeast showed the importance to validate industrial processes for the food products to accurately predict the treatment effectiveness. Both the up-scaling of the PEF processes for wine applications and the possibility of applying HHP with a continuous flow continue to be an engineering challenge.[ES] La vinificación es una etapa de complejos cambios microbiológicos y fisicoquímicos. La fermentación alcohólica es dirigida principalmente por la especie Saccharomyces cerevisiae, aunque hay otras especies no-Saccharomyces también presentes que pueden influir en la calidad de los vinos. Entre las levaduras de la vinificación, puede existir alguna con una influencia negativa en el perfil organoléptico de los vinos. La levadura Brettanomyces bruxellensis es capaz de sobrevivir en el interior de los poros de la madera de la barrica en el envejecimiento y en las posteriores etapas de almacenamiento en botella. Además, actúa en detrimento de la calidad del vino cuando sintetiza fenoles volátiles indeseables para el perfil aromático del vino. La forma tradicional de asegurar la estabilidad microbiológica del vino ha sido el empleo del dióxido de azufre. El sulfitado del mosto o vino es una práctica enológica dirigida a asegurar la inactivación de microorganismos perjudiciales para el vino así como prevenir la oxidación del mismo. El sulfitado se lleva a cabo en mosto, tras fermentación alcohólica y maloláctica y durante el envejecimiento en barrica y en botella. Cuando se realiza mediante la quema de una forma sólida de dióxido de azufre dentro de la barrica, se genera una atmósfera insegura para la salud de los empleados. Aunque sigue siendo muy importante en enología, el dióxido de azufre puede provocar alergias tras su consumo, por lo en un futuro cercano las dos is máximas legales pueden sufrir una reducción importante. Los consumidores actuales demandan vinos de calidad, naturales y libres de aditivos. Así, se deben investigar tecnologías alternativas para reducir el empleo de conservantes y evitar el deterioro de la calidad del vino por algunos microrganismos. Ésta nueva situación ha hecho que la industria enológica busque nuevas técnicas de conservación no basadas en la aplicación de calor, como por ejemplo los pulsos eléctricos de alto voltaje (PEAV) y las altas presiones hidrostáticas (APH). Dos tratamientos distintos de PEAV fueron testados en un flujo continuo para inactivar B. bruxellensis en vino tinto. Las inactivaciones alcanzadas fueron moderadas, entre 1,97 unidades logarítmicas con un tratamiento de 21 KV/cm y 2,34 con 23 KV/cm, aunque la aplicación de una mayor energía no aumentó la inactivación. Por otra parte, distintos tratamientos de APH fueron testados sobre un población de B. bruxellensis, pero con distintos pH y etanol en vinos sintéticos. E n condiciones de pH y etanol elevados una aplicación corta de la menor presión testada (100 MPa) hizo prácticamente indetectable la población de B. bruxellensis (8 unidades logarítmicas); a bajos pH y etanol el tratamiento más eficaz fue el de 200 MPa y con la mayor presión (300 MPa) se inactivó la población de B. bruxellensis en todas las condiciones testadas. Así la inactivación de B. bruxellensis dependió de la técnica empleada, PEAV o APH, y para ésta última, de las características del tratamiento. Las distintas resistencias microbianas a estas dos tecnologías demostraron la importancia de validar a nivel industrial ambos procesos. El escalado de PEAV y la posibilidad de aplicar APH en continuo son herramientas de higienización muy prometedoras pero pendientes de optimización.[FR] Vinification est une étape complexe de microbiologiques et physico-chimiques des changements. La fermentation alcoolique est entraînée principalement par l'espèce Saccharomyces cerevisiae, bien que d'autres espèces non-Saccharomyces aussi présents qui peuvent influer sur la qualité des vins. Parmi la levure de vin, il peut y avoir certaines avec une influence négative sur le profil organoleptique des vins. La Levure Brettanomyces bruxellensis est capable de survivre dans les pores du bois du canon au cours du vieillissement et dans les étapes ultérieures de la bouteille de stockage. Il agit également préjudiciable à la qualité du vin lorsque synthétise phénols volatils indésirables pour le profil de saveur du vin. La manière traditionnelle pour assurer la stabilité microbiologique du vin a été l'utilisation de dioxyde de soufre. Le sulfitage du moût ou du vin est une pratique œnologique visant à assurer l'inactivation des micro-organismes nocifs pour le vin et éviter l'oxydation. Le sulfitage est effectué dans le moût, après la fermentation alcoolique et malolactique au cours du vieillissement et dans le fût et en bouteille. Quand elle est réalisée en brûlant une forme solide du dioxyde de soufre à l'intérieur du canon, une atmosphère dangereuse pour la santé des employés est générée. Bien qu'il soit encore très important en œnologie, le dioxyde de soufre peut provoquer des allergies après la consommation, dans un proche avenir, les doses maximales légales peuvent subir une réduction significative. Les consommat eurs d'aujourd'hui exigent des vins de qualité, naturels et sans additifs. Donc, devrait étudier les technologies alternatives pour réduire l'utilisation de conservateurs et d'éviter la détérioration de la qualité du vin par certains micro-organismes. Cett e situation nouvelle a fait le look de l'industrie du vin pour les nouvelles techniques de conservation ne sont pas basées sur l'application de la chaleur, tels que des champs électriques pulsés (CEP) et haute pression hydrostatique (HPH). Deux autres que CEP traitements ont été testés dans un écoulement continu pour inactiver B. bruxellensis dans le vin rouge. Les inactivations ont été modérées atteint entre 1,97 unités log avec un traitement de 21 KV / cm et 23 KV avec 2,34 / cm, bien que l'application de plus d'énergie n'a pas augmenté l'inactivation. De plus, divers traitements HPH ont été testés sur une population de B. bruxellensis, mais avec un pH différent, et de l'éthanol dans le vin synthétique. Dans des conditions de pH élevé et d'éthanol une courte application d'une pression moins testée (100 MPa) était pratiquement indétectable population B. Bruxellensis (8 unités log); à faible pH et de l'éthanol le traitement le plus efficace était de 200 MPa et la pression plus élevée (300 MPa) population B. bruxellensis trempé dans toutes les conditions testées. Donc, l'inactivation de B. bruxellensis dépendait de la technique utilisée, CEP ou HPH, et pour ce dernier, les caractéristiques de traitement. Divers résistance microbienne à ces deux technologies a démontré l'importance de valider industriellement les deux processus. Mise à l'échelle CEP et la possibilité d'appliquer HPH continue sont des outils prometteurs mais sanitization optimisation en attente.Peer Reviewe

Gentle Sterilization of Carrot-Based Purees by High-Pressure Thermal Sterilization and Ohmic Heating and Influence on Food Processing Contaminants and Quality Attributes

Pressure-enhanced sterilization (PES) and ohmic heating (OH) are two emerging sterilization techniques, currently lacking implementation in the food industry. However, both technologies offer significant benefits in terms of spore inactivation using reduced thermal intensity in food products, as well as minimized effects on sensory and nutritional profiles. In this study, PES and OH were tested based on possible food safety process windows in comparison to thermal retorting, to optimize the food quality of carrot-based purees. The following parameters related to food quality were tested: texture, carotenoid content, color, and detectable amount of food processing contaminants (FPC) formed. Application of the innovative sterilization techniques resulted in a better retention of color, texture, and carotenoids (for PES) as well as a reduced formation of food processing contaminants. Importantly, a significant reduction in the formation of furan and its derivates was observed, compared to the retorted samples. Hence, both sterilization technologies showed promising results in the mitigation of potential toxic processing contaminants and retention of quality attributes.TU Berlin, Open-Access-Mittel – 202