Describing the heat shock response of Bacillus spp. under isothermal inactivation conditions

[ESP] El estrés ambiental y los métodos de procesamiento de alimentos, como el calentamiento, la acidez, son responsables de provocar respuestas adaptativas a las bacterias. La respuesta general al estrés en la mayoría de las bacterias Gram positivas, incluidas B. subtilis, L. monocytogenes, está regulada por el factor sigma alternativo σΒ que induce la transcripción de genes capaces de proporcionar a las células vegetativas resistencia al estrés. En este estudio, se analizó la resistencia al calor de las células vegetativas de B. subtilis bajo calentamiento isotérmico, así como la influencia de la ausencia del gen sigB en la resistencia al calor bacteriano. Los experimentos isotérmicos se llevaron a cabo en agua peptonada (pH 7) a 51, 52,5, 55 y 57,5°C y mostraron que ambas cepas eran bastante sensibles al calor. El mutante sigB presentó mayor inactivación a 51 y 52.5°C. [ENG] Adaptive responses to bacteria are triggered by environmental conditions and food processing processes such as heating and acidity. In the majority of Gram positive bacteria, including B. subtilis and L. monocytogenes, the overall stress response is governed by the alternative sigma factor σB (sigB), which stimulates the transcription of genes that provide resistance to stress to the vegetative cells. The heat resistance of B. subtilis vegetative cells was investigated under isothermal heating, as well as the effect of the sigB gene absence on bacterial heat resistance. Isothermal studies at 51, 52.5, 55, and 57.5°C in peptone water (pH 7) demonstrated that both strains were extremely heat sensitive. At 51 and 52.5°C, the sigB mutant presented more inactivation.Leonidas Georgalis is grateful for the “beca asociada a actividades de I+D+I”, convocatoria B- 077/20, for awarding him a pre−doctoral grant

Different model hypotheses are needed to account for qualitative variability in the response of two strains of Salmonella spp. under dynamic conditions

In this article, the thermal inactivation of two Salmonella strains (Salmonella Enteritidis CECT4300 and Salmonella Senftenberg CECT4565) was studied under both isothermal and dynamic conditions. We observed large differences between these two strains, with S. Senftenberg being much more resistant than S. Enteritidis. Under isothermal conditions, S. Senftenberg had non-linear survivor curves, whereas the response of S. Enteritidis was log-linear. Therefore, weibullian inactivation models were used to describe the response of S. Senftenberg, with the Mafart model being the more suitable one. For S. Enteritidis, the Bigelow (log-linear) inactivation model was successful at describing the isothermal response. Under dynamic conditions, a combination of the Peleg and Mafart models (secondary model of Mafart; t* of Peleg) fitted to the isothermal data could predict the response of S. Senftenberg to the dynamic treatments tested (heating rates between 0.5 and 10 °C/min). This was not the case for S. Enteritidis, where the model predictions based on isothermal data underestimated the microbial concentrations. Therefore, a dynamic model that considers stress acclimation to one of the dynamic profiles was fitted, using the remaining profiles as validation. In light of this, besides its quantitative impact, variability between strains of bacterial species can also cause qualitative differences in microbial inactivation. This is demonstrated by S. Enteritidis being able to develop stress acclimation where S. Senftenbenberg could not. This has important implications for the development of microbial inactivation models to support process design, as every industrial treatment is dynamic. Consequently, it is crucial to consider different model hypotheses, and how they affect the model predictions both under isothermal and dynamic conditions.The financial support of this research was provided by the Ministerio de Economía, Industria y Competitividad, Spain, through Project PID2020-116318RB-C32 and by FEDER funds. Dr. Alberto Garre was supported by a Maria Zambrano scholarship

Modelos matemáticos para la descripción del crecimiento de microorganismos patógenos en alimentos

[ESP] Los requerimientos actuales de calidad y seguridad microbiana en los alimentos sólo pueden ser satisfechos a través de una descripción detallada del comportamiento de los microorganismos patógenos durante el ciclo de vida del producto. La microbiología predictiva es clave en este aspecto, ya que describe por medio de modelos matemáticos la evolución de la población microbiana bajo diferentes condiciones ambientales. En esta contribución se presentan los modelos matemáticos más utilizados actualmente para la descripción de crecimiento microbiano. [ENG] Current standards on food quality and microbial safety can only be fulfilled through a detailed description of the behaviour of the pathogen microorganism during the life cycle of the product. Predictive microbiology serves a key role in this aspect. This science describes through mathematical models the evolution of a microbial population under different environmental conditions. This contribution presents the mathematical models most commonly used for the description of microbial growth.Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT), Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Escuela Técnica Superior de Ingeniería Industrial (ETSII), Escuela Técnica Superior de Arquitectura y Edificación (ETSAE), Escuela Técnica Superior de Ingeniería de Caminos, Canales y Puertos y de Ingeniería de Minas (ETSICCPIM), Facultad de Ciencias de la Empresa (FCCE), Parque Tecnológico de Fuente Álamo (PTFA), Vicerrectorado de Estudiantes y Extensión de la UPCT, Vicerrectorado de Investigación e Innovación de la UPCT, y Vicerrectorado de Internacionalización y Cooperación al Desarrollo de la UPCT

Dynamics of microbial Inactivation and acrylamide production in high-temperature heat treatments

In food processes, optimizing processing parameters is crucial to ensure food safety, maximize food quality, and minimize the formation of potentially toxigenic compounds. This research focuses on the simultaneous impacts that severe heat treatments applied to food may have on the formation of harmful chemicals and on microbiological safety. The case studies analysed consider the appearance/synthesis of acrylamide after a sterilization heat treatment for two different foods: pureed potato and prune juice, using Geobacillus stearothermophilus as an indicator. It presents two contradictory situations: on the one hand, the application of a high-temperature treatment to a low acid food with G. stearothermophilus spores causes their inactivation, reaching food safety and stability from a microbiological point of view. On the other hand, high temperatures favour the appearance of acrylamide. In this way, the two objectives (microbiological safety and acrylamide production) are opposed. In this work, we analyse the effects of high-temperature thermal treatments (isothermal conditions between 120 and 135 _C) in food from two perspectives: microbiological safety/stability and acrylamide production. After analysing both objectives simultaneously, it is concluded that, contrary to what is expected, heat treatments at higher temperatures result in lower acrylamide production for the same level of microbial inactivation. This is due to the different dynamics and sensitivities of the processes at high temperatures. These results, as well as the presented methodology, can be a basis of analysis for decision makers to design heat treatments that ensure food safety while minimizing the amount of acrylamide (or other harmful substances) produced.The financial support of this research work was provided by the Ministry of Science, Innovation and Universities of the Spanish Government and European Regional Development Fund (ERDF) through project AGL2017-86840-C2-1-R. J.L.P.-S. is grateful to the JAE-INTRO program from CSIC (Grant no JAEINT19_EX_0797). A.G. was supported by a postdoctoral grant from the Fundación Séneca (20900/PD/18)

The potential of essential oils from active packaging to reduce ethylene biosynthesis in plant products. Part 2: fruits (Blueberries and blackberries)

Plant essential oils (EOs) have an important ability to inhibit ethylene biosynthesis. Nevertheless, the effects of EOs on the key components of ethylene biosynthesis (l-aminocyclopropane1-carboxylic (ACC) oxidase activity, ACC synthase activity, and ACC content) have not yet been thoroughly studied. Accordingly, this study focused on the effects of emitted EOs from active packaging (EO doses from 100 to 1000 mg m−2 ) on the key components of ethylene biosynthesis of blueberries and blackberries under several storage temperatures. Anise EO and lemon EO active packaging induced the greatest inhibitory effects (60–76%) on the ethylene production of blueberries and blackberries, respectively, even at high storage temperatures (22 ◦C). In terms of EO doses, active packaging with 1000 mg m−2 of anise EO or lemon EO led to the highest reduction of ethylene production, respectively. At 22 ◦C, the investigated EO active packing reduced the activities of ACC synthase and ACC oxidase up to 50%. In order to minimise ethylene biosynthesis in blueberries and blackberries when they are stored even under improper temperature scenarios at high temperatures, this EO active packaging is a natural and efficient technological solution.The authors are grateful to the SPANISH MINISTRY OF SCIENCE AND INNOVATION for the grant PID2020-119882RB-I00 funded by MCIN/AEI/10.13039/501100011033. Ginés Benito Martínez- Hernández was supported by a Beatriz Galindo scholarship (BG20-00069) from the SPANISH MINISTRY OF SCIENCE AND INNOVATION. Alberto Garre was supported by a Ramón y Cajal scholarship (RYC2021-034612-I) from the SPANISH MINISTRY OF SCIENCE AND INNOVATION. The authors are grateful to the company, Plus Berries, for facilitating the transport of blackberries to the facilities of the Universidad Politécnica de Cartagena

Kinetics of carvacrol release from active paper packaging for fresh fruits and vegetables under conditions of open and closed package

The carvacrol release kinetics from active packaging (including carvacrol-βcyclodextrin inclusion complex) was studied under the following possible scenarios found in fresh produce packaging and marketing facilities: different storage temperatures (2, 8, 15 and 22 ºC), relative humidity (60% and 95% RH), as well as different packaging conditions (open or closed). Release kinetics for the closed and open packaging systems were described using first-order and n-order power law kinetics, respectively. Increasing temperature and RH enhanced the carvacrol release rate. The release rate (k) increased by 1.3–1.7-fold when the RH was augmented from 60% to 95%. An initial release burst effect was observed with the highest k rate (0.14/2.0 × 10− 2 1/dayn ) under open active packaging at 8/15 ºC (95% RH). In conclusion, the use of active packaging will ensure a proper essential oil release, with even a higher initial release (burst effect) in open packages, leading to a potential extension of the product shelf life.The authors are grateful for the grant PID2020-119882RB-I00 funded by MCIN/AEI/ 10.13039/501100011033. Alberto Garre was supported by a Ramon y Cajal scholarship from the Spanish Ministry of Science and Innovation/State Investigation Agency from Spain (RYC2021-034612-I)

Impact of heating rates on alicyclobacillus acidoterrestris heat resistance under non-isothermal treatments and use of mathematical modelling to optimize orange juice processing

Alicyclobacillus acidoterrestris is a spoilage microorganism responsible for relevant product and economic losses in the beverage and juice industry. Spores of this microorganism can survive industrial heat treatments and cause spoilage during posterior storage. Therefore, an effective design of processing treatments requires an accurate understanding of the heat resistance of this microorganism. Considering that industrial treatments are dynamic; this understanding must include how the heat resistance of the microorganism is affected by the heating rate during the heating and cooling phases. The main objective of this study was to establish the effect of heating rates and complex thermal treatments on the inactivation kinetics of A. acidoterrestris. Isothermal experiments between 90 and 105 C were carried out in a Mastia thermoresistometer, as well as four different dynamic treatments. Although most of the inactivation takes place during the holding phase, our results indicate the relevance of the heating phase for the effectiveness of the treatment. The thermal resistance of A. acidoterrestris is affected by the heating rate during the heating phase. Specifically, higher heating rates resulted in an increased microbial inactivation with respect to the one predicted based on isothermal experiments. These results provide novel information regarding the heat response of this microorganism, which can be valuable for the design of effective heat treatments to improve product safety and stability. Moreover, it highlights the need to incorporate experimental data based on dynamic treatments in process design, as heating rates can have a very significant effect on the thermal resistance of microorganisms.This research was funded by Ministerio de Economía, Industria y Competitividad of the Spanish Government, grant number AGL2017-86840-C2-1-R. Alberto Garre acknowledges the support from a postdoctoral grant by the Fundación Séneca, Murcia Region (20900/PD/18) in WU

Pharmacogenetic Predictors of Response to Interferon Beta Therapy in Multiple Sclerosis

The results of this investigation are part of the doctoral thesis presented by María Isabel Carrasco Campos at the University of Granada.First-line therapy with interferon beta (IFN-β), involved in gene expression modulation in immune response, is widely used for multiple sclerosis. However, 30–50% of patients do not respond optimally. Variants in CBLB, CTSS, GRIA3, OAS1 and TNFRSF10A genes have been proposed to contribute to the variation in the individual response. The purpose of this study was to evaluate the influence of gene polymorphisms on the IFN-β response in relapsing–remitting multiple sclerosis (RRMS) patients. CBLB (rs12487066), GRIA3 (rs12557782), CTSS (rs1136774), OAS1 (rs10774671) and TNFRSF10A (rs20576) polymorphisms were analysed by Taqman in 137 RRMS patients. Response to IFN-β and change in the Expanded Disability Status Scale (EDSS) after 24 months were evaluated using multivariable logistic regression analysis. Carriers of at least one copy of the C allele of CTSS-rs1136774 had a better response to IFN-β (p = 0.0423; OR = 2.94; CI95% = 1.03, 8.40). Carriers of TT genotype of TNFRSF10A-rs20576 had a higher probability of maintaining their EDSS stable after 24 months of IFN-β treatment (p = 0.0251; OR = 5.71; CI95% = 1.39, 31.75). No influence of CBLB (rs12487066), OAS1 (rs10774671) and GRIA3 (rs12557782) gene polymorphisms in the variation of the individual response to IFN-β was shown. Our results suggest that the TNFRSF10A-rs20576 and CTSS-rs1136774 gene polymorphisms influence the response to IFN-β after 24 months, while the CBLB (rs12487066), OAS1 (rs10774671) or GRIA3 (rs12557782) gene polymorphisms had no effect on the variation of the individual response to IFN-β

Effect of the synergy of electric pulses and oregano essential oil in the inactivation of L. monocytogenes

[SPA] Listeria monocytogenes es actualmente una de las principales preocupaciones de la industria alimentaria. Aunque el número de casos reportados en la Unión Europea es relativamente, tiene una gran gravedad, con unas tasas de hospitalización y mortandad del 97% y del 16,7%, respectivamente. Debido a la ubicuidad de este microorganismo y su capacidad de crecer en numerosas matrices alimentarias, las empresas agroalimentarias deben aplicar tratamientos que inactiven las células de L. monocytogenes. En este trabajo, se estudió la cinética de inactivación de L. monocytogenes aislada de productos marinos sometida a un tratamiento combinado de PEAV con un aceite esencial de orégano. Los resultados demuestran esta sinergia, ya que se consiguió una mayor inactivación microbiana con un campo de 20 kV/cm, 1 Hz de frecuencia, 150 pulsos y una concentración de orégano de 1/2 MIC, superior a la obtenida en las muestras control. Llegando a la conclusión de que los PEAV impulsan el efecto del orégano sobre la membrana de la bacteria. [ENG] Nowadays Listeria monocytogenes is one of the main concerns of the food industry. The number of cases reported in the European Union is relatively low it is very serious, with rates of hospitalization and mortality of 97% and 16.7%, respectively. Due to the ubiquity of this organism and its capacity to grow in many food matrices, agri-food companies must apply treatments that inactivate the cells of L. monocytogenes. In this work, it was studied the kinetics of inactivation of L. monocytogenes isolated from marine products subjected to a combined treatment of PEF with an essential oil of oregano. The results show this synergy, since it got a greater inactivation microbial with a field of 20 KV/cm, 1 Hz frequency, 150 pulses and an oregano concentration of 1/2 MIC, higher than that obtained in control samples. Concluding that the PEF promote the effect of oregano on the bacterial cell membrane.Investigación apoyada por el MICINN (es) y FEDER a través de los proyectos AGL2017-86840-C2-1-R y AGL2016-82014-REDT