Observations on the water distribution and extractable sugar content in carrot slices after pulsed electric field treatment

peer-reviewedThe impact of pulsed electric field (PEF) processing conditions on the distribution of water in carrot tissue and extractability of soluble sugars from carrot slices was studied. Time domain NMR relaxometry was used to investigate the water proton mobility in PEF-treated carrot samples. Three distinct transverse relaxation peaks were observed in untreated carrots. After PEF treatment only two slightly-overlapping peaks were found; these were attributed to water present in the cytoplasm and vacuole of carrot xylem and phloem tissues. This post-treatment observation indicated an increase in water permeability of tissues and/or a loss of integrity in the tonoplast. In general, the stronger the electric field applied, the lower the area representing transverse relaxation (T2) values irrespective of treatment duration. Moreover an increase in sucrose, β- and α-glucose and fructose concentrations of carrot slice extracts after PEF treatment suggested increases in both cell wall and vacuole permeability as a result of exposure to pulsed electric fields.The authors acknowledge financial support from the Irish Phytochemical Food Network (IPFN) project funded under the Food Institutional Research Measure (FIRM, 06/TNI/AFRC6) of the Irish Department of Agriculture, Food and Marine. Dr. Aguiló-Aguayo thanks Generalitat of Catalonia for the postdoctoral grant Beatriu de Pinós (BP-DGR2010). E. Balagueró thanks the Lifelong Learning Programme for the internship grant Leonardo da Vinci MOTIVA3 (201 1-1-ES1-LEO02-34225)

Adding Value to Ready-to-Crustacean Products: Process optimization for "entire" crustaceans using novel technologies

El objetivo general de esta Tesis Doctoral fue optimizar y evaluar el potencial de diferentes tecnologías de procesado en la producción de buey de mar (Cancer pagurus) irlandés listo para el consumo. El primer capítulo de introducción general proporciona una visión global de las diferentes estrategias para la conservación de alimentos y de las tecnologías de procesado disponibles actualmente. Además, se lleva a cabo una revisión de la optimización del procesado de alimentos haciendo énfasis en los tratamientos térmicos. Finalmente, este capítulo resume una visión general del buey de mar, su importancia en la Industria Irlandesa y las prácticas actuales para su procesado. Tras el capítulo de introducción, en primer lugar, se caracterizó la principal flora bacteriana responsable de la alteración del buey de mar listo para consumo y su resistencia frente a los tratamientos térmicos. De los resultados obtenidos, se deduce la importancia de Bacillus spp. y Staphyloccocus spp. como los principales microorganismos presentes en el buey de mar listo para el consumo. El estudio de caracterización termobacteriológica demostró que el tratamiento para inactivar Listeria monocytogenes (F70°C7.5°C = 2 minutos), en este tipo de productos, es efectivo para inactivar todas las células vegetativas presentes de manera natural en el buey de mar. Sin embargo, el mismo estudio también reveló que el tratamiento más severo recomendado para inactivar Clostridium botulinum no proteolítico tipo E, en cangrejo, (F90°C8.6°C = 57 minutos) no resultaba suficiente para alcanzar un nivel similar de inactivación (6 ciclos logarítmicos) de la bacteria esporulada más termorresistente aislada del buey de mar, Bacillus weihenstephanensis. Tras la caracterización de la microbiota del buey de mar, se evaluó el potencial de incorporar la tecnología de ultrasonidos para mejorar el cocinado del buey de mar. Los resultados mostraron que la incorporación de ultrasonidos al cocinado del buey de mar mejoraba los fenómenos de transferencia de calor, lo cual permitió reducir el tiempo total del proceso hasta un 15%. Además, los ultrasonidos también probaron ser efectivos para mejorar los procesos de transferencia de masa producidos durante el cocinado mejorando así la limpieza de los cangrejos en el cocinado. Esto permitiría evitar la etapa de limpieza de los cangrejos antes del envasado que se realiza actualmente en el proceso industrial. Dado el potencial de los ultrasonidos para mejorar los procesos de transferencia de masa durante el cocinado del cangrejo, se evaluó su uso para reducir la concentración de cadmio del buey de mar. Los resultados obtenidos probaron que la combinación de los ultrasonidos con temperaturas moderadas de tratamiento es capaz de reducir el contenido total de cadmio del buey de mar hasta un 22.8%, abriendo la posibilidad de utilizar esta tecnología para afrontar este importante reto en la producción de estos productos.Tras la caracterización de las primeras etapas de la producción de buey de mar (cocción y lavado), se realizó un estudio de optimización del segundo tratamiento térmico, la pasteurización, basado en la cinética de cambio de calidad del producto. De los resultados obtenidos, se deduce que el color de la carne blanca es el parámetro de calidad que se ve más afectado debido al tratamiento térmico, por lo que se caracterizó su cinética de cambio de color, utilizándose como indicador para la optimización del proceso. En base a las ecuaciones desarrolladas en este estudio, el tratamiento térmico requerido para inactivar B. weihenstephanensis sería demasiado severo para retener una buena calidad en el producto final pasteurizado. Por este motivo, se evaluó el uso de tecnologías alternativas (Mano-Sonicacion, Mano-Termo-Sonicacion y radiaciones ionizantes aplicando electrones acelerados) para la inactivación de los esporos aislados del buey de mar. La combinación de ultrasonidos con presión y temperatura mostró un efecto sinérgico para la inactivación de las bacterias esporuladas, lo cual permitiría reducir hasta un 80% el tiempo total de procesado manteniendo unos niveles de inactivación adecuados. La irradiación también probó ser una tecnología efectiva para inactivar las bacterias esporuladas a dosis de tratamiento por debajo del límite establecido por la WHO de 10kGy. Además, la irradiación fue la tecnología para la inactivación de bacterias esporuladas menos afectada por cambios en la especie microbiana contaminante o en las condiciones del medio de tratamiento, lo cual reduciría el riesgo sanitario de los productos pasteurizados si se produjese un error al definir el microorganismo diana o en la composición del producto. Los resultados de esta Tesis Doctoral muestran por tanto el potencial del uso de tecnologías de procesado alternativas a los procesos tradicionales, principalmente el calor, para mejorar la producción de buey de mar irlandés listo para su consumo y afrontar sus retos presentes y futuros. The aim of the present study was to optimize and evaluate the potential of novel technological interventions in the production of ready-to-eat Irish edible crab (Cancer pagurus). The Thesis begins with a general overview of food preservation and main characteristics of edible crab including its significance for the Irish seafood industry. An initial study characterized the main microbiota present in raw and ready-to-eat brown crab and their thermal resistance. Results obtained showed the importance of Bacillus spp. and Staphylococcus spp. in these products. Characterisation of bacterial thermal resistance proved the effectiveness of recommended heat treatments to inactivate Listeria monocytogenes (F70°C7.5°C = 2 minutes). However, the study also revealed that the most severe heat treatment currently recommended, which has Clostridium botulinum non-proteolytic type E as a target microorganism (F90°C8.6°C = 57 minutes), is not sufficient to achieve a comparable inactivation (i.e. 6 Log10 cycles) of the most heat resistant bacterial spore isolated from crab samples namely, Bacillus weihenstephanensis. Following the microbial characterization studies, the potential for incorporating ultrasound to improve early stages in ready-to-eat crab production (i.e. the initial cooking step) was evaluated. The application of ultrasound during cooking enhanced the rate of heat transfer, allowing up to a 15% reduction in total cooking time. In addition, ultrasound also proved its efficacy for enhancing mass transfer from the crab to the cooking water. This improved crab cleaning during cooking would in turn allow the omission of the normal post cook cleaning process prior to packaging. Ultrasounds potential to enhance mass transfer from crab to the cooking water also prompted an investigation into its possible use to remove cadmium from crab. Results showed that ultrasound combined with mild temperatures has the capability to reduce the total cadmium content in edible crab by up to 22.8%. The results open the possibility for using ultrasound as alternative to resolve this issue for the crab industry. Following these studies the second heat treatment step (i.e. in-pack pasteurization) of ready-to-eat crab was optimized to minimize the impact of the treatment on the quality of the final product. Results showed that the colour of crab white meat was the parameter most affected by the heat treatment and therefore, a colour change kinetic for these heat induced changes was developed and used as a quality indicator for process optimization. Based on this study an optimal set of treatment conditions were proposed for the inactivation of C. botulinum non-proteolytic type E. However, based on the models developed the required heat treatment for a process which is solely thermal, would be too severe to retain a good quality. This situation would be further aggravated by the requirement for even more severe heat treatments if B. weihenstephanensis is considered as the target microorganism. Therefore, the use of alternative technologies (i.e. mano-sonication, mano-thermo-sonication and electron beam ionizing radiation) for the inactivation of the main bacterial spores isolated from brown crab was also evaluated. The use of ultrasound in combination with pressure and mild temperatures (i.e. Mano-Thermos-Sonication) showed a synergistic effect in terms of bacterial spore inactivation, which in turn would allow a reduction in the total processing time by over a 80% while still maintaining a similar level of inactivation to heat only. The use of irradiation also proved to be an effective technology to inactivate bacterial spores while still remaining below the limit of 10kGy established by WHO. In addition radiation was the technology least affected by changes in bacterial species or treatment media composition. Overall, the results of this thesis shows the potential for a number of alternative technologies and technical interventions to improve the processing of Irish edible crab and address present and future challenges in the production of these ready-to-eat products. <br /

Efficacy of ultraviolet light (UV-C) and pulsed light (PL) for the microbiological decontamination of raw salmon (Salmo salar) and food contact surface materials

peer-reviewedThe decontamination effect of two light-based technologies on salmon, polyethylene (PE) and stainless steel (SS) was evaluated. Optimization of treatment conditions for ultraviolet light (UV-C) and pulsed light (PL) was carried out on raw salmon, obtaining inactivation levels of 0.9 and 1.3 log CFU/g respectively. The effects of treatments on several microbial groups present in salmon were then evaluated. For both technologies, Pseudomonas spp. were found to be the most resistant group of microorganisms tested. Three different strains from within this group were isolated and speciated, including a P. fluorescens strain which was selected for subsequent studies. PE and SS surfaces were inoculated with a suspension of the P. fluorescens suspended in a ‘salmon juice’ solution, and treated with UV-C and PL at different doses (mJ/cm2). PE surfaces were effectively decontaminated a low doses for both technologies, with a reduction of >4 log cycles observed. Decontamination of SS was also effective when treated with PL, although at higher doses than for PE. When SS was treated with UV-C, the maximum reduction of P. fluorescens achieved was 2 log cycles, even at the highest dose

Impact of pulsed electric field pre-treatment on nutritional and polyphenolic contents and bioactivities of light and dark brewer's spent grains

peer-reviewedPulsed electric field (PEF) pre-treatment, at 2.8 kV/cm with 3000 pulses of 20 μs pulse-width, was applied on brewer's spent grains (BSG) followed by aqueous extraction at 55 °C, 220 rpm for 16 h. PEF pre-treatment showed significantly increased yields (p 50 mg/mL) with lowest MIC value of 1.56 mg/mL against Staphylococcus aureus. All the BSG extracts induced the release of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) and chemokines (IL-8, MCP-1 and MIP-1α) confirming immunomodulatory activity.The authors acknowledge financial support from the ‘NovTechIng’ project funded under the Food Institutional Research Measure (Project No. FIRM/11/F/050) by the Irish Department of Agriculture, Food and Marine. The immunomodulatory study was performed using funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 634086 (NEPHSTROM). TPG is funded by a Hardiman Research Scholarship from the College of Medicine, Nursing and Health Sciences, National University of Ireland, Galway.The authors acknowledge financial support from the ‘NovTechIng’ project funded under the Food Institutional Research Measure (Project No. FIRM/11/F/050) by the Irish Department of Agriculture, Food and Marine. The immunomodulatory study was performed using funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 634086 (NEPHSTROM). TPG is funded by a Hardiman Research Scholarship from the College of Medicine, Nursing and Health Sciences, National University of Ireland, Galway

Increasing the Yield of Irish Brown Crab (Cancer pagurus) during Processing without Adversely Affecting Shelf-Life

During the processing of Irish Brown Crab (Cancer pagurus), protein and moisture are released and losses up to 10% (by weight) are common. The objective of this study was to investigate the use of clean label ingredients to reduce this loss, without adversely affecting shelf-life or promoting the growth of spoilage bacteria. Following preliminary studies, 5% (w/v) sodium caseinate (SC) and (5%, w/v) potato starch (PS), with and without (0.5%, w/v) ascorbic acid (AA) were selected. Ninety crabs (30 per treatment) were soaked and boiled in water (control 1), AA (control 2), SC, PS, SC plus AA, or PS plus AA and analyzed for cook loss as well as pH, aw, water holding capacity (WHC), and microbial shelf-life (total viable count (TVC), total Enterobacteriaceae count (TEC), and spoilage bacteria) during 28 days storage at 4 ◦ C. On average, 11.1% of the control 1 weight was lost during processing. This was reduced to 8.0% when treated with AA (control 2) and to 3.5%, 4.7%, 5.8%, and 2.3% with SC, PS, SC plus AA, and PS plus AA, respectively. None of these treatments negatively impacted on shelf-life and similar growth curves were observed for TVC, TEC, Pseudomonas spp., Clostridium spp., lactic acid bacteria (LAB), and hydrogen disulphide producing bacteria, regardless of treatment. It was therefore concluded that, subject to sensory evaluation and validation under commercial conditions, these natural ingredients could be used to substantially increase the yield and hence commercial value of crab meat, without adversely affecting shelf-life.Department of Agriculture, Food and the Marin

Recovery of ergosterol and vitamin D2 from mushroom waste - potential valorization by food and pharmaceutical industries

Background A large amount of mushroom waste is generated during mushroom production (accounting for up to 20% of total production) and is mainly composed of mushrooms that do not meet the specifications set by retailers because of misshapen caps and/or stalks. Mushrooms are notable for their ergosterol (a precursor of vitamin D2) content which is converted to vitamin D2 after exposure to natural or artificial ultraviolet (UV) irradiation. Therefore, mushroom waste could be used as a source for the recovery of both ergosterol and vitamin D2 which could be valorized by both pharmaceutical and food industries. Scope and approach The current review presents a comprehensive summary of research performed regarding the extraction, purification and determination of ergosterol and vitamin D2 (ergocalciferol) from mushroom matrices. Additionally, studies related to the impact of sample preparation and especially of drying methods on the retention of ergosterol and vitamin D2 are presented. Finally, the potential valorization of mushroom waste sterols by food and pharmaceutical industries is discussed. Key findings and conclusions Ergosterol and vitamin D2 contents vary among different mushroom species. Sample drying is a crucial step that precedes sterol extraction and has a significant impact on the retention of ergosterol and vitamin D2. The extraction of sterols from mushrooms can be conducted by either conventional (e.g., Soxhlet extraction) or non-conventional methods (e.g., ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE), deep eutectic solvents (DES) extraction, supercritical fluid extraction (SFE), and pressurized liquid extraction (PLE)) or their combination. The application of non-conventional methods such as UAE and MAE facilitate in shorter extraction times than the conventional methods. The valorization of mushroom extracts enriched in ergosterol and vitamin D2 by both pharmaceutical and food industries requires further work

Tales from the Drop Zone: roles, risks and dramaturgical dilemmas

This paper critically revisits conventional understandings of ethnographic fieldwork roles, arguing that representations of the covert insider as heroic and adventurous are often idealistic and unrealistic. Drawing on one of the authors’ experiences of being both a covert and overt researcher in an ethnographic study of skydiving, we identify some of the dramaturgical dilemmas that can unexpectedly affect relations with participants throughout the research process. Our overall aim is to highlight how issues of trust, betrayal, exposure and vulnerability, together with the practical considerations of field research, combine to shape the researcher’s interactional strategies of identity work

Microarray scanner calibration curves: characteristics and implications

BACKGROUND: Microarray-based measurement of mRNA abundance assumes a linear relationship between the fluorescence intensity and the dye concentration. In reality, however, the calibration curve can be nonlinear. RESULTS: By scanning a microarray scanner calibration slide containing known concentrations of fluorescent dyes under 18 PMT gains, we were able to evaluate the differences in calibration characteristics of Cy5 and Cy3. First, the calibration curve for the same dye under the same PMT gain is nonlinear at both the high and low intensity ends. Second, the degree of nonlinearity of the calibration curve depends on the PMT gain. Third, the two PMTs (for Cy5 and Cy3) behave differently even under the same gain. Fourth, the background intensity for the Cy3 channel is higher than that for the Cy5 channel. The impact of such characteristics on the accuracy and reproducibility of measured mRNA abundance and the calculated ratios was demonstrated. Combined with simulation results, we provided explanations to the existence of ratio underestimation, intensity-dependence of ratio bias, and anti-correlation of ratios in dye-swap replicates. We further demonstrated that although Lowess normalization effectively eliminates the intensity-dependence of ratio bias, the systematic deviation from true ratios largely remained. A method of calculating ratios based on concentrations estimated from the calibration curves was proposed for correcting ratio bias. CONCLUSION: It is preferable to scan microarray slides at fixed, optimal gain settings under which the linearity between concentration and intensity is maximized. Although normalization methods improve reproducibility of microarray measurements, they appear less effective in improving accuracy