Search

The aim of this work was to evaluate the effect of pulsed electric field (PEF) pre-treatment on mass transfer phenomena, water distribution and some physico-chemical parameters of osmo-dehydrated organic strawberries. For PEF treatments 100 near-rectangular shaped pulses, with fixed pulse width of 100 μs and repetition time of 10 ms were used. Electric fields strength applied were 100, 200 and 400 V cm−1. Afterwards, samples were subjected to OD treatments carried out in two different hypertonic solutions (40% w/w), one with sucrose and the other one with trehalose. The results shown that PEF treatment positively affected the mass transfer during OD even at the lowest electric field strength applied (100 V/cm), partially preserving the cell viability and maintaining at the same time the fresh-like characteristics of strawberries.

Pulsed electric field (PEF) treatment is a non-thermal technology that has shown good potential for microbial inactivation. However, in many cases, it cannot be sufficient to avoid microbial proliferation, and the combination with other stabilizing technologies is needed. In the framework of the hurdle concept, several researches have been focused on the use of PEF in combination with heat and/or antimicrobials to increase its efficacy. This study investigated the inactivation effect of PEF on a strain of Saccharomyces cerevisiae (isolated from spoiled beverages) in a model system (growth medium). The efficacy of PEF treatment was evaluated in relation to different variables, such as electric field strength (25 and 50 kV/cm), treatment time (from 1 to 5 s), initial inoculum level (4 or 6 log cfu/ml), preheating at 50 degrees C, medium pH (4 or 6), and addition of citral at sublethal concentration (i.e., half of minimum inhibiting concentration). The data from plate counting, modeled with the Weibull equation, showed that one of the main factors affecting yeast inactivation was the preheating of the suspension at 50 degrees C. Indeed, higher cell load reductions were obtained with heat-assisted PEF, especially in the presence of citral. The effect of initial cell load was negligible, while pH affected yeast inactivation only without preheating, with higher death kinetics at pH 6. Flow cytometry (FCM) analysis confirmed higher mortality under these conditions. However, the occurrence of injured cells, especially in samples treated at pH 4, was observed. The ability of these cells to recover from the damages induced by treatments was affected by both citral and preheating. The synergic effects of PEF, preheating, and citral were likely due to the increase of membrane permeability (especially at pH 6), as the primary target of electroporation, which favored the solubilization of citral in the cell membrane, enhancing the efficacy of the whole process. The multi-analytical approach (traditional plate counting and FCM) allowed defining parameters to increase PEF efficacy against S. cerevisiae. Moreover, FCM, able to discriminate different physiological states of the yeast population, was helpful to better clarify the action mechanism and the potential recovery of cells after treatment.

The present work aims to study the effects of cold gas plasma on some quality parameters of apple slices belonging to four different cultivars (Pink Lady®, Fuji, Red Delicious and Modi®), with particular attention to polyphenoloxidase (PPO) inhibition and related changes in colour and visual quality. Upon plasma exposure a noticeable reduction of superficial browning was observed in all cultivars but not always proportionally to treatment time; the effect on PPO activity was very variable and not correlated to the effect on enzymatic browning. Textural parameters were affected by plasma treatments only in Red Delicious apples. Generally, the response of the tissue to the treatments was variable according to the cultivar considered. The results obtained in this study indicate the necessity of further investigation about consequences of plasma treatment on specific tissue physiology in order to choose the better treatment parameters, optimizing its effect for the specific final product. Industrial relevance The application on cold plasma to minimally processed fruit and vegetable has shown a good potential for enzymatic browning inhibition making it an interesting alternative to traditional dipping methods. Nevertheless, the effect on the tissue to the exposure to plasma active particles is not fully known yet. For the industrial application of the treatment, the response for example of different cultivars to the treatment is of high importance, in the first place for the selection of the more appropriate raw material but also to eventually adapt the process parameters to the specificity of the matrix.

The decontamination efficacy of a dielectric barrier discharge (DBD) gas plasma generator equipped with four different interchangeable electrode materials (stainless steel, brass, silver and glass/brass) was tested towards Listeria monocytogenes 56Ly and Escherichia coli NCFB 555. Bacteria were suspended in sterile saline solutions and placed for 20, 40 and 60 min under the discharge generated at atmospheric conditions by using air as the working gas. Significant differences emerged only for L. monocytogenes (after 40 and 60 min). Highest reductions (up to about 8 log CFU/ml) were observed by using the silver and brass electrodes after 60 min. Differences in terms of electrical parameters (voltage, current, active power) and chemical species generated in the liquid medium (nitrites and nitrates concentrations) were not significant, relevant or directly attributable to the decontamination efficacy of the different electrodes. Ozone production was higher for oxidation-resistant electrode materials. The decontamination effect was influenced by silver and brass antibacterial properties. Industrial relevance The results of the present work, focused on the impact of the electrode material on the decontamination performance, introduced a new aspect in the technology panorama that could improve possible industrial application. The selection of the electrode material played a role in terms of decontamination efficacy.

Pulsed electric field (PEF) technology is gaining momentum as a pre-treatment to enhance mass transfer of vegetable tissues obtained by further processing. In this study PEF pre-treatment increased osmotic dehydration (OD) effectiveness, in terms of water loss and solid gain in apples, as a function of electric field strength and number of pulses. Mass transfer was particularly high when average electric fields of 250 and 400 V cm -1 were applied. Time domain nuclear magnetic resonance (TD-NMR), with the use of a contrast agent, clarified structural changes that drive mass transfer. Treatments at 100 V cm -1 redistributed water between vacuole, cytoplasm and extracellular space, while at 250 and 400 V cm -1 the membrane breakages caused the loss of cellular compartmentalization. Two non-destructive and fast acquirable parameters, the longest measured relaxation time (T 2 ) and water self diffusion coefficient (D w ), allowed the separate and accurate observation of PEF treatment and osmotic dehydration effects. Industrial relevance The developed non-destructive method, here described, allows the measure of the effects of PEF treatment on apple tissue which can be exploited to have reliable control of the process within minutes. Since mass transfer parameters depend on subcellular water redistribution, the present work provides a tool to boost the development and optimization of agri-food processes on fresh vegetable tissues.

Cold plasma is an emerging non-thermal processing technology that could be used for large scale leaf decontamination as an alternative to chlorine washing. In this study the effect of an atmospheric cold plasma apparatus (air DBD, 15 kV) on the safety, antioxidant activity and quality of radicchio (red chicory, Cichorium intybus L.) was investigated after 15 and 30 min of treatment (in afterglow at 70 mm from the discharge, at 22 °C and 60% of RH) and during storage. Escherichia coli O157:H7 inoculated on radicchio leaves was significantly reduced after 15 min cold plasma treatment (-1.35 log MPN/cm2). However, a 30 min plasma treatment was necessary to achieve a significant reduction of Listeria monocytogenes counts (-2.2 log CFU/cm2). Immediately after cold plasma treatment, no significant effects emerged in terms of antioxidant activity assessed by the ABTS and ORAC assay and external appearance of the radicchio leaves. Significant changes between treated and untreated radicchio leaves are quality defects based on the cold plasma treatment. Atmospheric cold plasma appears to be a promising processing technology for the decontamination of leafy vegetables although some criticalities, that emerged during storage, need to be considered in future studies.

The aim of this study was to evaluate the effect of gas plasma treatment on fresh-cut melon stability during controlled storage. Plasma treatments of 15 + 15 and 30 + 30 min were conducted on fresh cut melon using a dielectric barrier discharge (DBD) generator. Samples were packed and stored for 4 days at 10 °C and evaluated for qualitative, metabolic and microbiological indexes. Qualitative parameters of fresh-cut melon (titratable acidity, soluble solid content, dry matter, colour, texture) were only weakly affected by plasma treatment. Peroxidase (POD) and pectin methylesterase (PME) activities were slightly inhibited by the treatment up to respectively about 17 and 7%. Tissue metabolic heat production decreased proportionally to the treatment duration, while a partial conversion to anaerobic metabolism was observed. Microbial results showed that a significant increase in microbial shelf-life was achieved following the 15 + 15 min plasma treatment due to a delayed growth of spoilage mesophilic and psychrotrophic microflora. Industrial relevance The demand for fresh-cut products characterized by high qualitative and nutritional values and an acceptable shelf-life has promoted the research for non-thermal treatments. Fresh-cut melon is considered to be highly perishable and potentially hazardous food because it can support the growth of spoilage microflora and several pathogens. Cold plasma has shown its potentiality as an antimicrobial treatment and has been tested on different food products, but the impact on product quality and metabolism is still scarcely known. The results obtained in this study contributed to deepen the knowledge on the effect of plasma treatment on microbial, qualitative and metabolic aspects of fresh-cut melon.

The antimicrobial efficacy of dielectric barrier discharge atmospheric gas plasma (DBD) was tested against Listeria monocytogenes and shigatoxin-producing Escherichia coli serogroups O157 and O26. Challenge tests were carried out with samples of cut celery and radicchio leaves inoculated with a mix of five strains of L. monocytogenes or the two strains of E. coli immersed in deionised water. The treatment efficacy was also assessed considering only the contaminated deionised water. For deionised inoculated water alone, a treatment time-dependent strong effect was observed and a pathogens reduction higher than 6 Log CFU/mL was obtained after 40 min of treatment. With the vegetables presence in the liquid medium, the efficacy appeared reduced and related to the treatment time, microorganism, substrate and storage duration (reduction up to 2.5 and 3.7 Log CFU/cm 2 for L. monocytogenes and E. coli , respectively). No significant changes were observed on celery visual attributes, soluble solids content and textural parameters. A significant decrease of the chroma colour parameter during storage was noted in treated radicchio samples respect to control ones.

The increasing demand for high quality and safe food led to important technological innovations in food processing. Cold plasma appears as an emerging technology that has demonstrated efficiency in the removal of microbial contamination from fresh and minimally processed food. In this study, the proteomic profile of Salmonella Enteritidis SE86 subjected to cold plasma treatment was investigated. The number of viable S. Enteritidis SE86 cells was analyzed at different time intervals upon exposure to cold plasma and approximately 100 μg of S. Enteritidis SE86 protein extracts were analyzed by Multidimensional Protein Identification Technology (MudPIT). The results demonstrated that no significant changes in cell counts were detected for up to 20 min exposure to cold plasma, and 2 log reduction was achieved after 60 min. Overall, 1096 proteins were identified, with 249 detected only in plasma-treated samples, and 9 exclusive in non-treated control samples. The proteins uniquely detected in cold plasma-treated cells that showed higher abundance were glyoxalase I, ABC transporter substrate-binding protein and transcriptional activator OsmE, followed by some oxidoreductases. Proteins related with carbohydrate and nucleotide metabolism were mostly overexpressed in cold plasma treated cells, suggesting energy metabolism was increased.

Cold atmospheric plasma (CAP) has shown good potentiality for the decontamination and stabilization of fresh fruit and vegetable products, however, information about its effect on nutritional quality is still scarce. The aim of this research was to evaluate the impact of a form of indirect treatment known as Dielectric Barrier Discharge (DBD) on apple slices&mdash, more specifically, the polyphenolic profile and antioxidant activity of fresh-cut Pink Lady apples. Atmospheric plasma was generated using air as feed gas, and directed to apple slices for up to 30 min. The effect of plasma treatment on physico-chemical parameters was mainly observed as a slight acidification of the tissue and reduction of browning after an extended period of exposure. The samples&rsquo, phenolic profile was significantly affected after 10 min of treatment, both in quantitative (an approximately 20% increase) and qualitative terms, while with increasing exposure time a progressive decrease of all polyphenol classes was observed. The antioxidant activity, evaluated by different in-vitro methods, followed a similar trend, increasing after 10 min of processing and then decreasing. Results highlighted how plasma exposure promotes a metabolic response of the fresh tissue, and the importance of carefully controlling the exposure time in order to minimize the loss of nutritional properties.

[EN] Osmotic dehydration (OD) is a widely used preservation technique that consists in the reduction in food water activity by the immersion of the biological tissue in hypertonic solutions. The aim of this work was to analyze the effect of pulsed electric fields (PEF) in mass transfer as a pre-treatment of the OD using NMR. In this sense, PEF pre-treatments were done using three different voltages (100, 250 and 400 V/cm) and 60 number of pulse. The OD of kiwifruit was carried out in 61.5% of sucrose solution at 25 °C, for a contact period from 0 to 120 min. The water distribution into the cellular tissue was studied by NMR relaxometry. In conclusion, NMR is an excellent technique for quantifying water molecules according to their interactions in the fruit tissue, obtaining the adsorbed water and opening the possibility to apply the BET model to fit the adsorbed isotherm over the whole range of water activity., The authors Urszula Tylewicz and Marco Dalla Rosa want to thank for the financial support provided by funding bodies within the FP7 ERA-Net CORE Organic Plus, and with cofounds from the European Commission. The author Maria Victoria Traffano Schiffo wants to thank the FPI Predoctoral Program of the Universidad Politecnica de Valencia for support her PhD studies, ERASMUS PRACTICAS program to finance her mobility to Italy. The authors Pedro J. Fito, Marta Castro-Giraldez and M. Victoria Traffano-Schiffo acknowledge the financial support from the Spanish Ministerio de Economia, Industria y Competitividad, Programa Estatal de I+D+i orientada a los Retos de la Sociedad AGL2016-80643-R.

[EN] This work analyzes the effect of Pulsed Electric Fields (PEF) as a pre-treatment of the osmotic dehydration (OD) of kiwifruit (Actinidia deliciosa cv Hayward) in the internal structure and in the internal water transport. PEF pre-treatments were done using three PEF intensities (100, 250 and 400 V/cm) and analyzed by TD-NMR. The OD was carried out by immersing the samples in 61.5% sucrose solution at 25 °C. The application of a PEF pre-treatment before the OD produces a process of plasmolysis proportional to the electric field applied. It is because the PEF removes the mobile charges of the medium, such as electrolytes, organic acids, amino acids; Ca+2 is the major culprit of the plasmolysis because it fixes some of the junctions of the microtubules between the cell wall and the membrane. Therefore, a previous plasmolysis produces an increase in the apoplastic transport increasing the rate of dehydration., The authors Urszula Tylewicz and Marco Dalla Rosa want to thank for the financial support provided by funding bodies within the FP7 ERA-Net CORE Organic Plus, and with cofounds from the European Commission. The author Maria Victoria Traffano Schiffo wants to thank the FPI Predoctoral Program of the Universidad Politecnica de Valencia for support her PhD studies, ERASMUS PRACTICAS program to finance her mobility to Italy. The authors Pedro J. Fito, Marta Castro-Giraldez and M. Victoria Traffano-Schiffo acknowledge the financial support from the Spanish Ministerio de Economia, Industria y Competitividad, Programa Estatal de I + D + i orientada a los Retos de la Sociedad AGL2016-80643-R, Agencia Estatal de Investigacion (AEI) and Fondo Europeo de Desarrollo Regional (FEDER).

The main objective of this study was to evaluate the synergistic effect of atmospheric cold plasma (ACP), Sodium Dodecyl Sulphate (SDS) and lactic acid (LA) on L. monocytogenes and verotoxin-producing E. coli in red chicory. Experimentally inoculated samples were pre-treated with either SDS, or SDS + LA for 5, 10 or 15 min. Pre-treated samples were then submerged in deionized water and either exposed to ACP generated by dielectric barrier discharge device (DBD: fixed parameters: 19.15 V and 3.15 A) for 15 min or left untreated. All combinations of treatments were evaluated for sensory effects. Viable counts of verotoxin-producing E. coli on red chicory decreased by more than 4 logs (4.78 Log CFU/cm2 vs control) after a treatment with LA + SDS for 5 min and ACP for 15 min and often dropped below the limit of quantification. L. monocytogenes showed a higher tolerance to this sanitizing treatment and the level of inactivation was higher than 3 logs (3.77 Log CFU/cm2 vs control) only by increasing the duration of the washing step in LA + SDS to 15 min. The different treatments had no detrimental effects on colour, freshness and texture of red chicory, but odour and overall acceptability of the samples treated by ACP slightly decreased during storage. Further optimization of treatment parameters for maintaining fresh characteristics are needed, but the effectiveness of combinations of sanitizers and ACP on other pathogens and fresh produce worth to be investigated.

Dairy industry has a strong interest in quick and inexpensive techniques able to estimate milk fat content both in off and on-line processes. In the present study, a simple and inexpensive optical technique is preliminary described, discussed, and then tested for the prediction of this parameter. It's essentially based on the different intensity and spectral emission of a tungsten lamp during its progressive lighting combined with the photodiode wavelength sensitivity. Measurements were carried out at 22 °C on thirteen samples of commercialized milk (and mixture of them) (fat content ranging from 0.05% to 3.8%). The influence of the milk temperature on the optical behaviour was also investigated. The detected voltage waveform was strictly and not-linearly correlated with the fat content (R 2 up to 0.985) and predictions with R 2 up to 0.997 were obtained by using artificial neural networks (ANN). Milk temperature differently influenced the measurements for milks with various fat content.

Pulsed electric field (PEF) treatments can induce metabolic stress responses in plant tissue as a function of the applied conditions. This study highlighted the metabolic effects of reversible and irreversible electroporation in fresh-cut apple tissue, by adjusting the electric field strength to 100, 250 and 400 V/cm (100 μs pulse width, 60 pulses, 100 Hz). Metabolic heat, O 2 and CO 2 gas analysis, along with metabolomics, were employed to jointly evaluate the PEF-induced effects after 24 h at 10 °C. Marked metabolic changes were registered when the threshold of irreversible electroporation was exceeded, at 250 and 400 V/cm. With such treatments, a drop of metabolic heat and respiration rate was observed, as a probable consequence of the loss of the cell viability, anaerobic respiration pathways were noticeably lowered, while γ-aminobutyric acid metabolism was activated. Conversely, minimal modifications of the metabolism heat and metabolites concentrations were noticed when 100 V/cm was applied. Industrial relevance Metabolic response of fresh-cut fruit and vegetables as function of the manufacturing process is a fundamental aspect directly related to the quality of the final products. Pulsed electric fields (PEF), as well as other innovative technologies, can induce undesired effects on tissue metabolism that might limit the industrial application. Furthermore, the analytical methods used in the present work provide useful tools for the optimization of the PEF treatment conditions for fresh-cut manufacturers.

The efficacy of atmospheric plasma treatment on microbial decontamination of different kinds of food products is already known. Recently, new applications of this innovative technology have been proposed, in order to test the improvement of quality maintenance of minimally processed fruit and vegetables. Nevertheless, the knowledge on the modifications of functional and nutritional properties of minimally processed fruit is still scarce. The objective of this study was to evaluate the effect of atmospheric double barrier discharge (DBD) plasma treatment on the quality maintenance of fresh-cut kiwifruit. Treatments of 10 and 20 min per side were performed and their consequences were evaluated during four days of storage in controlled conditions by monitoring parameters related to visual quality, texture, chlorophyll, carotenoids and polyphenols. The in vitro antioxidant activity was evaluated through a multimodal approach, combining different assays for the analysis of antiradical activity and reducing activity of antioxidants. According to the obtained results, plasma treatments positively influenced the quality maintenance of the product, by improving colour retention and reducing the darkened area formation during storage, not inducing any textural change compared with the control. Plasma treatments caused an immediate slight loss of pigments, but a better retention during storage. No significant changes in antioxidants content and antioxidant activity were observed among treated samples and control ones.