Combination Of Pulsed Electric Fields Research Articles

Physicochemical, structural and functional properties of pomelo peel pectin extracted by combination of pulsed electric field and cellulase hydrolysis

In this study, pectin extracted from pomelo peel was investigated using three different combination methods of pulsed electric field (PEF) and cellulase. Three action sequences were performed, including PEF treatment followed by enzymatic hydrolysis, enzymatic hydrolysis followed by PEF treatment, and enzymatic hydrolysis simultaneously treated by PEF. The three corresponding pectins were namely PEP, EPP and SP. The physiochemical, molecular structural and functional properties of the three pectins were determined. The results showed that PEP had excellent physiochemical properties, with the highest yield (12.08 %), total sugar (80.17 %) and total phenol content (38.20 %). The monosaccharide composition and FT-IR analysis indicated that the three pectins were similar. The molecular weights of PEP, EPP and SP were 51.13, 88.51 and 40.00 kDa, respectively. PEP showed the best gel properties, emulsification stability and antioxidant capacity among the three products, due to its high galacturonic acid and total phenol content, appropriate protein and low molecular weight. The mechanism of PEF-assisted cellulase hydrolysis of pomelo peel was also revealed by SEM analysis. These results suggested that PEF pretreatment was the best method, which not only improved the efficiency of enzymatic extraction, but also reduced resource waste and increased financial benefits.

Characterization of the electropermeabilization induced by pulsed electric field (PEF) technology and its effect on the ultrasonic-assisted drying of yellow turnip

Obtaining snacks from the drying of surplus vegetables is an alternative to reduce waste. A combination of pulsed electric field (PEF) pretreatments and ultrasonic-assisted (US) drying could significantly enhance the process, as this is the aim of this study. PEF pretreatments of yellow turnip significantly affected the cell disintegration index (CDI) and the water holding capacity (WHC): the more intense the PEF treatment, the greater the CDI and the lower the WHC. Both parameters, CDI and WHC, showed a high degree of correlation which indicated that WHC can be an alternative index to CDI to assess PEF effects on food matrices. Regarding yellow turnip drying (40 °C), PEF pretreatments (CDI 0.25 and 0.75) and US application (20.5 kW/m3) significantly accelerated the operation, but it was the combination of both technologies that provided the shortest process (CDI 0.75). PEF could generate changes in the food matrix which enhance the US effects on mass transfer.

Selective extraction of recombinant membrane proteins from Hansenula polymorpha by pulsed electric field and lytic enzyme pretreatment

BackgroundIn yeast, recombinant membrane proteins including viral scaffold proteins used for the formation of enveloped Virus-like particles (eVLPs) typically accumulate intracellularly. Their recovery is carried out by mechanical disruption of the cells, often in combination with detergent treatment. Cell permeabilization is an attractive alternative to mechanical lysis because it allows for milder and more selective recovery of different intracellular products.ResultsHere, we present a novel approach for extraction of integral membrane proteins from yeast based on cell envelope permeabilization through a combination of pulsed electric field and lytic enzyme pretreatment of the cells. Our primary experiments focused on Hansenula polymorpha strain #25-5 co-expressing the integral membrane small surface protein (dS) of the duck hepatitis B virus and a fusion protein of dS with a trimer of a Human papillomavirus (HPV) L2-peptide (3xL2-dS). Irreversible plasma membrane permeabilization was induced by treating the cell suspension with monopolar rectangular pulses using a continuous flow system. The permeabilized cells were incubated with lyticase and dithiothreitol. This treatment increased the cell wall permeability, resulting in the release of over 50% of the soluble host proteins without causing significant cell lysis. The subsequent incubation with Triton X-100 resulted in the solubilization and release of a significant portion of 3xL2-dS and dS from the cells. By applying two steps: (i) brief heating of the cells before detergent treatment, and (ii) incubation of the extracts with KSCN, an 80% purity on the protein level has been achieved. Experiments performed with H. polymorpha strain T#3-3, co-expressing dS and the fusion protein EDIIIWNV-dS consisting of dS and the antigen from the West Nile virus (WSV), confirmed the applicability of this approach for recovering dS. The treatment, optimal for solubilization of 3xL2-dS and a significant part of dS, was not effective in isolating the fused protein EDIIIWNV-dS from the membranes, resulting in its retention within the cells.ConclusionsThis study presents an alternative approach for the recovery and partial purification of viral membrane proteins expressed in H. polymorpha. The factors influencing the effectiveness of this procedure and its potential use for the recovery of other integral membrane proteins are discussed.

Testing the Efficacy of a Prototype That Combines Ultrasound and Pulsed Electric Field for Extracting Valuable Compounds from Mitragyna speciosa Leaves

This work aimed to test the efficacy of an ultrasound (US) and pulsed electric field (PEF) apparatus to extract mitragynine from dried Mitragyna speciosa cv. Karn Dang leaves. Four modes of the device were tested: PEF, US, US + PEF, and PEF + US, and the modes were compared using a conventional technique (maceration, as the control). The liquid chromatography/mass spectrometry (LC-MS/MS) analysis revealed that the mitragynine contents from M. speciosa leaves using the four different modes were significantly different (p < 0.05). The highest extraction (106.63 ± 0.85 mg/L) of mitragynine was obtained by the mode using a combination of PEF + US, followed by US + PEF (97.27 ± 1.33 mg/L), with increased extraction efficiencies of 45.81 ± 0.59% and 33.00 ± 1.85%, respectively. Moreover, the total energy consumption under the combination technique was 25.0% lower than that with PEF assistance. Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to analyze the structural and functional features of the alterations in M. speciosa leaves. This study demonstrated that a combination of PEF and US devices may be regarded as a green alternative technique and can assist in streamlining the implementation of agricultural products.

Optimization of pulsed electric fields combined with mild heat treatment on microbial inactivation of tender coconut water and evaluation of quality attributes during storage

This work aimed to investigate the processing conditions of pulsed electric fields (PEF) combined with mild heat for microbial inactivation in tender coconut water (TCW) using response surface methodology and to evaluate the quality of the products. Combining 40 °C with PEF at a field strength of 22.5 kV/cm and specific energy of 119 kJ/l was optimal to inactivate Escherichia coli K12 and Listeria innocua by a 6.60 and 5.90 log CFU/ml from the initial numbers of 6.65 and 6.04 log CFU/ml, respectively, thereby meeting USFDA requirements. This was seen to damage bacterial cell membrane and reduce total plate and yeast mould count in TCW comparable to thermal pasteurization (85 ± 2 °C for 10 min), resulting in a shelf-life extension of >35 days at 8 ± 2 °C while retaining physicochemical properties and polyphenols similar to the untreated sample. During refrigerated storage, the development of a pink colour in the TCW was also delayed for 7 days compared with the heat treatment. This study proved that the combination of PEF with mild thermal treatment (40 °C) was effective in regard to microbial inactivation for food production while preserving the fresh-like attributes of TCW as confirmed by volatile profile along with sensorial analysis. Industrial relevanceThis research provides the industry with an original investigation into the use of a combination of mild heat treatment and pulsed electric fields (PEF) to inactivate Escherichia coli K12 and Listeria innocua, achieving more than a 5-log reduction. The results highlighted the potential of PEF as an alternative technique for pasteurizing tender coconut water and extending the shelf-life. This approach shows promise in extending the shelf-life of the product, which can be advantageous for both transportation and stock management purposes.

Enhancing Antioxidant Properties of Prunus spinosa Fruit Extracts via Extraction Optimization

Prunus spinosa fruit, commonly known as blackthorn or sloe, possesses a wide range of health-promoting properties, including antioxidant and antibacterial activities. In this study, we investigated the effects of various extraction parameters, such as temperature, time, and solvent composition, on the extraction of bioactive compounds from P. spinosa fruit. Response surface methodology was employed to optimize these parameters and evaluate their impact on the antioxidant properties of the extracts. Furthermore, techniques such as ultrasound (US) and pulsed electric field (PEF) were applied, both individually and in combination, to explore their potential effects on the extraction process. The optimal extraction technique proved to be the combination of PEF and US, followed by stirring. The most suitable solvent was 75% ethanol, whereas the optimum extraction time and temperature were 30 min and 80 °C, respectively. Our findings revealed that under the optimum extraction parameters, a significant improvement in the extraction efficiency of bioactive compounds from P. spinosa fruit was achieved. More specifically, the optimal conditions, according to partial least squares (PLS) analysis, were a combination of all three extraction modes (PEF‒US‒ST), the shorter extraction time of the present study (30 min), and the corresponding higher temperature (80 °C). As expected, the presence of ethanol was considered necessary, even in an amount of 25%. The total polyphenol content was found to be 30.74 mg gallic acid equivalent (GAE)/g, the total flavonoids content 3.23 mg rutin equivalents (RtE)/g and the total anthocyanins 125.2 μg cyanidin-3-O-glucoside equivalents (CyE)/g. HPLC-DAD analysis showed that neochlorogenic acid was the polyphenol with the highest concentration (4.13 mg GAE/g) in P. spinosa fruit. The antioxidant activity of the optimized, according to PLS analysis, extract was evaluated and found to be 146.09 μmol ascorbic acid equivalent (AAE)/g determined by ferric reducing antioxidant power (FRAP) assay, and by the radical scavenging activity (DPPH) assay was 18.56 μmol AAE/g. Additionally, the ascorbic acid was determined to be 119.4 mg/100 g. Overall, this study contributes valuable insights into the extraction optimization process and the potential applications of P. spinosa fruit in the development of functional foods and pharmaceutical products.

Abstract 6392: Combination of pulsed electric field, immunotherapy and cisplatin significantly prolongs survival in an orthotopic breast cancer mouse model

Abstract Introduction: Pulsed Electric Field (PEF) therapy is a novel approach to treat cancer by providing focal tumor ablation while sparing sensitive structures within the tumor micro-environment. Previous studies have demonstrated that PEF induces immunogenic cell death by activating inflammatory signaling pathways and stimulation of antigen presenting cells withing the tumor micro-environment. PEF ablation provides a tumor focused in situ vaccination strategy that combines with checkpoint blockade. We hypothesized that PEF ablation should synergize with chemotherapy and anti-PD1 in a model where checkpoint inhibitors are inactive. Experimental Design: To test this hypothesis, we utilized a highly aggressive syngeneic orthotopic triple negative breast cancer 4T1 mouse model that is non-responsive to anti-PD1 and only marginally responsive to cisplatin to determine if this combination treatment could prolong survival. Thirty-two Balb/c mice were inoculated in the mammary fat pad with 200,000 4T1 cells. Once tumors were established (5mm in diameter), animals were randomized to the following groups: (A) Sham/IgG control (n=8; needle inserted but no PEF), (B) PEF only (n=8), (C) cisplatin + anti-PD-1 (n=8) and (D) PEF + cisplatin + anti PD-1 (n=8). Tumors in groups B and D were treated once with PEF. Anti-PD1 and isotype matched control IgG was administered once per week (200μg, i.p injections) starting on the day of PEF (Group D) for four weeks. Cisplatin was administered (2mg/kg, i.v) once per week for four weeks starting on the day of PEF (d=0) for four weeks. All the mammary fat pad tumors were resected when they achieved a tumor volume of ~200 mm3 to recapitulate post-resection metastatic relapse (See Schematic 1). Results and Conclusions: All mice in the Sham-control IgG group needed to be euthanized by day 43 due to metastases in multiple organs including lungs, bones, liver and brain. All mice in the cisplatin + anti PD-1 group had to be euthanized by day 74. Interestingly, all groups that were treated with PEF survived much longer. On day 90, 28% of mice in the PEF alone group were alive and 43% were alive in the PEF + anti-PD1 + Cisplatin (see Figure 1). The rank-log p-value for the Kaplan-Meier survival curve was statistically significant. In conclusion, our results demonstrate that PEF treatment in combination with anti-PD1 and Cisplatin significantly prolongs survival in a highly aggressive triple negative breast tumor mouse model that is non-responsive to immunotherapy. These findings support evaluation of PEF in cancer patients that are receiving combination of checkpoint blockade and chemotherapy. Citation Format: Chiara Pastori, Mukta Wagh, Ebtesam Nafie, Fatima Murad, Mohit Trikha, Robert Neal. Combination of pulsed electric field, immunotherapy and cisplatin significantly prolongs survival in an orthotopic breast cancer mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6392.

A preliminary multistep combination of pulsed electric fields and supercritical fluid extraction to recover bioactive glycosylated and lipidic compounds from exhausted grape marc

This article reports the first multistep combination of pulsed electric field (PEF; 3 kV/cm, 100 kJ/kg, 2 Hz, 100 ms) and supercritical fluid extraction (SFE) with CO2 (10–20 MPa, 25 mL/min [10% EtOH], 50 °C, 60 min) for exhausted grape marc (EGM). This current protocol was mainly created to recover bioactive glycosylated and lipidic compounds. In this regard, total antioxidant capacity (TAC) was enhanced up to 68% after PEF treatment compared to conventional soaking. However, re-extracting PEF-treated EGM after the application of SFE (PEF + SFE) boosted the efficiency by up to 87%. Several polyphenols (kaempferol, luteolin, scutellarin, and resveratrol, among others), together with other glycosylated structures, were identified by liquid chromatography coupled with mass spectrometry analysis. The bioactive lipidic compounds extracted by SFE, along with the carbohydrate fraction (free sugars) favourably extracted by PEF pre-treatment (mainly glucose, but also fructose and sucrose), were concurrently detected by nuclear magnetic resonance. The remaining solid fraction after treatment was also characterised. Different microscopic morphology was observed by scanning electron microscopy (SEM) on untreated, PEF, and PEF + SC–CO2–treated EGM. Differential thermogravimetric (DTG) curves determined by thermogravimetric analysis (TGA) also suggested alternative and potential means for the valorisation of this matrix.

Combination of pulsed electric field and pH shifting improves the solubility, emulsifying, foaming of commercial soy protein isolate

In this study, the effects of a new dual modification method, pulsed electric field (PEF) and pH shifting treatment, on the solubility, emulsifying and foaming properties of commercial soy protein isolate (SPI) were investigated. Results showed that the combination of PEF and pH shifting treatment, particularly at moderate PEF strength (10 kV/cm) and alkaline conditions (pH 11), facilitated protein structure unfolding and formation of smaller aggregates, substantially enhancing the solubility of SPI from 26.06% to 70.34%. Higher flexibility, surface hydrophobicity, and free sulfhydryl content were also found in the modified SPI, which boosted interfacial activity and significantly enhanced emulsifying and foaming properties. In alkaline environments, the enhanced functional properties of SPI at moderate PEF strength may be attributed to the appropriate oxidation of proteins by free radicals produced by electrochemical processes and the additional unfolding of protein conformations by polarization. The functional characteristics of SPI were decreased by an increase in PEF strength (20 kV/cm), which may be due to the tendency of the protein to aggregate and undergo excessive oxidation. This work may provide an effective methodological and theoretical basis for the modification of SPI by combining PEF and pH shifting treatment. • PEF combined with pH shifting treatment efficiently improved the solubility of SPI. • The treated SPI showed dramatic enhancement in emulsifying and foaming properties. • Enhanced unfolding in pH shifted SPI were observed after PEF introduction. • PEF-induced polarization and proper oxidation enhanced the functional property of SPI.

Physicochemical characteristics of pulsed electrical field–sterilized sugarcane (Saccharum officinarum L.) juice with added ginger extract

This study aimed to investigate the effect of the voltage of the pulsed electric field (PEF) and ginger extract concentration on sugar cane juice's physicochemical and organoleptic quality. The experiments were carried out at voltages of 20 kV and 40 kV, and ginger extract concentrations of 2, 4, and 6%. The PEF with 40 kV and 6% ginger extract concentration resulted in the most efficient microbial reduction by 99.54%. Sugarcane juice has a total number of microbes of 3.7x103 CFU/ml, antibacterial activity 1.48, pH of 6.26, total solids dissolved of 20.5 °Brix, a viscosity of 4.67 Cp, reducing sugar of 2.17%, brightness of 24.4, redness of 7.17, and yellowness of 8.1. The combination of pulsed electric field and ginger extract addition can preserve the shelf life and maintain sugarcane juice quality. The higher the PEF voltage and ginger extract concentration, the longer the quality of the sugarcane juice can be preserved.

Influence of Geographical Location of Spirulina (Arthrospira platensis) on the Recovery of Bioactive Compounds Assisted by Pulsed Electric Fields

Spirulina (Arthrospira platensis) has been consumed by humans since ancient times. It is rich in high added-value compounds such as chlorophylls, carotenoids and polyphenols. Pulsed electric fields (PEF) is an innovative non-thermal technique that improves the extraction of bioactive compounds from diverse sources. PEF pre-treatment (3 kV/cm, 100 kJ/kg) combined with supplementary extraction with binary solvents at different times was evaluated to obtain the optimal conditions for extraction. In addition, the results obtained were compared with conventional treatment (without PEF pre-treatment and constant shaking) and different strains of Spirulina from diverse geographical locations. The optimal extraction conditions for recovering the bioactive compounds were obtained after applying PEF treatment combined with the binary mixture EtOH/H2O for 180 min. The recovery of total phenolic content (TPC) (19.76 ± 0.50 mg/g DM (dry matter) and carotenoids (0.50 ± 0.01 mg/g DM) was more efficient in the Spirulina from Spain. On the other hand, there was a higher recovery of chlorophylls in the Spirulina from China. The highest extraction of total antioxidant compounds was in Spirulina from Costa Rica. These results show that PEF, solvents and the condition of growing affect the extraction of antioxidant bioactive compounds from Spirulina. The combination of PEF and EtOH/H2O is a promising technology due to its environmental sustainability.

Postharvest Preservation of Thai Mango var. Chok-Anan by the Combination of Pulsed Electric Field and Chemical Pickling

Mango is one of the most favorable tropical fruits grown and consumed in several parts of the world. However, there is overproduction during the ripening stage. In this situation, appropriate techniques are needed to utilize the abundant supply. Pickling is one of the oldest and most successful methods for preserving mango. In this study, mango pickles were prepared by using chemical pickling assisted with pulsed electric field (PEF). The physicochemical and textural properties of mango pickles prepared with PEF at 30 and 50 °Brix were studied in comparison with the conventional pickling process. The water loss, solids gain, and diffusion efficiency were increased by twofold when PEF was applied in pickling Thai mango variety Chok-anan. This process also reduced the moisture content and water activity. The PEF-assisted pickling process caused changes in lightness (L*) and redness (a*) values. The textural properties of the mango pickles produced by the PEF-assisted pickling process were also changed. In addition, the PEF-assisted pickling process caused a 20% increase in beta-carotene content and a 47% decrease in ascorbic acid content. The microstructure of the mango was more disintegrated on the surface after PEF than that from the conventional pickling process.

Combination of Pulsed Electric Field and Ultrasound in the Extraction of Polyphenols and Volatile Compounds from Grape Stems

Increasing the yield of extraction of bioactive compounds from plants is of high importance. Grape stems are widely discarded during the wine-making process, despite their high content in many valuable compounds. The aim of this work was to examine whether the use of pulsed electric field (PEF) treatment of the stems could increase the yield of polyphenol and volatile compounds in the extracts. For this reason, a relatively low-energy consuming PEF process was employed (low-electric field strength, 1 kV/cm) for a short time (30 min) at the grape stems. In addition, the effect of different solvents during this pretreatment step was examined. With the use of Folin–Ciocalteu assay, the extracts were compared with the respective control samples (not pretreated with PEF). Moreover, extracts were prepared to assess whether changes occur to the volatile profile of the extracts. The results were conclusive that not only PEF can increase the yield of polyphenols (up to 35% increase recorded), but also that the solvent used during PEF pretreatment can affect the process. Furthermore, a 234% increase in the total content of volatile compounds was recorded, when PEF was used as a pretreatment step. Therefore, the combination of PEF and ultrasound-assisted extraction is highly promising to obtain grape stem extracts with a higher content of bioactive compounds.

The Effect of Pulsed Electric Fields (PEF) Combined with Temperature and Natural Preservatives on the Quality and Microbiological Shelf-Life of Cantaloupe Juice.

Pulsed electric field (PEF) is an innovative, non-thermal technology for food preservation with many superiorities. However, the sub-lethally injured microorganisms caused by PEF and their recovery provide serious food safety problems. Our study examined the effects of pH, temperature and natural preservatives (tea polyphenols and natamycin) on the recovery of PEF-induced, sub-lethally injured Saccharomyces cerevisiae cells, and further explored the bactericidal effects of the combined treatments of PEF with the pivotal factors in cantaloupe juice. We first found that low pH (pH 4.0), low temperature (4 °C), tea polyphenols and natamycin inhibited the recovery of injured S. cerevisiae cells. Then, the synergistic effects of PEF, combined with cold-temperature storage (4 °C), a mild treatment temperature (50 and 55 °C), tea polyphenols or natamycin, on the inactivation of S. cerevisiae in cantaloupe juice were evaluated. Our results showed that the combination of PEF and heat treatment, tea polyphenols or natamycin enhanced the inactivation of S. cerevisiae and reduced the level of sub-lethally injured cells. Moreover, PEF combined with 55 °C heat treatment or tea polyphenols was applied for cantaloupe juice. In the practical application, the two combined PEF methods displayed a comparable inactivation heat pasteurization ability, prolonged the shelf life of juice compared with PEF treatment alone, and better preserved the physicochemical properties and vitamin C levels of cantaloupe juice. These results provide valuable information to inhibit the recovery of PEF-injured microbial cells and shed light on the combination of PEF with other factors to inactivate microorganisms for better food preservation.

Modelling the mechanical properties and sorption behaviour of pulsed electric fields (PEF) treated carrots and potatoes after air drying for food chain management

One of the major challenges of the food industry is to develop more sustainable processing technologies. To address this change, it is necessary to have more information about available innovative technologies and their effect on different food matrices and processes to ensure efficiency in food chain management. The aim of this research was to increase the understanding of the physical modifications induced by the combination of pulsed electric field (PEF) pre-treatment and further drying in carrot and potato tissues by modelling the sorption isotherms and the textural properties. High coefficient of determination up to 0.980 for GAB and 0.977 for BET were obtained confirming the good ability of both models to describe the sorption isotherm of foodstuff. Either BET and GAB classified carrot in a III type shape and potato in II type shape for sorption isotherm. Mechanical properties for carrot and potato considering all PEF treatment and a w levels were reported and fitted by modified Fermi distribution. High coefficient of determination up to 0.995 confirm the ability of Fermi model to describe mechanical properties in relation to water activity ( a w ). • Potato and carrot treated at 3 PEF intensities and dried at 60 °C. • High determination coefficient of 0.980 (GAB) and 0.977 (BET) were obtained. • Mechanical properties of all PEF treatments; a w levels were fitted by Fermi model. • Potato maximum force significantly increases with PEF treatment at 1 and 1.5 kV cm −1 . • Carrot maximum force showed loss of firmness only for lowest water activity levels.

Pulsed electric field combined with microwave-assisted extraction of pectin polysaccharide from jackfruit waste

The present methodology uses the combination of pulsed electric fields (PEF) and microwave-assisted extraction (MAE) of pectin from the jackfruit wastes. Two optimization tools such as Box-Behnken design (BBD) and artificial neural network (ANN) were used to study the extraction yields. The optimized operating conditions obtained after desirability analysis were PEF strength (11.99 kV/cm), PEF treatment time (5.47 min), followed by MAE at power density (647.30 W/g) and time of exposure (5.00 min). From the optimization results, the R2 values of BBD ranged from 0.89 to 0.98 as well as the SSE (sum of squared error) values varied across 0.076 to 0.781 whereas R2 values of ANN fluctuated around 0.95 to 0.99 and MSE (mean squared error) values varied from 0.008 to 0.1. It was observed the ANN was found to be more superior in execution than the BBD model. The extracted pectin was analyzed for structural and functional properties with the comparison to conventionally extracted pectin. The degree of esterification and methoxyl percentage of PEF and MAE pectin was less than the conventionally extracted pectin. The experimental and predicted values were similar for the pectin yield (%), but a higher prediction rate was observed in ANN modelling than BBD. Scanning Electron Micrographs showed an increased rupture and severing of parenchymal cells attributing to enhance extraction yields. Therefore, it can be concluded that the pulsed electric field treatment followed by microwave-assisted extraction resulted in higher pectin extraction with enhanced functional properties than the conventional method.

Quality Retention of Fresh Tuna Stored Using Supercooling Technology.

The present study was focused on the investigation of physiochemical changes in tuna subjected to a novel supercooling preservation, which was assisted using a combination of pulsed electric fields (PEF) and oscillating magnetic fields (OMF). Fresh tuna fillets were stored without freezing at −3.2 °C for 8 days. The electrochemical impedance spectroscopy (EIS) parameter indicated that there was a significant difference between the frozen-thawed samples (36.3%) and fresh (46.6%) and supercooled (45.9%) samples, indicating that cell damage from ice crystal growth did not occur in the supercooled tuna sample. The microstructure observation and drip loss measurement further confirmed that the ice crystal damage was present in frozen tuna, whereas no cellular damage was found in the supercooled samples. The EIS proved its ability to distinguish between tuna samples that were frozen or chilled (i.e., refrigerated and supercooled) during storage; however, it was less sensitive in detecting the extent of spoilage. Instead, the K-value was used to evaluate tuna freshness, and the measured K-values of the refrigerated, supercooled, and frozen tuna samples after 8 days of storage were 74.3%, 26.4%, and 19.9%, respectively, suggesting that the supercooling treatment significantly preserved the tuna fillets fresh with the improved shelf-life when compared to conventional refrigeration.

Effect of innovative pre-treatments on the mitigation of acrylamide formation in potato chips

The aim of this research was to evaluate the reduction of acrylamide (AA) formation in potato chips applying innovative pre-treatments. Raw potato slices were subjected for 5 and 15 min to: dipping in water; dipping in Aureobasidium pullulans L1 yeast water suspension; dipping in water or in yeast water suspension after pulsed electric fields (PEF) in order to investigate a possible synergistic effect of pre-treatments. The raw potato samples were analysed for AA precursors and, after frying, for AA by using HPLC-MS/MS. In addition, the final potato chips main quality parameters were evaluated.Compared to untreated potato chips, yeast treatment promoted a reduction of AA formation mainly at the longest dipping time (15 min). PEF treatment followed by water dipping was the most effective in reducing AA for both the studied treatment times. The combination of PEF and yeast treatments led only a slight reduction of AA formation. Industrial relevanceThe Commission Regulation (EU) 2017/2158 has established new acrylamide (AA) benchmark levels in different foods due to its negative classification as “probably carcinogenic to human”. For this reason, food industries are interested in developing different processing methods to reduce the AA formation and at the same time to maintain an acceptable quality of final products. Fried potatoes (French fries and chips) are the most vulnerable foods in terms of high content of AA formation, being rich in the main Maillard reaction substrates, such as asparagine and reducing sugars, and characterized by a high surface to volume ratio. Among the strategies recently suggested for the reduction of AA in potato chips, pulsed electric fields (PEF) and yeast pre-treatments are very promising, having the potentiality to reduce AA precursors in raw potato tissues. In this study the possibility to apply yeast and PEF pre-treatments on raw potato slices with suitable processing times for a possible industrial application were evaluated.

Impact of a combined pulsed electric field (PEF) and enzymatic mash treatment on yield, fermentation behaviour and composition of white wine

The aim of this work was to study the combined application of a pulsed electric field (PEF) and an enzymatic treatment to white wine mash. The resulting impact of membrane permeabilisation by electroporation and pectin degradation by enzymes on fermentation behaviour and quality of white wine was assessed. The mash of two varieties, Traminer and Grüner Veltliner, was PEF treated (3 and 10 kJ/kg) using a continuous co-linear treatment chamber. Pectinases were added immediately afterwards and maceration was performed for 4 and 24 h. Various physico-chemical parameters were analysed at different stages of the production process and the impact of the combined treatment on volatile compounds such as esters and terpenes was analysed by gas chromatography–mass spectrometry and a sensory panel in the final white wine after bottling and storage. Regardless of the PEF treatment intensity, the variety and the maceration time, the release of juice was not significantly influenced. For Traminer, the fermentation time was reduced through the enhanced extraction of nitrogen from 322 to 359 mg/L due to PEF treatment (10 kJ/kg). The release of phenols which were localized in the pulp, were significantly more affected than phenols from the skin. Although the concentration of selective esters especially of the variety Traminer significantly increased, the sensory evaluation indicated no positive effect on the olfactory properties. Overall, the combination of PEF and enzyme pretreatment showed benefits in reducing the fermentation time and increasing the content of selective esters for Traminer.

The impact of combination of pulsed electric field and ultrasound treatment on air drying kinetics and quality of carrot tissue

In the study, the impact of combined pulsed electric field (PEF) and ultrasound (US) pre-treatments on drying kinetics and quality of dried carrot was evaluated. Carrot samples were subjected either to US followed by PEF (US-PEF) treatment or to PEF followed by US (PEF-US) treatment. Afterwards material was dried using convective method at 70 °C. Drying time of the samples subjected to combined treatment ranged from 180 to 255 min, whereas in the case of untreated carrots the drying time was equal to 298 min. The highest water diffusion coefficient (11.5·10−10 m2/s) was calculated for the samples subjected to PEF treatment followed by immersive sonication and it was 63% higher than reference ones. No significant differences were stated when comparing the rehydration properties of all investigated samples. However, samples pre-treated by combined method exhibited lower ability to adsorb water vapour from environment. Subjecting carrots to combined treatments resulted in a better carotenoids retention (60.5–80.6%). The material treated by PEF-US or US-PEF exhibited higher values of redness (a*) and lower of yellowness (b*) in comparison to untreated dried carrots.