IntroductionImpact of processing on product characteristics, sustainability, traceability, authenticity, and public health along the food chain becomes more and more important not only to the producer but also to the customer and the trust of a consumer toward a brand. In recent years, the number of juices and smoothies containing so called super foods or fruits, which have been “gently pasteurized,” has increased significantly. However, the term “gentle pasteurization” related to the application of emerging preservation technologies such as pulsed electric fields (PEF), high pressure processing (HPP) or ohmic heating (OH) is not clearly defined.MethodsTherefore, the presented study investigated the influence of PEF, HPP, OH, and thermal treatment on quality characteristics and microbial safety of sea buckthorn syrup. Syrups from two different varieties were investigated under the following conditions HPP (600 MPa 4–8 min), OH (83°C and 90°C), PEF (29.5 kV/cm, 6 μs, 100 Hz), and thermal (88°C, hot filling). Analyses to test the influence on quality parameters like ascorbic acid (AA), flavonoids, carotenoids, tocopherols, antioxidant activity; metabolomical/chemical profiling (fingerprinting) via U-HPLC-HRMS/MS (here especially flavonoids and fatty acids); sensory evaluation, as well as microbial stability including storage, were conducted.Results and discussionIndependent from the treatment, the samples were stable over 8 weeks of storage at 4°C. The influence on the nutrient content [Ascorbic acid (AA), total antioxidant activity (TAA), total phenolic compounds (TPC), tocopherols (Vit E)] was similar for all tested technologies. Employing statistical evaluation Principal Component Analysis (PCA) a clear clustering based on the processing technologies was observed. Flavonoids as well as fatty acids were significantly impacted by the type of used preservation technology. This was obvious during the storage time of PEF and HPP syrups, where enzyme activity was still active. The color as well as taste of the syrups were found to be more fresh-like for the HPP treated samples.

Cherry kernels occur in significant amounts as waste material during the processing of fruits. However, their subsequent use is limited due to the presence of cyanogenic glycosides, which are potentially dangerous to human health. In this study, the application of pulsed electric fields (PEF) was investigated as pre-treatment to improve the debittering process and to facilitate the degradation of cyanide precursors, naturally present in cherry kernels. Diverse PEF treatments were carried out at constant electric field strength of E = 2.2 kV/cm and specific energy input was varied between 10 and 50 kJ/kg, varying the number of pulses. Two different debit-tering procedures were performed with a common incubation time 0-20 h at 40 degrees C: a) incubation of whole kernels in deionized water; b) incubation of whole kernels without water stored in air at 80% relative humidity. HPLC analysis was used to examine the kinetics of the amygdalin and HCN contents. In both debittering methods, the PEF-treated samples with the highest intensity (2.2 kV/cm, 50 kJ/kg) showed higher and faster detoxification efficiency for the investigated compounds as compared to the untreated sample. In particular, the PEF treated samples incubated with water showed a reduction in the amygdalin and HCN contents of up to 86% (up to 72% of the raw material content.). Moreover, the PEF pre-treatment led to comparable efficiency in amygdalin reduction in both debittering processes: 86% reduction for the incubation with water and 81% for the incubation without water. Consequently, the combined application of PEF and the debittering process including incubation without water has remarkable potential as an industrial application due to its inherent reduced water con-sumption, and therefore, diminished wastewater management issues. A further advantage of this process is the minimizing of sugar loss typically occurring during the debittering through soaking.

In this study, the effect of matrix compounds from natural curcuminoid resources on the stability of curcuminoids and emulsions thereof was evaluated. Curcuminoid emulsions were prepared curcuminoid rich sources (curcuminoid extract, an aqueous turmeric concentrate and turmeric powder) with medium-chain triglyceride oil as lipid phase, lecithin, and pectin as emulsifiers. The curcuminoid emulsions were exposed to light in the visible wavelength range (300 nm–800 nm) at the specific energy input of 0.47 kW/m 2 for 7 days and to the temperature of 4 °C, 25 °C, 40 °C for 49 days. The total curcuminoid retention (TC), droplet size (DS) change, instability index (InI), and yellowness reduction (YR) was observed during the storage time. The half-life of curcuminoids in emulsions was increased to 21 h, while the half-life of free curcuminoids was 1.3 h in the light exposure test. The co-compounds from the curcuminoid sources contributed to the emulsion stability by increasing the viscosity. In the thermal exposure test, the matrix compound system retained more than 93% curcuminoids after 49 days of storage at 40 °C, whereas the phase separation increased significantly. However, the TC reduction was independent of the InI change and droplet agglomeration. The YR depended on the TC and the amount of co-components in the emulsion.

Pulsed electric field (PEF) technology is currently successfully used to a larger extent in the food industry for two key application areas: pre-treatment of potatoes in French fries and snack production and fruit juice preservation. Although numerous other application areas have been investigated in lab and pilot scale, they did not find their way into industrial application yet. Certain requirements have to be met in order to successfully translate electroporation phenomena into improved product quality, process efficiency, or innovative processing concepts. This chapter aims at identifying such requirements based on a process performance analysis of the application of PEF for the treatment of foodstuffs. Emphasis is put on the two main fields of application, nonthermal inactivation of microorganisms and cell disintegration of plant raw materials for the improvement of mass transfer processes. A systematic process analysis is performed based on effects related to the micro-, meso-, and macroscale and considering the interactions between process and product.

Cell structure modification techniques have the potential to improve curcuminoid recovery in Curcuma longa . In this study, different pre-treatments such as high hydrostatic pressure (HPP, high pressure processing), ultrasound (US), pulsed electric field (PEF), and ohmic heating (OH) were used on dried C. longa before aqueous extraction at pH 2.0, 5.0, and 8.0. The released curcuminoids, cell disintegration index (Z p ), particle size distribution (PSD), and color (CIE L*, a*, b*) were used to evaluate the different pre-treatment impacts on plant structure and extract properties. In untreated turmeric, the highest amount of released curcuminoids (3.89 mg/g dry matter) was obtained after extraction for 30 min at 95° in the aqueous phase. After pre-treatments, the acidic conditions showed a considerable improvement in curcuminoid recovery; PEF, HPP, and OH improved the curcuminoid recovery by 3.39-, 3.13-, and 1.24-fold, respectively; while US did not lead to an increased release of curcuminoids compared to the untreated material. The highest curcuminoid recovery (with PEF and extraction at pH 5.0) was 6.6% w/w of the total curcuminoids. The non-thermal pre-treatments have less impact on the extract’s color compared to the extraction pH, with alkaline conditions reducing the lightness of the extract.

Since 2010, the potato-processing industry has successfully implemented the application of pulsed electric fields (PEF) in their process lines in a large scale, and PEF pre-treatment has already become a standard processing step. Overall more than 100 machines have been installed in the industry today, the majority of which have been for French fries and potato crisps. The success of the PEF application in the potato industry is due to the multiple benefits deriving from the pre-treatment. Due to the cell disintegration and tissue softening occurring as a result of the PEF treatment the raw potato sticks have improved cutting properties and a better quality of the cutting surface. Furthermore, the improved flexibility of the tissue helps to reduce the amount of breakage during cutting and starch losses are reduced during further processing due to the smoother surface. Subsequently, quality improvement can be observed that is linked to homogeneous browning and a more uniform color, less oil uptake and the possibility to produce longer French fries. This chapter is focused on the impact of PEF on industrial relevant processing steps of the French fries production and gives an overview of relevant treatment parameters and requirements for a successful PEF application. Separate chapters include specific findings regarding the impact of PEF on crisps production and the effects of electric fields on side streams and by-products of the potato industry.

Curcuminoids, the bioactive compounds with many beneficial effects on human health, exist in Curcuma longa (turmeric). In the present study, the impact of different cell disintegration techniques to enhance total curcuminoid recovery (TC) from fresh and dried turmeric was investigated. The impact of thermal pretreatment (TP), ultrasound pretreatment (UP), enzyme pretreatment (EP), and pulsed electric field pretreatment (PEF) on the recovery of curcumin (CUR), demethoxycurcumin (DMC), and bis-demethoxycurcumin (BDMC) from fresh and dried turmeric were studied. The cell disintegration index (Zp) and high-performance liquid chromatography (HPLC) analysis of curcuminoids were performed to evaluate the efficiency of the applied techniques. With fresh turmeric, the highest curcuminoid recovery was 83.6 mg/g dry basis with EP. The highest structural tissue damage was obtained with UP achieving a cell disintegration level of 92.5%. The technology with the highest time-saving and low specific energy input was PEF with a total curcuminoid recovery of 80.9 mg/g dry basis. Working with dried turmeric, the drying required high specific energy input for 72 h at 50 °C; however, the untreated dried sample reached 125.3 mg/g dry basis of TC without further pretreatment after drying.

Culinary herbs and spices are an important sector of the food industry worldwide, but are often characterized by high levels of microbial contaminations. Therefore, irradiation is often applied to control the microbial burden. In this study, two spice decontamination technologies were compared: the established gamma irradiation as well as a newly developed low energy electron beam (LEEB) treatment. The aim of the study was to evaluate the efficacy of microbial surface inactivation for both treatments and their influence on quality attributes. Allspice berries, caraway seeds, oregano, and rosemary leaves were used as model matrices. Both treatments were shown to effectively reduce Enterococcus faecium counts below the detection limit (>3.3–5.5 log10). No differences in color, water activity, chlorophyll, and carotenoid contents, as well as 31 terpenoic compounds were determined between LEEB and gamma treatments in comparison to the untreated reference, for storage times of up to 105 days. Untargeted fingerprinting (SPME-GC-HRMS) showed a clustering of LEEB-treated rosemary samples, but no significant differences for the other samples.

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.

This research aims to evaluate whether the electroporation of Rhodotorula glutinis fresh biomass improved the subsequent extraction of carotenoids from dry biomass using supercritical CO2 and traditional solvent extraction. Supercritical CO2 extraction yields were low after all treatments assayed. Similarly, solvent extraction of carotenoids from untreated or PEF treated cells that were immediately freeze-dried after the pre-treatment was neither effective (extraction yield < 20% total content). Conversely, PEF-treatment and subsequent intermediate incubation in aqueous buffer for 24 h, followed by freeze-drying and extraction, led to a large improvement with the three solvents assayed (acetone, hexane, ethanol). Ethanol was the most efficient, reaching an extraction yield of 80% of total carotenoid, which represents a recovery of 267 mu g/g(dw). Torularhodin esters constituted the main carotenoid found in the extracts. This is of great interest, as ethanol is eco-friendly solvent and potential applications of torularhodin range from food to medical purposes.

For this study, strawberries and red bell peppers were pre-treated with pulsed electric fields (PEF) to reduce the negative effects on physical properties of the products after freeze-drying. PEF treatment was carried out at constant electric field strength of E = 1.0 kV/cm and specific energy input was varied between 0.3 and 6.0 kJ/kg (treatment time 2.0-28.6 ms). Additionally, the impact of different pre-freezing temperatures (- 4 and - 40 degrees C) on the final product quality was described. Investigations showed that due to PEF treatment a significant reduction of the shrinkage phenomena for both bell peppers and strawberries was detected compared to untreated samples with 30% and 50% lower volume losses, respectively. The rehydration capacity of PEF pre-treated freeze-dried samples increased for both matrices up to 50%. Furthermore, the mechanical properties of the final product were improved for both matrices with a significant firmness reduction up to 60%. The results of this study suggest that PEF can be an effective pretreatment with low energy requirements to improve the quality of freeze-dried fruits and vegetables.

The objective of this work was to optimize pulsed electric field (PEF) or ohmic heating (OH) application for carrot and apple mashes treatment at different preheating temperatures (40, 60 or 80 °C). The effect of tissue disintegration on the properties of recovered juices was quantified, taking into account the colour change, the antioxidant activity and the enzyme activity of peroxidase (POD) in both carrot and apple juice and polyphenol oxidase (PPO) in apple juice. Lower ΔE and an increase of the antioxidant activity were obtained for juice samples treated with temperature at 80 °C with or without PEF and OH pretreatment compared with those of untreated samples. The inactivation by 90% for POD and PPO was achieved when a temperature of 80 °C was applied for both carrot and apple mash. A better retention of plant secondary metabolites from carrot and apple mashes could be achieved by additional PEF or OH application. Obtained results are the basis for the development of targeted processing concepts considering the release, inactivation and retention of ingredients.

Gluten-free (GF) batters usually present several technological challenges that limit the performance during conventional baking and the resulting product quality. Due to the volumetric heating principle and faster heating rates, ohmic heating (OH) may be advantageous compared with conventional baking. Therefore, the potential of using ohmic heating as a novel approach for gluten-free bread baking was explored. In detail, the effect of different OH process parameters (power input, holding time) on the chemical and functional properties (specific volume, crumb firmness and relative elasticity, pore properties, color, starch gelatinization) and digestibility of breads was investigated. Results showed that GF breads could benefit from the uniform rapid heating during processing, as these breads showed superior functional properties (specific volume, 2.86–3.44 cm 3 /g; relative elasticity, 45.05–56.83%; porosity, 35.17–40.92%) compared with conventional oven-baked GF bread (specific volume, 2.60 cm 3 /g; relative elasticity, 44.23%; porosity, 37.63%). In order to maximize bread expansion and the OH performance, it was found that the OH process could be improved by applying the electrical energy in three descending power steps: first step with high power input (in this study, 2–6 kW for 15 s), followed by 1 kW for 10 s, and 0.3 kW for 1–30 min. In total, ohmic baking only needed a few minutes to obtain a fully expanded GF bread. The determination of pasting properties and starch digestibility demonstrated that these breads were comparable or even superior to GF breads baked in a conventional baking oven.

The aim of this work was to quantify the recovery of juice and bioactive compounds of apple and carrot mashes treated by the electrotechnologies (PEF or OH) at different pre-heating temperatures (40, 60 or 80 degrees C), considering thermal and electric field based cell disintegration. In general, a higher cell disintegration resulting from the applied pre-treatments also resulted in higher juice yield (around 10% increase for carrot and 5% for apple compared to untreated). Regarding the carotenoid content of obtained carrot juices, only the PEF pre-treatment at 20 degrees C resulted in an increased extractability. A release of total polyphenols from apples into the juice increased in all pre-treated samples compared to the control. This study suggests that a combined pre-treatment can further improve the cell disintegration and juice yield and may have the potential to increase the recovery of bioactive compounds depending on the treatment parameters. Industrial relevance: Thermal treatment followed by PEF or conducted by OH can still improve the cell disintegration and yield of juice. Moreover, the combination of thermal and electric field effects may also improve the recovery of bioactive compounds depending on the chosen treatment conditions. Therefore, the combined treatments show high potentiality for the application at industrial level to improve the release of the juice and at the same time to obtain novel products with high quality.

The application of pulsed electric fields in industrial scale potato processing was investigated regarding its impact on process performance and product quality. The PEF induced cell disintegration was measured by impedance analysis and texture softening was analyzed by cutting force measurements. Softening of the tissue was found to improve the cutting behavior leading to a smoother cutting surface and up to 80% less feathering. Thereby, starch loss was reduced and a significant reduction of fat uptake from 7.5 to 6.8% was found. The breaking loss decreased significantly from 11.0 to 6.0% regardless of the applied energy input (0.2-1.0 kJ/kg), due to improved elastic properties of the potato sticks. No effect was detectable on the peeling behavior of potato and on Theological characteristics of processing by-products such as puree, although the lump formation in puree produced from PEF pretreated potato increased. Overall, PEF was shown to deliver similar and higher quality improvements conventionally achieved by applying thermal preheating at much lower energy consumption. (C) 2018 Elsevier Ltd. All rights reserved.