Giovanna Ferrari | University of Salerno (original) (raw)

Papers by Giovanna Ferrari

FoodBalt .., Apr 27, 2017

Pulsed electric fields (PEF) treatment induces transmembrane potential by means of an externally ... more Pulsed electric fields (PEF) treatment induces transmembrane potential by means of an externally applied electric field of sufficient intensity, which causes an increase in the permeability of a cell membrane. PEF can be applied for plant cell disruption as upstream step to enhance the efficiency of mass transfer in further processing such as hydraulic pressing or extraction. The objective of the study was to evaluate the potential of using PEF technology for the increase of the juice yield and improved extraction of bioactive compounds from sour cherries (Prunus cerasus L.) and their by-products. PEF treatments (1-5 kV cm-1 at 10 kJ kg-1) were applied to cherries before the juice pressing. The by-products (press cake) generated were extracted with aqueous methanol. The samples from PEF pre-treated cherries and their by-products were compared to both untreated (control) samples and samples obtained from freezethawed (PEF untreated) cherries. The highest increase in juice yield by 45% was obtained at PEF intensity of E=3 kV cm-1 , showing similar results to freeze-thawed sample (41%). The application of PEF significantly increased the release of total anthocyanins (48.3-53.3 mg 100 mL-1) and total phenolics (126.6-133.9 mg 100 mL-1) into juice as compared with the control (33.8 and 112.9 mg 100 mL-1 , respectively), whereas juice from freeze-thawed sample exhibited the highest value only for total phenolics content (164.4 mg 100 mL-1). The extracts from by-products obtained after PEF assisted juice pressing of cherries showed significantly higher contents of bioactive compounds and higher antioxidant power as compared with the control extract and the extract of freezethawed sample. Overall, the results of this work demonstrated promising use of PEF technology in sour cherry processing.

Frontiers in Bioengineering and Biotechnology, Sep 4, 2020

The present study aimed to investigate the effect of the main pulsed electric field (PEF) process... more The present study aimed to investigate the effect of the main pulsed electric field (PEF) process parameters on the cell damages of A. platensis microalgae and the extractability of valuable compounds [water-soluble proteins (WSP), C-phycocyanin (C-PC), and carbohydrates (CH)]. Aqueous microalgae suspensions (2%, w/w) were PEF-treated at variable field strength (E = 10, 20, 30 kV/cm), total specific energy (W T = 20, 60, 100 kJ/kg susp), and inlet temperature (25, 35, 45 • C), with either monopolar or bipolar square wave pulses (5 µs of width, delay time between pulses of opposite polarities = 1, 5, 10, 20 µs), prior to extraction with water at room temperature (25 • C) for up to 3 h. High-pressure homogenization (HPH) treatment (P = 150 MPa, 3 passes) was used to achieve complete cell disruption to quantify the total extractable content of target intracellular compounds. Scanning electron microscopy (SEM) and optical microscopy analyses clearly showed that PEF merely electroporated the membranes of algae cell, without damaging the cell structure and forming cell debris. The application of PEF treatment (monopolar pulses, 20 kV/cm and 100 kJ/kg susp) at room temperature significantly enhanced the extraction yield of WSP [17.4% dry weight (DW)], CH (10.1% DW), and C-PC (2.1% DW), in comparison with the untreated samples. Bipolar pulses appeared less effective than monopolar pulses and led to extraction yields dependent on the delay time. Additionally, regardless of pulse polarity, a clear synergistic effect of the combined PEF (20 kV/cm and 100 kJ/kg susp)-temperature (35 • C) treatment was detected, which enabled the extraction of up to 37.4% (w/w) of total WSP, 73.8% of total CH, and 73.7% of total C-PC. Remarkably, the PEF treatment enabled to obtain C-phycocyanin extract with higher purity than that obtained using HPH treatment. The results obtained in this work suggest that the application of PEF combined with mild heating could represent a suitable approach for the efficient recovery of water-soluble compounds microalgal biomass.

Algal Research-Biomass Biofuels and Bioproducts, Jul 1, 2021

In this work, the use of a mechanical pre-treatment such as high-shear homogenization (HSH) in co... more In this work, the use of a mechanical pre-treatment such as high-shear homogenization (HSH) in combination with cell permeabilization by pulsed electric fields (PEF) was proposed to efficiently recover water-soluble proteins (WSP), carbohydrates (CH), and C-phycocyanin (C-PC) from A. platensis suspensions during water extraction. Efficiencies of combined treatment (HSH + PEF) were compared with those of individual HSH and PEF treatments. HSH promoted the breakage of microalgal trichomes, whereas PEF induced only the permeabilization of cell membranes, without affecting cell size and morphology. Combined treatments synergically increased the extractability of WSP and C-PC from A. platensis, as compared with individually applied treatments, while an additive effect was detected in the recovery of CH. The synergistic effect of HSH + PEF allowed reducing the specific energy requirement for protein recovery to lower values than for individual treatments or full cell disruption techniques, such as high-pressure homogenization (HPH).

Zemdirbyste-agriculture, Feb 15, 2016

Pulsed electric field (PEF) is a non thermal treatment, which could be employed for plant tissue ... more Pulsed electric field (PEF) is a non thermal treatment, which could be employed for plant tissue disintegration which leads to increased juice yield and enhanced extraction of bioactive compounds. Since 97% of red raspberries (Rubus idaeus L.) are sold processed into juices or other products, it is important to increase juice yield and bioactive compounds extraction. This study investigated the effect of PEF pretreatment on red raspberries processing. After PEF pretreatment and mechanical pressing (1.32 bar for 6 min) the juice recovery from raspberries increased in the range of 9-25%. Compared to the untreated sample, press cake extracts contained significantly higher amounts of total phenolics (up to 22%), total anthocyanins (up to 26%) and higher ferric reducing antioxidant power (FRAP) (up to 24%). Mild PEF pretreatment (1 kV cm-1 electric field strength and 6 kJ kg-1 total specific energy) was sufficient to achieve higher raspberry juice recovery and to enhance extraction of bioactive compounds from raspberry press cake left after the juice pressing. PEF pretreatment of red raspberries is a promising technique to improve the efficiency of industrial processing of raspberries.

Journal of Food Engineering, Sep 1, 2018

The combination of steam blanching (SB) with Pulsed Electric Fields (PEF) treatments of whole tom... more The combination of steam blanching (SB) with Pulsed Electric Fields (PEF) treatments of whole tomatoes, in addition to reducing the energy required for tomato peeling, can significantly contribute to the recovery of carotenoids from the peels. In this work, PEF (0.25-0-75 kV/cm, 1 kJ/kg) and SB (1 min at 50-70°C), as pretreatment prior to hand peeling, were investigated to assess their ability, separately and in combination, to induce the cell permeabilization of tomato peels, and hence to improve the carotenoids extraction in acetone (4 h at 25°C). PEF and SB, by inducing significant damages at the cuticular level, caused the increase of the yield in total carotenoids (up to 188% for PEF and 189% for SB) and antioxidant power (up to 372% for PEF and 305% for SB) with respect to the peels from untreated tomatoes. The application of a combined treatment (PEF+SB) significantly increased the carotenoid content and the antioxidant power of the extracts, with a synergistic effect observed already at 60°C (37.9 mg/100 g fresh weight tomato peels). HPLC analyses revealed that lycopene was the main carotenoid extracted and that neither PEF nor SB caused any selective release or degradation of lycopene. Results obtained from this study demonstrate that the integration of PEF in the processing line of tomato fruits prior to SB contributes to the valorization of tomato processing byproducts.

Algal Research-Biomass Biofuels and Bioproducts, Apr 1, 2018

Pulsed Electric Fields (PEF) and High Pressure Homogenization (HPH) are promising and scalable ce... more Pulsed Electric Fields (PEF) and High Pressure Homogenization (HPH) are promising and scalable cell disruption technologies of microalgae cells. In this work, the permeabilization degree, morphological properties, and extractability of intracellular compounds from microalgae Chlorella vulgaris suspensions (1.2%, w/w) were investigated as a function of PEF treatment at different electric field strengths (10-30 kV/cm) and total specific energy input (20-100 kJ/kg), in comparison with the more disruptive HPH treatment (150 MPa) at different number of passes (nP=1-10). The conductivity and the particle size analyses, as well as the SEM images, clearly showed that PEF induces the permeabilization of the cell membranes in an intensity-dependent manner, without producing any cell debris, whereas HPH treatment causes the total disruption of the algae cells into small fragments. Coherently with the lower permeabilization capability, PEF promoted the selective extraction of carbohydrates (36 %, w/w, of total carbohydrates), and low molecular weight proteins (5.2 %, w/w, of total proteins) with a relatively low energy input (2.9 kWh/kgDW). On the other hand, at the biomass concentration tested in this work, HPH required a significantly higher energy (20.0 kWh/kgDW) to induce the undifferentiated release of all the intracellular content, resulting in a 1.1 and 10.3 fold higher yields than PEF, respectively of carbohydrates and protein. These results suggest that, in a multi-stage biorefinery, PEF could represent a suitable cell disruption method for the selective recovery of small-sized cytoplasmic compounds, while HPH should be placed at the end the cascade of operations allowing the recovery of high molecular weight intracellular components.

Abstract Microalgae are evaluated as a prosperous and sustainable source of natural bioactive com... more Abstract Microalgae are evaluated as a prosperous and sustainable source of natural bioactive compounds with therapeutic properties. They include fatty acids, chlorophylls, carotenoids, phycobiliproteins, polyphenols, and vitamins, which have a commercial relevance for the potential applications as natural additives or active ingredients in food, feed, cosmetic, and pharmaceutical products. Conventional extraction of these high-value compounds from microalgae is traditionally conducted via organic or aqueous solvents following the dry or wet route. However, these methods are time-consuming and require large amounts of solvent, relatively high temperature that may cause loss of valuable compounds, and may lead to low extraction yields and selectivity (purity). In light of these drawbacks, the challenge is the development of more sustainable, environment-friendly extracting technologies enabling high recovery yields and selectivity with reduced operative costs. This chapter provides an overview of the microalgae-derived compounds with potential therapeutic properties and details the most advanced extraction techniques for the future microalgae biorefinery. To this end, the chapter first covers the simple steps of the biorefinery process of microalgae that integrate different technologies for the sustainable recovery of a gamut of valuable compounds with suitable quality and sufficient quantities. Later, the chapter extensively details the conventional and emerging extraction technologies based on the use of electrotechnologies (pulsed electric fields, moderate fields, and high voltage electric discharges), liquid pressurization, supercritical fluids, microwaves, ultrasounds, as well as high-pressure homogenization, highlighting advantages and drawbacks concerning their potential for the future microalgae biorefinery. The general discussion includes the detailed analysis of the extraction efficiency of these technologies, when used alone or in a hurdle or cascade approach, in terms of recovery yield of target biomolecules with antioxidant properties and purity (selectivity) of the extracts.

Food Engineering Reviews, Aug 24, 2020

The application of edible coatings (EC) in combination with pulsed light (PL) treatments represen... more The application of edible coatings (EC) in combination with pulsed light (PL) treatments represents an emerging approach for extending the shelf life of highly perishable but high value-added products, such as fresh-cut fruits and vegetables. The surface of these products would benefit from the protective effects of ECs and the PL decontamination capability. This review describes in detail the fundamentals of both EC and PL, focusing on the food engineering principles in the formulation and application of EC and the delivery of efficient PL treatments and the technological aspects related to the food characterization following these treatments and discussing the implementation of the two technologies, individually or in combination. The advantages of the combination of EC and PL are extensively discussed emphasizing the potential benefits that may be derived from their combination when preserving perishable foods. The downsides of combining EC and PL are also presented, with specific reference to the potential EC degradation when exposed to PL treatments and the screening effect of PL transmittance through the coating layer. Finally, the potential applications of the combined treatments to food products are highlighted, comparatively presenting the treatment conditions and the product shelf-life improvement.

Chemical engineering transactions, Jul 1, 2021

Edible coatings (ECs) have attracted increasing attention in the last years as a simple yet effec... more Edible coatings (ECs) have attracted increasing attention in the last years as a simple yet effective approach to increase the storability of perishable foods, such as fresh or fresh-cut fruits and vegetables, contributing to maintaining their quality by reducing respiration rate and water loss. The incorporation of antimicrobial agents, such as essential oils, was reported to add also antimicrobial properties to the coatings, through the controlled release of the antimicrobial compounds on the food surface, contributing to further reduce microbial growth over extended periods of storage. Pulsed light (PL) treatments have been widely investigated as non-thermal processes for superficial decontamination of food and food-contact surfaces, because of their ability to cause, through a short exposition, a significant reduction in the microbial population. Therefore, the combination of ECs and PL treatments represents a promising hurdle approach in food preservation, for extending the shelf life of fresh products. ECs in combination with optimum PL treatment condition (4 J/cm 2) improved the quality of tomato fruits in terms of reducing the growth of the endogenous flora, as well as of preserving the quality attributes (pH, total soluble solids, and color) over a 15-d storage at room temperature.

PEF treatments of different intensities (Electric field ranging from 0.5 to 5 kV/cm and total spe... more PEF treatments of different intensities (Electric field ranging from 0.5 to 5 kV/cm and total specific Energy from 1 to 20 kJ/kg) were applied during the pressing process to enhance the expression of grape juice of Aglianico and Piedirosso varieties. Preliminary measurements of electrical impedance were used to define the optimal PEF treatment conditions to obtain maximum tissue permeabilization: at the pressure of 1.3 bar, sufficient to obtain a satisfactory juice expression from both varieties, the specific energy for complete tissue permeabilization was 12 kJ/kg for Aglianico grapes, but only 3 kJ/kg for Piedirosso. Juice extraction experiments showed that PEF treatment increased the yield of juice of about 15% for Aglianico in comparison with control, while for Piedirosso a higher increase was observed (+20%), which was comparable to the effect of freeze-thawing. PEF treatment did not affect the content of polyphenols in Aglianico juices, while it increased the content of more than 30% in juice obtained from Piedirosso. Remarkably, the antioxidant activity, measured by DPPH method, on PEF-treated samples was always significantly higher (up to 6-folds higher) than in untreated samples for both Aglianico and Piedirosso juices

Over the last decades, there has been an increasing demand by consumers for fresh and minimally p... more Over the last decades, there has been an increasing demand by consumers for fresh and minimally processed food products capable of satisfying their high nutritional and sensorial requirements. This has subsequently promoted the development of alternative novel technologies for food preservation. These include high hydrostatic pressure technology (HHP), high pressure homogenization (HPH) and pulsed electric field technology (PEF) which have attracted the attention of numerous researchers from both the academic and industrial worlds, as highlighted by the increasingly large number of scientific publications dealing with the potential applications of novel technologies to either preserve or improve food quality. HPH and HHP processes consist of either the direct or indirect pressurization of foods up to a very high pressure level (HHP can be also used to process solid foods), while very short electric pulses of high intensity are used to treat food products placed between two electrodes in PEF processing. While HHP processes are already being used for several commercial applications, HPH and PEF processed foods are still not available on the market. This is principally due to a delay in the regulatory approval process as well as the lack of a reliable mathematical model capable of predicting microbial inactivation under different processing conditions and accounting for the role played on inactivation by the physical and chemical characteristics of foods. This chapter summarizes the latest experimental results obtained in the processing of liquids as well as semi-solid and solid foods. It not only discusses the advantages deriving from the use of the innovative technologies but also defines the criteria adopted for the selection of the technology as well as the design of the processing cycles, with particular attention being given to the impact of each technology on both the sensorial (colour, aroma, taste) and nutritional properties. Particular consideration is given to the effect of novel technologies on the content of nutraceutical compounds, which are generally degraded when using conventional thermal technologies.Microbial stability is also considered in order to ensure the safety of the processed products. Finally, the residual activity of some enzymes, such as polyphenoloxidase (PPO), which causes the degradation of the nutraceutical compounds, reducing the shelf-life of the processed products, is also taken into account as an additional parameter for the optimization of the processing conditions

Foods

The tomato processing industry can be considered one of the most widespread food manufacturing in... more The tomato processing industry can be considered one of the most widespread food manufacturing industries all over the world, annually generating considerable quantities of residue and determining disposal issues associated not only with the wasting of invaluable resources but also with the rise of significant environmental burdens. In this regard, previous studies have widely ascertained that tomato by-products are still rich in valuable compounds, which, once recovered, could be utilized in different industrial sectors. Currently, conventional solvent extraction is the most widely used method for the recovery of these compounds from tomato pomace. Nevertheless, several well-known drawbacks derive from this process, including the use of large quantities of solvents and the difficulties of utilizing the residual biomass. To overcome these limitations, the recent advances in extraction techniques, including the modification of the process configuration and the use of complementary no...

The aim is to compare the effectiveness of three innovative technologies, the pulsed electric fie... more The aim is to compare the effectiveness of three innovative technologies, the pulsed electric fields (PEF), the high pressure homogenization (HPH) and the high hydrostatic pressure (HHP) processes, for the stabilization of the Annurca apple juice by preserving the nutritional, functional and sensory properties. The juice, inoculated with a known concentration of Saccharomyces cerevisiae cells, has been subjected to PEF, HPH and HHP treatment cycles able to reduce the microbial load of 3 log-cycles at least. The experimental results show that the PEF technology preserves the total content of polyphenols, the HPH technology the natural color of the juice and the HHP technology improves the bioavailability of the vitamins. By evaluating an overall quality score, dependent on six parameters (antioxidant activity, total polyphenol content, vitamin A, vitamin C, color change, polyphenol oxidase inactivation), the HHPtreatment proves to be the technique suitable to preserve the juice overall quality

Chemical engineering transactions, 2017

Effect of PEF Treatment on Extraction of Valuable Compounds from Microalgae C. vulgaris Gianpiero... more Effect of PEF Treatment on Extraction of Valuable Compounds from Microalgae C. vulgaris Gianpiero Pataro, Martina Goettel, Ralf Straessner, Christian Gusbeth, Giovanna Ferrari, Wolfgang Frey a Department of Industrial Engineering, University of Salerno, via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy b Karlsruhe Institute of Technology (KIT), Institute for Pulsed Power and Microwave Technology (IHM), 76344 EggensteinLeopoldshafen, Germany c ProdAlScarl – University of Salerno, via Ponte don Melillo, 84084 Fisciano (SA), Italy gpataro@unisa.it

PEF treatments of different electric field intensity (E=0-7 kV/cm) and total specific energy (WT=... more PEF treatments of different electric field intensity (E=0-7 kV/cm) and total specific energy (WT=0-20 kJ/kg) were applied during the pressing process (0.35-1.65 bar) to enhance the expression of fresh and thawed blueberry juice. Results demonstrate that PEF treatment is able to induce the permeabilization of blueberry tissues. The higher is the intensity of the applied electric field, the lower is the energy required to obtain the desired degree of cell membrane disintegration. The application of a PEF treatment of moderate intensity (E=1 kV/cm, WT=12 kJ/kg) in combination with pressures below 1 bar allows to obtain higher extraction yields (up to 75%) and the production of juices with a higher content of polyphenols and antioxidant activity than those achievable with a conventional pressing process

Antioxidants, 2021

Nowadays, the food industry is heavily involved in searching for green sources of valuable compou... more Nowadays, the food industry is heavily involved in searching for green sources of valuable compounds, to be employed as potential food ingredients, to cater to the evolving consumers’ requirements for health-beneficial food ingredients. In this frame, agri-food by-products represent a low-cost source of natural bioactive compounds, including antioxidants. However, to effectively recover these intracellular compounds, it is necessary to reduce the mass transfer resistances represented by the cellular envelope, within which they are localized, to enhance their extractability. To this purpose, emerging extraction technologies, have been proposed, including Supercritical Fluid Extraction, Microwave-Assisted Extraction, Ultrasound-Assisted Extraction, High-Pressure Homogenization, Pulsed Electric Fields, High Voltage Electrical Discharges. These technologies demonstrated to be a sustainable alternative to conventional extraction, showing the potential to increase the extraction yield, de...

Journal of Food Engineering, 2018

The suspension of micronized agri-food residues, such as tomato peels and spent coffee grounds, a... more The suspension of micronized agri-food residues, such as tomato peels and spent coffee grounds, at 25% vol in peanut oil, results in the formation of a sample-spanning network (capillary suspension) upon the addition of a secondary immiscible fluid, such as water (at 0.17e0.57 vol with respect to the oil), to preferentially wet the particle surface, thus forming capillary bridges. The strength of the capillary bridges, measured through the rheological characterization of the structured oil suspensions, depends on (a) the surface properties of the particles (in both cases prevalently hydrophilic, with the three-phase contact angles < 90), (b) the fraction of added water, and (c) the mean particle size of the residues. In fact, the suspensions prepared with high-pressure homogenized particles (70 MPa, 3 passes) exhibit an apparent yield stress more than one order of magnitude higher than those prepared with coarser, high-shear mixed particles (>100 Pa vs. < 10 Pa). Finally, also the addition of a surfactant to the water phase dramatically affects the formation of the capillary bridges, reducing the interfacial tension at the oil/water interface. These results suggest a potential alternative route to vegetable oil structuring, to develop innovative foods and food ingredients based on low-calorie, health-beneficial agri-food residues, which not only induce the formation of a oleogel structure, but which also replace a fraction of the lipids.