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Influence of comminution degree on the PEF- assisted extraction of phenolic compounds from artichoke bracts
No full textThe concept of "agri-food wastes valorisation" has become of great importance in the last decades, due to the possibility of extracting valuable bioactive compounds to be potentially used as supplements and nutraceuticals in feed, food, pharmaceutical and cosmetic sectors. Pulsed electric field (PEF)-assisted extraction has showed the potential to improve the efficiency of conventional extraction processes, even thought more investigation is needed including the effects of raw material properties (e.g., size, conductivity, moisture content) on the yield of the extracts.
In this work, the effect of the size of artichoke bracts of circular shape (0.5 - 3 cm in diameter) and of PEF treatment parameters (E = 0.5 - 5 kV/cm; WT = 1 — 20 kJ/kg) on the cellular permeabilisation degree of tissue, as well as on the extractability of phenolic compounds, was investigated. Optimal PEF conditions (3 kV/cm; 5 kJ/kg) were chosen on the basis of impedance measurements and used for the subsequent PEF-assisted extraction tests, which were carried out for 6 h in pure water at room temperature. The obtained extracts were then analyzed in terms of total phenolics content and FRAP antioxidant power. Results showed that the permeabilization effect of cell membranes induced by PEF led to a greater extraction yield of phenolic compounds (+175% on average) with respect to the control samples. Moreover, the smaller the size of artichoke discs, the greater the initial diffusion rate. Coherently, FRAP values of extracts from PEF treated artichoke discs resulted to be higher (+190% on average) than those detected for untreated ones. However, the higher the comminution degree, the lower the percentage increase in the extraction yield from PEF treated samples as compared with the control ones. These results demonstrated the efficacy of PEF in avoiding the need for high comminution degrees of the raw materials, with subsequent reduction in operative costs and a better preservation of antioxidant compounds
The use of PEF technology for improving mass transfer phenomena in traditional unit operations of food industry
No full textSeveral unit operations of the food industry are based on mass transfer phenomena which promote the extraction of a given substance of interest (fruit juices, sugars, colorants, antioxidants, etc.) removing water from foods (drying), or introducing a given substance into the food matrix (osmotic dehydration, salting, or curing). Interestingly, the recovery of valuable compounds (natural colorants or nutraceuticals) from food wastes and by-products, which have been matter of concern by the agri-food industry due to their environmental impact, is gaining increasing interest in the last years. In all these cases it is necessary to improve mass transfer through food tissues by means of the permeabilization of the cell membranes which represents the main factor controlling the mass transfer rate. Pretreatments that modify the permeability of the cell membranes, such as grinding, heating, or enzymatic treatment, may significantly enhance the mass transfer. However, these techniques may require a significant amount of energy and can cause losses of valuable food compounds. Moreover, chemical methods may require the application of unsafe organic solvents, and enzymes. Recently, the interest in electroporation or PEF technology has considerably grown, as it also offers the possibility different milder and more efficient non-thermal alternatives to the traditional processing methods of the food industry requiring the disintegration of cell membranes. The purpose of this work is to give an overwiev of the state of the art of application of PEF for improving mass transfer in the food industry. Finally, the industrial feasibility of PEF technology, its integration in the processing lines and the cost estimation of the treatments required to permeabilize the cell membranes are discusse
PEF assisted green solvent extraction of high–added value compounds from agri-food by-products
No full textThe recovery of valuable compounds (natural colorants or nutraceuticals) from food wastes and by-products, which have been matter of concern by the agri-food industries due to their environmental impact, is gaining increasing interest in recent years. However, traditional extraction methods are generally very time-consuming and require large quantities of solvents in order to achieve sufficiently high extraction yield of target compounds from agri-food products. Moreover, these methods may do not comply with criteria of green chemistry concept, since they may require application of toxic organic solvents for the selective recovery of target compounds. Consequently, demand is increasing for extraction techniques that improve yield, shorten the extraction time and reduce the use of organic solvents. Recently, the interest in Pulsed Electric Fields (PEF) treatment of plant material before extraction with solvent, has considerably grown, due to its ability to induce a selective permeabilization of the cytoplasmatic membranes (electroporation), facilitating the release of intracellular compounds from the plant cells. In this study the efficiency of PEF-assisted extraction of valuable compounds from food by-products derived from the industrial transformation of artichoke (external bracts, stems and leaves) was investigated, as an example of total-use concept of wastes. PEF treatments were carried out at field strengths in the range 0.25 - 5 kV/cm and energy input between 0.25 and 20 kJ/kg. The cell disintegration index (Zp) was used to identify the PEF processing conditions for the pre-treatment of the artichoke wastes before the extraction with water. The optimal PEF processing were defined, and the extraction yield of total phenolic compounds and antioxidant activity was determined. Results showed that, regardless the type of artichoke waste (external bracts, leaf, or stem), the permeabilisation effect induced by the application of PEF pre-treatments led to significantly higher total polyphenols content (+ 300% on average) and antioxidant power (+ 280% on average) of the aqueous extracts, as compared to the untreated samples. HPLC analyses revealed that the most abundant phenolic compound in the extract was chlorogenic acid. In conclusion, it was demonstrated that PEF can allow the green extraction of valuable compounds from artichoke wastes leading to a greater diversity of products and decreasing waste problems
Application of Pulsed Electric Fields technology for improving peeling of tomato fruits
No full textTomato peeling is one of the most critical phase in the industrial transformation of tomato fruits. It generally consists of either a thermophysical treatment (steam blanching +vacuum cooling), or a chemical treatment (adding of caustic soda), which lead to, respectively, a high-energy consumption or a strong environmental impact. The aim of this study was to assess the potential of pulsed electric field (PEF) technology to facilitate the peeling phase of tomato. The effect of PEF treatments of different field strength (E=0.125 — 0.75 kV/cm) and 4 energy input (WT=0.25 — 0.75 kJ/kg), used alone or in combination with steam blanching at different temperatures (50-70°C), on the textural properties (hardness, peel strength) of different Tomato variety (Minitor, Cherry, Taylor, Impact and Dress), was investigated.
Results showed that, regardless the tomato variety, single PEF treatment applied at 25°C in the range of values 0.25-0.5 kV/cm and 0.25-0.50 kJ/kg, significantly affected the textural properties and thus the peelability of tomato fruits. Under these conditions, it was observed a reduction of the peel strengths of, respectively, 47% for Minitor, 55% for Cherry, 69% for Taylor, 62% for Impact, and 41% for Dress variety. No or a slight further improvement was observed when PEF was combined with SB. Consequently, PEF pre-treatment of tomatoes
has the potential to facilitate the peeling of the fruits with considerable reduction of the steam consumption
PEF treatments of different varieties and maturity degrees of apples: effect on juice and polyphenols extraction
No full textThe effects of electrical parameters (field strength E and total specific energy input WT) and of maturity period on juice expression and phenolic compounds present into juices belonging to different cider apple varieties (Marie Menard and Dous Cout Lignée) have been studied. Firstly, an impedance analysis has been performed on different sample geometries (mash and disc) in order to look at the effect of the electrical parameters on the permeabilization degree of tissues. Results coming from this part showed that the disintegration index (Z) is just depending on the energy input, whatever the electric field strenght applied (E = 200 - 800 - 1500 V/cm). After that, apple mash has been PEF treated with constant electric field strenght (E = 800 V/cm) and variable specific energy (Wt = 1-37 kJ/kg) and subsequently pressed for 20 min at 3 bar. Results showed that, whatever the specific energy applied during the PEF treatment and whatever the maturity period, the yield of juice collected after the pressing phase has been kept constant and significatively greater than the untreated samples one: this suggest an optimum condition for pressing experiments at the minimum energy input (W = 1 kJ/kg). PEF assisted pressing tests carried out on common dessert apples ( Golden Delicious) have underlined a dependancy of the juice yield from the electric field strenght applied (E) while once again it was not possible to see any differences among the treated samples for different values of the specific energy: it arises that the permeabilization index Z is not a suitable indicator of the pressing efficiency, being just energy dependent. Phenolic compounds of ”Marie Menard " apple juices didn’t undergo a significative change due to the PEF treatments while it was observed a slight decrease in them for "Dous Cout Lignée” juices, favoured by the PPO enzymatic activity, as the specific energy has increased
Improving the extraction yield of juice and valuable compounds from sweet cherry and their by-products by Pulsed Electric Fields
No full textPulsed Electric Fields (PEF) treatment has recently gained interest as a milder and efficient alternative to conventional cell disintegration techniques of plant cell. In this work the influence of PEF pre-treatment on the extraction yield and antioxidant properties of juice obtained after pressing of sweet cherry (Prunus Avium) fruits of "Duroni Nero" variety and on the recovery of bioactive compounds from cherry by-products (pressed cakes) were investigated and compared to both untreated and freeze-thawed samples. The cellular disintegration index (Zp) of fruit tissue increased progressively with PEF treatment at field strengths of 0.5, 1 and 3 kV/cm and at a fixed total specific energy input of 10 kJ/kg, up to a maximum value of 0.76. PEF (0.5, 1, and 3 kV/cm at 10 kJ/kg) assisted mechanical pressing (1.64 bar for 5 mM) led to significant increase in juice yield (1-40%) with respect to the control, showing similar results than freeze-thawed sample. The juice obtained from PEF pre-treated cherries (E = 1 kV/cm) contained significantly higher amounts of anthocyanins (+85%) and antioxidant power (+28%) with respect to untreated samples, while freeze thawed samples showed the highest value only for the anthocyanins. Further increases of the electric field strength (E = 3 kV/cm) did not lead to additional advantages in quali-quantitative characteristics of the juice. Extracts from electroporated pressed cakes led to the highest increase in anthocyanins (+40%) and antioxidant power ( 40%) for the lowest electric field strength investigated (E = 0,5 kV/cm). The extractability of bioactive compounds from cherries press cake was not significantly increased by further increasing the field strength applied (1 - 3 kV/cm). The results obtained from this study demonstrate the possibility to implement a PEF system into a cherry juice production line to increase yield and quality of juice as well as to valorize the cherry by-product
PEF-assisted green solvent extraction of high-added value compounds from agri-food by-products
No full textExtraction of valuable compounds from biomaterials of microbial, algae or plant origin is a crucial step for the use of these compounds in the food and pharmaceutical industries. In particular, the recovery of valuable compounds (natural colorants or nutraceuticals) from food wastes and by-products, which have been matter of concern by the agri-food industry due to their environmental impact, is gaining increasing interest in recent years. However, traditional extraction methods are generally very time-consuming and require large quantities of solvents in order to achieve sufficiently high extraction yield of target compounds from agri-food products. Moreover, these methods may do not comply with criteria of green chemistry concept, since they may require application of toxic organic solvents for the selective recovery of target compounds. Consequently, demand is increasing for extraction techniques that improve yield, shorten the extraction time and reduce the use of organic solvents.
Recently, the interest in Pulsed Electric Fields (PEF) treatment of plant material before extraction with solvent, has considerably grown, due to its ability to induce a selective permeabilization of the cytoplasmatic membranes (electroporation), facilitating the release of intracellular compounds from the cells.
This manuscript gives an overview of the PEF-assisted solvent extraction, and presents the experimental results on the recovery of antioxidants and pigments (phenolic compounds and anthocyanins) from red fruits and vegetables by-products, which can be used as potential food additives and/or nutraceuticals. The effects of PEF process parameters (field strength, total specific energy input), as well as individual green solvents (water, ethanol) or their mixtures on the extraction yield of the compounds of interest is discussed
Recovery of lycopene from industrial tomato processing wastes by pulsed electric fields
No full textIn this work, the influence of the main PEF parameters (E = 1 - 5 kV/cm; WT = 5 - 10 kJ/kg) as well as of the extracting solvent (acetone, ethyl lactate) on the recovery of lycopene from tomato processing wastes (peels and seeds) derived from the industrial production of peeled tomato, was investigated. Experimental data of lycopene extraction kinetics from untreated and PEF treated samples were mathematically modelled by means of the empirical Peleg's approach. Results revealed that, regardless the extracting solvent, a PEF treatment at 3 kV/cm and at 10 kJ/kg resulted in the highest increase in the lycopene yield (+18%) and of antioxidant power (+21%) as compared to the control samples, with the possibility to drastically accelerate the solid/liquid extraction processes, thus potentially reducing lycopene degradation phenomena. Moreover, acetone showed a higher capability of solubilising lycopene with respect to ethyl lactate, leading to extracts with higher antioxidant power value, for both untreated and PEF treated tomato peels samples. The Peleg's model was able to ensure an accurate fit of the experimental data (R2adj=0.97 - 0.99).
Results obtained from this work have shown the potential of PEF technology to enhance the valorisation of low cost sources of carotenoids, like tomato processing wastes, in order to positively impact on their disposal costs and to grant an additional economic income to tomato processing industry
Extraction improvement of water-soluble compounds from Arthrospira platensis through the combination of high-shear homogenization and pulsed electric fields
Full text linkThe use of a mechanical pre-treatment such as high-shear homogenization (HSH - 20,000 rpm, 96 kJ/kgSUSP) in combination with pulsed electric fields (PEF - 20 kV/cm, 100 kJ/kgSUSP) was proposed to selectively and efficiently recover water-soluble proteins, carbohydrates, and C-phycocyanin from A. platensis suspensions during water extraction (25 °C, 3 h). Efficiencies of combined treatment (HSH + PEF) were compared with those of individual high-shear homogenization and pulsed electric fields treatments. The high-shear homogenization treatment promoted the breakage of microalgal trichomes, whereas pulsed electric fields treatment induced only the permeabilization of cell membranes, without affecting cell size and morphology. Combined treatments synergistically increased the extractability of water-soluble proteins and C-phycocyanin from A. platensis, as compared with individually applied treatments, while an additive effect was detected in the recovery of carbohydrates. The combination of high-shear homogenization and pulsed electric fields treatments in a cascade approach 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)
Pulsed electric fields assisted extraction of carotenoids from tomato by-products
No full textTomato fruit is among the most widely consumed vegetables in the world and represents an important source of many traditional nutrients and a predominant source of several carotenoids. Within the class of carotenoids, lycopene is the most abundant and represents more than 80% of total tomato carotenoids content. Tomato by-products, namely peel and seeds, account for about 10-40% of the millions of tons of tomato fruit processed every year to produce different type of products. This by-product, thus, represents a cheap and reach source of the above mentioned bioactive compounds. They are traditionally recovered by extraction with solvents which is a time consuming process and requires large quantities of solvents. This study was conducted to evaluate the effect of pulsed electric field (PEF) treatment for enhancing carotenoids extraction from tomato by-product resulting from the production of tomato sauce. The process was based on the application of moderate electric fields (1-5 kV/cm) and low total specific energy input (1-20 kJ/kg) to the tomato peels. The cell disintegration index (Zp) was used to identify the PEF processing conditions for the pre-treatment of the tomato peel before the carotenoid extraction. The optimal PEF processing and extraction conditions were defined, and the extraction yield of carotenoids was determined. Results showed that, compared to the untreated sample, significantly higher amounts of total carotenoids, lycopene and antioxidant activity were detected in the extracts from PEFtreatment samples. The antioxidant capacity of the extracts obtained from tomato peel was correlated with the carotenoid concentration. The results of this study indicate that the utilization of PEF technology as pre-treatment of tomato by-products before the carotenoid extraction could add new value to the tomato processing chain, improving economic performance and decreasing waste problems
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