pulsed electric field assisted juice extraction of frozen thawed blueberries

Pulsed electric field is an efficient method for cell membrane permeabilization of food tissues with most research being done on fresh plant cells. Freeze/thawing is also known to be capable of cell membrane permeabilization. In this work, frozen/thawed European blueberry (Vaccinium myrtillus L.) fruits were treated with pulsed electric field in order to further enhance the cell membrane permeabilization and, hence, the quality of blueberry juice during the subsequent pressing process. Blueberries tissues were exposed to 20 μs monopolar square wave pulses of different electric field strength (E = 1–3–5 kV cm-1) and total specific energy input (WT = 1–5–10 kJ kg -1), with their permeabilization being characterized by electrical impedance measurements and cell disintegration index (Zp). The juice, obtained after pressing (1.32 bar), was characterized for total polyphenols, anthocyanins content and antioxidant activity. The cell disintegration index (Zp) significantly (p < 0.05) increased from 0.2 up to 0.6 with increasing pulsed electric field treatment intensity (E and WT). As a results, in comparison with control, pulsed electric field treatment induced a slightly higher release of polyphenols (up to +8.0%) and anthocyanins (up to +8.3%), thus improving the antioxidant activity of the juice (up to +16.7%). In conclusion, frozen/thawed blueberries could be pulsed electric field treated in order to further increase juice quality

Improved extractability of carotenoids from tomato peels as side benefits of PEF treatment of tomato fruit for more energy-efficient steam-assisted peeling

Abstract 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 pre-treatment 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 by-products

Implementation of PEF treatment at real-scale tomatoes processing considering LCA methodology as an innovation strategy in the agri-food sector

In Europe, science and innovation are boosting the agri-food sector and, in parallel, are helping to decrease greenhouse gas emissions (GHG) and European dependency on non-renewable resources. Currently, it is well-known that this sector contributes to the consumption of energy and material resources, causing significant environmental impacts that require a complex and comprehensive environmental evaluation in order to manage them effectively. This becomes even more complicated when new technologies are reaching the level of technological maturity needed to be installed in the production lines. To address this scientific challenge, the life cycle assessment (LCA) has been used in this paper to evaluate the potential of pulsed electric fields (PEF) technology at an industrial scale to facilitate the steam peeling of tomato fruits. Considering the thermo-physical peeling stage, the LCA has shown that PEF technology is environmentally friendly, because when PEF technology is applied, all the considered environmental indicators improve between 17% and 20%

Enhancing extraction of food-grade pigments from the microalgae Chlorella Vulgaris through application of ohmic heating

[Excerpt] Introduction: The use of ohmic heating (OH) with the associated non-thermal effects due to the presence of an electrical field and frequency, has been suggested for extraction of compounds from biological matrices. Microalgae are considered as a very valuable source of compounds of interest for food sector (i.e. pigments, lipids, carbohydrates, and proteins) and the selection of extraction technique to recover these compounds is very challenging due to the intrinsic nature of the microalgae cell walls, which limits the mass transfer through it. The main objective of this study is to investigate the effects of OH on the extraction of pigmented solutes from Chlorella vulgaris. [...

Selective extraction of intracellular components from the microalga Chlorella vulgaris by combined pulsed electric field–temperature treatment

Author's accepted version (post-print).Available from 16/12/2017

A comparison of the molecular mechanisms underpinning high-intensity, pulsed polychromatic light and low-intensity UV-C hormesis in tomato fruit

Postharvest treatment of tomato fruit with high-intensity, pulsed polychromatic light (HIPPL) has previously been shown to induce delayed ripening and disease resistance comparable to that of low-intensity UV-C (LIUV). Little, however, is known of the mechanisms underpinning postharvest HIPPL hormesis in tomato fruit. Expression of genes involved in plant hormone biosynthesis, defence, secondary metabolism and ripening were monitored 24 h post treatment (24 HPT), 10 d post treatment (10 DPT) and 12 h post inoculation with Botrytis cinerea (12 HPI). All genes monitored were constitutively expressed and changes in expression profiles following treatment were highly similar for both HIPPL and LIUV treatments. Expression of pathogenesis-related proteins P4, β-1,3,-Glucanase and Chitinase 9 and a jasmonate biosynthesis enzyme (OPR3), were significantly upregulated at 10 DPT and 12 HPI. Both treatments significantly downregulated the expression of polygalacturonase and flavonol synthase at 10 DPT and 12 HPI. Ethylene biosynthesis enzyme ACO1 and β-carotene hydroxylase were significantly upregulated at 24 HPT, and phenylalanine ammonia-lyase (PAL) was significantly upregulated at 12 HPI. Both HIPPL and LIUV treatments stimulate defence responses that are mediated by salicylic acid, jasmonic acid and ethylene. This may lead to broad range resistance against both necrotrophic and biotrophic pathogens as well as abiotic stresses and herbivorous pests. Following inoculation with B. cinerea only PAL showed indication of a gene priming response for HIPPL- and LIUV-treated fruit

Electrochemical Reaction in PEF Treatment

Pulsed electric fields (PEF) is an innovative non-thermal technology which has attracted considerable interest in the last decades as a valuable and sustainable alternative to conventional techniques in several processes of food industry involving improvement of mass transfer phenomena, liquid food preservation and targeted structural modifications. The first commercial scale applications have been achieved in potato processing industry and fruit juice preservation. However, the full exploitation of PEF technology in food industry requires that the unavoidable electrochemical and chemical reactions accompanying the flow of electric current through the PEF treatment chamber must be minimized, since it may seriously affect food safety and quality, as well as process efficiency, equipment reliability and cost aspects. The occurrence of these reactions is a very complex phenomena, which is affected by several factors, such as circuit topology of the pulse generator, PEF chamber design and electrode material, PEF electrical parameters, as well as composition and chemical-physical properties of the treated products. This chapter describes in detail the electrochemical behavior of a PEF chamber with specific reference to the phenomena that occur at the electrode-solution interface, and explains the main factors controlling the rate and amount of electrochemical reactions. Finally, the main side effects associated to the occurrence of electrochemical and chemical reactions are described, and strategies to eliminate, or at least reduce, the extent of electrochemical phenomena that cause these undesired effects are also suggested