Applications of Pulsed Electric Field Treatments for the Enhancement of Mass Transfer from Vegetable Tissue

Abstract

In the last decades, several non-thermal technologies have been proposed as alternative to the traditional ones to improve the competitiveness of the food industry. The key to success was identified in offering to food industries the opportunity to improve food quality, to introduce new foods in the market, and to optimize the processing procedures while reducing energy costs. Pulsed electric fields (PEF) showed the potential to be one of the most promising novel technologies to reach these objectives.\ud The application of PEF as a pretreatment of permeabilization of vegetable and animal tissue to enhance the efficiency of mass transfer of water or of valuable compounds from biological matrices demonstrated its efficiency in drying, extraction, and diffusion processes. \ud This article reviews the basic mechanisms of electroporation of plant tissues, discusses the methods of detection of electrically\ud induced cell damage, and analyses the influence of process parameters on the efficiency of the treatment.\ud Furthermore, this article focuses on the applications of PEF, its advantages, and energy costs in different fields of food processing, such as juice expression, drying, and extraction, with special emphasis on the relevance of PEF to the winemaking industry

Application of pulsed electric field in the production of juice and extraction of bioactive compounds from blueberry fruits and their by-products

“…It has previously been reported that PEF treatment also improves the antioxidant activity of the wine obtained after pressing PEF pre-treated grapes by 20 % (Donsi et al 2010a). In addition, an investigation of apple juice extracts obtained after pressing PEF pre-treated cut or whole apples revealed an increase in antioxidant activity in the range 30-50 % compared to the control extraction (Grimi et al 2011).…”

“…According to Jaeger et al (2012), high intensity treatment may cause softening of the plant tissues to an extent that is unfavourable for de-juicing i.e., causes the compaction and closing of the capillaries in the press cake. The application of PEF in combination with mechanical juice expression by pressing was demonstrated to be effective for improving juice yield from different plant-based materials (Donsi et al 2010a). The reported improvement of the juice yields varies widely, most likely due to different intrinsic characteristics of the tissues and process conditions employed in different studies (degree of particles fragmentation, PEF parameters and compression pressure) (Jaeger et al 2012).…”

“…The determination of Z p is based on a given chamber geometry and on the frequency dependence of the absolute value (|Z|) of the electrical complex impedance of intact and permeabilized plant tissue (Donsi et al 2010a;Pataro et al 2011). Therefore, for the Z p determinations, measurements of electrical complex impedance in frequency sweep were carried out by loading 10 g of untreated or PEF-treated blueberries into a test vessel, which consisted of two parallel plate cylindrical electrodes (3 cm in diameter) separated by a polycarbonate tube.…”

“…The electrodes were connected to an impedance analyzer (Solartron 1260, UK), which was working in the frequency range of 10 3 -10 7 Hz. For each PEF treatment condition investigated, a Z p value was calculated on the basis of the measurement of the absolute value of complex impedance of untreated (Z untr ) and PEF-treated tissue (Z tr ) in the low (1 kHz) and high (10 MHz) frequency ranges (Donsi et al 2010a;Pataro et al 2011).…”

“…Pulsed Electric Fields (PEF) treatment has been shown to be promising as a milder and more efficient alternative to conventional cell disintegration techniques (Donsi et al 2010a). The exposure of plant tissue to an electric field of moderate intensity (0.5-10 kV/cm) and relatively low energy (1-10 kJ/kg), applied in the form of repetitive very short voltage pulses (typically from few μs up to 1 ms), induces a permeability of cell membranes that facilitates the release of juice and valuable compounds from the inner parts of the cells.…”