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DC Electrical Field Effects on Plant Tissues and Gels

  • Amos Nussinovitch
  • Ronit Zvitov
Chapter
Part of the Food Engineering Series book series (FSES)

Abstract

Gels (intermediate between a solid and a liquid) have similarities to both animal and vegetative materials. Most food products are solids composed of 50–90% water, and they can be regarded in many ways as multicomponent gels. Moreover, the cellular structure of fruits and vegetables can be considered a “foam” with a closed-cell geometry, filled with gel. Gels are omnipresent, and as such gel electrification seems to be a necessary step in studying the effects of electrical fields in biology and life. Early studies described the collapse of polyacrylamide gels and the shrinkage of ionic gel beads near the phase-transition point under DC and AC excitations. The similarity between food gels (i.e., alginate, agar, agarose, and gellan) and vegetative materials (cut pieces of potato, sweet potato, kohlrabi, radish, and pear) is reflected in their similar behavior under application of a low DC electrical field (nonthermal effect). Both moieties’ samples shrink under such a field. Surface changes in the shrunken sample, mineral diffusion, changes in the treated specimens’ mechanical properties, and local changes in sample pH have also been observed. In potato, inhibition of browning and reduction in polyphenol oxidase activity are detected. Similar to gels, pores are produced in the vegetative tissue (from the anode side), promoting slow release of cell components. Electrification of vegetative tissues in fluid results in induced extraction of soluble solids, pigments, and minerals with almost no alteration of those tissues’ gross textural properties. It is therefore possible to simultaneously obtain the desired ingredients and utilize the tissue that is left for further applications, such as pieces to be included in jams or soups, or for individual quick-frozen processes. The electrical treatment displays advantages over ingredient extraction performed by freezing the tissue. Electrification of leaves results in stomatal opening on both sides of the leaf lamina (from both anode and cathode sides), as compared to the closed stomata of the untreated tissues. Possible implications of this stomatal opening could be facilitating water loss from the tissue to enhance drying processes and perhaps ethylene production

and involvement in the ripening process of fruits. Electrification of vegetative and animal materials, gels in particular, by low-intensity DC electrification could be of interest in many future biotechnological, medicinal, food, and agricultural applications.

Keywords

Pulse Electrical Field Stomatal Opening Electrical Treatment Pulse Electrical Field Treatment Enzymatic Browning 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  1. 1.The Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality SciencesInstitute of Biochemistry, Food Science and Human NutritionRehovot 76100Israel

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