Low DC electrification of gel-plant tissue ‘sandwiches’ facilitates extraction and separation of substances from Beta vulgaris beetroots

Abstract

Low DC electrification (up to 40 V/cm) of a system composed of cylindrical red beet tissue samples sandwiched between agarose, agar or alginate cylindrical layers yielded extraction of pigments and minerals into the gels. Separation of different charged ions was detected in the different gel layers, i.e. cations in the gel near the cathode and anions in the gel near the anode. During the short electrification, the gel layers as well as the beet tissue developed higher pH values near the cathode and lower values near the anode, with a minor temperature elevation of less than 4.5 °C in both the tissue and the gel. As a result of the extraction and separation, the gel layer close to the anode was red and that close to the cathode was yellow. This was demonstrated by higher measured a* values in the gel closer to the anode and higher b* values in the gel near the cathode. The occurrence of yellow and red pigments was presumably not due to the separation between red betanin and yellow vulgaxanthin, but rather to a separation between betanin and its reduced form, as evaluated by spectrophotometric measurements. The stiffer the gel, the lower the amount extracted by the method and the smaller the weight loss of the red beet specimens due to fluid loss. This simple method and apparatus appear to constitute an easy way to extract and separate pigments and minerals from vegetative tissues, mainly for research purposes. The tissue with reduced soluble solids, minerals and pigments can still be utilized in other food applications (for baking, filling, etc.), whereas the ground tissue obtained using the more traditional extraction procedures is of almost no use in food products.