Global_Ethics

The anthocyanins are common plant pigments. They are water-soluble with some or all of the sugar groups removed. The colors of the charged anthocyanin pigments are dependent on the pH of the intracellular medium containing these pigments. The betalains are subdivided into two structural groups: the red-violet betacyanins and the yellow betaxanthins.Beetroot contains a complex mixture of betalain pigments. However, the characteristic purple-red-violet colour of beetroot is mainly derived from a betacyanin pigment called betanin. After betanin, the yellow betaxanthin pigments vulgaxanthin-I and vulgaxanthin-II are the next most significant in beetroot. Mario Piattelli and colleagues, working in Naples, first described these pigments in beetroot in the 1960s. They found at least six betaxanthins in the cultivar they studied (Piatta d’Egitto), all present in minute quantities. The characteristic root colouration of beetroot cultivars is due to variations in levels of different betalain pigments, especially the relative concentrations of betanin and the yellow betaxanthin pigments. The color of betanin depends on pH; between 4-5 it is bright bluish-red, becoming blue-violet as the pH increases, and hydrolyzing at alkaline pH to yellow-brown color. When the beet root is cut, cells are sliced open and the pigment spill out, however, if the plasma membrane is altered, more subtly leakage of betacyanin is induced. Betacyanin leakage from beet root cells was found to increase with decreasing pH of its surrounding medium. The lower the pH, the greater the effect is as it denatures the proteins in the membranes causing leakage of red pigments.