S. Dyankova*, M. Doneva
Institute of Cryobiology and Food Technologies, 53 Cherni Vrah, 1407 Sofia, Bulgaria (Manuscript received 2 November 2015; accepted for publication 19 January 2016)
Abstract. Natural pigments (and especially those of anthocyanins) are a valuable source of bioactive compounds and may be used in the production of new functional food ingredients. Furthermore, their applications in the treatment and prevention of chronic disorders are becoming more and more widespread. In the last few years consumers have focused their attention on the natural biologically active compounds as functional food ingredients, and therefore, it may be assumed that natural colorants are an alternative source of synthetic additives. The aim of the study was to determine the quantitative content of monomeric anthocyanin pigments in extracts obtained from eight plants. The total content of monomeric anthocyanin pigments was measured by a pH-differential method. The TLC analysis of the pigment extracts from the different plants showed intensive rose, red and violet stripes corresponding to the anthocyanin content. The extracts from chicory and lavender petals were unstable and their color decreased in intensity in 1 month. The analysis of the experimental data shows that the yield of pigment substances depends on a few factors: the type of plant, the preliminary treatment of the plant and the solvent that is used. The largest quantity of extracted substances in the studied plants were isolated from chokeberry (2 195.9 cyd eq mg/l), followed by blackberry (1 466.2 cyd eq mg/l) and one variety of the grapes (1 199.3 cyd eq mg/l). In the case of chokeberry, the pigment content included a large number of anthocyanins and the combination of these components was the reason for the deep red/violet color of the extract. Fresh or frozen materials are the most suitable for extraction of anthocyanin pigments. On the whole, fruit pulp yielded a larger quantity of pigments than juice. Anthocyanins are water-soluble compounds and for that reason their isolation requires water and other polar solvents. Better stabilization of color is obtained by a slight acidification of the solvent with diluted hydrochloric acid. Due to the high content of organic acids in fruits, this effect is attained in a natural way.