Concentration of anthocyanins by the membrane filtration

Nowadays the use of synthetic dyes in the food industry is popular. As these compounds can cause the development of various diseases, including the cancer or heart disease, it is a pressure on the technologies of recovery of natural dies from the natural resources (fruits, vegetables, etc.). One of the valuable natural dyes are anthocyanins, which are present in the aronia fruits available in abundant amounts in Poland. In this work the investigations on the concentration of anthocyanins by nanofiltration have been presented. The aronia solutions containing Na2SO3 – one of the most efficient extractants of anthocyanins – have been used. In order to determine its influence on the retention of anthocyanins, the filtration of aronia solution with and without Na2SO4 has been also performed. The retentions of anthocyanins, sodium ions and ionic species have been investigated. It has been found that in the presence of sodium sulfate(IV) anthocyanins are almost completely rejected (>99%). In the case of pure solution or containing sulfate(VI) the retention is lower (91–95%). Thus, sodium sulfate(IV) is not only a good extractant and preserve but also its presence highly increases the efficiency of the filtration process.