Extraction and formulation of anthocyanin-concentrates from grape residues

The interest in natural food colorants shows an increasing tendency due to the strictening rules and consumers' concerns over synthetic additives. One of natural pigments with high potential are anthocyanins, which are providing colours from yellow to blue in berries, flowers and vegetables. However the use of anthocyanins as food colorants is still limited because of their relatively low stability during processing, formulation and storage. In this work extraction of anthocyanins from grape marc was investigated with different concentrations of acetone (50 wt%, 70 wt% and 100 wt%) at 20 °C and at 60 °C temperatures. Pilot-scale extraction of grape marc was performed upon the results obtained from laboratory scale experiments. High-pressure concentrated powder form (CPF) technique was applied in order to formulate the obtained extracts in powderous form. Carrier materials, such as starch and silica were tested. Colorimetric properties (lightness, chroma and hue angle) of powderous products were measured and compared with synthetic colorants. Colour stability was monitored during storage at different conditions (light/dark and ambient temperature/refrigerator). The results were compared with the non-formulated extracts, which were stored at same conditions. Product formulation with CPF improved the colour stability of anthocyanin extracts, while for the non-formulated extracts degradation of colour rapidly occurred. The results show that formulated anthocyanin extracts have potential use as natural colorants. However, the major difference compared to synthetic colorants is still in the saturation of the colour.