Effect of drying technique and particle size of bilberry press cake on the extraction efficiency of anthocyanins by pressurized carbon dioxide extraction

- Pre-treatments can improve the efficiency of carbon dioxide extraction.
- Drying technique and particle size influence the anthocyanin extraction.
- More efficient anthocyanin extraction with small size fractions (<710 μm).
- Large size fraction (>710 μm) showed higher anthocyanin content.

To improve the extraction efficiency of anthocyanins from bilberry press cake using pressurized carbon dioxide, the combined effect of drying technique and bilberry press cake particle size was assessed. Pressurized carbon dioxide using ethanol as co-solvent was compared with a simple and efficient solvent extraction using methanol. The press cake with large (>710 μm) size particles had a higher anthocyanins content (84 g/kg dry matter to 87 g/kg dry matter) than did the small (<710 μm) size particles (60 g/kg dry matter to 65 g/kg dry matter). Although, the large size particles contained more anthocyanins, more efficient anthocyanins extraction using pressurized carbon dioxide extraction was obtained with the small than the large size particles. The press cake dried by freeze-drying generated a powder with smaller particles and lower bulk density than either the microwave-assisted hot-air-dried or hot-air-dried powders. In comparison to methanol extraction, the most efficient anthocyanins extraction was obtained from the freeze-dried small size particles. This work showed that there is a potential to improve the extraction efficiency of anthocyanins extracted by pressurized carbon dioxide by selecting appropriate drying technology and particle size distribution of the press cake.