Optimization of Aqueous Extraction of Anthocyanins from Hibiscus sabdariffa L. Calyces for Food Application

Abstract

Aqueous extracts of Hibiscus sabdariffa calyces are worldwide used for the production of several products such as polyphenolic-antioxidant containing beverages. However, optima conditions for extraction of polyphenolics such as anthocyanins from this plant species were unknown. For this, the influence of particle size and calyx/water ratio on the anthocyanins extraction and biochemical composition during extraction were investigated using bright red and dark red Hibiscus sabdariffa calyces.Results showed that the pH of the bright red calyces was 2.24 ± 0.01 corresponding to 12.66 ± 0.15 g/100g dry weight (DW) titratable acidity equivalent of malic acid. The pH of the dark red calyces was 2.15 ± 0.01 corresponding to 15.44 ± 0.15 g/100g DW titratable acidity equivalent malic acid. Total sugars content was 3.24±0.04 and 3.13±0.06 g/100g DW for bright red and dark red, respectively. Proteins content ranged from 4.56 ± 0.04 to 6.96 ± 0.17 g/100g DW. The level of the total phenols ranged from 3.82 ± 0.33 to 5.22 ± 0.08 g/100g DW. Average anthocyanins content was 2.61 ± 0.11 and 2.98 ± 0.02 g/100g DW for dark red and bright red calyces, respectively. Calyces were found to show an antioxidant capacity of up to 300 µmolTrolox equivalent/100g. For all calyx/water ratios, the anthocyanins content increased with extraction time till 60 min and remained almost stable thereafter.The optimization of the aqueous extraction was obtained at the ratio 1/10 (calyx/water) for the production of roselle concentrated extract, using calyces size less than 250 µm,at 30°C, for one hour percolation.

Keywords: Hibiscus sabdariffa L, anthocyanins water, calyx/water ratio, particle size, optimization, extraction.