Sustainable Recovery of Anthocyanins and Other Polyphenols from Red Cabbage Byproducts

Abstract

The objective of this work was to develop a sustainable process for the extraction of anthocyanins from red cabbage byproducts using, for the first time, apple vinegar in extractant composition. Our results showed that the mixture 50% (v/v) ethanol-water, acidified with apple vinegar, used in the proportion of 25 g of red cabbage by-products per 100 mL of solvent, was the best solvent for the preparation of an anthocyanin extract with good stability for food applications. The chemical characterization of this extract was performed by FTIR, UV-VIS, HPLC-DAD, and ICP-OES. The stability was evaluated by determining the dynamics of the total polyphenol content (TPC) and the total monomeric anthocyanin pigment content (TAC) during storage. On the basis of the statistical method for analysis of variance (ANOVA), the standard deviation between subsamples and the repeatability standard deviation were determined. The detection limit of the stability test of TPC was 3.68 mg GAE/100 g DW and that of TAC was 0.79 mg Cyd-3-Glu/100 g DW. The red cabbage extract has high TPC and TAC, good stability, and significant application potential. The extracted residues, depleted of anthocyanins and polyphenols with potential allelopathic risks, fulfill the requirements for a fertilizing product and could be used for soil treatment.

Keywords: apple vinegar; food color additives; organic fertilizers; red cabbage byproducts; storage stability; total monomeric anthocyanin pigment content; total polyphenol content.

Figure 1

Chromatogram of red cabbage extract (EtOH50%) with apple vinegar (A) and without apple vinegar (B). Catechin (tr = 6.9 min); Epicatechin (tr = 8.8 min.); Kaempferol (tr = 14.6 min.) and quercetin 3-rutinoside (tr = 11.7 min.), λ = 280 nm.

Figure 2

Chromatogram of extraction solvent: EtOH 50% with apple vinegar λ = 280 nm (red line) and 350 nm (blue line).

Figure 3

FTIR spectrum of the red cabbage extract obtained by the solvent system EtOH 50% + apple vinegar, compared with the FTIR spectra of gallic acid, quercetin 3-rutinoside, and catechin.

Figure 4

Red cabbage extract—total polyphenol content (TPC) and total monomeric anthocyanin content (TAC) results of the short-term stability in the temperature range between 2 °C and 4 °C (n = 12; a = 4); (A)—ANOVA−TPC, EtOH50%−AA1%; (B)—ANOVA−TAC, EtOH50%−AA1%.