Removal of off-flavours from radish (Raphanus sativus L.) anthocyanin-rich pigments using chitosan and its mechanism(s)

Abstract

In this paper, we examined the role of chitosan in the removal of off-flavours from radish anthocyanin-rich pigments and studied the mechanisms of the process. Four radish glucosinolates (glucoraphenin, dehydroerucin, glucobrassicin, and glucoerucin) were identified by LC-MSn from root extracts and dehydroerucin was found to be the major glucosinolate in red radish roots. Application of chitosan with 76%, 83% or 89% deacetylation in radish extracts attributed to 26%, 35% or 43% adsorption rate for glucosinolates, and 28%, 26% or 22% for anthocyanins, respectively. HS-SPME/GC-MS analysis demonstrated that the concentration of volatile compounds decreased by 70%, resulting in the loss of odorous compounds. The changes in chitosan spectra before/after adsorption and after desorption at 1590 and 3360cm(-1) and at broad bands from 2600 to 2000cm(-1) suggest that the dominant adsorption mechanisms of glucosinolates on chitosan may be electrostatic attractions, including hydrogen bonds and charge neutralisation.

Keywords: Adsorption mechanism; Anthocyanin; Chitosan; Glucosinolate; Radish.