Study of an Extraction Process as the Pretreatment Step for Sugar Production from Acid Hydrolysis

Abstract

This work involves the residues of three plant species used in industry: Brazilian ginseng (Pfaffia glomerata), palm (Elaeis guineensis) and annatto (Bixa orellana L.). The studied plant residues come from oil and biocompounds extraction: Soxhlet extraction (SE), Pressurized liquid extraction (PLE) and Supercritical fluid extraction (SFE). The effects of these extraction processes on the structures of plant matrices were observed using scanning electron microscopy (SEM). Plant residues were subjected to acid hydrolysis. The hydrolysis process was conducted using a 0.5 L reactor at atmospheric pressure and the solvent at boiling temperature. Brazilian ginseng was hydrolyzed in hydrochloric acid solution (0.5, 2.5 and 5.0%, v/v) for 60 min. Palm pressed fiber and annatto were hydrolyzed in sulfuric acid solution (1.5 and 3.0%, v/v) for 90 min. Sugars produced by the hydrolysis were quantified and interpreted as Reducing sugars (RS) (g glucose/100 g raw material) and Total reducing sugars (TRS) (g sucrose/100 g raw material) by a spectrophotometric method. The results observed by SEM showed that the extraction treatments modified the vegetable matrix with respect to its structure and component ratio. The acid hydrolysis process of each vegetable matrix showed different reaction kinetics. The availability and source of the sugar polymers and the acid concentration were variables that affected the hydrolysis reaction.