PERSPECTIVES OF DEEP EUTECTIC SOLVENTS FOR EXTRACTION OF PECTIN FROM WASTE APPLE POMACE

Abstract

The present study reports the development of the lab-scale procedure for extraction of pectin from the waste industrial apple pomace using deep eutectic solvents (DES) as extraction medium. Compared with conventional extraction solvents, DES have attracted considerable attention due to the fact that they not only are eco-friendly, non-toxic, and biodegradable organic compounds

but also have a low cost, being easy to produce in the own laboratory. The research included a’

screening study that covered extraction using different DES based on choline chloride ([Ch]Cl) as hydrogen bond acceptor (HBA), and organic acids as hydrogen bond donors (HBD). The applied HBA:HBD molar ratio was 1:2. The pectin was extracted by employing solid-liquid (SLE) and ultrasound assisted extraction (UAE). The DES based on [Ch]Cl and lactic acid turned to be most promising in terms of obtained extraction yields, that reached 35% when applying UAE. It has been shown that structure of HBD plays a major role with its hydrophilicity and hydrophobicity influencing the number of established bonds. The HBD with lower amount of carbon molecules and higher number of hydroxyl and carboxylic groups formed DES that are more efficient at extracting pectin. Hidotopy study showed significant influence of water on pectin yield due to more prominent hydrogen interaction established in the system. Depending on the type of DES, the highest yields were obtained at 30-50 wt% of water, while an additional increase in water content resulted in reduced yield. The structural properties of extracted pectin, including esterification degree, was determined using FTIR spectroscopy.