OPTIMIZATION OF MICROWAVE-ASSISTED EXTRACTION OF PECTIN FROM TOMATO POMACE

Nikolina Golub1, Dubravka Vitali Čepo1, Emerik Galić1, Kristina Radić1, Ilija Djekic2, Nada Smigic2
1University of Zagreb Faculty of Pharmacy and biochemistry, Ante Kovačića 1, 10 000 Zagreb, Croatia
2University of Belgrade Faculty of Agriculture, Nemanjina 6, 11080 Beograd,
Serbia

Tomato is one of the most produced vegetables in the world. Its processing into sauce, paste, juice and other food products, creates a substantial amount of waste in the form of tomato pomace, primarily composed of tomato peel, seeds and small amounts of pulp. Despite being rich in bioactive compounds with significant potential for creating value-added products, tomato pomace is typically discarded in landfills or used as livestock feed and fertilizer. One of the valuable functional ingredients that can be extracted from tomato pomace is pectin, a cell wall polysaccharide with galacturonic acid backbone which can be methylesterfied and acetylated. Its functionality depends on molecular size and degree of methoxylation, which may vary depending on the source and extraction conditions. In this research we optimized microwave-assisted extraction (MAE) of pectin from tomato pomace using citric acid as solvent. Response surface methodology using the central composite design was used to model the optimization process. The physico-chemical properties (equivalent mass, methoxyl content, degree of esterification, galacturonic acid content) were determined using titrimetric methods, yield was determined gravimetrically, and the structure was characterized by FTIR spectroscopy. Life Cycle Assessment (LCA) was applied to assess the environmental impact of MAE and conventional water bath extraction (CE). Optimal microwave conditions (12 min/600 W/pH 1) yielded two times more pectin than CE (2 h/85 °C/pH 1.5). Results suggest that MAE can be used as an efficient method for pectin extraction from tomato pomace.