Humic acid formation during subcritical water extraction of food by-products using accelerated solvent extractor

In this study, the effect of extraction temperature (180 and 200 degrees C), static extraction time (15, 30 and 45 min) and sample amount (5 and 10 g) on humic acid formation during subcritical water extraction of food by-products by accelerated solvent extractor was investigated. Subcritical water extraction was carried out with three food by-products as flaxseed meal, lemon peel and mandarin peel at constant pressure of 1500 psi. The highest total humic acids were found as 71.73, 64.52 and 62.91% in the solid residue of flaxseed meal, mandarin peel and lemon peel after subcritical water extraction at 200 degrees C and 15 min, respectively. Besides, the highest free humic acids were determined as 60.62, 52.60 and 50.64% in the;solid residue of flaxseed meal, mandarin peel and lemon peel after subcritical water extraction at 200 degrees C and 15 min, respectively. The study results suggested that accelerated solvent extractor has a great potential as green technology to produce humic acids during subcritical water extraction of food by-products. (C) 2019 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.