One stage hydrothermal treatment: A green strategy for simultaneous extraction of food hydrocolloid and co-products from sweet lime (Citrus Limetta) peels

Abstract

The present study is focused on the potential of one stage hydrothermal (HT) treatment using water as a solvent for the simultaneous extraction of pectin and phenols from sweet lime (Citrus Limetta) peels. The effect of temperature (100–120 °C); time (5–25 min) and liquid to solid ratio (LSR) (10–20) were investigated for optimizing the HT process using response surface methodology. The experiments were designed using the Box-Behnken method. The optimum conditions obtained for the highest yield of pectin (23.8%) and TPC (1.18%) were at 112.2 °C, 17.1 min and LSR 14.3. Deviations between predicted and experimental values were statistically insignificant (p > 0.05). The HT process yielded higher pectin and TPC with a significant reduction in extraction time as compared to the conventional extraction process (CSE) i.e., 22.4 and 0.46% of pectin and TPC in 1.5 and 20 h respectively. The HT extracts were characterized at the optimum processing conditions. The degree of esterification (%) and molecular weight (KDa) obtained for HT extract (71.2 ± 1.0 and 330.9) was close to that of commercial citrus pectin (76.6 ± 0.6 and 423.8). The major flavonoids identified (mg/g dw) in HT extract were kaempferol (0.84), rutin (0.82), quercetin (0.71), ferulic (0.46), caffeic (0.4) and gallic (0.31) acid and found to be higher than CSE. The higher antioxidant activity of HT extract was indicated by lower IC 50 (0.62 mg/mL), higher FRAP (37.3 μM/g dw) and ABTS (119.6 μM TE/g dw) values. These results demonstrate the suitability of HT as a one-step green extraction process for simultaneous recovery of pectin and phenols. • Simultaneous extraction of pectin and phenols using hydrothermal (HT) technique. • Citrus Limetta peel was used as substrate and water as a medium of extraction. • Highest pectin (23.8%) and phenol (1.2%) obtained at 112.2 °C, 17.1min and LSR 14.3 • HT yielded high methoxy pectin with molecular weight closer to commercial pectin. • DPPH, FRAP, and ABTS values indicated higher antioxidant potential of HT extract.