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

The potential of a one-stage hydrothermal (HT) process using water as an extraction medium was investigated for the simultaneous extraction of pectin and phenols from Citrus limetta peels (CLP). A statistical experimental design based on response surface methodology was applied to evaluate the effect of temperature (100-120 ?), time (5-25 min), and liquid-to-solid ratio (10-20 mL/g) on extraction yield and optimize the process. The optimal conditions for the highest extraction yield (23.8% pectin and 1.2% phenol) were obtained at 112.2 ?, 17.1 min, and 14.3 mL/g. Experimental results were well matched with predicted values (p > 0.05). The pectin obtained under optimal HT conditions was evaluated for its physicochemical, structural, and thermal properties and the phenolic extract for its antioxidant potential and individual phenolic. The results indicated that the HT extract was rich in galacturonic acid (70.6 & PLUSMN; 1.3%), high in degree of esterification (71.2 & PLUSMN; 1.0%), and molecular weight (330.9 kDa), and the values were comparable to commercial pectin. Further, spectroscopy analysis (FT-IR and H-1 NMR) confirmed the purity of pectin. Thermo-gravimetric analysis revealed the optimum degradation temperature of HT extract (227.3 ?) to be similar to the commercial pectin (231.3 ?) indicating its thermal stability. The higher antioxidant activity of the phenolic extract was indicated by lower IC50, higher FRAP, and ABTS values. The major flavonoids (mg/g dw) identified were kaempferol (0.84), rutin (0.82), quercetin (0.71), ferulic acid (0.46), caffeic (0.4) and gallic acid (0.31). These results suggested the suitability of HT as a one-step green extraction process for co-extracting pectin and phenols from CLP.

Automated summary

The potential of a one-stage hydrothermal process in using water as an extraction medium for the simultaneous extraction of pectin and phenols from Citrus limetta peels was investigated. The optimal conditions for the highest extraction yield of pectin and phenol were determined. The obtained pectin exhibited comparable physicochemical and thermal properties to commercial pectin. The phenolic extract showed higher antioxidant activity and contained various identified flavonoids. These results suggest the suitability of the hydrothermal process as a green extraction method for co-extracting pectin and phenols from Citrus limetta peels.