Green extraction of pectin from Citrus limetta peels using organic acid and its characterization

The approach of converting waste to wealth has become a crucial topic and intense research has been ongoing globally for their proper management and utilization. With an aim to follow up this concept, this study is aimed to valorize Citrus limetta peels by extracting pectin using green organic acid. A Box-Behnken experimental design was used to optimize the extraction process and study the effect of process parameters, i.e., temperature (70–100 °C), extraction time (30–120 min), pH (1–2.5), and liquid:solid ratio (10–40 v/w) on the yield of pectin. The maximum pectin yield of 22.03 ± 0.13% was obtained at optimum extraction conditions of 90 °C temperature, 95-min time, 1.8 pH, and 30 v/w LSR which was observed to be in close agreement to the predicted value of 22.7%. Furthermore, the pectin extracted under optimal conditions was low methoxy pectin with a degree of esterification of 45.62 ± 0.64% and methoxyl content of 5.45 ± 0.04%. The structural properties of pectin were characterized using analytical techniques including X-ray diffraction and Fourier transform infrared spectroscopy. The morphological analysis of peel powder before and after pectin extraction examined using scanning electron microscope indicated that the peel structure after extraction treatment was damaged and disrupted. Besides, the emulsifying activity, emulsifying stability, water holding, and oil holding capacities of extracted pectin were evaluated to determine its potential to be considered as a natural food additive. The results suggested that C. limetta peels have a great potential to be used as a novel low-cost source for the pectin extraction having good properties.