Value Addition to Agro-Industrial Waste Through Pectin Extraction: Chemometric Categorization, Density Functional Theory Analysis, Rheology Investigation, Optimization Using Response Surface Methodology and Prospective Applications Through Hydrogel Preparation

The preservation of a healthy, green environment by valorizing the substantial amount of waste generated by the fruit industries is the primary responsibility of the current scientific community. This article addresses the challenges of strategic waste management through cleaner production with the development of the circular economy. Here, the extraction of pectin has been reported from industrial apple pomace using organic acid to enhance pectin yield (26.09%) with better galacturonic acid content (51.03%) under optimal conditions (2 N concentration of citric acid, 90 °C temperature, 110 min reaction time and 450 rpm agitation speed). The central composite design model of response surface methodology was employed for the optimization of the process. The extracted pectin elucidated low methoxyl content (4.43%) and low degree of esterification (34.80%), making itself a favorable choice for food industries. The rheological analysis established its pseudoplastic flow behavior. The Principal Component Analysis was applied to the FTIR spectra to categorize the extracted pectin based on the degree of methyl esterification. Density Functional Theory analyses of polymeric pectin compounds were carried out to determine the effect of the degree of polymerization and methylation on pectin gelation. Nuclear Magnetic Resonance analysis confirmed its chemical structural similarity with that of the commercial low methoxyl pectin. Extracted pectin/nanocellulose-based hydrogel was successfully developed using this improvised low methoxyl pectin, for the potential versatile application in biomedical and other pharmaceutical fields. This will be a ground-breaking concept for the circular economy via generating profit from such horticultural wastes. [ABSTRACT FROM AUTHOR]