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Green Extraction of Pectin from Lime Peel: Modeling and Optimization Using Response Surface Methodology | ||
| تحقیقات علوم چوب و کاغذ ایران | ||
| Articles in Press, Accepted Manuscript, Available Online from 14 December 2025 | ||
| Document Type: Research Paper | ||
| DOI: 10.22092/ijwpr.2025.371455.1820 | ||
| Authors | ||
| Seyedeh Motahareh Mohseni Shektaii1; Maryam Ghorbani Kokandeh2; Ghasem Asadpur2 | ||
| 1PhD student, Cellulosic Industry, Department of Wood and Cellulosic Products Engineering, Sari Agricultural Sciences and Natural Resources University, Mazandaran, Iran | ||
| 2Department of Wood and Cellulosic Products Engineering, Sari Agricultural Sciences and Natural Resources University, Mazandaran, Iran | ||
| Abstract | ||
| Abstract Background and objectives: Pectin is a multifunctional polysaccharide widely used in the food, pharmaceutical, and packaging industries. Owing to its valuable functional properties, global demand for pectin exceeds 30,000 tons per year, with an annual market growth of approximately 4–5%. Lime peel (Citrus aurantifolia), particularly its inner white layer (albedo), is rich in pectin and represents an economical and sustainable raw material for pectin production. Utilizing this agro-industrial by-product not only provides added economic value but also contributes to reducing the environmental impacts associated with waste disposal. Conventional pectin extraction methods rely on mineral acids, which, despite ensuring high extraction yields, are associated with elevated production costs and environmental concerns. In contrast, organic acids such as citric acid function as green solvents, providing desirable yields while minimizing adverse environmental effects. Accordingly, the present study aimed to optimize acid extraction of pectin from lime peel to achieve maximum yield and desirable quality characteristics, including high purity and adjustable degree of methoxylation. Methodology: Lime albedo was separated from fresh fruit, washed, chopped, and dried at 50 °C to a constant weight, then ground and passed through a 20-mesh sieve. For acid extraction, 10 g of albedo powder was mixed with an aqueous citric acid solution at a fixed liquid-to-solid ratio of 30:1 (v/w) under three pH levels (1, 2, and 3). The resulting suspension was subjected to extraction at temperatures of 65, 80, and 95 °C and for extraction times of 30, 60, and 90 minutes. After centrifugation, pectin was precipitated using absolute ethanol, washed with 96% ethanol, dried at 40 °C, and subsequently powdered. A Box–Behnken experimental design was employed with three independent variables (temperature, time, and pH) at three levels, comprising 15 experimental runs. Extraction yield was calculated gravimetrically; galacturonic acid content (GalA) was determined by a colorimetric method using the m-hydroxydiphenyl reagent with absorbance measured at 520 nm; and degree of esterification (DE) was quantified via a two-step titration method (neutralization and saponification). Data were fitted to a second-order polynomial model using Design Expert version 13, and the optimal model was selected based on analysis of variance (ANOVA), coefficient of determination (R²), adjusted R², and lack-of-fit tests. Results: The pectin extraction yield was significantly influenced by the processing conditions and varied between 8.21% and 53.8%. The highest yield was obtained at 80 °C, 90 minutes, and pH 1, whereas the lowest yield occurred at pH 3 under lower temperature conditions. The degree of esterification (DE) also showed a clear dependency on extraction parameters; the highest DE value (61.11%) was achieved under milder conditions (80 °C, 30 minutes, pH 3), indicating the production of high-methoxyl pectin. In contrast, more severe extraction conditions—such as pH 1 combined with prolonged extraction time—led to a marked reduction in DE to approximately 9.13%, resulting in low-methoxyl pectin. Galacturonic acid content was similarly affected by extraction severity; the highest purity (87.83%) was observed at pH 3, 30 minutes, and 80 °C, while significantly lower purity values were recorded under highly acidic conditions. The regression models developed for yield, DE, and GalA exhibited excellent statistical performance, with coefficients of determination (R²) exceeding 0.98, confirming the high accuracy and predictive capability of the models in describing the extraction system. Conclusion: The findings of this study confirm the effectiveness of citric acid as a green and environmentally friendly solvent for extracting pectin from lime peel. Under optimized conditions, pectin with high yield, high purity, and an adjustable degree of esterification was successfully obtained. The application of response surface methodology enabled precise modeling of the extraction process, and the close agreement between predicted and experimental values demonstrated the strong validity and reliability of the developed model.Given its high purity and tunable methoxyl content, the extracted pectin is suitable for a wide range of applications in the food, pharmaceutical, and bio-based packaging industries. Utilizing lime peel - an abundant by-product of the lime juice industry - as a raw material not only provides a valuable source for pectin production but also contributes to sustainable development, agricultural waste management, and the reduction of environmental impacts. This approach offers an effective strategy for converting plant-based waste materials into value-added products within related industries. | ||
| Keywords | ||
| Keywords: Lime; Albedo; Citric acid; Pectin; Response surface methodology (RSM); Optimization | ||
| References | ||
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