Development and Characterization of a Natural Hydrating Pectin Gel Using Mixed Pectin Extracted from Citrus Fruit Peels and Watermelon Rinds

Lim, Caleb Kai Min (2026) Development and Characterization of a Natural Hydrating Pectin Gel Using Mixed Pectin Extracted from Citrus Fruit Peels and Watermelon Rinds. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Pectin is a vital structural component that can be found in the primary cell walls and the middle lamella of most plants providing firmness and helps hold adjacent plant cells together by acting as the "glue" between adjacent plant cells. Pectin is widely utilized in the food, pharmaceutical, and cosmetics industry for its gelling, thickening, and stabilizing properties. This study aimed to characterize pectin extracted via acid extraction from orange peels powder (OPP) and watermelon rinds powder (WRP) and utilize this natural biopolymer to develop a hydrating pectin gel formulation. In this study, the pectin extracted from orange peels powder (OPP) and watermelon rinds powder (WRP) was characterized by evaluating its equivalent weight, methoxyl content, AUA content, degree of esterification, solubility, moisture content, and antioxidant effect. The highest pectin yield achieved was 20.02 ± 0.23% and 12.07 ± 0.26% from OPP and WRP respectively. Specifically, the pectin derived from OPP showed an equivalent weight of 949.45 ± 10.47mg/mL, 9.53 ± 0.07% methoxyl content, 73.45 ± 0.40% AUA content, and 73.66 ± 0.13% esterification. On the other hand, the pectin derived from WRP showed an equivalent weight of 553.52 ± 3.53mg/mL, 6.78 ± 0.03% methoxyl content, 70.58 ± 0.98% AUA content, and 54.55 ± 0.31% esterification. OPP-derived pectin suggested a higher methoxyl content than WRP-derived pectin, indicating its greater gelling properties. Moreover, the pectin derived from OPP and WRP demonstrated an antioxidant activity with the IC50 about 2457.58ppm and 11390.00ppm. The acid-extracted pectin from both orange peels and watermelon rinds was used in the hydrating pectin gel formulation; and the pectin gel formulation was then evaluated via viscosity vest, centrifugation test, moisturizing effect, water vapour transmission rate (WVTR), water activity, antioxidant effect, and patch test.